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1951 Thiocyanate, thiourea, and dithiooxamide complexes of ruthenium Ruth Powers Yaffe Iowa State College

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THIOCYANATE, THIOUREA, AND DITHIOOXAMIDE COMPLEXES OP RUTHENIUM

by

Ruth Pov;ers Yaffe

A Dissertation Submitted to the Graduate Faculty in Partial Pulfillment of The Requirements for the Degree of

DOCTOR OP PHILOSOPHY

Major Subject: Physical Chemistry

Approved:

Signature was redacted for privacy.

Signature was redacted for privacy. Head of Major Department

Signature was redacted for privacy. Dean o^t Graduate College

Iowa State College

1951 UMI Number: DP13067

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TABLE OP CONTENTS Page I. INTRODUCTION 1

II. REVIEW OP LITERATURE 2 A. Ruthenium Chemistry in General .... 2 B. Thiocyanate as a Complexlng Agent ... 6 C. Thiourea as a Complexlng Agent .... 10 D. Dithiooxamide as a Complexlng Agent . . l4

III. INSTRUMENTS 1? IV. MATERIALS 19 A. Ruthenium rv Perchlorate 19 B. Ruthenium III Perchlorate 25 C. Sodium Thiocyanate 27 D. Thiourea 28 E. Dithiooxamide 30 P. Miscellaneous ...... 33 V. METHOD OP INTERPRETATION OP DATA 3^ VI. EXPERIMENTAL INVESTIGATIONS 47 A. Ruthenium-Thiocyanate System 47 B. Ruthenium-Thiourea System . 66 C. Ruthenium-Dithiooxamide System .... 103 VII. SUMMARY AND CONCLUSIONS 127 VIII. LITERATURE CITED . 132 IX. ACKNOWLEDGEMENTS 13T

r/oiss - 1 -

I. INTRODUCTION

Ruthenium is one of the large group of elements present in the fission products. It is represented by several activities, among them Ru^^^ which has a 1.0 year half-life and, by reason of its 30 second daughter activity, has a fairly high energy of radiation. The specific interest in its active isotopes, together with the general lack of knowledge about its chemistry, has given strong impetus to the study of all aspects of the chemistry of ruthenium. As is to be expected of a transition element, ruthenium, in its +2, +3, and +4 oxidation states, forms numerous coordination compounds. Many of these coordination com­ pounds which have stable crystalline states have been studied, but virtually no Investigations have been carried out on the fundamental nature of ruthenium complexes stable only in solution. It is the purpose of this work to study, by means of spectrophotometry, three colored complexes of ruthenium

which are stable only in solution. The investigation has as its immediate objective the determination of the formulae and the stability constants of these complexes. In this way, it is hoped that another small fragment will be added to our knowledge of the fundamental chemistry of ruthenium, and to the more general topic of the nature of complexes in solution. - 2 -

II. REVIEW OP LITERATURE

A. Ruthenium Chemistry In General

The chemistry and literature of ruthenium, prior to 19^8, have been reviewed by Deford (1) In his thesis The Chemistry of Ruthenium. His bibliography, containing more than 250 entries. Is exceedingly useful since, previously, no complete and critical review of the chemistry of ruthe­ nium had ever been published. In his extensive review, Deford (1) surveyed the general chemistry of ruthenium. Then he discussed at length ruthenium metal, ruthenium oxides and hydroxides, ruthenates and perruthenates, halogenldes and halogen com­ plexes, ruthenium ammlnes, carbon compounds, sulfur com­ pounds, nitrogen compounds, and cyanide complexes. To supplement this survey, Deford performed many experiments in order to corroborate the findings reported in the litera­ ture or to serve as a basis for deciding between conflicting reports. The discovery of ruthenium is generally credited to C. Claus who extracted the pure metal from platinum residues in 1844. The name ruthenium, derived from Ruthenia, meaning

Russia, was given to the element by G. W. Osann in I827. The compounds that Osann obtained were very impure and did not establish the existence of the element with certainty. - 3 -

Ruthenium Is found In platinum ores to the extent of a few per cent. The metal Is very resistant to attack by acids. Including aqua regia, but it is quite rapidly attacked by molten hydroxides.

The atomic weight for ruthenium accepted in 19^9 by the International Union for Chemistry is 101.7. This is based on the ratio of ruthenium to oxygen in ruthenium dioxide, and is probably high since the dioxide is usually contaminated by traces of metallic ruthenium. The atomic

weight found from analysis of highly purified chloro- pentammlneruthenlum III chloride is 101,1. Ruthenium is unique among elements in that it exhibits all possible oxidation states from 0 to +8. The zero state is considered to exist in such com­

pounds as the carbonyls. The existence of monovalent ruthenium has been estab­ lished from the carbonyl halogenldes, such as Ru(C0)Br. The bivalent state is well established. With very strong reducing agents, the deep-blue ruthenium II chloride may be obtained. Although ruthenium II is very unstable, many stable complex compounds of bivalent ruthenium such as trlsdipyridylruthenium II chloride have been prepared. The trlvalent state is probably the most typical of ruthenium. Ruthenium III forms complex salts with many

acid radicals including chloride, sulfate, nitrate, nitrite. _ 4 _ and oxalate. Both the simple and complex salts are exten­ sively hydrolyzed In solution. Trivalent ruthenium in solu­ tion is easily oxidized to the tetravalent state. Hydrous ruthenium III oxide is slowly precipitated from solutions of ruthenium salts by the addition of alkaline hydroxides. It is readily oxidized to ruthenium dioxide. Of the lower valence states, the most stable in solu­ tion is ruthenium IV. Like trivalent ruthenium, tetra­ valent ruthenium forms numerous complex compounds. Both the simple and complex salts are extensively hydrolyzed in solution. Ruthenium in these compounds is easily re­ duced to the trivalent state. When solutions of the salts of tetravalent ruthenium are treated with alkaline hydrox­ ides, hydrous ruthenium dioxide is slowly precipitated. The dioxide shows no acidic properties and does not form

ruthenites. If any generalities may be drawn about the relative

stabilities of the trivalent and tetravalent states, it may be said that ruthenium III is the more stable in solid phase, whereas ruthenium IV is the more stable in solution. However ruthenium III is greatly stabilized by complex

formation. The only known compound of pentavalent ruthenium is the very unstable fluoride, RuP^, formed by the action of fluorine on ruthenium at elevated temperatures. - 5 -

The most Important compounds of hexavalent ruthenium are the ruthenates, M2RuOj^, formed when ruthenium tetroxlde Is absorbed in solutions of metal hydroxides. The alkali ruthenates readily dissolve in water to give orange-colored solutions which are unstable, decomposing slowly to give the hydrous dioxide and oxygen.

The only known compounds of heptavalent ruthenium are the perruthenates which are prepared by absorbing ruthenium tetroxlde in solutions of ruthenates. Although the solid perruthenates are relatively stable, the aqueous solutions rapidly decompose to ruthenates, ruthenium dioxide, and oxygen.

Octavalent ruthenium is known only as the tetroxlde,

RuO]|., which is formed when acid solutions of ruthenium salts are acted upon by very strong oxidizing agents. The com­ pound is quite volatile, and has a characteristic unpleasant odor resembling ozone. The dry compound is stable if kept in the dark, but, in light and in the presence of moisture, ruthenium tetroxlde is decomposed to the hydrous dioxide. Although the tetroxlde is slightly soluble in water, it exhibits no acidic properties and there is no evidence that it is capable of salt formation. The oxide is a powerful oxidizing agent, reacting at times with explosive violence. It is reduced by hydrogen peroxide in the presence of

acid to the tetravalent salt of that acid. - 6 -

Like other members of the transition series, ruthenium exhibits a very strong tendency to form complex Ions. The only simple Ions known In any of the valence states are the perchlorates, ruthenium being complexed by all other adds Including hydrochloric, sulfuric, and nitric. This tendency to form covalent complexes Is probably largely due to the somevjhat electronegative character of ruthenium, which per­ mits It to bear a much higher formal negative charge than la possible for the more electropositive elements. The usual coordination number of ruthenium II, III, and IV is six.

B. Thlocyanate as a Complexlng Agent

Almost every transition element reacts with thlocyanate,

CNS~, to form either a v/ater-soluble complex or a precipitate. Many of the compounds are suitable for colorlmetric determina­ tions. Mellan in his book Organic Reagents lists approximately 125 references (2, p. 42) on the chemistry of thlocyanate. Cuprlc, mercuric, lead, silver, and tungsten ions yield Insoluble thiocyanates. Colorless complexes are formed by manganese, zinc, mercury, cadmium, and antimony. Titanium yields a yellow color with thlocyanate. Trivalent vanadium gives a red color similar to iron, while vanadyl-vanadium with thlocyanate gives a blue color. Trivalent chromium

thlocyanate is violet. Trivalent iron gives the well known - 7 - deep-red color. Cobalt thlocyanate, K2Co(CNS)2j^, is blue (3) or pink depending upon the conditions of formation. Nickel thiocyanates are green. Molybdenum III with thiocyanate is red, while molybdates are yellow or amber. Trivalent tungsten thiocyanate is yellow. Rhenates react with thiocyanate to yield a yellow-brown color. Octavalent osmium with thiocyanate yields a blue color, whereas the tetravalent osmium does not. Thiocyanate reacts with trivalent bismuth to produce a yellow color.

The formulae of a few of these complexes are known. The complexes formed from molybdates and rhenates are

thought to contain oxygen, as MoO(CNS)2 and ReOCCNS)^^. The molybdenum system obviously involves several complexes since numerous colors have been observed. In an investiga­ tion of the thiocyanate complexes of divalent nickel. Kiss

and Csokan (4) identified NiCNS"^, Ni(CNS)2^ and NiCCNS)^"^. Kingery and Hume (5) in a spectrophotometric investigation of bismuth thiocyanate complexes found that in solution the tri- and pentathiocyanate complexes of bismuth exist in negligible amounts in comparison to the mono-, di-, tetra-, and hexathiocyanate complexes; They found the formation constants for the mono-, di-, tetra-, and hexathiocyanate complexes to be l4, 13, 14, and 7 respectively. Furman and Garner (6) studied the association of vanadium III and vanadium IV with thiocyanate. Their spectrophotometric - 8 -

Investigation revealed the presence of VOCNS'^j with a forma­ tion constant of 8.3 - 0.6, at ionic strength 2.60. The formation constant of the complex VCNS"*^, was found to be approximately 100, but more accurate evaluation was not possible because of the presence of higher complexes. BJerrum (7) used conductance measurements to study the chromium III thiocyanate system. The complex CrCNS'''^ has an extrapolated formation constant of 1260, at zero ionic

strength.

In an investigation of ruthenium, for the purpose of comparison it is of Interest to discuss in some detail the behavior of its well-known homolog, iron. Iron reacts with thiocyanate to produce a deep-red color. For many years there has been a controversy as to the formula of this iron-thlocyanate complex (8-15). Recently spectropho- tometrlc work has essentially resolved the controversy. Bent and French (l6) in their spectrophotometric investiga­ tion found evidence for only the one-to-one complex,

Pe(CNS)In solutions of ionic strength equal to O.665 the stability constant was found to be 30 2 2. This work was done in chloride solutions, and the accuracy of their correction for chloride coraplexlng has since been questioned.

Edmonds and Birnbaum (17)^ unaware of the work of Bent and French, also investigated the iron-thlocyanate system. Their measurements, made at unit ionic strength in - 9 -

1 M. perchloric acid, with ferric perchlorate, established 42 the existence of Fe(CNS)^ with a formation constant of 126 + 10. Gould and Vosburgh (l8) also Investigated the Iron- thlocyanate complex and again found evidence for only the monothlocyanate complex. They did not attempt to determine a stability constant.

Prank and Oswalt (19) made a very careful spectropho- tometrlc Investigation of the ferrlc-thlocyanate system using perchlorates. They found a stability constant for the monothlocyanate complex of 136 at Ionic strength 0.5, and an extrapolated constant of 89I at zero ionic strength. Although the Identification was not made. Prank and Oswalt stated that they believed the next higher complex to be the three-to-one complex rather than the two-to-one. Polchlopek and Smith (20) attempted unsuccessfully to study the higher complexes of Iron with thlocyanate. They succeeded In showing that higher complexes existed, but they were not able to Identify them definitely although they stated that they believed the next higher one to be the dithlocyanate complex.

As a result of migration experiments, Babko (21) concluded that complexes all the way from Fe(CNS)]_'*^ to Pe(CNS)g~^ could be produced by increasing the thlocyanate concentration. Prom spectrophotometrlc studies he estimated - 10 - the formation constants of the mono-, dl-, tri-, tetra-, and pentathlocyanate complexes to be 200, 90, 25, 6, and 1.1 respectively. No details of his procedure were avail­ able.

The reaction of ruthenium with thlocyanate was mentioned first by Ogburn (22) In an Investigation of the platinum metals ;vlth numerous complexlng agents. Ogburn states that ruthenium III chloride reacts with a concentrated aqueous solution of potassium thlocyanate to produce a red to violet color. Sandell (23, p. 391) In his book Colorlmetrlc Determination of Traces of Metals states that low concen­ trations of ruthenium III chloride In dilute acid solution react with thlocyanate to yield a pink color. Deford (1, p. 124) reports that heating potassium thlocyanate with ruthenium IV chloride in dilute hydrochloric acid produces a pink to violet color. Ruthenium II nitrosochloride when heated with potassium thlocyanate produces a deep-blue solu­ tion, according to Deford (1, p. 53). Aside from noting the production of a color, no in­

vestigation into the nature of the reaction between ruthenium and thlocyanate has ever been made.

C. Thiourea as a Complexlng Agent

Thiourea, (H2N-^-NH2)j reacts with a number of transl- S tion elements. In an investigation of the reactions of - 11 - seventy-eight inorganic ions with sixty substituted thioureas, Yoe and Overholser (24) studied the reactions of thiourea. Their results are summarized in Table 1.

In his series of volumes on organic analytical reagents, Welcher (25, p. 177) gave a fairly lengthy discussion of thiourea with numerous references. Thiourea is used as a reagent in micro-analysis for the detection of the platinum metals (26). Ruthenium III yields a blue color; rhodium III forms red brown hexagonal plates J and palladium II forms a yellow color. Osmium rv gives a rose color, while iridium IV becomes decolorized; platinum II yields a red-brown precipitate; and gold III gives a brownish-black precipitate. The reaction of osmium with thiourea in the presence of hydrochloric acid and with heating to give a rose to dark-red color has been used as a colorlmetric method of

analysis for osmium (27-33j 23). The formula of the colored compound has been given (28) as OsCl2*H20*6 Thiourea. The blue-green color produced when thiourea reacts

with either ruthenium III or ruthenium IV in acid solution was observed by a number of investigators (31-35^ 22). Sandell (23, p. 387) made preliminary investigations which indicated that the thiourea reaction would be suitable for the colorlmetric determination of ruthenium. - 12 -

Table 1

The Reactions of Thiourea

Ion Medium Reaction

Neutral Tan precipitate kQ* Atninoniacal Black precipitate Bi"*3 Acid Bright yellow color

Ce-^^ Acid Decolorized Cu"^^ Acid White precipitate Atnmoniacal Brown precipitate Pe"^3 Acid Light pink color Acid Grey precipitate irci^-^ Acid Decolorized OsOj."^ Acid Red color 5 -2 OsO^ Ammoniacal Grey color Pd''^ Ammoniacal or Acid Yellow color PtOlg-® Atninoniacal Brown color RU"*3 Acid . Blue-green color Sb'^3 Acid Pale yellow color

SeOj-^ Acid Red precipitate Tl"^ Neutral White precipitate Tl"" Acid Heavy white precipitate - 13 -

Deford (1, p. 133) investigated the color reaction further and developed it into a colorimetric method of analysis for ruthenium. This procedure involves, first, the standard distillation of ruthenium tetroxide to free the ruthenium from any interfering ions including osmium. The ruthenium tetroxide is absorbed in sodium hydroxide, and the resulting hydrous dioxide precipitate redissolved in hydrochloric acid. The tetravalent ruthenium is reduced to trivalent ruthenium by potassium iodide. This is done to prevent loss of thiourea, and production of sulfur which would occur if the thiourea were used as the reducing agent. Immediately after the reduction, an aqueous solution of thiourea is added. The solution is then heated five minutes in a boiling water bath and cooled to room temperature in an ice bath. The optical density of the solution is measured at 650 mu. The procedure is applicable for concentrations of ruthenium up to ten micrograms per milliliter, with the Beer-Lambert law being obeyed.

Ayres and coworkers (36,37) developed the analytical procedure still further, making a more extensive study of errors and interferences. In Ayres' procedure ethyl alcohol and hydrochloric acid are used to reduce the tetra­ valent ruthenium to trivalent ruthenium. After the addi­ tion of an aqueous solution of thiourea the solution is heated ten minutes in an 85°C water bath. After cooling _ 11^ _ the solution to room temperature, the optical density is measured at 620 mu. The optimum concentration range is from 2 to 15 micrograms per milliliter.

Both of these analytical procedures for ruthenium are extremely empirical, with precise limits being set upon the concentration of ruthenium, thiourea, and acid present, and upon the length of heating to develop the color. How­ ever, none of these investigators have reported any study on the nature of the reaction to find out why the limits are so rigid, nor any determination of the formulae of the complexes involved.

D. Dithiooxamide as a Complexing Agent

Dithiooxamide, frequently called rubeanic acid,

(H2N-^-^-NH2)> reacts with a number of metals to form salts S 3 often called rubeanates. Welcher (25> p. 1^8), in a dis­ cussion containing a number of references, reports that the salts of dithiooxamide with zinc, copper, palladium, I platinum, gold, cobalt, and nickel are insoluble in water.

In many cases the precipitate is suitable for determina­ tion of the element either gravimetrically, or, by solu­ tion in a suitable solvent, colorimetrically. Iron, silver, cadmium and mercury form salts which decompose rapidly to sulfides. These salts are reported to be of the form (38^39)

Els IH. - 15 -

Nllsaon (40), investigating the behavior of iron with dithlooxamide, reported that an alcoholic solution of dithiooxamlde added to a neutral or acid solution of ferrous or ferric ion gives a dark precipitate in which the iron is divalent. In alkaline solution, a blue color is produced, probably the ferrous-dithlooxamide complex. Nickel and cobalt also form soluble complexes in alkaline solution. None of these soluble complexes are stable.

The reaction of dithiooxamlde with the platinum metals has been quite thoroughly investigated (4l,30). Wolbling and coworkers (30j^l) were the first to report that in acetic acid solution it reacts with ruthenium III or ruthenium IV to produce a blue color. Osmium salts were reported by Wolbling to give no appreciable color change. This state­ ment has been misinterpreted to mean that osmium gives no reaction. Ayres and Young (^2) have pointed out this error, stating that osmium when mixed with dithiooxamlde gives first a greenish color, then on heating a brownish-red, and finally slowly gives an olive-green. The spectral changes accompanying these color changes are marked and the whole reaction bears further investigation. In the case of iridium and rhodium salts, Wolbling and Stelger (4l) have reported that no noticeable reaction was observed. Palladium and platinum salts when treated with dithiooxamlde yield yellow to red colored solutions first, and then dark-red precipitates. - 16 -

With a large excess of dithlooxamlde present the precipita­ tions are quantitative after standing, and decompose on heating with the formation of sulfur dioxide. The formula of the precipitates is reported to be

S=C-NH2 I y/2 . HN=C-S

Ayres and Young (^2) used the blue color of ruthenium with dithlooxamlde as a colorlmetrlc method for ruthenium.

In their procedure ethyl alcohol and hydrochloric acid are used to reduce ruthenium IV to ruthenium III, to prevent the oxidation of the complexing agent. An acetic acid solution of dithlooxamlde is added to the ruthenium and the solution is heated in an 85°C water bath for thirty minutes. After cooling to room temperature, the optical density is measured at 65O mu. The best results are ob­ tained when solutions contain about 2 micrograms per

milliliter. This analytical procedure for ruthenium, like that Involving thiourea, is extremely empirical. Again none of the Investigators studied the nature of the reaction, nor endeavored to determine the formulae of the complex

or complexes Involved. - 17 -

III. INSTRUMENTS

A Gary automatic recording photoelectric spectropho­ tometer, Model 12, Serial 15, was used for all of the work Involving the scanning of solutions at varying wave length. This Instrument is manufactured by the Allied Physics Corporation of Pasadena, California, and is designed for use in both the ultraviolet and visible regions of the spectrum. It is equipped with a double prism monochromator in order to obtain high dispersion and minimize scattered radiation (^3). The light beam is chopped at 90 cps., and the radiation receiver is a photomultlplier tube. The output of the photomultlplier tube is fed through an electronic amplifier to a recorder which automatically plots optical density of solutions under examination as a function of wave length. Widely differing scanning speeds are made possible by changing the gear ratio between the drive shaft of the motor and the prism table which it rotates. This varies the length of the wave length coordi­ nate on the recorder, when the recorder is rotating at con­ stant speed, A further variation in coordinates is made possible by changing the gear ratios in the driving mechanism of the recorder itself. The Instrument is equipped with a so-called "multiplot" control to permit unmatched cells to be effectively matched throughout the spectrum. The spectrophotometer is adjusted to have a maximum instability - 18 - of 0.005 optical density units, although the recorder may be read to 0.001 optical density units. The Gary spectro­ photometer Is particularly useful for rapid determination of absorption spectra. It is also convenient for kinetic studies to obtain a continuous recording of optical density with time. - 19 -

IV. MATERIALS

A. Ruthenium IV Perchlorate

It Is a well known fact that both ruthenium III and ruthenium IV are complexed by almost all common Inorganic acids. Including nitric, sulfuric, and hydrochloric (1, 44-46). Since any Investigation Involving the study of complex Ions should be made In a non-complexlng medium, perchlorate was the most suitable anion for this Investiga­ tion. Several methods have been investigated for the prepara­ tion of ruthenium IV perchlorate solutions which are free of all other anions, particularly chloride. Kilpatrick (44) found that ruthenium IV perchlorate could be satisfactorily prepared from ruthenium IV sulfate by metathesis with barium perchlorate. The solutions so obtained had absorp­ tion spectra in agreement with that for ruthenium IV per­ chlorate. Wehner (45,4?) investigated the reduction of ruthenium tetroxlde in perchloric acid at a platinum cathode by electrolysis at controlled cathode potentials. This proved to be a most satisfactory method and yielded ruthenium IV perchlorate solutions of reproducible spectral character­

istics. Investigators at the Knolls Atomic power Laboratory (48,49) reported that a chloride-free solution of ruthenium IV perchlorate could be produced by absorbing ruthenium - 20 - tetroxlde In an ice-cold solution containing approximately a two-hundred-fold excess of hydrogen peroxide, and suf­ ficient perchloric acid to make the resulting ruthenium solution 1 M. in perchloric acid. In this work it was decided not to use the metathetical procedure since it introduces a small amount of barium sulfate. The controlled cathode electroreduction could not be used since the necessary equipment was not available. Therefore the peroxide-perchloric acid reduction of ruthenium tetroxide was the method chosen to prepare ruthenium IV perchlorate. Reagent grade ruthenium metal powder, from Eimer and Amend, analyzed spectrographically by Dr. V. A. Fassel and his department, showed only a faint trace of rhodium. All other platinum and iron group elements were absent. Potas­ sium ruthenate, from an alkali fusion of the metal (1, p. 122, 50,51) was oxidized by potassium permanganate in sulfuric acid (52) to ruthenium tetroxide. This method, although not the most satisfactory for quantitative recovery of ruthenium, is especially v/ell suited for preparation of solutions free of contaminating ions. The tetroxide was reduced to ruthenium IV perchlorate by the peroxide-perchloric acid procedure (48,^9). This solution was used as the stock solution in all subsequent experiments. - 21 -

For a quick approximate analysis of the stock solution, ruthenium IV perchlorate was reduced to the metal with powdered magnesium (5^). Direct weighing of the dried metal gave an analysis of 0.57 mg. of ruthenium per ml. of solution.

To standardize the stock solution, Hoffman and Lundell's procedure (55) for the quantitative distillation of the tetroxide from 70^ perchloric acid was followed. This method is rapid, and generally considered the most satisfactory method proposed for the complete removal of ruthenium (1, p. 129). The tetroxide was absorbed in an alcoholic solution of potassium hydroxide (1, p. 128, 53), and the hydrous dioxide reduced to the metal in hydrogen by the standard Gilchrist and Wichers' procedure (56). The results of the standardization are given In Table 2. The stock solution was found to contain 0.5675 rag. of ruthenium per ml. of solution, which equaled 5.585 x 10"^ M. To determine the exact concentration of perchloric acid in the stock solution, aliquots were titrated against standardized sodium hydroxide, using both a Beckman Model G pH meter, and phenolphthaleln Indicator to determine the end-point. Both the free acid and the ruthenium perchlorate were titrated. Just before the end-point the ruthenium precipitated as ruthenium dioxide, leaving a clear solution, so that the end-point was easily detected. By calculation. - 22 -

Table 2

Standardization of the Stock Solution of Ruthenium IV Perchlorate

Determination d d2

# 1. 0.1116 g. 0.0019 0.00000361 # 2. 0.1133 g. 0.0002 0.00000004

# 3. 0.1148 g. 0.0013 0.00000169 # 0.1141 g. 0.0006 0.00000036 4/0.453» g. 4 /O.00000570 0.1135 g. 0.000001425 „ 0.0012 Average! 0.1135 - 0.0012 g./200 ml. ^0.00000143 - 23 - correcting for the ruthenium perchlorate, the concentration

of perchloric acid in the stock solution was I.270 M. The absorption spectra (Figure 1) of this ruthenium IV perchlorate solution agreed with the published spectra (44,45,^7). As is to be expected, the solution obeyed the Beer-Lambert law within the accuracy of measurement. Main­

taining the ionic strength constant at 3.0 by addition of lithium perchlorate, the absorption spectra of ruthenium IV perchlorate were studied as a function of perchloric acid concentration. It was found that the absorption spectra

were virtually identical from 0.127 M. to I.270 M. but that above 1.270 M. differences became apparent. This agrees exactly with Wehner and Hindman's work (45,47). The stock solution of ruthenium IV perchlorate, 5.585 X 10~3 M. in 1.270 M. perchloric acid has been quite stable, and has shown virtually no spectral evidence of decomposition after eleven months at room temperature. The solution which initially gave no test for chloride ion, after eleven months gave a faint trace. These conclusions

on the stability of ruthenium IV perchlorate in perchloric acid are in agreement with those of Kllpatrick, (44) and

of Wehner and Hlndman (45,47). 300 400 500 600 700 800 Wavelength in Millimicrons Figure 1 - Absorption Spectra of Ru(C102j^)2^ 7 = 2.285 M.; = 3.00. cell Length = 2.00 cm.

A- IpiJ = 1.117 X 10-3 M. C. IpxJ - 2.234 X 10"^ M.

B. /Ru_y' = 5.585 X 10"^ M. D. /RU_7 = 1.117 X 10"^ M. - 25 -

B. Rutheniutn III Perchlorate

As In the case of the tetravalent state, it was neces­ sary to prepare all solutions of ruthenium III perchlorate free of contaminating anions, particularly chloride. Wehner and Hindman (45,^7) investigated the reduction of ruthenium IV perchlorate in perchloric acid at a platinum cathode by electrolysis at controlled cathode potentials. This resulted only in the reduction of the perchloric acid when it was carried out at room temperatures. If, however, the reduc­ tion were carried out at -5 to -10°C, solutions of ruthenium III perchlorate were obtained free of chloride ion. Using a Diehl graded cathode electrodeposition apparatus

(57J p. 9)* generously loaned by Dr. Harvey Diehl of the analytical chemistry department of Iowa State College, ruthenium III perchlorate was prepared by Wehner and Hindman's method (^5j^7). The absorption spectra of the ruthenium III perchlorate (Figure 2) solutions agreed with the published ones (^5>^7). It was found, again in agreement with Wehner and Hindman, that solutions of ruthenium III perchlorate were stable for about two days at 0°C and for less than four hours at room temperature. 2.0 A. 2.795 X 10-3 M. B. 2.234 X 10~3 M. C. 1.775 X 10-3 M. D. 1.117 X 10-3 M. E. 5.585 X 10-'^ M.

_ 0.8 o 0.6 Q. ^ 0.4 0.2

300 400 500 600 700 Wavelength in Millimicrons Figure 2 - Absorption Spectra of RuCclOj^)^

Cell Length = 2.00 cm. - 27 -

C. Sodium Thiocyanate

The sodium thiocyanate used in this investigation was Mallinckrodt's reagent grade chemical. It was found that after careful drying of the salt, the sodium thiocyanate could be used as a primary standard to prepare solutions of the desired concentrations. At first, all sodium thiocyanate solutions were standardized by titration with standard silver nitrate solution. However, since the analyses agreed exactly, within the limits of experimental error, with the "weighed-in" concentrations, it was decided that standardization of the solutions was unnecessary. In the investigations undertaken, the sodium thiocyanate solutions must contain perchloric acid. The question was raised as to the effect of perchloric acid on sodium thiocy­ anate. The possibility of forming thiocyanic acid need be considered for if thiocyanic acid were a weak acid, this would produce important changes in the ionic strengths of solutions.

A literature search revealed that thiocyanic acid is a strong

acid. Gorman and Connell (58) measured the pH's of freshly prepared solutions of thiocyanic acid using a glass electrode. They showed that thiocyanic acid solutions have the same pH's as perchloric acid solutions of equal concentrations.

Therefore, they concluded thiocyanic acid must be as strong as perchloric. Suzuki and Hagisawa (59)^ who also used pH measurements made with a glass electrode. - 28 - found the dissociation constant of thiocyanlc acid to be 0.142. Since thiocyanlc acid is a strong acid, the ionic strength should not be affected by the fact that sodium thlocyanate solutions contain perchloric acid. Additional difficulty might occur from the oxidation of thiocyanlc acid in the presence of perchloric acid. It was found that thiocyanlc acid is oxidized by hot iodic acid, sulfuric acid, or potassium permanganate in sulfuric acid (60, p. 333). It is stable in concentrated hydro­ chloric acid, both hot and cold. Therefore it is to be expected that thiocyanates will not be oxidized in the presence of cold dilute perchloric acid, but some attack may be anticipated in hot solutions. As a precaution, all sodium thlocyanate solutions were prepared fresh each time they were used. The absorption spectra of sodium thlocyanate are given

in Figure 3. It was found that freshly prepared solutions of sodium thlocyanate obeyed Beer's law. However, if these solutions were heated, the absorption Increased in the longer wave length regions (Figure 3) and the solutions no longer obeyed Beer's law.

D. Thiourea

The thiourea used, recrystalllzed Eastman's Organic

Chemical # 497, was treated as a primary standard. To 2.0 A. Without Heating B. With Heating; 15 min. at 70°C

ae 06

0.4 0.2

250 300 350 400 450 500 550 Wavelength In Millimicrons Figure 3 - Absorption Spectra of NaCNS AaCNS_7 = 0.5585 M.; ^ClO^^^JZ = 0.12? M. Cell Length - 5-00 cm. j - 1.00 - 30 - minimize the effect of oxidation in the presence of per­ chloric acid, all thiourea solutions were prepared fresh each time they viere used. Mlcewlcz (6l) reported that the perchlorate salts of thiourea explode when heated. The absorption spectra of thiourea are given in Figure 4-. Freshly prepared thiourea solutions obey Beer's lav/, as do solutions which have been heated only a short length of time. Longer heating produces a turbidity in the thiourea solutions which is apparently sulfur.

Rivier and Borel (62) studied thiourea spectroscopi- cally to determine whether the sulfur atom in the thiourea

was linked by a double bond /s=C(NHp)p 7 the normal structure, or by a single bond in the tautomeric form

^NC(NH2)SH_J7. The normal derivative would have a stronger absorption, caused by the C=S in the structure, than would the tautomer. On the basis of their investigations, Rivier and Borel concluded that thiourea can exist only as the tautomer, and hence it does not contain the C=S group.

E. Dithiooxamide

Dithlooxamide, Eastman's Organic Chemical # ^394, was weighed out directly to provide solutions of the desired concentrations. Since it is only slightly soluble in cold water, the solvent used was a mixture of water, perchloric

acid, and acetic acid. Since both sodium thlocyanate and 2.0

-1 -2 i.6 1.117 X 10 M.

m

0.2

200 250 300 350 400 450 Wavelength in Millimicrons Figure 4 - Absorption Spectra of Thiourea = 2.285 M.; = 3.00

Cell Length = 2.00 cm. - 32 -

c..6

-2 2.2 2.0

.6 M. 1.6 1.4 1.2 1.0 0.8 0.6

0.4

400 500 600 700

Wavelength in Millinnicrons Figure 5 - Absorption Spectra of Dithlooxamide

= 0.127 M.; ^0Ac_7 = 50^ Cell Length = 5-00 cm.^'^ = 1.00 - 33 - thiourea undergo oxidation in the presence of perchloric acid, it was to be expected that dithiooxamide would be attacked too. Therefore, the dithiooxamide solutions were prepared fresh each time they were used.

The absorption spectra of dithiooxamide are given in Figure 5. The solutions obeyed Beer's law within the limit of accuracy of the measurements.

P. Miscellaneous

In all work, the ionic strength was maintained con­ stant by addition of the required amount of G. Frederick Smith's reagent grade lithium perchlorate. G. Frederick Smith's doubly vacuum distilled perchloric acid was used throughout the investigation. To prevent traces of iron contamination, no metal spatulas were ever employed. Instead, spatulas of hard rubber porcelain, or glass were used with all solids. The pipettes and volumetric flasks used in the preparation of solutions were Kimble's Normax brand. - 34 -

V. METHOD OP INTERPRETATION OF DATA

Various methods have been applied to the interpreta­ tion of spectrophotometric data for the determination of empirical formulae of colored complexes in solution. A recent publication by Harvey and Manning (63) both surveys old methods and proposes two new methods for the analysis of spectrophotometric data. Historically the first, and undoubtedly the best known approach is Job's method of continuous variations {6k), For the reaction involving the formation of a single complex ion, A + nB ^ to determine n, equimolar solutions of A and B are mixed in varying proportions and the optical densities measured. The difference (y) between the optical density found and the corresponding value calculated for no reaction is plotted against the composition. The resulting curve should have a maximum or minimum. The composition at the maximum or minimum bears a simple relation to n, and is independent of the equilibrium constant. If the concentra­ tions of A and B are not equimolar, the position of the maximum in the curve is a function of the equilibrium con­ stant as well as n. After n is known, and providing the stability of the complex is not too great, the equilibrium constant can be determined.

Vosburgh and coworkers (18,65) extended Job's method not only to determine whether or not more than one complex - 35 - formed, but also to identify the species when two or more complexes coexist. They developed mathematical equations to show that if only one complex is present, the maximum in the "Y" curve will be independent of the wave length of light used. When more than one compound is formed, the results obtained are a function of the wave length of light used. However, if more than one complex is formed. Job's method can still help in obtaining the formulae of the complexes if they are sufficiently stable. In that case, it is frequently possible to select a region of the spectrum in which the absorption of one com­ plex predominates. Then, in that region, the data may be treated as if only one complex were present.

Bent and French (l6) developed a logarithmic approach which is suitable if there is only one complex with a small formation constant. For the reaction: mA + nB AmBn# the dissociation constant is;

K = Z"A.7 " . C^J "

rVnJ'

Taking the logarithm of both sides of the expression gives;

log A®n_7 = m log /~A_7 + n log /~B_7 - log K.

If the concentration of one of the ions is kept constant, the equation for a straight line is obtained by plotting the logarithm of the optical density, which is proportional - 36 - to the concentration of the colored complex, against the logarithm of the concentration of the other Ion. The slope of this straight line then gives the value of m or n. Since it is frequently impossible to obtain the concentration of the ion A or B at equilibrium, as is required in the logarithm expression, it is usually necessary to plot the logarithm of the total concentration of this ion. In dilute solutions where the colored complex is largely dissociated, this will give a straight line, but devia­ tions will occur as soon as an appreciable fraction of the ion is present in the form of the complex. Molland (66) has published a method which is based on the assumption that, with one component present in excess, the maximum amount of the complex present will be determined by the other component. This assumption is correct only when dissociation may be ignored. Hence, the method is valid only in the case of complexes with fairly high stability constants.

Edmonds and Birnbaum (17) used an approach involving a large excess of complexlng agent. For the reaction:

A •¥ nB ^ ABn, the equilibrium constant 1st

K-i = rA-7 • .

If the initial concentrations of A, B, and ABj^ are a, b, and zero, the equilibrium concentrations will be a-x, b-nx, and - 37 - and X respectively. With a large excess of B, its equilibrium concentration will essentially equal its initial concentra­ tion and the equilibrium constant may be written;

K-l =

For a fixed cell length, and constant values of a, K may be evaluated for any two measurements of the optical density by the simultaneous solution of two equations. In a series of such experiments, only the correct choice of n will give reproducible values of K. Only complexes of low stability should be analyzable by this method. For a complex, with a large formation constant, Yoe and Jones (67) found that a plot of optical density against the molar ratio of component B to component A, with A constant, rises from the origin as a straight line and breaks sharply to a constant optical density at the molar ratio of the components in the complex. Harvey and

Manning (63) extended the applicability of this method to complexes which undergo appreciable dissociation by maintain­ ing high the ionic strengths. This procedure is based on the fact that the degree of dissociation of a complex is sometimes suppressed by the addition of an electrolyte.

In the same paper Harvey and Manning (63) presented their slope-ratio method. In the reaction: mA + nB ^ Aj^B^, if the concentration of B is constant and in sufficient - 38 - excess to make dissociation negligible, the equilibrium constant will be essentially proportional to the analytical concentration of A added in the reaction, so ~ where the brackets refer to the equilibrium concentration and C is the total concentration. Prom Beer's law,

D = 1 Z^ni®n_7 where D is the measured optical density, e the molar extinction coefficient, and 1 the cell length in centimeters. Substituting for ^in®n_7'

D = ^ °A « . m

D is plotted against different analytical concentrations of A, keeping the concentration of B constant and in excess. Over the straight line portion of the curve, the equation

is valid. This straight line will have a slope given by: Slopej^ = el/m. Similarly if A is the component In excess, and the concentration of B is varied, Slope2 = el/n. Thus the ratio of n to m will be the ratio of the two slopesi Slope^^/Slopeg = n/m.

Preliminary investigations of the reactions of ruthenium IV perchlorate with thiocyanate, thiourea, and dithiooxamlde revealed that before any complex formation occurred the ruthenium IV v;as reduced to ruthenium III at the expense of the complexlng agent. These experiments also revealed that none of the complexes formed was very stable. The fact that ruthenium was being reduced by the complexlng agent meant, first, that the extinction - 39 - coefficient of the starting material was unknown, and second that at low concentrations of complexing agent, the concen­ tration of the complexing agent was unknown. In order to keep the relative loss of complexing material insignificant, it was necessary to work only in the region of high con­ centration of complexing agent. Consequently, none of the above techniques for the analysis of spectrophotometric data was applicable as presented. Kingery and Hume (5) in studying bismuth-thiocyanate complexes made use of a technique of evaluating the extinc­ tion coefficient of the "last complex" formed. If a large excess of a colorless complexing agent is added to a low constant concentration of a colored metal ion to form a series of complexes, the optical density will change as the species in solution change. It will eventually reach a constant value, when all of the metal ion is in the form of the "last complex", that complex containing the maximum number of complexing molecules that the metal ion is capable of holding. When Kingery and Hume's technique of obtaining the extinction coefficient of the last complex was coupled with Edmonds and Birnbaum's (17) method of evaluating an equilibrium constant, the following method was developed. Case I: The formation of a single complex

For the reaction: - 40 -

A nB ^ AB^ (1) the non-thermodynamlc stability constant equals;

K = . (2)

Let the total concentration of A equal c. When most of A Is In the form AB^ the following will be true: = c-x;

/~A_7 - X. If a large excess of B Is present, the equilibrium concentration of B will essentially equal the total concen­ tration of B. The equilibrium constant then is:

K = n • (3)

If the extinction coefficient of A Is eQj of AB^^ is e^^, and If B Is colorless, the optical density of the solution at any wave length may be written:

D = Ixe^ + l(c-x)e]^ (4)

where 1 Is the cell length. For a constant concentration of A equal to c, making use of the Beer-Lambert law, d = Ice, to eliminate the extinction coefficients, equation (4) may be written:

D = ^lo ^ (c-x)di (5) " c Solving for x, and c-x from equation (3) gives: - 41 -

c c-x = cKZ:-BJ7" (6) " K/"BJ7"^ + 1 KZ"BJ7" 1

Substituting these into equation (5) yields:

D ^o ^ K/-BJ7" d;L (7) kZ'B_7" + 1 K^B_7" + 1

Rearranging gives:

D = do + K^Bj7"(d;L-D). (8)

Now at any given wave length, D is the experimentally determined optical density at any concentration B, and Is the experimentally determined optical density of the last complex. By plotting D against ^B_7'^(<3^-D), a straight line should be obtained, with slope K and in­ tercept dQ. The constant n is evaluated by trial and error, since only the correct choice of n will yield a straight line of positive slope. As K is not a function of wave length, the determination of K at numerous wave lengths permits averaging and Improved precision. Once K and n have been evaluated, the absorption spectra of the starting material A, with optical density dQ, may be calculated.

Case II: The formation of two complexes For the reactions:

A + nB (1) - H-2 -

+ qB ABfi+q, the non-thermodynamlc stability constants equal:

Z^n-7 ^aJ7-^BJ7"

ZMn*q_7 Kg =

Let the total concentration of A remain constant, A = c. Then at equilibrium the concentration of A = Cq, of

ABfi = C2> and of ABj^^q = C2. If B is present to a suf­ ficiently large excess, the equilibriUTn concentration of B will essentially equal the total concentration of B. Thus, the following equations may be written;

c = Cq ci + C2, (3)

Kl = _!i (f)

K2 = Co2 Oi • ^bJT^

Ct °o ~ (5) KirB_7"

0 - (6) - k3 -

°1~ I T /- -TQ 1 4 1 + KirB_7''

If the extinction coefficient of A = eQ, of = e]_ of

AB^^q = 62# and if B is colorless, the optical density, D, of the solution at any wave length may be written:

D = lCo®o ^°1®1 * ^°2®2 • (^)

Substituting for the extinction coefficients by using the Beer-Lambert law, d = Ice, for a constant concentration of A = c, and a constant cell length, equation (8) becomes;

D = ^o^o ^ ^1*^1 4 °2^2 . (9) c c c

Substituting equations (5)* (6), and (7) into equation

(9) yields:

io , di -t D = K,rB_7" • (10) —i ^ • 1 * K2^_7^ KirB_7" ^ ^

After adding a sufficient excess of complexing agent B, the curve obtained by plotting optical density against concen­ tration of complexing agent will asymptotically approach

the optical density, dg* of the last complex. Hence, it is possible to experimentally evaluate d2. When virtually - 44 - all of A Is In the form AB^^q, the contribution of A Itself to the total optical density will be small, and as a first approximation may be neglected. In that case equation (10) may be reduced to:

n = di « (11) 1 K2Z~B_7q

D = d]^ f K2/~Bj7^(d2-D). (12)

Consequently by the correct choice of q, a straight line of slope Kg and intercept d]^ may be obtained by plotting

D against /~B_7^(d2-D). To obtain and d^, equation (10) may be rearranged:

D = do - [(D-di)^Bj7" + (D-d2)K2Z~B_7'^*^^ . (13)

Substituting into equation (13) the first approximations . to d]^ and Kg* and plotting D against the expression in brackets, with the correct choice of n, the slope obtained will be K]_, and the intercept d^. Rearranging equation (10) again gives:

° ^ * (<32-D)Z-BJ7'K2. (W)

By substituting the first approximations to dQ, and K^, and by plotting the left hand side of equation (14) against

(d2-D)/~!B_J7^, the second approximation to K3 and d]^ may be - 45 - obtained from the slope and Intercept respectively. This series of successive approximations, using equations (I3) and (l4), may of course be repeated as many times as neces­ sary to obtain precise values of dQ, dj^, and K2. It should be pointed out that this method gives a precise determination of the equilibrium constant, since It Is evaluated at a number of different wave lengths. The accuracy of the constant Is dependent not only upon the accuracy of the physical measurements, but also upon the accuracy of the assumption that the equilibrium concentra­ tion of the complexing agent B is essentially equal to the total analytical concentration of B. The equilibrium con­ centration of B is always less than the analytical concen­ tration for tv;o reasons; first, some B is bound in the com­ plex, and second, some B is lost in the reduction of ruthenium from the tetra- to the tri-valent state. These losses in B become important for small ratios of B to ruthenium. Under those conditions the equilibrium con­

stant evaluated will be precise but of necessity some­ what Inaccurate.

The Importance of the effects of ionic strength on the study of equilibria cannot be ignored. Vosburgh and Cooper (65) Indicated that activity coefficients should be Included in the equilibrium expressions derived from optical density measurements, and that constant ionic - 46 - strength should be maintained. If the ionic strength is constant, the activity coefficients should be constant, and should have a constant effect on the equilibrium con­ stant. Unfortunately, since ruthenium salts are readily hydrolyzed, all solutions had to have a fairly high con­ centration of perchloric acid present. Therefore, the ionic strength of the solutions had to be kept high. As !t a consequence, the Debye-Huckel limiting law could not be applied, and it was impossible to calculate the true thermodynamic equilibrium constants. - 47 -

VI. EXPERIMENTAL INVESTIGATIONS

A. Ruthenlum-Thiocyanate System

Preliminary investigations showed that ruthenium IV perchlorate reacted very slowly with sodium thlocyanate to give a deep-blue colored solution. The color faded slowly, and was eventually completely discharged. Heating the solution speeded the formation of the complex. A simple ion migration apparatus was set up to deter­ mine the charge of the complex. This consisted of only a storage battery, a milliammeter, and a variable resistance connected to two platinum electrodes. The complex, pre­

pared from 5 X 10~5 m. Ru(C10j^)|j^, and 1 M. NaCNS was placed in the center of a U tube with 0.25 M. LiClOij. carefully layered into the arms. With a current of 5 ma., in l8 hours the blue-purple complex had migrated approximately one centimeter toward the cathode. Thus the blue-purple ruthenium thlocyanate complex behaves as a cation. In preparing the complex for spectrophotometry it was necessary to heat the solutions in order to attain equilibrium within a reasonable length of time. A study was made, spectrophotometrically, to determine the effect of heating — R a solution containing ruthenium IV perchlorate, 5.585 x 10"^ M., with a thlocyanate to ruthenium ratio of 9000. Stock solu­ tions of ruthenium IV, and thlocyanate were mixed to give the - ^8 - final solution the desired concentration. The solution so prepared was placed in a boiling water bath for the desired length of time, as measured by a stop watch. After the required heating period, the solution was plunged immedi­ ately into an ice bath. As soon as the temperature of the solution reached 25 - 1°C, the solution was removed from the ice bath, placed in the spectrophotometer cuvette, and scanned on the spectrophotometer. This was done for heat­ ing periods from zero to ten minutes. It was found that the color developed for heating periods from zero to three minutes, attained a constant maximum from three to five minutes, and decomposed with heating periods longer than five minutes. In an attempt to extend the plateau of constant maximum optical density, it vms decided to repeat the above procedure at a somewhat lower temperature. The temperature chosen was 70 ~ 1°C, and the procedure fol­ lowed was identical with that given for the higher tem­ perature . The length of heating was varied from 3 to 45 minutes. With heating periods from 3 to 12 minutes the optical density increased. It attained a constant maximum value from 13 to 27 minutes and decreased with heating for longer periods of time. When In the plateau region, no change was observed in the optical density _ 49 - over wave lengths from 400 to 750 inu, with various lengths of heating. Below 400 rau a slight Increase In optical density was observed with increased length of heating.

This effect may be directly attributed to the oxidation of thiocyanate in the presence of perchloric acid. The 70°C heating period seemed satisfactory for the prepara­ tion of the ruthenium-thiocyanate complex so in all succeeding work a 15.0 minute heating period at JO i 1°C was used. Next the stability and rate of fading of the thiocyanate-ruthenium coloi' were investigated. A solution containing 5.585 x 10"^ M. ruthenium and a thiocyanate- ruthenium ratio of 9000 was prepared, and the color developed by the usual heating and cooling. The Gary recording spectrophotometer was set at 590 mu. and the fading of the solution was studied as a function of time. In the first half hour after preparation no fading could be detected. After that a slow fading occurred, which was less than 0.01 O.D, units in three hours. With the preliminary investigations completed, the determination of formulae and stability constants was begun.

In all subsequent work the ruthenium concentration was maintained constant at 5.585 x 10"^ M., v/ith the ionic strength constant at 1.0. The perchloric acid concentra­

tion was 0.127 M. unless stated otherwise. Solutions were - 50 - prepared by mixing necessary quantities of a stock solution of ruthenium IV perchlorate and a freshly prepared solution of sodium thiocyanate to give the desired final concentra­ tions. Each solution was placed immediately in a 70°C water bath for exacly 15.0 minutes, then plunged into an ice bath until the temperature of the solution reached 25 - 1°C. Finally the solution was scanned as quickly as possible on the Gary recording spectrophotometer. In no case did the time required^ for scanning exceed ten minutes. Solutions which contained ratios of sodium thiocyanate to ruthenium from 13,500 to 10 were so prepared and scanned. These data are given in Table 3. A plot at constant wavelength (590 mu.) of the optical density as a function of the ratio of NaCNS to ruthenium shows clearly that the optical density of the solution does not change for ratios of NaCNS/Ru greater than 8OOO. This is shown by the line labeled d^^ in Figure 6. Hence the optical density of the last complex is known from experimental data. The absorption spectrum of this complex is given in Figure 7 and in Table 4. Using a constant thiocyanate concentration of

5.026 X 10 ^ M., which is sufficient to put all of the ruthenium in the form of the last complex, a study was made of the complex to see if it obeyed Beer's law. As to be expected, it did, as Figure 7 shows. •r-l UJ :e^ •P O 22o2oo o5ooS 06066 00000 66666 o'o'ooo 66666 66666 o o S2SSSS mm pisi i oooooo 00000 ooooo 00000 00000 00000 00000 00000 SSKSs sI§5P HIP. I oooopo ooooo ooooo ooooo ooooo ooooo ooooo ooooo saSS? SKS^ ISHP S|SH ooooo ooooo ooooo ooooo OOOC.Ti 'w oooooo ooooo ?ssg=is ssip^ mm HHs 51^ ooooo ooooo ooooo ooooo oasoo —OOO-. oooooo ooooo 55§g|g HIS S» SI aiH if^S HS5S ...... • • ooooo ooooo ooooo ooooo 0000- -w0'_.0 oooooo ooooo £3i5«sS ggscs 5^^ imm S|f^ |S?S5 SSSss •t .'t •. ooooo oodoo doood ooooo oooc-ci -.oooo I oooooo ooooo

sssssi mm mm sm ¥m ...... q'oqoo Ooooo ooooo ooooo ooooo ooccc I oooooo ww«ww 3S£sSg SSSil Psgg Hps P;lf5 ?5I5S I do'dddd ooooo ooddd ooooo ooooo ooooo ooooo ccoco •SSE58S ESSS mM SS S|SS.IiB5 3K? ?K=S dddddd ooooo ooooo ooooo ooooo ooooo ooooc ccoo^

mm ^P.P. dddddd ddddd ooooo ooooo ooooo ooooo coooo coccs

SSI- mm hps SII55 St5S.I dddddd ddddd ooooo ooooo ooooo ooooo ooooo ouooc S^SSss rkSsI s=g^ SS HssI SfSSs sr?m ?;§Sls dddddd ddddd doddd ddddd ddddd ddddd oocoo coocc SSSsss sSsll sSIH Hiss sfl5l Ssp.S dddddd ddddd ddddd ddddd ddddd ddocd cooo'c ccoo^ ?S§8§§ ss^l HSSS I dddddd ddddd ooooo ooooo ooooo ooooo ooooo cc«jo^ SS£Sla i|SI? Ssps ipH ?pISS SipS Ssf.ti I dddddd ddddd ddddd ddddd ddddd ddc*o*d cdddo* ccodd 1 SSsssg gggis Si ggga S QQQQQQ OOOOO OOOOO ooooo OOCCO ooOOO CO00^^ i £Sgs^ sSsI? sHIs iSSss Hsil siSqs 2 dddddo OOOOO ooooo ooooo ooooo ooooo c.*ocoo occco sSSs^ sHSf ss^s SsssE S^SS siSsS 5?ISI SsIM S i g S dddddd odddd ooooo ooooo oooco ooooo ooooo oocoo

ggggpl §i£ls Issis ISk§S IKSSS fISI? ISLBI Ji6

- 51 -

Table 3 Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of CNS~/R^j with ^ equal to 0.127 M.

aooo 1800 1600 700 500 225 150 90

0.14B 0.153 0,140 0.136 0.159 0.144 0.154 0.170 0.168 0.163 0,165 O.m 0.178 0.172 0.175 0.175 0.171 0.170 0,167 0.164 0.150 0.152 0.161 0.158 0.143 0.156 0.169 0.154 0.160 t:\ll 0.179 0.177 0.166 0.173 o.idi 0.183 0,179 0.178 0.176 0.175 0.171 0.168 0.165 0.151 0.15 0.159 o.m 0.172 0.155 0,174 0.182 0.164 0.170 0,176 0.192 O.IB7 0.182 0.185 0.194 0.195 0.167 0.182 0.179 0.175 0.171 0.166 0.158 0.15 0.19d 0.190 0.172 0.162 0.200 O.lBO 0.186 0.191 0.211 0.200 0.197 0.197 0.210 0.209 0.197 0.191 0.185 i-m 0.176 0.174 0,165 0.192 0.221 0.211 0.192 0.204 0.224 0.205 0,199 0.213 0.227 0.220 0.217 0.2ld 0.224 0.222 0.213 0.202 0.1^ 0.195 l:\i 0.185 0.182 0.169 0.217 0.243 0.233 0.217 0.226 0.247 0,229 0.230 0.233 0.248 0.240 0.23d 0.237 0.239 0.238 0,228 0.219 0.213 0.212 0.201 0,198 0.194 0.179 0.213 0.270 0.265 0.244 0.244 0,271 0.256 0.255 0.255 0.272 0.264 0.259 0.258 0.259 0.259 0,245 0.234 0.224 0.213 0.207 0.202 0,184 0.267 0.306 0.298 0.271 0.286 0.304 0.286 0.286 0.285 0.306 0,285 0.289 0.287 0.263 0.281 0.265 0.248 0.236 0.226 0.2ld 0.213 0.193 0.307 0.3^0 0.330 0.307 0.326 0.339 0.327 0.321 0.317 0.338 0.323 0.317 0.314 0.311 0.306 0.287 0.266 0.254 0.251 0.23B 0.232 0.223 0.202 0.339 0.383 0.376 0.346 0.375 0.379 0.367 0.357 0.350 0.361 0.352 0.347 0.340 0.345 0.312 0.284 0.271 0,269 0.244 0,236 0.214 0.C310.301 0«I29 0.421 0.393 0.413 0.420 0.419 0.400 0.393 0.398 0.389 0.382 0.378 0.363 0.337 0.304 0.291 0.285 t:m 0.259 0.250 0.228 0.496 0.4B7 0.457 0,481 0.483 0.484 0.459 0.445 0.473 0.449 0.442 0.432 0.420 0.403 0.370 0.332 0.315 0.310 0.267 0.278 0.264 0.242 0,502 0.565 0.551 0.561 0.527 0.500 0.533 0.4B4 0.469 0.446 0.405 0.358 0.331 0.312 0.579 0.533 0.549 0.493 0.339 0.298 0.288 0.257 l:Ul 0.647 0.611 0.632 0.630 0.639 O.6O3 0.568 0,602 0.558 0.540 0.523 0.490 0.452 0.392 0.369 0.358 0.339 0.321 0.300 0.273 0.665 0.728 0.712 0.680 0.701 0.691 0.702 0.665 0.62s 0.653 0.621 0.612 0.587 0.5G1 0.530 0.490 0.415 0.391 0.3dl 0.357 0.338 0.31? 0.2d9 '0.739 0.708 0.667 0.652 0.646 0.623 0.556 0,413 0.785 0.777 0.758 0.729 0.745 0.734 0.745 0.693 0.593 0.503 0.442 0.402 0.379 0.355 0,336 0.308 . 0.810 0.801 0.786 0.763 0.778 0.767 0.769 0.741 0.695 0.721 0.686 0.669 0.643 0.610 0.575 0.516 0.424 0.419 0.395 0.369 0.342 0.316 0.800 0.783 0.765 0.778 0.764 0.773 0.741 0.720 0.687 0.666 0.641 0.606 0.575 0.519 0.422 0.396 0.376 0.355 0.327 0.&07 0.786 0.634 0.466 0.426 o.ioo 0.789 0.771 0.750 0.768 0.752 0.746 0.729 till 0.713 0.678 0.661 0.598 0.570 0.516 l-Ml 0.382 0.361 0.335 0.750 0.740 0.738 0.730 0.721 0.707 0.66C 0,692 0.668 0.640 0.618 0.584 0.561 0.466 0.430 0.403 0.386 0.364 0.338 0.76ft 0.681 0.669 0.602 0.569 0.5'»B 0.466 0.404 0.735 0.735 0.716 l-M 0.710 0.702 0.698 0.642 0.636 0.633 0,429 0.388 0.372 0.342 0.712 0.708 0.688 0,683 0.691 0.684 0.678 0.663 0.625 0.656 0.625 0.610 0.589 0.559 0.540 0.493 0.467 0.439 0.430 0.407 0.390 0.376 0.350 0.694 0.680 0.663 0.679 0.671 0.665 0.646 0.616 0.643 0.614 0.601 O.5BO 0.552 0.537 0.4QO 0.467 0.437 0,430 0.409 0.395 0.3S4 0.360 0.6§u 0.636 0.606 0.605 0.592 0.568 0.546 0.489 0.467 0.436 0.432 0.412 0.660 0.678 0.674 0,648 0.661 0.659 0.645 0.532 0.«02 0.390 0.372 0.6t5 0.651 0.637 0.635 0.637 0.622 0.619 0.587 g;i?l 0.589 0.575 0.558 0.538 0.527 0.487 0.466 0.438 0.417 0.408 0.399 0.362 0.60? 0.606 0.607 OIsbJ 0,591598 0.600 0.581 0.579 0.556 0.587 0.562 0.548 0.548 0.519 0.512 0.480 0.465 0.441 l-Ml 0.4;!3 0.414 0.403 0.394 0.556 0.547 0,537 t).55l 0.556 0.539 0.525 0.550 0.534 0.528 0.510 0.494 0.492 0.459 0.443 0.443 0.427 0.422 0.416 0.405 0.1^4 0.W5 0.496 0,489 0.505 0.516 0.497 0.483 0.518 0.502 0.487 0.486 0.479 0.479 t'Mi 0.457 0.446 0.447 0.432 0.430 0.415 0.^(62 0.473 0.466 0.454 0.472 0.48% 0.459 0.472 0.466 0.491 0.481 0.475 0.469 0.467 0.471 0.467 0.457 0.452 0.452 0.444 tiii 0.444 0.429 0.442 0.456 0.445 0.434 0.451 0.468 0.443 0.455 O.U78 0.471 0.464 0.462 0.463 0.469 0,470 0.462 0.45? 0.469 0.456 0.461 0.465 0.44B 0.^3? 0.449 0.430 0,424 0.441 0.461 0.436 pll 0.453 0.468 0.469 0.464 0.464 0.468 0.476 0,477 0.479 0.474 0.482 0.475 0.477 0.4B5 0.470 0.^37 0.451 0.440 0,424 0.441 0.V60 0.442 0.449 0.455 0.481 0.475 0.469 0.470 0.478 0.485 0.492 0.489 0.489 0.496 0.490 0.497 0,505 0.487 •C.m4Y 0.460 0.446 0,426 0.444 0.467 0.444 0.453 0.462 0.486 0.481 0.477 0.479 0.4^ 0.494 0.504 O.506 0.497 0.515 0.5ti6 0.513 0,529 0.500 0.462 0.444 0.429 0.446 0.467 0.442 0.465 0.46B 0.485 0.4W 0.462 0.488 0.503 0.510 0.514 0.517 0.527 0.524 0.529 0.541 0.520 C.-iL'l 0.446 0,*29 0.412 0.436 0.456 0.425 0.45'» 0,484 0.477 0.475 0.478 0.485 0.501 0.510 0.522 0,525 0.533 0.540 0,554 0.533 0.3-l) 0.427 0.401 0,391 0.403 0.435 0.399 0.422 0.439 0.468 0.464 0.457 0.465 0.476 0.490 0.507 0.527 0.530 O.OM 0.551 0.566 0.540 0.3V I 0.393 0.379 0,365 0.379 0.412 0,402 0.420 0.450 0.450 0.445 0.455 0.467 0.485 0.506 0.531 0.534 0.550 0.550 0.559 0.580 0.548 C. "'.'l 0.377 0.361 0.373 0.385 l:m 0.411 0.442 0.442 0.440 0.450 0.467 0,4B6 0.513 0.535 0.543 0.554 0.557 0.572 0.592 0.557 0.369 0.355 0.373 0.390 0.371 0.388 0.416 ' 0.444 0.448 0,447 0«449 0.480 0.492 0.533 0,549 C.57J 0.569 0.600 0.572 0.387 0.372 0.392 0.404 0.411 0.4l8 O.U45 0.478 0.479 0.477 0.48O 0.516 0.534 .0.573 0.577 t-M O.6O3 0.615 0.640 0.601 0.433 0.429 g:r5i 0.470 0.461 0.503 0,485 0.519 0.556 0.556 0.547 0.568 0.595 0.600 0.650 0.628 0.637 0.653 0.655 0.664 0.666 0.647

I slengths tlos of L27 M.

300 225 200 175 150 185 ^00 90 80 75 70 60

0.177 0.170 0.172 0.17; 0.175 0.171 0.170 0.167 0,l6l| 0.150 0.1*9 0.152 O.IHJ O.U) O.lkl O.ljB 0,198 0.130 0.125 0.11* o.idi 0.183 0,179 0.178 0.176 0.175 0.171 0.168 0.16; 0,151 0.151 0,151 0,11)7 0,1*5 0.1*2 0,135 0,129 0.133 0.120 0,112 0.194 0.195 0.187 0.182 0.179 0,179 0.175 0,171 0,166 0.158 0,158 0,155 0,155 0,1*9 0.1*8 0.1*0 0.132 0.135 0.125 0,115 0.210 0.209 0,197 0.191 0,185 0,186 0,17° O.I76 0.17* 0,165 0,163 0.160 0.I5B 0.153 0.150 0,1«5 O.I38 0,138 0.128 O.lll 0.22i| 0.222 0.213 0.202 0.190 0.195 0.168 0.182 0,169 0.170 O.I65 0,165 0,159 0,156 0,1*8 0,1*0 0,1*0 0.I3I 0.II3 0.239 0.23S 0.228 0.219 0.213 0.212 0.201 0.198 0.19* 0.179 0.179 0,173 0,171 0.168 0.160 0,155 0,1*7 0,1*9 0,138 0.118 0.259 0.259 0,2*5 0.23* 0,22* 0.223 0.213 0.207 0.202 0.18* O.lB* 0,180 0,178 0.I7I 0,16* 0,159 0,1*9 0,150 0.139 0.119 0.283 0.281 0.265 0.2*8 0.238 0.236 0.2:6 0.218 0.213 0.193 0.191 0.188 0.185 0.178 0,175 0,165 0,152 0,155 0.1*3 0,121 0.311 0.306 0,287 0,266 0,25* 0.251 0.238 0.232 0.223 0.202 0.203 0,200 0,192 0,186 0,18* 0.172 0,161 0.16* 0,150 0.125 0.340 0.345 0.312 0.28* 0.271 0.269 0.253 0.2** 0.236 0.21* 0,21* 0,212 0.203 0.195 0.191 0.177 0,166 0,169 0,151 0,128 0.378 0.363 0,337 0.30* 0.291 0.285 0.268 0.259 0.250 0.228 0.228 0.22* 0,219 0,209 0,199 0.189 0.173 0.177 0.160 O.I38 0.420 0.403 0.370 0.332 0.315 0.310 0.287 0.278 0.26* 0.2*2 0.2*0 0,236 0,227 0.216 0.213 0,195 0,180 0,180 0,165 0,1*1 0.469 0.446 0,*05 0,358 0,339 0.331 0.312 0,298 0,288 0,257 0,257 0.252 0,2*3 0,230 0.226 0.207 0,190 0.190 0.173 0.1*9 0.523 0,490 0.*52 0.392 0.369 0.358 0,339 0,321 0,300 0.273 0;268 0.262 0.255 0.2*3 0.233 0.220 0.196 0.195 0.17B 0.153 0.561 0.530 O.*0O 0,»15 0.391 O.jBl 0.357 0.338 0.319 0.289 0.286 0.275 0,268 0,25* 0.2*7 0,228 0,207 0,205 0,186 0,159 0.593 0.556 0.503 0.**2 0.*13 0.*02 0,379 0,355 0.336 0.308 0.300 0.293 0.280 0.267 0.258 0.2*0 0.217 0.216 O.I95 0.165 0.610 0.575 0.518 0.*59 0.*2* 0.*19 0.395 0.369 0.3*2 0.316 0.311 0.299 0.291 0.279 0.262 0.2*9 0.225 0.219 0,199 0,168 0.606 0.575 0.519 0.*6l 0.*35 0.»22 0.396 0.376 0.355 0.327 0.320 0.310 0.306 0.296 0.275 0,257 0,236 0,231 0.210 0.178 0.598 0.570 0,516 0.*66 0.*38 0.*26 O.*00 0.382 0.361 O.335 O.33I O.3I8 0.315 0.300 0.288 0.266 0.2*7 0.2** 0.223 0.18* 0.5U4 0.561 0.507 0.«66 O.J39 0.;30 0.«03 0.386 0.36* 0.33B 0.335 O.327 O.320 0.306 0.295 0,275 0.253 0.292 0.232 0.192 0.569 0.546 O.S98 0,*66 0,**0 0.«2g 0.*0« 0.388 0.372 0.3*2 0,3*0 0.333 0.328 0.313 0.306 0.285 O.265 0.26* 0.2*5 0.203 0.559 0.540 95 S'i?' 2'?32 "•iil 0.390 0.376 0.350 0.3*9 0.3*0 0.335 0,323 0.317 0.298 0.275 0,279 0,255 0,218 0.552 0.537 -iS" S'hS S'S" S'5120,*30 S'iSI0.«09 0,395 0,38* 0,360 0,358 5*3520,3*7 0.3*5 " 0.335 5'3JI0.330 ?•???0.313 5'?I50.291 S*S?0.291 2'S550.270 S-™0.230 0.546 0.532 0,*89 0.*67 0.*3| 0.532 0.*12 o,*02 0.390 0.372 0.370 0.360 0,357 0,3*9 0,3*0 0,327 0,309 0,308 0,285 0,2*5 0.538 0.527 0.*87 0.J66 0,»33 0,*35 0,*17 o,*08 0,399 0,382 0,381 0,370 0,370 0.360 0,355 0,3*2 0,325 0,321 0.305 0.260 0.519 0.512 0,*80 0.»65 0.»*1 0.*36 0.432 o.*l* 0.*03 0.39* 0.399 0,381 0,383 0,377 0,371 0,360 0,3*0 0,338 0.322 0.275 0.49^ 0.492 0,*73 0.«59 0.**3 0.**3 0.»27 o.*22 0.»18 0.*05 0.»05 0.396 O.397 0.390 0.387 0.378 0.359 0.356 0.3*3 0.292 0.479 0.479 O.I166 0.*57 0.**6 0.**7 0.432 o.*33 0.*30 0.415 0.*1B 0.S09 0.412 0.*07 0.401 0.397 0.380 O.3BO O.363 0.317 0.467 0.471 0.467 0.*57 0.»52 0.*52 0.»4» o.**» 0.*29 0.*35 0.*24 0.429 0.423 0.421 0.415 0.*00 0.*03 0.368 0.336 0.463 0.469 0,*70 0.462 0.*5? 0.*69 0.456 o.*61 0,*65 0,**B 0,**5 0.**7 0,*50 0,*42 0,446 0,440 0,422 0,427 0.413 0,355 0.466 0.476 0.477 0,479 0,474 0.482 0,475 0.477 0,485 0.470 0.473 0.469 0.470 0.467 0.*69 0.465 O.*50 0.*52 0,*37 0,480 0.478 0.485 0,492 0,489 0,489 0,*96 0.490 o.*97 0.505 0.487 0.495 0,438 0,493 0,48? 0,488 0.468' 0.476 0,*79 0.465 0,401 0.4^ 0.494 0.504 0.506 0.497 0.515 0.506 o.513 0.529 0.500 0.519 O.505 0.512 0,508 0.5W 0,510 0,497 0,499 0,490 0,425 0.488 0.503 0.910 0.914 0,917 0,927 0.52* 0,529 0,541 0,520 0,530 0,525 0,929 0,929 0,527 0,530 0,922 0,925 0.510 0.450 0.485 0*501 0,510 0.522 0.525 0.939 0.933 0.540 0.994 0.933 0.9*3 0.93* 0.542 0.539 0.943 0.5*9 0.939 0.9** 0.528 O.*70 0.476 0.490 0.907 0.927 0.930 0.9** 0.941 0,991 0,966 0,9*0 0,990 0,948 O.99O 0.9*7 0.993 0.597 0.990 0.999 0.5*7 0.485 0.467 0.485 0.506 0.931 0.93* 0.990 0,990 0,959 0.980 0.9*8 0.997 0.558 O.559 0.558 0.566 0.570 0,569 0,974 0.526 0.500 0.467 0.486 0.913 0.935 0.943 0.99* 0.557 0.572 0.992 0.597 0.970 0.969 0.572 0.570 0.578 0.580 0.580 0.59* 0.578 0.523 0.4Q0 0.492 0.533 0.549 0.557 0.573 0,573 0.589 0,600 0,572 0,589 0.590 O.59I 0.588 0.600 0.615 0,60* 0,614 0,601 0,549 0.516 0.534 0.973 0.577 0.986 0.604 O.6O3 0,619 0.6*0 0.601 0.619 0.620 0,620 0.617 0.628 O.633 0,631 0.6*1 0.630 0,970 0.595 0.600 0.690 0.628 0.637 0.653 0.655 0,66* 0,686 0.647 0.671 0.662 0.661 0.654 0.665 O.67O 0.667 0.679 0.667 0,60*

I

o Maximum Experimental Error

ui ro

10 II 12 13 14 Ratio of (CNS')/(Ru) x 10-3 Figure 6 - Optical Densities at 590 mu. of Various Solutions with Excess Thlocyanate Present ^u_7 = 5.585 X 10-5 M.; = 0.127 M. Cell Length = 5-00 cm.; - 1.00 Circles = Experimental Points Curve = Calculation on the Basis of Ru(CMS)^ +2 0.9

0.8

0.7

.•t 0.6 (A I 0-5 - 0.4 o 0.3 O 0.2 0.1

300 350 400 450 500 550 600 650 700 750 Wavelength in Milllnnicrons Figure 7 - Absorption Spectra of Ru(CNS) - 0.127 M.; = 1.00 Cell Length = 5-00 cm. _ 54 -

Table 4

'fO The Absorption Spectrum of Ru(CNS)^

Wavelength Optical Density Wavelength Optical Density*

750 0.150 540 0.757 740 0.157 530 0.735 730 0.172 520 0.712 720 0.190 510 0.672 710 0.220 500 0.617 700 0.246 490 0.548 690 0.280 480 0.490 680 0.315 470 0.450 670 0.355 460 0.421 660 0.405 450 0.409 650 0.460 440 0.411 640 0.536 430 0.425 630 0.625 420 0.432 620 0.721 410 0.415 610 0.805 400 0.380

600 0.851 390 0.350 590 0.890 380 0.327 580 0.890 370 0.322 570 0.865 360 0.344 560 0.827 350 0.382 550 0.785

*^u_7 = 5.585 X 10-5 M. = 0.127 M. = 1.0 Cell Length = 5.00 cm. - 55 -

The data in Table 3 were used to calculate the formulae and extinction coefficients of the complexes formed. Using the hypothesis that the simplest explanation is preferable until proven incorrect, it was assumed that only one com­ plex formed. The equation may be written:

Ru"^^ + nCNS' Ru(CNS)^" , (1) and the equilibrium constant iss

^u(0NS)3""_7

^u*3_7^ns-_7"

By use of the method for one complex, given in Section V, the following equation may be derived;

D = do + K/CNS-_7" (d^-D) . (3)

Knov/ing that iron forms a one-to-one complex with thiocyanate,

/ \ +2 Pe(CNS)]^ , it seemed logical to start with the assumption that n equals one, namely, that ruthenium also forms a one-to-one complex with thiocyanate. The experimentally determined optical density D, at

any given wavelength, was plotted against /5'NS"'_7^(d^-D). This gave a straight line, the slope of which was inter­ preted to be K, and the intercept dg. Values of n equal to one-half, two, three, three-halves, and four were tried in the calculations, but none gave as good results as were - 56 - obtained from the choice of n equal to one. The entire system was also analyzed using the assumption that two complexes were formed, but the data could not be fit as well as could be done with the assumption of a single complex. Therefore it may be concluded that ruthenium reacts with thiocyanate to yield only one complex, the mono- thiocyanate complex. If higher complexes are present, they exist with concentrations too small to be detected by this spectrophotometric method, or have an absorption spectra essentially identical to that of the first complex. It is seen from Figure 6 that the curve of optical density asymptotically approaches the optical density d]_ of the complex. Points near d^^ in value were not useful in the calculation since small differences (d^-D) could not be expected to be accurate.

A sample calculation at 590 mu. is given in Table 5. The graph of the data in Table 5, showing the plot of D against given in Figure 8. This figure shows clearly, by the scattering of points as D approaches d]^, the inaccuracy in the calculation caused by small differences of (d^^-D). From the graph it is found that the slope, hence, the equilibrium constant, equals 59.0, while the intercept d^ equals 0.155. - 57 -

Table 5

The Calculation of K at 590 mu.

Z&NS'JT' D (d^-D)* ^NS-_7(d3^-D)

1.396 X 10-1 0.801 0.089 1.24 X 10"^ 1.117 X 10-1 0.786 0.104 1.16 X 10-2 1.005 X 10-1 0.763 0.127 1.28 X 10-2 8.936 X 10-2 0.778 0.112 1.00 X 10-2 8.378 X 10-2 0.767 0.123 1.03 X 10-2 7.819 X 10-2 0.769 0.121 9.46 X 10-3 6.072 X 10-2 0.741 0.149 9.99 X 10-3 5.585 X 10-2 0,695 0.195 1.09 X 10-2 5.026 X 10-2 0.721 0.169 8.49 X 10-3 4.468 X 10-2 0.686 0.204 9.12 X 10-3 3.910 X 10-2 0.669 0.221 8.64 X 10-3 3.351 X 10-2 0.643 0.243 8.14 X 10-3 2.793 X 10-2 0.610 0.280 7.82 X 10-3 2.234 X 10-2 0.575 0.315 7.04 X 10-3 1.676 X 10-2 0.518 0.372 6.23 X 10-3 1.257 X 10-2 0.459 0.431 5.42 X 10-3 1.117 X 10-2 0.424 0.466 5.21 X 10-3 9.774 X 10-3 0.419 0.471 4.60 X 10-3 8.378 X 10-3 0.395 0.495 4.15 X 10-3 6.981 X 10-3 0.369 0.521 3.64 X 10-3 5.585 X 10-3 0.342 0.548 3.06 X 10-3 5.026 X 10-3 0.316 0.574 2.89 X 10-3 4.468 X 10-3 0.311 0.579 2.59 X 10-3 4.189 X 10-3 0.299 0.591 2.48 X 10-3 3.910 X 10-3 0.291 0.599 2.34 X 10-^ 3.351 X 10-3 0.279 0.611 2.05 X 10-3 2.793 X 10-3 0.262 0.628 1.75 X 10-3 2.234 X 10-3 0.249 0.641 1.43 X 10-3 1.676 X 10-3 0.225 0.665 1.11 X 10-3 1.396 X 10-3 0.219 0.671 9.37 X 10-J 1.117 X 10-3 0.199 0.691 7.72 X 10-J 5.585 X 10-^ 0.168 0.722 4.03 X 10"^

*d^, found from Figure 6, equals O.89O. 0.9 0.8 _ G jO^ © O o 0.7 0 Oi lO 0.6 < >t 0.5

'(/> c e> 0.4 <5^ Slope = 59.0 O nw 0.3 o •- Q. 0.2 —J§^ O 0.1

1 1 1 1 1 ! i 1 1 1 1 1 1 1 1 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15

(CNS") (d,-D) xiO^ Figure 8 Graph of Data in Table 5 for Calculation of K at 590 mu. - 59 -

This procedure was carried out at a number of wave­ lengths. The data so obtained are tabulated In Table 6. The equilibrium constants were averaged to give a value of 60 ± 1.

Using this equilibrium constant, the absorption spectrum of the uncomplexed ruthenium was calculated from equation (3). The results are shown graphically in Figure S, and are tabulated in Table 7. This absorption spectrum is similar to, but slightly higher than, that of ruthenium III perchlorate. The difference is real. There are several possible explanations for this difference, the most probable being that the heating altered the hydration state of the ruthenium. This seems plausible in view of both Wehner's (47) and Nledrach's (49) obser­ vations on the complex nature of the ionic species present in solutions of both ruthenium III and ruthenium IV per­ chlorate, and the slow kinetics of the reactions involved.

Using the calculated equilibrium constant and the calculated value of do, together with the experimental value d;^, the optical density curve as a function of the thiocyanate to ruthenium ratio was calculated at 590 mu. This is the curve drawn through the experimental points in Figure 6. As is seen from Figure 6, the calculated curve fits the experimental points very well. - 60 -

Table 6

+2 Average of the Ru(CNS)]l Stability Constant in 0.127 M. HClOij.

Wavelength K d

510 60.0 0.2 0.04 520 61.8 1.6 2.56

530 60.0 0.2 0.04 540 60.9 0.9 0.81

550 60.0 0.2 0.04 560 60.0 0.2 0.04

570 60.0 0.2 0.04 580 58.2 2.0 4.00

590 59.0 1.2 1.44 600 60.0 0.2 0.04

610 59.0 1.2 1.44 620 61.2 1.0 1.00

630 62.7 1.5 2.25 13/782.8 13/13.74 60.2 1.06

1.0 Average: K = 60 ± 1 y 1.06 ® 0.5 f ;

0\ • M I 1I 1

300 350 400 450 500 550 600 650 700 750 Wavelength in Millimicrons Figure 9 - Calculated Absorption Spectra of from Thlocyanate Data ° _7 = 5.585 X 10~5 M.; = 0.127 M. Cell Length = 5.00 cm.; = 1.0 - 62 -

Table 7

The Absorption Spectrum of from Thiocyanate Data

Wavelength Optical Density* Wavelength Optical Density*

750 0.113 740 0.110 540 0.200 730 0.113 530 0.213 720 0.109 520 0.230 710 0.110 510 0.246 700 0.114 500 0.264 690 0.114 490 0.284 680 0.115 480 0.312 670 0.117 470 0.332 660 0.119 460 0.352 650 0.127 450 0.379 640 0.128 440 0.401 630 0.133 430 0.425 620 0.134 420 0.451 610 0.137 410 0.472 600 0.142 400 0.488

590 0.144 390 0.505 580 0.154 380 0.530 570 0.161 370 0.552 560 0.171 360 0.578 550 0.183 350 0.611

= 5.585 X 10~5 M. /"H+J7 = 0.127 M. = 1.0 Cell Length = 5.00 cm. - 63 -

In order to teat the acid dependence of the system, the above procedure was repeated at a perchloric acid con­ centration of 0.254 M. instead of 0.127 M. This work was not done In as great detail as previously employed since the nature of the reaction was now known. The experimental data are given In Table 8. Using a method of calculation Identical with that already described, an equilibrium con­ stant of 67 i 2 was found (Table 9). If sodium thlocyanate In the presence of perchloric acid gave thlocyanlc acid which In turn reacted with ruthenium, the equation would be written:

+ HONS Ru(CNS)3^'^^

The equilibrium constant would be:

(5) /CNS"_7

Substituting the experimental data Into this equation:

K = 60 (0.127)^ = 67 (0.254)^

§0 = (0.254)^ . gq (6) 67 (0.127)^

q log 2 = log 60 - log 67,

and q = - 0.16. (7) - -

Table 8 Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of CNS~/R^j with equal to 0.254 M.

Hatlo of V CNS' ~ . Ru 9000 7000 5000 1000 800 600 1(00 50 . Wavelength^

750 0.165 0.l6g 0.152 0.148 0.148 0.152 0.152 0.155 0.168 0.172 0.180 7'I0 0.170 0.168 0.155 0.148 0.148 0,157 0.160 0.150 0.172 0.175 0.175 730 0.177 0.175 0.170 0.160 0.162 0,167 0,172 0.170 0.180 0.180 0,175 720 0.203 0.197 0.190 0.182 0.180 0.187 0.189 0.185 0.190 0.1B8 0,178 710 0.228 0.225 0.213 0.203 0.198 0.205 0.207 0,204 0,202 0.194 0,182 700 0.252 0.250 0.21(3 0.228 0.225 0.233 0.232 0,226 0,219 0.204 0.188

690 0.283 0.280 0.270 0,253 0.247 0.252 0,255 0,243 0,230 0.213 0,190 680 0.320 0.318 0.305 0,282 0.275 0.280 0,278 0.265 0,245 0.223 0.195 670 0.355 0.352 0.31(2 0.317 0.309 0.314 0.312 0,292 0,265 0,235 0.203 660 0,1(05 0.1(00 0.385 0.354 0.342 0.350 0.345 0,323 0,237 0,248 0,215 650 0.1(52 0.1(50 0.1(30 0,406 0.380 0.388 0.378 0,350 0,305 0,258 0,218

6'I0 0.52'( 0.522 0.502 0.1(62 0.440 0.442 0.428 0.397 0.332 0,275 0.232 630 0.615 0.610 0.587 0.538 0.500 0,500 0.483 0.442 0.362 0,295 0.240 620 0.718 0.715 0.682 0.625 0.582 0,578 0.552 0.500 0.404 0.323 0.263 610 0.800 0.797 0.763 0.700 0.645 0.642 0.608 0.550 0.430 0.340 0.272 600 0.862 0.861 0.820 0.750 0,695 0.688 0.648 0,582 0.455 0.355 0.282

590 0.902 0.900 0.855 0.785 0,727 0,715 0.673 0,607 0.475 0.370 0.285 580 0.902 0.900 0.858 0.787 0,728 0,719 0.676 0,609 0.479 0.373 0.298 570 0.888 0.885 0,850 0.782 0,722 0,718 0.674 0,607 0.479 0.375 0.300 560 0.853 0.851 0.819 0.760 0.705 0,700 0.658 0.598 0.479 0.378 0.310 550 0.810 0.808 0,780 0.738 0.678 0.672 0.639 0,578 0.478 0.382 0,315 SltO 0.775 0.772 0,752 0.702 0.658 0.653 0.622 O.56B 0.478 0.385 0.325 530 0.755 0.750 0,733 0.688 0.645 0.645 0.613 0.562 0.475 0.398 0.339 520 0.730 0.725 0,718 0.672 0.633 0.635 0.608 0.558 0.475 0.405 0.352 510 0.693 0.692 0.688 0.647 0.610 0.618 0.593 0.550 0,475 0.412 0,368 500 0.638 0.635 0.620 0.602 0.572 0.583 0.562 0.522 0,475 0.422 0,385

tgo 0.563 0.562 0,561 0.548 0.528 0.542 0,530 0.500 0,470 0.428 0,403 M80 0.502 0.500 0,500 0.490 0.485 0.500 0.492 0.478 0,468 0.442 0.420 '170 0.1(55 0.1(53 0,460 0.450 0.450 0.462 0.470 0.460 0,463 0.452 0.443 '(60 0.1(28 0.1(25 0,1(35 0.428 0.430 0.458 0.458 0.451 0,463 0.472 0.474 150 0.1(15 0.1(13 0.1(25 0.415 0,420 0.448 0.450 0.449 0,463 0.483 0.485

4110 O.I(ll( 0.1(12 0.422 0.412 0.418 0.445 0.450 0.450 0,475 0.498 0.503 1(30 0.1(17 0.1(15 0.422 0.412 0.418 0.445 0,450 0,452 0.487 0.512 0.525 1(20 0.t22 0.1(20 0.423 0.412 0.418 0.448 0.450 0,460 0.495 0.530 0.548 >(10 0.'t20 0.1(18 0.420 0.408 0.415 0.445 0.450 0,460 0.500 0,546 0.565 1(00 O.ltOO 0.1(00 0.400 0.395 0,395 0.425- 0.440 0.458 0.500 0,555 0.579 390 0.387 0.385 0.380 0.362 0.378 0.410 0.425 0.448 0.500 0.560 0.600 380 0.385 0.382 0.370 0.355 0,362 0.398 0.419 0.44? 0.502 0.572 0.615 370 0.1(53 0.1(50 0.400 0.355 0.360 0.395 0.418 0.442 0.519 0.594 0.640 360 0.618 0.615 0.503 0.420 0.387 0.420 0.442 0.472 0.550 0,625 0 .669 350 0.685 0.682 0,670 0.525 0.453 0.490 0.505 0.529 0.605 0,670 0.713

• [RU(C10^)J 5.585 X 10"5 M. [HCIOJ 0.254 M. 1.0 Cell Length 5.00 cm. - 65 -

Table 9

Average of the Ru(CNS)^Stability Constant In 0.25^ M. HClOij.

Wavelength K d d2

550 65.5 1.3 1.69 560 68.9 2.1 4.41

570 69.8 3.0 9.00 580 65.5 1.3 1.69 590 6i^.5 2.3 5.29 600 67.1 0.3 0.09 610 66.3 0.5 0.25 7A67.6 7/22.42 66.8 3.20

1.8 Average: K = 6? i 2 \/^ - 66 -

Thus, It Is found that the hydrogen Ion dependence is 0.16 in the direction opposite to that anticipated. This is essentially zero, and so it may be said that the ruthenium thiocyanate system is independent of the acid concentra­ tion present. The conclusion was anticipated on the basis of the fact that thiocyanic acid is a strong acid. Since ruthenium III perchlorate is not stable at room temperature no extensive work was carried out using it as a starting material. However, ruthenium III per­ chlorate in the presence of sufficient excess of thiocyanate to put all of the ruthenium in the form of the complex gave an absorption spectrum identical with that obtained when ruthenium IV perchlorate was the starting material. In summary it may be said that ruthenium III and ruthenium IV perchlorate react with thiocyanate to give +2 a deep-blue complex, with a formula Ru(CNS)q^ . The com­ plex, essentially independent of the acid concentration present, has a stability constant of 60 i 1. No evidence was found for higher complexes; if such are present they exist at concentrations too small to be detected by this

spectrophotometric method.

B. Ruthenium-Thiourea System

Much of the preliminary investigation on the behavior of thiourea with ruthenium IV had been done by Deford (1), - 67 - and by Ayres and Young (42). It was found In this investi­ gation, as known previously, that heating was necessary to attain equilibrium within a reasonable length of time. The length of heating and the temperature used in this investi­ gation were those selected by Deford, namely five minutes in a boiling water bath. Immediately after preparation, all solutions were placed in a boiling water bath for the required length of time, then plunged into an ice bath until the temperature of the solution reached 25 - 1°C.

Solutions so prepared were found to be spectrophotometrlcally stable for only about twenty minutes. The optical density would remain constant, and then, would suddenly start in­ creasing as a turbidity appeared in solution. This tur­ bidity was most probably due to decomposition products from the reduction of the thiourea. No way was found to avoid the turbidity, so all spectrophotometric measurements were taken within ten minutes after preparation of the solutions. Furthermore, all spectrophotometric measurements were repeated a minimum of two times to check the precision of these data. An ion migration experiment was performed to determine the charge on the complex or complexes. A solution con­ taining a ratio of thiourea to ruthenium of 2000, with the ruthenium concentration equal to 3.351 x 10"^ M., was placed in the center of a U tube. When LiClO]!^ was - 68 - layered into the arms, and a current of 5 ma. applied, in twenty-four hours a slight migration toward the cathode was noted. When the LiClOi^ solution was replaced by LiCl, the migration was suppressed completely, so that in five days no migration was observed. Apparently the blue colored ruthenium-thiourea product is either a cation, or a neutral molecule which dissociates readily into a cation. In all the spectrophotometric measurements the ionic strength was constant at 3«0* and the perchloric acid con­ centration was 0.25^ M., unless otherwise stated. To determine the absorption spectrum of the last complex, ruthenium IV perchlorate was maintained constant at -h. 1.117 X 10 M. With a thiourea-to-ruthenium ratio from 9000 down to 2000, in the visible region, the optical density remained constant regardless of the concentration of the colorless thiourea. These data are not tabulated here for they are not necessary in the subsequent calcula­ tions. In the remainder of the investigation ruthenium rv perchlorate was constant at 3.351 x 10"^ M. Solutions were prepared by mixing the necessary quantities of a stock solution of ruthenium IV perchlorate and a freshly prepared solution of thiourea to give the desired final concentra­ tion. The prepared solution was placed into a boiling water bath for exactly 5.0 minutes and then plunged into an ice bath until the temperature of the solution reached - 69 -

25 1 1°C. Finally the solution was scanned as quickly as possible on the Gary recording spectrophotometer. Solu­ tions which contained ratios of thiourea to ruthenium from 2333 down to 3-33 were so prepared and scanned. These data are given in Table 10. Three curves. Figures, 10, 11, and 12, obtained by plotting at constant wavelength the optical density as a function of the thiourea to ruthenium ratio, show the behavior of the system. The optical densities of the solutions do not change for ratios of thiourea to ruthenium greater than 2000, as is seen from the lines labeled d^. Thus, the absorption spectrum of the last complex has been determined experimentally (Figure 13, and Table 11). Solutions were prepared containing 7.819 x 10"^ M. thiourea, 0.254 M. HClOij., with an ionic strength of 3.00. By varying the ruthenium concentration of these solutions, it was determined that the last complex obeyed Beer's law, as may be seen from Figure 13. Prom Figures 10, 11, and 12, it is noted that the optical density versus ratio curve goes through a maximum. Therefore, it is apparent that there must be at least two

complexes present, the last complex, and another with a higher extinction coefficient. If only one complex were present, the curve would rise smoothly and asymptotically approach the optical density of the last complex, as v;as Table 10 Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of Thlourea/Ru, with equal to 0.254 M.

Ratio of \ Thiourea

2333 1667 1000 66T 333 233 167 66.67 33.33 23.33 16.67 3-33 \ Wavelengtrt^

0.437 0.453 0.485 0.500 0.483 0.505 0.503 0.505 0.450 0.362 0.213 0.188 0.178 0.135 0.095 0.451 0.483 C.496 0.431 0.506 0.503 0.503 0.450 0.365 0.213 0.188 0.178 0.133 0.098 0.44if 0.452 0.484 0.500 0.485 0.510 0.507 0.507 0.454 0.366 0.214 O.I89 0.179 0.139 0.096 0.453 0.458 0.490 0.507 0.495 0.515 0.515 0.510 0.459 0.371 0.218 0.191 0.161 0.141 0.098 0.463 0.466 0.506 0.518 O.5O8 0.528 0.523 0.516 0.465 0.375 0.228 0.200 0.165 0.145 0.09a 0.483 0.483 0.518 0.533 0.525 0.542 0.538 0.513 0.476 0.387 0.241 0.217 0.180 0.157 0.103 0.517 0.516 0.548 0.564 0.550 0.570 0.566 0.538 0.491 0.403 0.266 0.232 0.190 0.165 0.107 0.548 0.535 0.578 0.590 0.582 0.595 0.590 0.562 0.513 0.429 0.285 0.250 0.215 0.185 0.112 0.570 0.580 0.610 0.622 0.610 0.620 0.608 0,575 0.540 0.453 0.308 0.278 0.238 0.218 0.115 0.617 0.614 0.639 0.644 0.637 0.644 0.624 0.599 0.562 0.469 0.329 0.302 0.249 0.217 0.116 0.639 0.639 0.667 0.669 0.651 0.664 0.647 0.621 0.578 0.485 0.354 0.322 0.272 0.236 0.119 0.649 0.648 0.670 0.678 0.667 0.673 0.653 0.643 0.591 0.490 0.370 0.333 0.282 0.240 0.128 0.653 0.653 0.676 0.681 0.666 0.676 0.656 0.651 0,599 0.492 0.381 0.348 0.300 0.248 0.135 0.653 0.649 0.664 0.679 0.655 0.672 0.656 0.654 0.602 0.495 0.392 0.358 0.305 0.253 0.140 0.639 0.639 0.63k 0.659 0.649 0.659 0.65k 0.654 0.605 0.500 0.402 0.365 0.322 0.268 0.148 0.627 0.625 0.640 0.650 0.630 0.652 0,650 0.650 0.606 0.502 0.405 0.375 0.323 0.273 0.160 0.620 0.622 0.628 0.635 0.625 0.650 0.650 0.650 0.609 0.498 0.410 0.381 0.332 0.280 0.168 0.603 0.603 0.610 0.628 0.608 0,643 0.643 0.653 0.610 0.492 0.418 0.382 0.335 0.285 0.172 0.577 0.575 0.585 0.600 0.588 0.625 0.630 0.645 0.607 0.496 0.415 0.385 0.351 0.300 0.192 0.556 0.559 0.569 0.579 0.571 0.623 0.624 0.644 0.608 0.492 0.427 0.388 0.355 0.305 0.205 0.550 0.544 0.561 0.574 0.567 0.623 0.634 0.647 0.615 0.510 0.432 0.395 0.360 0.310 0.218 0.540 0.540 0.547 0.512 0.560 0.618 0.640 0.660 0.638 0.520 0.450 0.409 0.385 0.329 0.240 0.519 0.520 0.532 0.554 0.544 O.6I5 0.640 0.662 0,640 0.520 0.460 0.415 0.395 0.340 0.250 0.473 0.476 0.499 0.525 0.516 0.599 0.629 0,656 0.639 0.518 0.462 0.415 0.405 0.353 0.272 0.444 0.442 0.464 0.494 0.485 0.592 0.624 0.654 0.638 0.518 0.464 0.422 0.410 0.360 0.295 0.414 0.414 0.440 0.467 0.465 0.577 0.625 0.654 0.650 0.522 0.474 0.435 0.432 0.382 0.315 0.391 0.386 0.416 0.450 0.454 0.581 0.641 0.674 0.672 0.540 0.491 0.455 0.458 0,408 0.338 0.370 0.368 0.390 0.440 0.442 0.588 0.650 0.692 0.692 0.551 0.515 0.464 0.484 0.436 0.364 0.361 0.360 0.380 0.435 0.452 0.600 0.665 0.720 0.720 0.584 0.530 0.497 0.514 0.469 0.399 0.361 0.361 0.389 0.441 0.464 0.627 0.704 0,755 0.755 O.6I9 0.574 0.537 0.554 0.514 0.431 0.361 0.361 0.388 0.443 0.471 0.653 0.738 0,785 0.795 0.650 0.618 0.571 0.599 0.554 0.461 0.357 0.357 0.384 0.442 0.482 0.679 0,764 0.820 0.836 0.694 0.671 0.621 0.651 0.605 0.499 0.35^^ 0.353 0.382 0.444 0.491 0.704 0.805 0.852 0.878 0.731 0.722 0.674 0.704 0.659 0.539 0.355 0.355 0.382 0.455 0.502 0.729 0.832 0.888 0.915 0.779 0.760 0.727 0,757 0.709 0.584 0.362 0.360 0.392 0.470 0.519 0.758 0.865 0.922 0.957 0.822 0.815 0.779 0.819 0.774 0.624 0.390 0.392 0.434 0,517 0.562 0.810 0.920 0.982 1.025 0.881 0.882 0.837 0.864 0.829 0.678 0.441 0.441 0.486 0.571 0.619 0.866 0.986 1.051 1.151 0.940 0.931 0.886 0.931 0.833 0.727 0.515 0.519 0.572 0.660 0.690 0.945 1.070 1.123 1.181 1.020 0.992 0.941 0.993 0.933 0.730 0.600 0.600 0.652 0,760 0.775 1.040 1.155 1.220 1.271 1.098 1.055 1.010 1.053 0,993 0.850 0,677 0.680 Q.735 0.841 0.858 1.125 1.238 1.298 1.365 I.I87 1.136 1.074 1.127 1.052 0.912 0.758 0.758 0.813 0.919 0.917 1.187 1.320 1.393 1,458 1.286 1.286 1.154 1.216 1.127 0.991 0.838 0.836 0.878 0.990 0.983 1.266 1.393 1.463 1.555 1.388 1.338 1.261 1,326 1.231 1.071 0.991 0.919 0.993 1.048 1.027 1.3'»0 1.468 1.533 1.654 1.492 1.530 1.392 1,467 1.357 1.173 1.148 1.070 1.053 1.148 1.123 1.453 1.578 1.633 1,760 1.615 1.700 1.574 1.650 1.525 1.285 1.450 1.350 1.330 1.360 1.375 1.900 1.800 1.850 i.o'iO 1.840 1.850 1.800 1.900 1.745 1.405 1.900 1.800 1.BlO 1.770 1.800 2.100 2.200 2.180 2.225 2.195 2.300 2.100 2.200 2.030 1.550 3.351 X 10" [hcioJ 0.254 K. 3.0 Cell Length 2.00 cm. o Maximum Experimental 0.9 Error

0.7 M

Si 0.5 ^ 0.4

2000 3000 4000 Ratio (Hth)/(Ru) Figure 10 - Optical Densities at 450 mu. of Various Solutions with Excess Thiourea Present /Ru_7 = 3.351 X 10"^ M.; C^'^J - 0-254 M. Cell Length = 2.00 cm.; ^ » 3.0 Circles: Experimental Points Curve: Calculated on Basis of Ru(th)3 and Ru(th)i-'2 ^ 0.8 o Maximum Experimental Error ID 0.7

•r 0.5

Q 0.41 -d ro S 0.3

1000 2000 3000 Ratio (Hth)/(Ru) Figure 11 - Optical Densities at 550 mu. of Various Solutions with Excess Thiourea Present - 3.351 X 10"^ M.; J = 0.254 M. Cell Length = 2.00 cm.; = 3.0 Circles: Experimental Points Curve: Calculated on Basis of RuCth)^ and Ru(th)^"^ 0.9 E 0.8 O S 0.7 0 0.6h- 7 r 0.5 1 a4- OS Maximum Expsrimantai Errof _ 03 e H 02 O 0.1 — i i i 1 i i 1 0 1000 2000 3000 Ratio [HTh] /[Ru] Figure 12 - Optical Densities at 650 rau. of Various Solutions with Excess Thiourea Present , ^uJ7 = 3.351 X 10"^ M.; ^•'_7 = 0.25^ M. Cell Length = 2.00 cm.; ^ =3.0 Circles; Experimental Points Curve: Calculated on Basis of Ru(th)2 and Ru(th)^ +2 0.9

0.7

0J6 « 9 0.5

0.3 0.2

0.1

350 400 450 500 550 600 650 700 750 800 Wavelength in Millimicrons Figure 13 - Absorption Spectra of Ru(th)2 ^+_7"= 0.254 M.; =3.0 Cell Length = 2.00 cm.

A. ~ 3.354 X 10"^ M. B. /RU__7 = 2.234 X 10"^ M. C. ^u_7 = 1.117 X 10"'^ M. - 75 -

Table 11

The Absorption Spectrum of Ru(th)2

Wavelength Optical Density* Wavelength Optical Density*

800 0.445 550 0.414 790 0.446 540 0.388 780 0.448 530 0.369 770 0.456 520 0.360 760 0.465 510 0.361 750 0.483 500 0.361

7^0 0.516 490 0.357 730 0.541 480 0.353 720 0.575 470 0.355 710 0.610 460 0.361 700 0.639 450 0.391 690 0.648 440 0.441 680 0.653 430 0.517 670 0.650 420 0.600 660 0.639 410 0.678 650 0.626 400 0.758

640 0.621 390 0.837 630 0.603 380 0.956 620 0.576 370 1.110 610 0.558 360 1.400 600 0.547 350 1.850 590 0.540 580 0.519 570 0.485 560 0.443

- 3.351 X 10"^ M.

- 0.25^ M. =3.0 Cell Length = 2.00 cm. - 76 - found in the ruthenium-thiocyanate system (Figure 6). The simplest possible assumption consistent with facts was made, namely, that only two complexes were present.

By making these assumptions the following equations may be written:

Ru"'"3 + n Hth pi Ru(th)^"'^ + nH'^> (1) n

Ru(th)„ + q Hth ^ Ru(th)^ ^ + q H"*. n+q

The equilibrium constants are;

(2)

Kn+q " n+q ^ Z^u(th)3-"j7

Using the method for two complexes given in Section V, the following equation may be derived:

, a , d3

P ^ Kn r»*J^ (3)

••q + i + 2. Kn Z"H - 77 -

As has been shown. If sufficient excess of thiourea is present, the optical density of the last complex, d^, may be determined experimentally.

When virtually all of the ruthenium is in the form of Ru(th)^_j^^ that is, in the region beyond the maximum in Figures 10, 11, and 12, the contribution of the uncomplexed ruthenium to the total optical density will be small, and as a first approximation may be neglected. In that case equation (3) may be reduced toi

D = di' Kn^q (^3-0) ^

By correct choice of q, a straight line of slope K^+q and intercept d]^ will be obtained by plotting D against

^th_7^ (d^-D) The behavior of the last complex in the ion migration experiments suggested the possibility that it was neutral. Thus Ru(th)^ could be Rufth),. n+q J If this were so, then the most probable values of q would be either one or two. Assuming q equals one, that is, two complexes Ru(th)2 and Ru(th)2''"i gave very Inconsistent results. Frequently the equilibrium constant obtained was negative, which is a thermodynamic impossibility. The positive values of K varied several hundred per cent. There fore q equals one could not be the correct choice. In addi­ tion to q equals one, less probable values of q equal to one - 78 - half, three-halves and three were tried. None of these were satisfactory. When q equal to two was used, that is, two complexes +2 Ru(th)2 and Ru(th)]^ , the data became Interpretable. Values of the equilibrium constant were calculated at 10 mu. intervals over the spectrum from 400 to 550 mu. These were averaged to give the first approximation to equal to 4.6 - 0.3. The value d]_ was obtained both graphically from the intercept, and by calculation from equation (4), after Kg was known. This gave the first approximation to +2 the absorption spectrum of the first complex Ru(th)2^ To illustrate this approximation, the calculation of and dQ_ at 460 mu. was chosen. Table 12 gives the data and calculations for this first approximation, using equa­ tion (4). This is graphed in Figure 14, from which it is found that the equilibrium constant equals 4.6 and the intercept d^ equals 1.095. The inaccuracy in the approxima­ tion, that the effect of the uncomplexed ruthenium may be neglected, is readily seen from the fact that the points

near the maximum are low. Similarly, in the region of the curve before the maximum in Figures 10, 11, and 12, the contribution of the

last complex, Ru(th)2i to the total optical density will be small, and as a first approximation may be neglected. In that case equation (3) may be reduced to: - 79 -

Table 12

The First Approximation In the Calculation of Ko at 460 mu. 3

^th_7 D (d2-D)^thJ72^Hj|7'

5.585 X 10"^ 0.392 -0.031 -1.52 X 10"! 3.351 X 10"^ 0.470 -0.109 -1.89 X 10"^ 2.234 X 10"^ 0.519 -0.158 -1.22 X 10"^

1.117 X 10~^ 0.758 -0.397 -7.68 X 10-2 7.818 X 10~2 0.865 -0.504 -4.78 X 10"^ 5.585 X 10-2 0.922 -0.561 -2.71 X 10-2

3.351 X 10-2 0.957 -0.596 -1.04 X 10-2 2.234 X 10"^ 0.822 -0.461 -3.57 X 10-3

*d3 = 0.361 ** = 0-25^ M. - 80 -

I.I -—

1.0 o E ON. 0.9 O (D o 0.8 t O 0.7 — >»

(/) 0.6 — c a> 0.5 O o Slope = 4.6 o 04 — u Q, 0.3 — O 0.2

0.1

1 1 1 1 1 1 1 1 1 2 4 6 8 10 12 14 16 18 20

Figure - Graph of Data In Table 12 for the Calcu­ lation of the First Approximation to Ko at 460 mu. - 81 -

D = do . Kn ZHthJ7"(di-D) ^

Z-hV"

Then using the previously calculated value of d]_, with a correct choice of n, by plotting D vs. ^^^-7 (^1 ,

Z"h-^_7" the equilibrium constant will be obtained as the slope of a straight line, and dQ as the intercept. To be con­ sistent with the hypothesis that the complexes present 4.2 are RuCth)^ and Ru(th)^ , n must be equal to one. Values of n equal to one-half, two, three, and three-halves were tried and found unsatisfactory. Using n equal to one, the equilibrium constant was calculated over the spectrum from 500 to 7OO mu. It was averaged to give the first approximation to K]_ equal to 18 i 2. The value of d^ was obtained both graphically as an intercept, and by calculation from equation (5) after was known. This gave the first approximation to the absorption spectrum of the uncomplexed ruthenium.

The method Just used gave the first approximation to d^ and dQ. To obtain K3 and d^ more accurately equation (3) was rearranged as follows:

p, (D-dp) Z-H-y ^ , (dg-D) K3 . Ki ^th_7i

Substituting the first approximations to do and K]_ and plotting the left hand side of equation (5) against - 82 -

(dg-D) save the second approximation to and d^^ from the slope and Intercept respectively. Prom these calculations, was found to be 5.2 - 0.2. The absorption spectrum of the first complex, d^^, was calculated at all wavelengths. Then, to obtain the second approximation to and d^ equation (3) was rearranged again:

(D-di) ^th_7 (D-d,) ] D =

ruthenium was calculated at all wavelengths. The technique used In the second approximation was repeated in the third approximation. The final results of these calculations are found in Tables I3 and l4. The

final value found for was 5.30 - 0.1, and that for K]_ was 16.3 - 0.5. Since, in going from the second to the third approximation no change in had occurred, there was no advantage in carrying out a fourth approximation. To illustrate the second and third approximations the calculation of K3 and d^^ at 460 mu. is continued from - 83 -

Table 13 , . 42 Average of the RuCth)]^ Stability Constant in 0.25^ M. HClOij.

Wavelength d

460 16.76 0.46 0.2116

480 16.26 0.04 0.0016

500 17.27 0.97 0.9409

520 16.10 0.20 0.0400

540 16.76 0.46 0.2116

560 15.85 0.45 0.2025

580 15.75 0.55 0.3025

600 16.76 0.46 0.2116 620 16.36 0.06 0.0036

640 16.15 0.15 0.0225 660 16.61 0.31 0.0961

680 16.76 0.46 0.2116

700 16.26 0.04 0.0016

720 15.24 1.06 1.1236

740 15.60 0.70 0.4900

15/244.49 15/4.0713

16.30 0.2714

0.52 Average: = 16.3 - 0.5 >y^0.2714 - 8IV -

Table 14

Average of the Ru(th).3 Stability Constant K3 in 0.254 M. HClOi^

Wavelength d d2 ^3

400 5.32 0.02 0.0004

410 5.30 0.00 0.0000

420 5.42 0.12 0.0121

430 5.29 0.01 0.0001

440 5.19 0.11 0.0121

450 5.16 0.14 0.0196

460 5.10 0.20 0.4000

470 5.16 0.14 0.0196

480 5.36 0.06 0.0036

490 5.19 0.11 0.0121

500 5.39 0.09 0.0810

510 5.35 0.05 0.0025

520 5.43 0.13 0.0169

530 5.39 0.09 0.0810

540 5.23 0.07 0.0049

550 5.51 0.21 0.0441

16/84.79 16/0.2042

5.30 0.0128 0.11 Average; = 5.30 ± 0.11 V0.012B - 85 - page 78. Table 15 gives the data and calculations for the second approximation. This is graphed in Figure 15, from vjhich it is found that the equilibrium constant equals 4.9, and the Intercept d^^ equals 1,132. Table 16 gives the data and calculations for the third approximation. This is graphed in Figure I6 from which it is found that the equilibrium constant equals 5.1 and the intercept d^^ equal I.I50. Figure 15 and I6 shovj clearly how the inclusion of and d^ in the calculations raise the low points near the maximum so they lie on the slope line. Using the final values found for the equilibrium con­ stants, and K-^, the absorption spectrum of the first com­ plex and that of the uncomplexed ruthenium were calculated. These data are found in Figures 17 and I8, and in Tables 17 and 18. The absorption spectrum of the uncomplexed ruthenium is slightly higher than the published absorption spectrum of ruthenium III perchlorate. It is felt that the difference is real and can be accounted for by the heating necessary to produce the complexes. As in the case of the ruthenlum-thiocyanate system, the heating very probably alters the hydration state of the ruthenium. Using the calculated equilibrium constants and the absorption spectra of all three species, the optical density curves as a function of the thiourea to ruthenium ratio Table 15

The Second Approximation in the Calculation of at 460 niu.

(d3-D)^th_72* ^ ** ZHth_7 D (D-d^) (D-do)zrHy , K]^th_7' K^thJ

5.585 X 10"^ -1.52 X 10"^ 0.392 -0.303 -8.47 X io"3 0.384 3.351 X 10"^ -I.89 X 10"^ 0.470 -0.225 -1.05 X 10"^ 0.460 2.234 X 10"^ -1.22 X 10-1 0.519 -0.176 -1.27 X 10-2 0.506 1.117 X 10"^ -7.68 X 10-2 0.758 +0.063 +8.36 X 10-3 0.766

7.818 X 10-2 -4.78 X 10-2 0.865 +0.170 •^3.23 X 10-2 0.897 5.585 X 10"^ -2.71 X 10-2 0.922 +0.227 +6.05 X 10-2 0.982

3.351 X 10-2 -1.04 X 10-2 0.957 +0.262 +1.16 X 10-1 1.073 2.234 X 10"^ -3.57 X 10-3 0.822 +0.127 +8.32 X 10~2 0.905

From Table 12

y y * do = 0.695 =16.3 - 87 -

09 E 0.6

^ 0.7 0.6

Slope = 4.9 04 03

2 4 6 8 10 14 16 18 20 , . « in2

Figure 15 - Graph of Data in Table 15 for the Calcu­ lation of the Second Approximation to at ^60 mu. Table l6

The Third Approxlination in the Calculation of at 460 mu.

(d3-D)^th_7^ / ^ \ t— -»*** ^th_7 (D-do)^Hj7 (D-do)^Hj7 D (D-cao) D + Ki/-Hth_7 K;i^^th_7

5.585 X 10"-1 -1.52 x 10-1 0.392 -0.298 -8.30 X 10-3 0.384 3.351 X 10"-1 -1.89 X 10-1 0.470 -0.220 -1,02 X 10-2 0.460 2.234 X 10--1 -1.22 X 10-1 0.519 -0.171 -1.19 X 10-2 0.507 1.117 X 10'-1 -7.68 X 10"^ 0.758 +0.068 +9.46 X 10-3 0.767 7.818 X 10"-2 -4.78 X 10-2 0.865 +0.175 +3.49 X 10-2 0.900 -2 5.585 X 10" -2.71 X 10-2 0.922 +0.232 +6.47 X 10-2 0.987

3.351 X 10--2 -1.04 X 10-2 0.957 +0.267 +1.24 X 10-1 1.081 -2 2.234 X 10" -3.57 X 10-3 0.822 +0.132 +9.20 X 10-2 0.914

* From Table 12

** = 0.690 = 16.3 - 89 -

«> 0.8

0.7 to ® 0.5 Slope = 5.1 0.4

CI 0.2

2 4 6 8 10 12 J4 16 18 20 xio^

Figure 16 - Graph of Data In Table l6 for the Calcu­ lation of the Third Approximation to Ko at 46o mu. 1.8

1 .6

1 .4 >» to 1.2 c a> n 1.0

0.8 O 0 u 0.6

a. 0 04 0.2

0.0 350 400 450 500 550 600 650 700 750 800 Wavelength in Millimicrons Figure 17 - Calculated Absorption Spectra of Ru(th)^ +2 Au_7 = 3.351 X 10"^ M.; = 0.25^ M Cell Length = 2.00 cm.; = 3.0 1.4

04

02 OX)

Woveiength in Miiiimicrons Figure l8 - Calculated Absorption Spectra of from Thiourea Data ^u_7 = 3.351 X 10-^ M.; - 0.254 M. Cell Length = 2.00 cm.; - 3.0 - 92 -

Table 17

+2 The Absorption Spectrum of Ru(th)^

Wavelength Optical Density* V/avelength Optical Density*

800 0.632 550 0.785 790 0.633 540 0.815 780 0.640 530 0.843 770 0.642 520 0.876 760 0,661 510 0.927 750 0.671 500 0.988 740 0.697 490 1.032 730 0.723 480 1.072 720 0.736 470 1.106 710 0.754 460 1.133 700 0.765 450 1.221

690 0.775 440 1.314 680 0.775 430 1.398 670 0.768 420 1.512 660 0.748 410 1.609 650 0.746 400 1.649

640 0.745 390 1.723 630 0.748 380 1.742 620 0.733 370 1.804 610 0.746 360 2.455 600 0.757 350 2.376 590 0.752 580 0.764 570 0.773 560 0.790

*^uJ7 = 3.351 X 10"^ M. /"H*_7 = 0.254 M. ^ - 3.0 Cell Length = 2.0 cm. - 93 -

Table l8

The Absorption Spectrum of /Ru'*"3_7o from Thiourea Data

Wavelength Optical Density* Wavelength Optical Density*

800 0.028 550 0.295 790 0.032 540 0.321 780 0.031 530 0.349 770 0.033 520 0.382 760 0.034 510 0.425 750 0.046 500 0.461 740 0.051 490 0.513 730 0.069 480 0.570 720 0.107 470 0.615 710 0.101 460 0.678 700 0.123 450 0.745 690 0.125 440 0.790 680 0.134 430 0.833 670 0.142 420 0.881 660 0.165 410 0.932 650 0.171 400 1.015 640 0.182 390 1.125 630 0.185 380 1.274 620 0.207 370 1.465 610 0.211 360 1.592 600 0.214 350 1.955 590 0.238 580 0.249 570 0.262 560 0.267

*3^J - 3.351 X 10"^ M. - 0.254 M. ^ = 3.0 Cell Length = 2.00 cm. _ 94 - were calculated at 450, 550, and 650 mu. These are the curves drawn through the experimental points in Figures 10, 11, and 12. In order to test the acid dependence of the system, the above procedure was repeated at double the perchloric acid concentration, at 0.508 M, instead of 0.254 M. This work was not done in as great detail since the nature of the reaction was now known. More difficulty in obtaining accurate results was experienced at the higher acidity, since at the higher perchloric acid concentration, the decomposition of the thiourea was more extensive and more rapid. It seemed sufficient to test the acid dependence *2 only over the Ru(th)^ -Ru(th)2 portion of the system. Only the first approximation was carried out in the calcu­ lations. This was compared to the first approximation cal­ culation at the lower acidity. The data taken at 0.508 M. HClOi^ are given in Table 19. In 0.508 M. HCIO]^, the equili­ brium constant in the first approximation was found to be equal to 4.6 - 0.8, which agreed very well with the first approximation to the equilibrium constant in 0.254 M.

HClOij., equal to 4.6 - 0.3. The equilibrium constants in all of the thiourea calculations have been written as a function of the hydrogen ion concentration. Thus, in

/5Ru(th)3J7/-H*_7® ° ^U(th)i*2j7/Sth_72 - 95 - Table 19 Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of Thlourea/Ru, with J equal to 0.508 M.

Ratio or Thlour>a Ru

1667 1500 1333 U67 1000 833 667 SCO 333 VlBvelsngth^

eoo 0.470 0.468 0.468 0.478 0.476 0.475 0.476 0.475 0.450 790 0.472 0.472 0.472 0.4^ 0.478 0.485 0.480 0.475 0.462 780 0.4B0 0.480 0.485 0.492 0.490 0.490 0.491 0.490 0.470 770 0.492 0.491 0.494 0.495 0.497 0.503 0.500 0.495 0.478 760 0.500 0.500 0.505 0.515 0.515 0.508 0.512 0.505 0.468 750 0.525 0.525 0.528 0.530 0.533 0.539 0.534 0.528 0.505 7*0 0.555 0.535 0.550 0.560 0.560 0.566 0.564 0.552 0.532 730 0.600 0.598 0.601 0.602 0.606 0.603 0.603 0.598 0.558 720 0.635 0.630 0.632 0.640 0.640 0.638 0.625 0.595 710 0.672 0.665 0.665 S:lll 0.678 0,673 0.671 0,645 O.6I8 700 0.695 0.688 0.688 0.695 0.700 0.695 0.691 0.670 0.648 690 0.710 0.708 0.705 0.710 0.712 0.712 0.708 0.685 0.650 660 0.722 0.710 0.710 0.718 0.715 0.715 0.713 0.688 0.655 670 0.715 0.705 0.708 0.710 0,713 0.708 0.710 0,685 0.655 660 0.710 0.700 0.702 0.708 0.702 0.703 0.704 0.680 0.652 650 0.680 0.685 0.688 0.700 0.688 0.691 0.688 0.672 0.640 eno 0.695 0.680 0.680 0,685 0,683 0.683 0.683 0.656 0.640 630 0.655 0.652 0.655 0.660 0.660 0,665 0.661 0.640 0.622 620 0.632 0.630 0.632 0.645 0.635 0.642 0.641 0.628 0.610 610 0.595 0.602 0.605 0.622 0.615 0.625 0.622 0.612 0.600 600 0.605 0.595 0.598 0.602 0.608 0.610 0.616 0.595 0.585 590 0.605 0.598 0.610 0.605 0.606 0.606 0.611 0.600 0.585 580 0.565 0.560 0.577 0.577 0.514 0.585 0.586 0.575 0.560 570 0.525 0.520 0-?39 0.540 0.529 0.540 0.548 0.542 0,550 560 0.475 0.470 0.480 0.492 0.490 0.504 0.511 0.515 0,522 550 0.445 0.442 0.455 0.460 0.468 0.475 0.485 0,492 0,505 SW 0.418 0,412 0.418 0.438 0.440 0.465 0.475 0.505 530 0.395 0.390 0.405 0.412 0.420 S:!IS 0.460 0.470 0.505 520 0.375 0.382 0.395 0.407 0.415 0.436 0.462 0.475 0.522 510 0.375 0.378 0.395 0.403 0.418 0.438 0.461 0.465 0.532 500 0.371 0.370 0.395 0.405 0.418 0.445 0,470 0.498 0.555 It 90 0.369 0.365 0,395 0.400 0.418 0,449 0,479 0.512 0.570 480 0.368 0.362 0.395 0.395 0.419 0,454 0.405 0.522 0.585 170 0.360 0.362 0.398 0.398 0.425 0.460 0.496 0.535 0.608 <160 0.385 0.370 0.415 0.412 0.441 0.488 0.526 0.555 0.638 t50 0.415 0.410 0.445 0.445 0.479 0.515 0.556 0.600 0.675 kHO 0.470 0.465 0.495 0.500 0.5't2 0.573 0.610 0.655 0.720 430 0.550 0.545 0,572 0,580 0.626 0.658 0,672 0,730 0,792 420 0.632 0.632 0,650 0,665 0.7)0 0.745 0.736 0.80? 0,852 410 0.715 0.715 0.725 0.750 0.800 0.825 0,832 0,865 0,930 400 0.800 0.790 0.820 0.835 0.883 0.932 0,948 0.960 1.000 390 0.822 0.830 0.875 0.898 0.943 0.961 1,000 1.026 1.060 380 0.920 0.915 0.930 0.935 0,990 1.016 1,098 1.086 1.120 370 1,030 1.010 1,020 1,015 1,075 1,113 1,139 1,170 1.225 360 1.265 1.240 1.240 1.205 1,300 1,320 1.362 1.380 1.440 350 1.645 1.680 1.645 1.565 1.708 1,710 1.775 1.780 1.610 CRU(C10^)J • 3.351 X 10- [HOIOJ I 0.508 «. yM- s 3.0 Call L«ngth : 2.00 cn. - 96 -

contains the hydrogen Ion concentration squared. If any other function of the hydrogen ion concentration Is used Instead of the square, then the equlllbrlutn constant Is not a constant at the two different acidities. The agree­ ment in K3 at the two different acidities proves that the constant, as written, contains the correct function of the hydrogen ion concentration. Therefore, it may be said with certainty that thiourea is behaving as an acid, with each molecule of thiourea releasing one proton.

Since ruthenium III perchlorate is not stable at room temperature, no extensive work was carried out using it as a starting material. However, ruthenium III perchlorate in the presence of sufficient excess of thiourea to complex all of the ruthenium as RuCth)^ gave an absorption spectrum identical with that obtained when ruthenium IV perchlorate was the starting material. It was known that ruthenium dlthiocarbanates of the type Ru(S2CNR2)2j where R is methyl, ethyl, or butyl, are paramagnetic with moments corresponding to one unpaired electron (1), so it seemed Interesting to attempt to determine the magnetic susceptibility of the ruthenlum- thiourea complex, Ru(th)2» The magnetic susceptibility measurements were made by Mr. Roy W. Vander Haar on his Gouy-type balance. Although the susceptibility of solid thiourea was known, Xg = -O.56 x 10""^ cgsu/g at 20°C, - 97 - it was felt that It was necessary to determine the suscepti­ bility of thiourea in aqueous solution. The data are given in Table 20. These data were used in the following equa­ tions to calculate the magnetic susceptibility per gram of thiourea.

^std " ^air _ ^ix ~ '^air (8) ^ ^^std-air ^%ix-air

K = f (9)

X.g + P2^2 * •••• + Pi^i + ••• (10)

K is the volume susceptibility, p is the density, Xg is the gram susceptibility, and A W is the apparent change in weight. Equation (10) is a statement of the law of ad- ditivity for gram susceptibilities, where pj|^ is the weight factor.

Using equation (8), and the constants given in Table

22, the data in Table 20 viere used to calculate " ^air' This was done for each of the seven readings given in Table 20, and then averaged. thiourea equaled -0.7256 cgsu/cm^ at 20°C. Prom equation (9), for thiourea equaled -O.7IO3 cgsu/g at 20°C. Equation (10) was written as: Xn,ix = PRth ^CRth PH2O ^HgO* %th calculated and found to be -0.60 x 10"^ cgsu/g at 20°C. - 98 -

Table 20

Magnetic Susceptibility Data for Thiourea

^mix-air ^^std-alr

- 1.01 + 17.35 - 4.26 + 73.80

- 9.95 +172.60 -13.76 4238.50 -15.92 +276.70 -17.14 +297.80 -18.66 +324.50

* [Thiourea] = 1.117 M. Sp. Gr. (20°C) = 1.0233 - 99 -

Table 21

Magnetic Susceptibility Data for Ru(th)2*

^ ^mix-air ^ ^std-air

- 0.80 + 13.80

- ^.33 + 75.00 -10.02 *115 -13.97 +243.70 -15.98 +278.90 -17.23 +300.55 -18.52 +322.76

[Thioureg^l = 1.117 M. [ru(C10i^)J3 = 1.117 X 10-3 M. [HCIOI].] = 0.254 M. Sp. Or. (20°C) = 1.0378 - 100 -

Table 22 Constants for Magnetic Susceptibility Calculations

%td '"'"'a) 13.128 cgsu/cm^ at 20°C 0.029 cgsu/cra^ at 20°C Kair -0.720 X 10"^ cgsu/g at 20°C

-0.297 X 10"^ cgsu/g at 20°C HCIO),. b -0.322 X 10"^ cgsu/g at 20°C ^0104- density of water 0.99825 g/cm^ at 20°C

^Experimentally determined by Roy W. Vander Haar. ^Selwood, P. W.j "Magnetochemistry", Interscience Publishers Inc., New York, 19^3. °Frivald, 0. E., and Guldberg Olaen, N., Avhandl. Norsk Videnskaps-Akad. Oslo. I. Mat.-Naturv. Klasse. No. 7, 30 (1944)J c. A. 4O,-53T2I~(IWT: - 101 -

The determination of the gram susceptibility of the rutheniura-thiourea complex was beset with difficulty. To put the ruthenium in the form of Ru(th)2 a 2000-fold excess of thiourea was necessary. But thiourea is saturated in water at 1.2 M. Therefore, the ruthenium concentration must of necessity be 10"^ M. or less. So one must endeavor to measure the effect of one gram of paramagnetic material in approximately 1100 grams of diamagnetic material. In order to keep the ruthenium in solution, acid must be present, v/hich means that another diamagnetic material is complicating the measurement. Using equation (8), and the data in Table 21, along with the constants in Table 22,

Kj^ix - Kg^ir was calculated. for the complex was found to equal -0.7235 cgsu/cm^ at 20°C. Prom this x^j^^ was found to equal -0.698^ cgsu/g at 20°C. Equation (lO) was written as:

•n, *mlx " ^complex ^complex * PHgO ^HgO "*• PHCIOj^ ^HCIO^ *

PHth ^th PciOj|- ^ClO^- •

Using the experimentally determined value of Xjj^j^ and con­ stants from Table 22, XQQj^piex calculated and found to be equal to +3.0 ± 1.5 cgsu/g at 20°C. The accuracy was very poor for the reasons already mentioned. However, the paramagnetic character of the complex cannot reasonably be questioned. If one assumes the formula RuCth)^# which has - 102 - a molecular v;elght of approximately 325j this gives a molar susceptibility of approximately 1000 - 500 cgsu/mole. The molar susceptibility with one unpaired electron Is 1300 cgsu/mole. These measurements, within the limit of experimental error, indicate the ruthenium in the complex is present as ruthenium III. In conclusion it may be said that both ruthenium III and ruthenium IV perchlorate react with thiourea to give two blue-green complexes, Ru(th),'''^ and Ru(th) . The com- J- 3 plexing agent behaves as an acid, each molecule of thiourea releasing a proton. The equations and equilibrium con­ stants for the system may be written as follows:

Hu'*^ •> Hth Ru(th),''® H'* J

^ : 16.3 i 0.5 J Zru*3_7 ^th_7

Ru(th)j^''® * 2 Hth RuCth), 2 H* J

K3 = 5.30 i 0.11.

No evidence was found for the existence of a complex Ru(th) Therefore the stability constant of this complex must be sufficiently small so that the amount of ruthenium in this form at any time is negligible. - 103 -

C. Rutheniura-Dlthlooxamlde System

Preliminary Investigations showed that ruthenium IV perchlorate reacted very slowly with dithiooxamlde, § § H2N-C-C-NH2i in acetic acid to give a blue to green colored solution. As known previously (42), it was found that heating was necessary to develop the color within a reasonable length of time. Dithiooxamide is only slightly soluble in water, and consequently all investigations using dithiooxamide were carried out in solutions containing either 50 or 75^ acetic acid. In addition the solutions contained LiClO^j^ and HC10]|. as usual. In the perchloric acid concentration most often used, 0.127 M., the ionization of 50^ acetic acid is slight, and the total hydrogen ion concentration

is 0.128 M. Therefore, the acetic acid contributes very little to the ionic strength and can almost be considered as an inert solvent. In an ion migration experiment, a solution containing a ratio of dithiooxamide to ruthenium of 180, with the ruthe­

nium concentration 2.793 x 10"^ M., was placed in the center of the U tube. When LiClOij. was layered into the arms, and a current of 5 ma. applied, in twenty-four hours the com­ plex migrated about 1 cm. toward the cathode. Apparently the blue-green dithiooxamide complex is either a cation, or

a neutral molecule which dissociates readily Into a cation. - 104 -

A study was made, spectrophotometrlcally, to determine the effect of heating a solution containing 50^ acetic acid, ruthenium IV perchlorate, 2.793 x 10"^ M., with a dlthlo- oxamlde to ruthenium ratio of l80. Stock solutions of ruthenium IV, and of dlthlooxamlde were mixed to give the final solution the desired concentration. The solution so prepared was placed in a boiling water bath for the desired length of time. After the required heating period, the solution was plunged immediately into an Ice bath. As soon as the temperature of the solution reached 25 - 1°C, it was scanned on the recording spectrophotometer. This was done for heating periods from five minutes to two hours. It was found that the color developed for heating periods from five to twenty-five minutes, and remained constant for heating periods from twenty-five minutes to two hours. A heating period of minutes in the boiling water bath, with the usual cooling, was chosen for all subsequent work. The rate of fading of the dlthiooxamide-ruthenlum color was investigated next. A solution containing 50^ acetic acid, 2.793 x 10"^ M. ruthenium and a dithiooxamide to ruthenium ratio of l80 was prepared. The color was developed by heating for 45 minutes in a boiling water

bath and cooling in the usual v/ay. The Gary recording spectrophotometer was set at 65O mu. and the fading of the - 105 - solution was studied as a function of time. In twenty- four hours no fading was detected. In all the remaining spectrophotometrlc measurements the Ionic strength was constant at 1.0, the perchloric acid concentration was 0.127 M., and the solution contained 50^ acetic acid unless otherwise stated. To determine the absorption spectrum of the last complex, ruthenium IV per- chlorate was maintained constant at 2.793 x 10"^ M. Since dlthlooxamlde Is not colorless In the visible region of the spectrum (Figure 5) all optical densities were corrected for the color of the complexlng agent. With a dlthlooxamlde to ruthenium ratio from 3^0 down to l40, the corrected optical density remained constant regardless of the concen­ tration of the dlthlooxamlde. The data for ratios from 3^0 to l60 are not tabulated here since they are not necessary In subsequent calculations. The data for solutions contain­ ing ratios from 150 down to 1 are tabulated In Table 23. A plot at constant wavelength (700 ra;a.) of the optical density as a function of the ratio of dlthlooxamlde to ruthenium shows clearly that the optical density of the solu­ tion does not change for ratios greater than l40. This Is shown by the line labeled d^ In Figure 19. Hence the optical density of the last complex Is known from experi­ mental data. The absorption spectrum of this complex Is

given In Figure 20, and In Table 24. - 106 -

Table 23

Optical Densities at Different Wavelengths of Solutl Dithiooxamide/Ru, with equal to 0.127 M., a

Ratio" of Hdt nu HavelongthX

600 0.433 0.425 0.415 0.413 0.413 0.413 0.405 0.366 0.387 0.378 0.357 O.36O 0.347 0.334 0.326 0.312 0.305 790 0.452 0.438 0.431 0.425 0.424 0.420 0.414 0.401 0.399 0.392 0.357 0.363 0.352 0.334 0.326 0.316 0.308 780 0.479 0.476 0.462 0.459 0,445 0.446 0.445 0.436 0.422 0.422 0.413 0.373 0.374 0.364 0.345 0.336 0.326 0.315 770 0.506 0.504 0.467 0.487 0.471 0.474 0.472 0.466 0.445 0.445 0.438 0.392 0.396 0.371 0.360 0.351 0.336 0.330 760 0.532 0.526 0.513 0.515 0.500 0.502 0.496 0.469 0.469 0.466 0.459 0.403 0.404 0.393 0.374 0.362 0.349 0.335 750 0.572 0.566 0.549 0.542 0.530 0.533 0.527 0.520 0.499 0.496 0.487 0.434 0.433 0.419 0.397 0.364 0.367 0.351 7J»0 0.607 0.603 0.585 0.579 0.570 0.571 0.558 0.548 0.531 0.525 0.517 0.462 0.456 0.445 0.419 0.404 0.360 0.364 730 0.645 0.639 0.620 0.615 0.603 0.601 0.596 0.565 0.559 0.556 0.546 0.485 0.465 0.469 0.445 0.427 0.396 0.386 720 0.661 0.677 0.655 0.650 0.635 0.637 0.630 0.617 0.595 0.590 0.576 0.514 0.515 0.492 0.471 0.449 0.417 0.402 710 0.710 0.703 0.684 0.677 0.663 0.666 0.657 0.645 0.620 0.614 0.603 0.539 0.536 0.516 0.4^8 0.471 0.432 0.417 700 0.732 0.729 0.702 0.700 0.684 0.666 0.670 0.670 0.643 0.639 0.622 0.558 0.553 0.535 0.510 0.486 0.449 0.435 690 0.747 0.747 0.722 0.718 0.701 0.704 0.695 0.686 0.656 0.655 0.637 0.570 0.566 0.547- 0.521 0.501 0.460 0.447 680 0.762 0.756 0.733 0.728 0.712 0.718 0.707 0.697 0.670 0.665 0.650 0.564 0.560 0.558 0.535 0.513 0.474 0.450 670 0.769 0.766 0.738 0.734 0:720 0.721 0.715 0.709 0.677 0.675 0.668 0.594 0.592 0.568 0.540 0.523 0.482 0.467 660 0.771 0.770 0.745 0.737 0.722 0.727 0.720 0.714 0.664 0.682 0.667 0.604 0.601 0.580 0.555 0.536 0.489 0.479 650 0.768 0.767 0.743 0.734 0.720 0.725 0.716 0.713 0.682 0.682 0.666 0.606 0.606 0.567 0.563 0.543 0.501 0.405 6^(0 0.763 0.762 0.736 0.731 0.716 0.725 0.716 0.712 0.664 0.682 0.667 0.611 0.611 0.595 0.571 0.559 0.508 0.493 630 0.755 0.757 0.733 0.726 0.712 0.719 0.712 0.709 0.679 0.676 0.662 0.611 0.612 0.593 0.574 0.553 0.515 0.502 6S0 0.742 0.742 0.721 0.714 0.699 0.708 0.701 0.702 0.672 0.674 0.660 0.609 0.611 0.587 - 0.578 0.559 0.520 0.509 610 0.710 0.714 0.695 0.668 0.676 0.662 0.676 0.677 0.650 0.654 0.641 0.601 0.608 0.592 0.573 0.556 0.519 0.509 600 0.673 0.673 0.654 0.645 0.639 0.644 0.642 0.642 0.618 0.630 0.611 0.586 0.594 0.582 0.560 0.549 0.518 0.509 590 0.623 0.621 0.604 0.601 0.592 0.603 0.597 0.605 0.564 0.591 0.561 0.567 0.578 0.566 0.554 0.543 0.517 0.509 560 0.659 0.561 0.546 0.542 0.551 0.548 0.553 0.537 0.544 0.536 0.533 0.548 0.541 0.530 0.532 0.513 0.499 570 0.503 0.503 0.4Q5 0.491 0.490 0.497 0.50? 0.495 0.504 0.504 0.511 0.529 0.534 0.519 0.519 0.506 0.496 560 0.447 0.450 0.440 0.435 0.437 0.446 0.452 0.454 0.455 0.480 0.469 0.468 0.506 0.504 0.501 0.496 0.400 550 0.392 0.395 0.390 0.368 0.393 0.405 0.413 0.429 0.419 0.431 0.438 0.462 0.464 0.469 0.469 0.492 0.464 510 0.342 0.345 0.347 0.345 0.349 0.365 0.377 0.393 0.388 0.404 0.411 0.440 0.470 0.478 0.481 0.494 0.486 0.462 530 0.307 0.309 0.315 0.313 0.316 0.333 0.345 0.362 0.364 0.381 0.394 0.426 0.457 0.464 0.477 0.493 0.482 0.482 520 0.276 0.277 0.278 0.263 0.293 0.307 0.318 0.339 0.342 0.363 0.381 0.417 0.446 0.459 0.475 0.491 0.491 0.466 510 0.241 0,244 0.250 0.255 0.264 0.292 0.300 0.322 0.322 0.344 0.369 0.420 0.447 0.464 0.495 0.502 0.49a 0.498 500 0.215 0.221 0.232 0.232 0.248 0.267 0.283 0.306 0.316 0.337 0.359 0.411 0.450 0.469 0.495 0.519 0.516 0.522 490 0.196 0.203 0.215 0.219 0.230 0.253 0.272 0.300 0.309 0.337 0.363 0.416 0.456 0.477 0.507 0.533 0.524 0.534 460 0.192 0.195 0.202 0.213 0.225 0.247 0.266 0.296 0.309 0.336 0.370 0.426 0.469 0.490 0.522 0.550 0.539 0.550 *70 0.169 0.190 0.205 0.205 0.230 0.249 0.272 0.300 0.3U 0.342 0.3B1 0.443 0.486 0.506 0.544 0.571 0.568 0.465 0.559 460 0.196 0.200 0.216 0.227 0.235 0.266 0.293 0.314 0.334 0.367 0.405 0.510 0.534 0.568 0.600 0.583 0.593 450 0.223 0.227 0.246 0.256 0.271 0.301 0.320 0.353 0.366 0.407 0.446 0.509 0.552 0.577 0.612 0.642 0.619 0.633 4*J0 0.264 0.265 0.308 0.31? 0.344 0.361 0.396 0.417 0.436 0.474 0.517 0.562 0.612 0.633 0.671 0.696 0.662 0.673 430 0.377 0.380 0.408 0.434 0.450 0.466 0.512 0.521 0.546 0.580 0.630 0.672 0.710 0.729 0.756 0.771 0.714 0.731 420 0.507 0.510 0.537 0.675 0.592 0.620 0.672 0.662 0.700 0.730 0.785 0.604 0.638 0.646 0.674 0.673 0.610 0.807 410 0.625 0.617 0.704 0.746 0.763 0.770 0.857 0.949 0.689 0.893 0.973 0.976 l.OOl 0.997 1.013 0.993 0.896 0.666 400 0.617 0.609 0.680 0.992 0.933 0.955 1.076 1.138 1.109 1.189 1.167 1.117 1.148 1.154 1.135 1.091 O.9BO 0.968

" Cru(C10J,)J ; 2.793 * 10 M. [hcio,3 0.127 H. (HOACJ 50% 1.0 Cell Length 5.00 en.

I

- 106 -

Table 23 it Wavelengths of Solutions Containing Various Ratios of Lth equal to 0.127 M., and v;ith ^0Ac_J7 equal to 50^

0.360 0.3*7 0.334 0.326 0.312 0.305 0.30I 0.296 0.209 0.205 0.27^* 0.266 0.2k7 0.23'» 0.225 0.196 0.178 0.104 O.O36 0.027 2*352 0.334 0.326 0.318 O.3OB 0.303 0.301 0.292 0.205 0.275 0.266 0.2k$ 0.235 0.225 O.I96 0.178 0.104 0.038 0.027 9,'ilc ®'355 0.336 0.326 0.315 0.318 0.307 0.302 0.292 0.205 0.265 O.26I 0.242 0.231 0.201 0.182 O.IO6 0.040 0.040 0*360 0.351 0.336 0.330 0.321 0.315 0.309 0.304 0.206 0.270 0.264 0.251 0.236 0.210 0.108 0.113 0.043 0,041 2 h,; ^*362 0.349 0.335 0.332 0.325 0.324 0.319 0.304 O.20O 0.273 0.254 0.245 0.215 0.194 0.119 0.04b 0.044 0.«»33 0.419 0.397 0.304 0.367 0.351 0.346 O.339 0.342 0.327 0.317 0.299 0.290 0.262 0.254 0.224 0.201 0.121 0.048 0.046 0.300 0.364 0.359 0.351 0.346 0.342 0.327 0.311 0.299 0.274 0.262 0.?37 0.209 0.126 0.047 0.046 A cVc S bSl 0.390 0.306 0.377 0.372 0.362 0.360 0.343 0.321 0.313 0.207 0.279 0.240 0.2l6 0.127 0.049 0.047 ama « 2?n « iio 2*;^? 0''»17 0.402 0.392 O.3Q7 0.379 0.376 O.361 O.JHO 0.327 O.3OO 0.288 0.2^1 0.225 0.137 0.057 0.048 n rr? Acie 0.417 0.409 0.400 0.388 0.389 0.378 0.352 0.341 0.308 0.300 0.260 0.234 0.143 0.061 0.049 U.5J3 0.535 0.510 0.408 0.449 0.435 0.427 0.419 0.413 0.403 O.389 O.37O 0.352 0.319 0.311 0.275 0.247 0.152 O.O63 0.052 S'iflA n'til 0.460 0.447 0.439 0.432 0.421 0.419 0.403 0.302 0.368 0.335 0.324 0.204 0.254 0.165 0.068 0.054 rt KQ9 n £co O.U74 0.450 0.450 0.446 0.433 0.422 0.416 0.393 0.388 0.352 0.335 0.298 0.264 0.171 O.O7O O.O56 nini rt CPA 0.482 0.467 0.460 0.455 0.441 0.440 0.426 0.403 0.392 0.362 0.345 O.3O7 0.277 0.178 O.O7O 0.053 Afinc S'ISS 2*215 0.489 0.479 0.472 0.464 0.451 0.453 0.430 0.416 0.404 0.375 0,356 O.32O 0.290 O.18O 0.074 O.O56 0.000 0.507 0.503 0.543 0.501 0.405 0.477 0.467 0,462 0.457 0.446 0.421 0.410 0.382 0,364 0.3iJ7 O.296 O.I88 0.070 0.047 A'IAI 2'^IH 0.508 0.493 0.487 0.481 0.468 0.469 O.457 O.436 0.422 0,393 0.373 0.338 0.300 0.193 0.070 0,047 A A A liS 2*''S 0.515 0.502 0.495 0.490 0.479 0.472 0.461 0.440 0.431 0,402 0.379 0.3'»3 0.314 0,209 0.067 0.046 A fiAO A cno 2'IZ? 2*"i 0.520 0.509 0.503 0.500 0.493 0.487 0.475 0.456 0.445 0.420 0.393 O.362 O.33I 0.205 O.O69 0.046 A EOH A 0.519 0.509 0.504 0.501 0.496 0.403 0.475 0,458 0.450 0,425 0.397 O.368 O.338 0.2X1 0.070 0.043 0.502 0.5D0 0.549 0.510 0.509 0.504 0.500 0.496 0.486 0.483 0.460 0.450 0.435 0.403 O.38I 0,352 0,221 O.O7O 0.045 i'tla 0.517 0.509 0.503 0.504 0.503 0.482 0.402 0.464 0.468 0.452 0.415 0.396 0.373 0.234 0.077 0.047 A ESS A*i5h 2*5?2 Z*??5 0.513 0.499 0.497 0.495 0.497 0.472 0.407 0.470 0.470 0.455 0.415 0.400 0,380 0.234 0.070 0.045 A SAC A IA* 2* A? 2*'^^ 0.506 0.496 0.494 0.404 0.496 0.472 0.409 0.475 0.474 0,464 0.424 0,412 0.392 0.244 O.O70 0.045 A Eflk X'Coa ^'io\ 2*?2A 0.496 0.400 0.485 0.409 0,493 0.465 0.490 0.474 0.477 0.473 0.429 O.1123 0.403 0.254 O.O69 0.045 O.HO* 0.409 0.4b9 0.490 0.492 0,404 0.486 O.490 O.495 0.476 0.494 0.483 0.489 0.483 0.430 0.434 0.415 0.260 0.068 0.046 2*512 2*HL? 2*L?I 2*!!®'' 0.486 0,402 0,486 0.490 0,497 O.M 0.503 0,491 0.49S O.48B 0.451 0.443 0.432 0.273 0.068 0.046 A'SKI 2'Sea 2*?n 0.482 0.482 0.482 0.491 0.503 0.487 0.509 0.497 0.510 0.511 0.463 0.464 0.448 0.279 0.060 0.045 A HHS A hi? 2*hAt 2'^^ 0.488 0.49? 0.501 0.514 0.495 0.519 0.509 0.528 0.525 0.481 0.400 0.463 0.291 0.069 0.044 2 hcA 2'?25 2*:SS 0,490 0.498 0.502 0.506 0.526 0.503 0.539 0.529 0.550 0.544 0.499 0.490 0.486 0.306 0.067 0.043 0.H5O 0.409 0.495 0.519 0.516 0.522 0,515 0.530 0.540 0.520 0.557 0.546 0.574 0.565 0.522 0.520 0.496 O.3I6 0.060 0.043 2*515 2*WII 2*521 2*533 0.524 0.534 0.534 o.54q 0.560 0.547 0.577 0.566 0.597 0.583 0.540 0.540 0.527 0.328 0.066 0.042 2*HQC 2*?X2 2*5?r °*550 0.539 0.550 0.551 0.570 0.580 0.571 0.602 0.589 0.617 0.605 0.573 O.566 0.532 0.345 0.067 0.046 2*52H 2*552 2'IP 0.559 0.568 0.572 0.596 0.599 0.594 0.625 0.612 0.642 0.631 0.598 0.588 0.554 0.354 0.068 0.048 2*ic2 2*214 2*I?S 2*lw 0.583 0.593 0.598 0.614 0.622 0.627 0,650 0.638 0.663 0.657 0.624 0.615 0.576 0.365 0.071 0.052 0.552 0.577 0.612 0.642 0.619 O.633 0.633 0.643 0.654 O.651 O.676 O.667 O.697 0,681 0.653 O.631 0.595 0.304 0.073 O.056 2'SJa 2*^53 0.671 0.696 0.662 0.673 0.670 0.607 0.683 0.687 0.711 0.698 0.731 0.702 0.682 0.678 0.610 0.401 0.075 0.057 2*2^0 2*2:1 °*][§L 0.714 0,731 0.733 0.737 0.734 0.741 0.752 0.733 0.766 0.733 0.721 0.692 0.642 0.418 O.O8O 0.066 0.038 0.046 0.074 0.873 0.010 0.607 0.805 0.811 0,796 0.782 0.804 0.784 O.8O9 0.701 0.749 0.718 O.652 0.437 0.004 0.073 1.001 0.997 1.013 0.993 0,898 0.888 O.865 O.869 0.847 O.867 0.845 O.819 0.039 0.790 O.781 0.751 O.678 0.444 0.086 0.085 1.140 1.154 1.135 1.091 0.980 0.968 0.935 0.928 0.905 0.900 0.880 0.840 0.850 0.800 0.792 0.T70 0.691 0.457 0.105 O.O9O

0.9

0.7 0.6

0.5 0.4- o = Maximum Experimental Error 0.3 0.2 Q.

20 40 60 80 100 120 140 Ratio Figure 19 - Optical Densitiee at 700 rau. of Various Solutions v/ith Excess Dithiooxamide Present /RU_7 = 2.793 X 10-5 M.; ^C10i^_7 = 0.127 M.

/EOkc_J = 50^; - 1.0 Cell Length = 5.00 cm.; Circles: Experimental Points Curve; Calculated on the Basis of Ru(dt)and Rufdt)^ o OD

o 0.2

400 500 600 700 800 Wavelength in Millimicrons Figure 20 Absorption Spectra of Ru(dt)2 ^C10i^_7 F 0.127 M.; ^0Ac_7 = 50^ Cell Length = 5.00 cm.; - 1.0 A. /^u_7 = 2.793 X 10-5 jyi. D. ^uJ7 = I.II7 x 10~5 m

B. ^u_7 = 2.234 X 10-5 M. E. ^u_7 = 5.585 X 10"^ M. C. ^u_7 = 1.676 X 10~5 M. - 109 -

Table 24

The Absorption Spectrum of Ru(dt)2

Wavelength Optical Density* Wavelength Optical Density*

800 0.433 790 0.452 590 0.620 780 0.475 580 0.561 770 0.505 570 0.503 760 0.528 560 0.450 750 0.567 550 0.395 740 0.604 540 0.345 730 0.641 530 0.309 720 0.677 520 0,277 710 0.706 510 0.244 700 0.728 500 0.221 690 0.745 490 0.203 680 0.756 480 0.195 670 0.765 470 0.190 660 0.770 460 0.200 650 0.766 450 0.227 640 0.763 440 0.285 630 0.755 430 0.380 620 0.742 420 0.510 610 0.710 410 0.651 600 0.673 400 0.860

*^uJ7 = 2.793 X 10~5 M. /"HClOiiJZ = 0.127 M.

^0AcJ7 = 50^ - 1.0 Cell Length = 5-00 - 110 -

Solutions were prepared containing 50^ acetic acid,

5.026 X 10"3 M. dithlooxamlde, 0.127 M. HC10|j^, with an ionic strength of 1.0. By varying the ruthenium concen­ tration of these solutions it was determined that the last coraplex obeyed Beer's law as may be seen from Figure 20. The data in Table 23 were used to calculate the formulae and extinction coefficients of the complexes formed. Noting the similarity in the plot of optical density against the ratio for the dlthlooxamlde system

(Figure 19) and that of the thiocyanate system (Figure 6), it seemed reasonable to assume that only one complex formed. Hence the reaction was written:

Ru"^3 + n Hdt Ru(dt)^^"" + nH"^ . (1)

The equilibrium constant would be written;

^u(dt)^/-H_7'^ K = . (2) ^dt_7"

As derived in Section V, for the formation of one coraplex

the optical density equation may be written?

D = do • K„ (3)

Values of n equal to one-half, one, two, three, three- halves, and four were tried, in equation (3). For each

value of n, D was plotted against (d^^-D) . - Ill -

In no case could a straight line be obtained, from \vhlch the slope and Intercept could be evaluated. Therefore, the assumption that only one complex Is present appeared to be erroneous.

Assuming that tv;o complexes are present, the follovj- Ing equations may be written:

Ru'^^ + ri Hdt ^ RuCdt)^^"*^ + n ^-n 3-n-q Ru(dt)^ + q Hdt Ru(dt)j^^q + q (^)

The equilibrium constants then become:

K "

(5)

Using the method given for two complexes In Section V, the following equation may be derived:

D = Kn Hdt " . (6)

, 1 , K„q^at_7

As has been shown, the optical density of last complex,

d^* is known experimentally. - 112 -

The method of calculation, using equation (6), and the data in Table 23, was identical in all respects with the thiourea system and only the results are presented. As with the thiourea system, a series of successive approxima­ tions were carried out for the evaluation of and d^.

It was found that the data were fit only if n is taken as one and q as two. Thus equations (^) should be written:

Ru*3 + 1 Hdt Ru(dt)3_-^2 + 1 H"^ ,

Ru(th)i^/ \ +2 + 2 Hdt ^ Ru(dt)2/ \ + 2 H 4 .

As in the case of thiourea, no evidence was found for the two-to-one complex, Ru(dt)2"'^' Pour successive approximations were carried out for the evaluation of and K^. The results of these calcu­ lations are summarized in Table 25. Tables 26 and 27 con­ tain the results of the fourth approximation calculations

of ^3* equilibrium constants are:

K, -_ = r„9.31 „ -4 0.241X„ 10,„2 (8) ^ /R^x:y ^dtj7 ^

Ko = -7; . [8.32 2 0.17] X lo3 , (9)

It should be pointed out, that while the precision of the calculations in the dlthiooxamide system is as good as in - 113 -

Table 25

Summary of Successive Approximations to and

Approximation

First /r.40 i 0.38J7 x 10^ /1.19 ^ 0.0iVj7 x 10^ second ^.91 1 0.93J7 x 10^ /g.si i 0.2.1J x 10^

Third /9.31 - 0.2k_J x 10^ Z^-^O * 0.26_J x 10^

Fourth /9.3I - 0.2k_J X 10^ /E.32 - 0.17_7 ^ - 114 -

Table 26 42 Average of Ru(cit)^ Stability Constant in 0.127 M. HClOj^ and 50jg HOAc

2 V/avelength d d ro

750 9.47 X 0 0.16 X 10^ 0.0256 X 10^

740 9.51 X 10^ 0.20 X 10^ 0.0400 X 10^

730 9.07 X 10^ 0.24 X 10^ 0.0576 X 10^

720 9.07 X 10^ 0.24 X 10^ 0.0576 X 10^

710 9.77 X 10^ 0.46 X 10^ 0.2116 X LO'^

700 9.33 X 10^ 0.02 X 10^ 0.0004 X 10^

690 8.92 X 10^ 0.39 X 10^ 0.1521 X 10^

680 9.14 X 10^ 0.17 X 10^ 0.0289 X 10^

670 9.51 X 10^ 0.20 X 102 0.0400 X 10^

660 9.41 X 10^ 0.10 X 10^ 0.0100 X 10^

650 9.07 X 10^ 0.24 X 10^ 0.0576 X 10^

640 9.41 X 10^ 0.10 X 10^ 0.0100 X 10^

12/111.68 X 10^ 12/0,6914 X 10^

9.31 X 10^ 0.0576 X 10^

0.24 X 10^ Average; = /^.31 - 0.24_7 x 10^ ^/0.0576 x 10^ - 115 -

Table 27

Average of RuCdt)^ Stability Constant in 0.127 M. HClOi,, and 50^ HOAc

Wavelength K-^ d d^

750 8.06 X 103 0.26 X 103 0.0676 X 10^

7^0 8.55 X 103 0.23 X lo3 0.0529 X 10^ 0 1 — 0 0 0 0 I

730 8.23 X• 103 0.09 X 103 X 10^

720 8.47 X 103 0.15 X 10^ 0.0225 X 10^

710 8.31 X 10^ 0.01 X 103 0.0001 X 10^

700 8.55 X 10^ 0.23 X 103 0.0529 X 10^

690 8.47 X lo3 0.15 X 10^ 0.0225 X 10^

680 8.31 X lo3 0.01 X 10^ 0.0001 X 10^

670 8.23 X 10^ 0.09 X 10^ 0.0081 X 10^ 1 660 8.47 X 103 0.15 X 10^ 0.0225 X 10^

650 8.23 X 10^ 0.09 X 10^ 0.0081 X 10^

640 8.06 X io3 0.26 X 103 0.0676 X 10^

12/99.94 X io3 12/0.3330 X 106

- 0.17 X 103 ^ Average: K3 - /E.3,2. ± 0.17_7 10^ Y^O.0278 X 10® - 116 - the thlocyanate and the thiourea systems, the accuracy is not. There are two reasons for this. The first is that the complexing agent, dithiooxamide is colored, making it necessary to correct all optical density measurements. The second is that the complexes are fairly stable, so that a smaller excess of ligand is necessary to complex the ruthenium. The approximation that the equilibrium con­ centration of dithiooxaraide is essentially equal to the total analytical concentration then becomes somewhat inaccurate. Using the final values found for the equilibrium con­ stants and the absorption spectrum of the first com­ plex was calculated. These data are given in Figure 21 and in Table 28. In the course of the successive approxima­ tions it was found that the calculated absorption spectrum of the uncomplexed ruthenium was almost identical with the experimentally-found values with a one-to-one ratio of dithiooxamide to ruthenium. Therefore, the experimentally- determined values were those used as the absorption spectrum of the uncomplexed ruthenium. These data are found in

Figure 22, and Table 29. In spite of the fact that the solution contained 50^ acetic acid, the absorption spectrum of the uncomplexed ruthenium is very similar to the published absorption spectrum of ruthenium III perchlorate. 1.8

1.6 1.4 >« i.2 c at O 1.0

o 0.8 u -

0;2

400 500 600 700 800 Wavelength In MMiimicrons 2 Figure 21 - Calculated Absorption Spectra of Ru(dt)^'^

/RU_J7 = 2.793 X 10-5 M.; /HClOl^_/ = 0.127 M. ^0Ac_7 = 50^; /^= 1.0 Cell Length = 5.00 cm. - 118 -

Table 28

The Absorption Spectrum of Ru(dt)^

Wavelength Optical Density* Wavelength Optical Density*

800 0.368 790 0.369 590 0.630 780 0.378 580 0.615 770 0.376 570 0.625 760 0.401 560 0.599 750 0.426 550 0.593

7kO 0.452 540 0.586 730 0.476 530 0.588 720 0.505 520 0.593 710 0.526 510 0.613 700 0.542 500 0.628

690 0.555 490 0.646 680 0.568 480 0.669 670 0.581 470 0.691 660 0.598 460 0.733 650 0.610 450 0.787 640 0.623 440 0.853 630 0.623 430 0.963 620 0.627 420 1.094 610 0.638 410 1.283 600 0.636 400 1.433

*^u_7 - 2.793 X 10-5 f/i, ^C10i,._7 = 0.127 M. /HOAc 7 = 50^ ^ = 1.0 Cell Length = 5.00 cm. 0.3 —

0.2 —

® 0.1 —

0.0 —

400 500 600 700 800 Wavelength in Millimicrons

Figure 22 - Calculated Absorption Spectra of Dithiooxamlde Data ^u_7 = 2.793 X 10-5 M.; ^ClOi,_7 = 0.127 M. ^0Ac_7' = 505^; = 1.0 Cell Length - 5.00 cm. - 120 -

Table 29

The Absorption Spectrum of from Dlthlooxamide Data

Wavelength Optical Density* Wavelength Optical Density*

A 800 0.027 790 0.027 590 0.047 780 0.033 580 0.045 770 0.041 570 0.045 760 0.044 560 0.045 750 0.045 550 0.046 740 0.046 540 0.046 730 0.047 530 0.045 720 0.048 520 0.044 710 0.049 510 0.043 700 0.051 500 0.043 690 0.053 490 0.042 680 0.055 480 0.046 670 0.053 470 0.048 660 0.054 460 0.052 650 0.047 450 0.056 640 0.047 440 0.057 630 0.046 430 0.066 620 0.046 420 0.073 610 0.043 410 0.085 600 0.045 400 0.090

*^u_7 = 2.793 X 10~3 M. #C102,J7 = 0.127 M.

^0AC_7 = 50% ^ = 1.0 Cell Length = 5.00 cm. - 121 -

Using the calculated equilibrium constants, and the absorption spectra of all three species, the optical density curve as a function of the dithiooxatnide to ruthenium ratio was calculated at TOO mu. This is the curve drawn through the experimental points in Figure 19. In order to test the acid dependence of the system, the procedure was repeated at double the perchloric acid concentration, at 0.254 M., instead of 0.127 M. As before this work was not done in great detail since the nature of the reaction was now known. It seemed sufficient to test . p the acid dependence only over the Ru(dt)^ -Ru(dt)2 portion of the system. Only the first approximation was carried out in the calculations. This was compared to the first approximation calculation at the lower acidity. The data taken at 0.254 M. HClOij^ are given in Table 30. In 0.254 M. HClOij., the equilibrium constant in the first approximation, was found to be equal to[i.05 - 0.27]x 10^ which agreed quite well with the first approximation to the equilibrium constant in 0.127 M. HClOi|^, where was found equal to [1.I9 1 0.04] x 10^. The equilibrium constant,

. #u(dt)3_7^HV® K3 - ^ Z^u(dt)i*^_7'^dtj^

is written as a function of the hydrogen ion concentration. Table 30

Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of Dithlooxamide/Ru, with ^ClO^^ equal to 0,254 M., and with ^OAcJ/ equal to 50^

Hatlo of Hdt , Ru 150 13c 90 60 50 30

Wavelength

800 0.366 0.365 0.364 0.363 0.362 0.365 0.371 0.363 0.365 0.364 C.355 0.351 0.343 0.327 0.299 790 0.384 0.385 0.384 0.383 0.380 0.332 0.384 C.386 0.334 0.376 0.375 0.372 0.353 0.330 0.299 780 0.411 0.415 0.414 0.411 0.407 0.407 0.409 0.410 0.408 0.408 0.389 0.387 0.371 0.3J<7 0.308 770 0.441 0.446 0.444 0.438 0.438 0.438 0.437 0.436 0.433 0.426 0.423 0.413 0.391 0.362 0.321 760 0.479 0.480 0.479 0.468 0.468 0.470 0.470 0.467 0.466 0.450 0.438 0.435 0.413 0.380 0.331 750 0.516 0.518 0.517 0.513 0.510 0.509 0.508 0.503 0.501 0.487 0.472 0.464 0.443 0.402 0.353 7»»0 0.556 0.556 0.558 0.549 0.547 0.546 0.545 0.546 0.537 0.522 0.505 0.501 0.470 0.429 0.371 730 0.595 0.598 0.598 0.589 0.586 0.585 0.579 0.574 0.571 0.556 0.536 0.530 0.499 0.454 O.3&9 720 0.634 0.634 0.635 0.624 0.620 0.620 0.614 0.611 0.605 0.583 0.569 0.561 0.536 0.478 0.408 ro 710 0.662 0.662 0.660 0.658 0.648 0.646 0.646 0.637 0.629 0.614 0.591 0.5fi9 0.548 0.500 0.423 ro 700 0.688 0.688 0,687 0.679 0.672 0.668 0.665 0.661 0.648 0.633 0.613 0.607 0.567 0.519 0.445 690 0.702 0.702 0.700 0.691 0.685 0.680 0.680 0.674 0.665 0.646 0.627 0.621 0.580 0.529 0.456 680 0.709 0.712 0.710 0.704 0.697 0.690 0.685 0.687 0.669 0.654 0.638 0.633 0.592 0.540 0.467 670 0.713 0.707 0.711 0.710 0.698 0.695 0.692 0.694 0.681 0.663 0.644 0.641 0.599 0.549 0.477 660 0.712 0.715 0.714 0.709 0.704 0.698 0.696 0.698 0.685 0.668 0.649 0.648 0.605 C.56O 0.4S7 650 0.716 0.720 0.715 0.709 0.706 0.701 0.698 0.698 0.687 0.670 0.651 0.651 0.612 0.568 O.49B 640 0.712 0.714 0.713 0.707 0.698 0.697 0.697 0.698 0.687 0.667 0.652 0.654 0.616 0.575 0.511 630 0.704 0.698 0.700 0.696 0.693 0.690 0.687 0.691 0.681 0.662 0.646 0.653 0.615 0.577 0.514 620 0.680 0.678 0.660 0.678 0.675 0.672 0.670 0.680 0.667 0.650 0.638 0.648 0.613 0.577 0.521 610 0.649 0.647 0.650 0.650 0,645 0.643 0.641 0.654 0.641 0.637 0.619 0.629 0.599 0.571 0.523 600 0.602 0.606 0.606 0.600 0.599 0.602 0.602 0.617 0.605 0.597 0.589 0.602 0.582 0.555 0.522 590 0.543 0.543 0.545 0.552 0.550 0.550 0.558 0.576 0.565 0.560 0.558 0.575 0.560 0.542 0.523 580 0.485 0.487 0.482 0.484 0.486 0.493 O.49S 0.515 0.507 0.512 0.510 0.533 0.529 0.511 0.518 570 0.414 0.409 0.416 0.423 0.425 0.434 0.444 0.465 0.459 0.465 0.464 0.496 0.500 0.504 0.511 560 0.354 0.350 0.354 0.367 0.373 0.379 0.392 0.415 0.411 0.419 0.428 0.460 0.476 0.481 0.508 550 0.292 0.294 0.291 0.305 0.321 0.327 0.342 0.364 0.370 O.3B2 0.395 0.434 0.465 0.471 0.503

[au(ciOi,)J : 2.793 r. 10-5 ^cio,j O.Z3'> M. flOAcJ 50# 1.0 Cell Length 5.00 cm. - 123 -

The agreement In at two different acidities proves that the constant, as written, contains the correct function of the hydrogen Ion concentration. Therefore, it may be said that dithiooxanilde is behaving as an acid, with each molecule of dlthiooxamlde releasing one proton. Although the acetic acid present in the dithiooxamide- ruthenlum system is really a solvent, it was of Interest to test the dependence of the reaction on the acetic acid concentration. The whole procedure was repeated at 75^ acetic acid, with 0.127 M. HClOij^, and an ionic strength of 1.0, for ratios of dlthiooxamlde to ruthenium from l80 down to 20. The data for ratios from 90 down to 20 are given in Table 31 • It was noted that all of the optical densities, corrected for the colored dlthiooxamlde, were somewhat higher than in 50J^ acetic acid. It was also noted that the optical density versus ratio curve at con­ stant wavelength remained constant for ratios greater than 70, instead of 1^0. In analyzing the data, it was found that it was impossible to fit the data assuming two com­ plexes present. Instead the data v;ere fit assuming only one complex present, Ru(dt)2. Thus the only detectable reaction occurring is;

Ru'^3 + 3 Hdt Ru(dt)2 ^ SH-* . (10)

The equilibrium constant for this reaction becomes: - 124 -

Table 31 Optical Densities at Different Wavelengths of Solutions Containing Various Ratios of Dithiooxamide/Ru, with ^C10|,J7 equal to 0.127 M.j and with /hOkcJ/ equal to 75^

Ratio of Hdt RU

90 80 70 60 50 ho 30 20 Wavelength^

800 0.501 0.505 0.503 0,489 0,465 0.436 0.350 0,296 790 0.528 0.527 0.526 0,511 0.495 0.454 0.392 0,303 780 0.557 0.562 0.559 0,541 0.514 0.484 0.421 0.323 770 0.591 0.597 0.594 0.577 0.547 0,517 0.444 0,342 760 0.631 0.636 0.634 0.614 0.486 0,545 0,473 0.365 750 0.683 0.682 0.681 0.671 0.621 0.587 0,512 0,389 740 0.724 0.729 0.729 0,705 0.675 0.633 0.549 0,417 730 0.787 0.782 0.778 0,753 0.724 0.677 0,588 0,448 720 0.823 0.825 0.825 0.801 0.766 0.721 0,624 0.476 710 0.866 0.870 0.868 0,844 0.792 0.765 0,659 0.508 700 0.900 0.898 0.897 0.877 0.844 0,793 0.690 0.532 690 0.928 0.928 0.927 0.895 0.866 0,811 0.709 0.549 680 0.945 0.944 0.938 0.921 0.887 0,838 0.728 0.564 670 0.957 0.960 0.960 0.935 0.896 0,854 0.744 0,578 660 0.976 0.974 0.976 0.944 0,912 0,868 0,757 0,591 650 0.988 0.983 0,988 0.954 0.923 0.871 0,764 0,599 6to 0.987 0.991 0.990 0.961 0,932 0,890 0,777 0,608 6jo 0.985 0.984 0.986 0.959 0,934 0,882 0,783 0,611 620 0.981 0.985 0.984 0.958 0,933 0.893 0,783 0,612 610 0.960 0.965 0.960 0.945 0.925 0,888 0,774 0,611 600 0.928 0.929 0.929 0.915 0.900 0,865 0.757 0,609 590 0.884 0.883 0.884 0,879 0.874 0,847 0,740 0,596 580 0.816 0.818 0.818 0,329 0.826 0.803 0.708 0.591 570 0.761 0.765 0.762 0,789 0.791 0.769 0.673 0,587 560 0.720 0.712 0,718 0,734 0.756 0,742 0,648 0.570 550 0.689 0.687 0.687 0,715 0.731 0,722 0,638 0,564

[ru(cio^)^] = 2,793 X 10-5 M, [HCloJ = 0.127 M,

[hOAcJ = 75^ = 1.0 Cell Length = 5-00 cm. - 125 -

. ^u(dt) 7/-hV^ - =[7.34 i .34] X 10^. (11)

^u:7 /R6tj^

When K equals [7.34 ± .34] x 10^ for 75^ acetic acid, is compared vrlth K]_K2 equals [7*75 - 0.26]x 10^ for 50^ acetic acidj it is seen that the reaction is essentially independent of the concentration of the acetic acid present. The increase in the optical densities, observed in going from 50^ to 75^ acetic acid, can be considered to be caused by a change in the solvent. It is to be expected that 50$^ acetic acid would alter the solvation of the ruthenium, and that in 75^ acetic acid the solvation would be still different. In conclusion it may be said that ruthenium IV per- chlorate reacts with dithiooxamide to give two blue-green complexes, Ru(dt)^^^, and Ru(dt)2' The dithiooxamide behaves as an acid, each molecule releasing a proton. The reactions themselves are independent of the concentration

of the acetic acid present, although changing the acetic acid concentration alters the solvation of the ruthenium. The equations and equilibrium constants for the system may be written as follows; - 126 -

Ru"'"^ + Hdt ,

Au(dt)/^_7^H'*_7 r 4 1 2 K = -= L^Lt i =[9.3 - 0.3]x 10'^, (la)

Ru(at) * 2 Hdt ^ Ru(dt)2 » ZH*

ZRu(dt)^Z-H-^ =[8.3 1 0.2]. 103. ^u(th)^-'2_7^dtJ7^

No evidence was found for the existence of a complex Ru(dt)2** indicating that the stability constant for this complex is so small that the amount of ruthenium in this form at any time is negligible. - 127 -

VII. SUMMARY AND CONCLUSIONS

A spectrophotometrlc study was made of the complexes formed by ruthenium IV perchlorate with thlocyanate, thiourea, and dlthlooxamlde. It was found that both ruthenium III and ruthenium IV react with thlocyanate to 42 form the same deep-blue complex, with a formula, Ru(CNS)]^ The absorption spectrum of Ru(CNS)^ was determined

experimentally. At an ionic strength of 1.0, the complex, which is essentially Independent of the concentration of acid present, has a formation constant of 60 i 1. No evidence was found for higher complexes. In comparing the ruthenium-thiocyanate system with the Iron-thiocyanate system, the similarity of the horoologs is apparent. In both the iron and the rutherllum system, the complex formed is the monothlocyanate complex. In both cases the formation constant is not large. For iron at unit ionic strength the formation constant is 126 i 10,

while for ruthenium under the same conditions it is 60 2 1. The investigation revealed that both ruthenium III and ruthenium IV perchlorate react with thiourea to give two blue-green complexes, Ru(th)^ and Ru(th)2. The complexing agent behaves as an acid, each molecule of thiourea releasing one proton. The equations for the system may be written as follows: - 128 -

Ru"^3 + Hth Ru(th)i'^^ ,

Ru(th)^'*^ + 2 Hth ^ Ru(th)3 + 2 H"* .

At an ionic strength of 3-0, the raonothiourea complex was found to have a formation constant, equal to l6.3 * 0.5, while the constant. Kg, for the trithiourea complex was found to be equal to 5-30 - 0.11. The absorption spectrum of Ru(th)2 was determined experimentally, and that of Ru(th)j^ •i2 was determined by calculation. The magnetic susceptibility per gram of Ru(th)2 was found to be 3.0 i 1.5 cgsu/g at 20°C. This determination, within the limit of experimental error, indicated that the ruthenium in the complex was present as ruthenium III. No evidence whatsoever v;a3 found for the existence of a complex Ru(th)2^' In the analytical procedure for ruthenium, using the ruthenium-thiourea color, the necessity for the precise limits set upon the concentrations of ruthenium, thiourea, and acid is now understood. Since ruthenium forms two similarly-colored complexes with thiourea, both of which have small formation constants, a very large excess of thiourea must be present so that all of the ruthenium

will be reproducibly complexed as Ru(th)2. Similarly, since the reaction is acid dependent, the acidity of the solution must be carefully controlled to assure the ruthenium being present as Ru(th)2. - 129 -

It was found that both ruthenium III and ruthenium IV perchlorate react with dithlooxamlde In acetic acid 42 to give two blue-green complexes, RuCdt)^ and Ru(dt)2. The dithlooxamlde behaves as an acid, each molecule releasing one proton. The reactions themselves are Independent of the concentration of acetic acid present, although changing the acetic acid concentration alters the solvation of the ruthenium. The equations for the system may be written as follows:

Ru'^^ + Hdt ^ Ru(dt)^*^ 4 ,

Ru(dt)2^*^ + 2Hdt RuCdt)^ + 2K*.

At an Ionic strength of 1.0, the monodlthlooxamlde complex was found to have a formation constant, K]^, equal to

/^•3 - 0*3_7 ^ while the trldlthlooxamlde complex was found to have a formation constant, equal to

/Q.3 t 0.2_y X lo3. The absorption spectrum of Ru(dt)2 was / V +2 determined experimentally, and that of Ru(dt)^ was determined by calculation. No evidence was found for the existence of a complex Ru(dt)2*. As in the case of the analytical procedure for ruthenium using thiourea, the necessity for the precise limits in the dithlooxamlde colorimetric procedure is now understood. Again, two similarly-colored, acid-dependent

complexes are formed, and the concentrations of the ruthenium, - 130 - dithlooxamlde and aold present must be carefully controlled for reproducible results. In comparing the thiourea system with the dithlo­ oxamlde system. It was noted not only that the formulae of the complexes are Identical in the two systems, but also that the absorption spectra are very similar. How­ ever, the formation constants in the dithlooxamlde system are much larger that those in the thiourea system. It is interesting to speculate that the structures of the

thiourea and dithlooxamlde complexes are similar, pro­ ducing similar formulae and absorption spectra. If the following structures are hypothesized,

HN = C - S s. HN = C Ru/3 and 1 . Ru/3 , ^ N'" S = C - N H2 H,

the differences observed in the formation constants might be considered to be a measure of the stability of the five-membered dithlooxamlde ring over that of the four- membered thiourea ring. There is, of course, no experi­ mental justification for such structural formulae, but the conjecture is reasonable on the basis of the data observed. Investigation of these complexes by infra-red and Raman spectroscopy might aid in determining the correct structural formulae. - 131 -

In this spectrophotometric investigation of the com­ plexes formed by ruthenium IV perchlorate with thiocyanate, thiourea, and dithiooxamide, it vjas found that the ruthe­ nium IV was being reduced to ruthenium III at the expense of the complexing agent. Consequently, the absorption spectrum of the uncomplexed ruthenium v;as unknown, and the usual methods of interpretation of spectrophotometric data were not applicable. A new method of Interpretation of spectrophotometric data was developed for systems contain­ ing either one or tvjo complexes. This method is applicable for systems in which the complexes have small formation constants, providing the absorption spectrum of the last complex can be determined experimentally. Equations were developed for calculation of the formulae, extinction coefficients, and formation constants of the complexes present. It is possible that this method will prove useful in similar systems of complexes. - 132 -

VIII. LITERATURE CITED

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IX. ACKNOWLEDGEMENTS

The author appreciates, and vflshes to express thanks for, the suggestions and encouragement received from Pro­ fessor Adolf p. Voigt throughout the course of this research. She also thanks Professor Charles V. Banks and Mr. Roy W. Vander Haar for performing the magnetic susceptibility measurements on the ruthenium-thiourea complex. She fur­ ther wishes to thank Dr. V. A. Passel and his spectro- graphlc department for performing the spectrographic analyses of the various samples of ruthenium; and Profes­ sor Harvey Diehl for loaning, and Mr. John P. Butler for giving advice on the operation of the graded cathode electrodepositlon apparatus for the preparation of ruthe­ nium III perchlorate. Thanks are also given to Mr. Lyle Knowles of the Iowa State College Instrument Shop for his Indispensable aid in servicing and maintaining the Cary recording spectrophotometer.

Acknowledgement is made to the Ames Laboratory of the Atomic Energy Commission for providing the funds and necessary facilities for the research.