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1969 The epS aration and Determination of Osmium and Ruthenium. Harry Edward Moseley Louisiana State University and Agricultural & Mechanical College
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MOSELEY, Harry Edward, 1929- THE SEPARATION AND DETERMINATION OF OSMIUM AND RUTHENIUM.
Louisiana State University and Agricultural and Mechanical College, PhJ>., 1969 Chemistry, analytical
University Microfilms, Inc., Ann Arbor, Michigan THE SEPARATION AND DETERMINATION OF OSMIUM AND RUTHENIUM
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Chemistry
Harry Edward Moseley B.S., Lpuisiana State University, 1951 M.S., Louisiana State University, 1952 J anuary, 1969 ACKNOWLEDGMENTS
Thanks are due to Dr. Eugene W. Berg under whose direction this work was performed, to Dr. A. D. Shendrikar for his help in the tracer
studies, and to Mr. J. H. R. Streiffer for his help in writing the com
puter program. The author also wishes to thank the National Science Found
ation for its support for several summers in the Summer Institute for
College Teachers of Chemistry and also in the Research Participation Pro
gram for College Teachers of Chemistry both directed by Dr. Robert V.
Nauman. The financial support of the National Science Foundation Academic
Year Extension of the Research Participation Program for College Teachers
and of Louisiana Polytechnic Institute is most gratefully acknowledged.
An immeasurable debt is owed to the author's wife, Joyce, with
out whose support and encouragement this effort might never have been
attempted.
ii TABLE OF CONTENTS
PAGE
ACKNOWLEDGMENTS...... ii
LIST OF TABLES....,...... iv
LIST OF FIGURES...... V
ABSTRACT...... vi
I. INTRODUCTION...... 1
II. EXPERIMENTAL
1. Simultaneous Determination of Osmium and Ruthenium...... 5
A. Reagents...... 5
B. Apparatus...... 5
C. Procedure...... 6
2. Separation of Osmium and Ruthenium by Solvent Extraction...... 8
A. Reagents...... 8
B. Apparatus...... 8
C. Procedure...... 11
III. RESULTS AND DISCUSSION
1, Simultaneous Determination of Osmium and Ruthenium...... 12
2. Separation of Osmium and Ruthenium by Solvent Extraction...... 19
IV. CONCLUSIONS AND SUGGESTIONS FOR FUTURE WORK......
V. BIBLIOGRAPHY...... 35
VITA...... 37
iii LIST OF TABLES
TABLE PAGE
I. Molar Absorptivitles of Complexes of Ru-thiourea and Hexabromosmate...... 7
II. Replicate Determinations of Os and Ru Mixtures...... 18
III. Extraction of Ru-thiourea and Bromosmate into Various Solvents...... 20
IV. Distribution Coefficients of Bromo Complexes of Os and Ru as a Function of Acidity Using Phases that were not Pre-saturated...... 22
V. Effect of Using Pre-saturated Phases Upon Extraction of Bromo Complexes of Os and Ru with 4 -methy1-2- pentanone at an Acid Concentration of 6 M HBr...... 23
VI. Effect of Increasing Concentration of Metal Upon Extraction of Bromo Complexes of Os and Ru into -methyl-2-pentanone at an Acid Concentration of 6 M HBr...... 28
VII. Revised Computer Program for the Craig Equation...... 3 0
VIII. Theoretical Data for Countercurrent Extraction of Bromo Complexes of Os and Ru on 13 Stage Craig Apparatus...... 31
IX. Theoretical Data for Countercurrent Extraction of Bromo Complexes of Pd and Pt on a 15 Stage Craig Apparatus...... 3 2
X. Theoretical Data for Countercurrent Extraction of Bromo Complexes of Ir and Rh on a 15 Stage Craig Apparatus...... 33
iv LIST OF FIGURES
FIGURE PAGE
I. Gamma Ray Spectrum of Os-191...... 9
II. Gamma Ray Spectrum of Ru-105...... 10
III. Absorption Spectrum of Ru-thiourea Complex...... 15
IV. Absorption Spectrum of Hexabromosmate Complex...... 14
V. Absorbance at k k 6 mn vs Time for Hexabromoosmate in Presence of Thiourea at Various Acid Concentrations 15
VI. Absorbance at 620 mx vs Time for Ru-thiourea Complex in 6.T M HBr...... 16
VII. Gamma Ray Spectrum of Os plus Ru Before Extraction...... 2 k
VIII. Gamma Ray Spectrum of Extractant...... 25
IX. Gamma Ray Spectrum of Raffinate...... 26
v ABSTRACT
Methods for the separation and determination of osmium and ruthenium were studied. A technique was devised whereby a mixture of
the bromo complexes of the two metals can be resolved by solvent extraction.
A 6 M HBr solution of the metals was extracted with ^-methyl-2-pentanone using a volume ratio of extractant to raffinate of two to one. Osmium was
quantitatively extracted from ruthenium after a two minute equilibration.
The extraction was followed by means of the radioactive isotope tracers,
osmium-191 and ruthenium-IO3 .
A spectrophotometric procedure was developed for the simultaneous
determination of osmium and ruthenium in the form of bromo complexes. It was found that a blue ruthenium thiourea complex could be formed in 6.7 M
HBr solutions while the osmium would be maintained as the hexabromosmate
complex. Absorption maxima were at 620 mx for the ruthenium complex and
at 41j-6 mx for the osmium complex. Molar absorptivities for the ruthenium
complex were 2 A 7 x 103 at 620 mx and 7 6 3 at ^h-6 mx. For the osmium com
plex molar absorptivities were 326 at 620 mx and 6 .8 l x 103 at M +6 mx. The
method is useable over the range of 3 to 30 ppm with an absolute error of
"il ppm over the range. Other platinum metals interfere.
A computer program for the Craig equation was written for use
in making theoretical calculations of the separation efficiencies of a
countercurrent extraction technique.
Suggestions for some future work are made.
vi I. INTRODUCTION
Methods for the separation and determination of the six platinum metals continue to attract the attention of analytical chemists. Every year numerous publications are cited in Chemical Abstracts for the deter mination of these metals. The reasons for this Interest are probably the rather complex chemistry of these elements and their increasing industrial
Importance.
Osmium and ruthenium are unique among the platinum metals in forming volatile tetroxides. The usual method of separation of osmium and ruthenium from the other platinum metals is by the vet oxidation of aqueous solutions of their salts. This results in the formation of the tetroxides which can be removed by distillation and collected in a suitable receiving 6 17 2 6 2 7 solution. The distillation may be done individually or collectively depending upon prior treatment of the sample.
Often it is advantageous to collect the osmium and ruthenium to gether. A further separation is then carried out since the presence of one of the metals interferes with the determination of the other.
Solvent extraction has often been used for the separation of osmium and ruthenium. "This has usually been done by forming a colored
complex with an organic reagent and then extracting the colored complex with a suitable solvent. The determination of the metal may then be
accomplished by measuring the absorption of the complex spectrophotometri-
cally. Methods may be found for the extraction and determination of osmium
alone^’^ , ruthenium alone^*^’^ ’^ or for both osmium and ruthenium'*’^ ’^ ’^. 23 Sauerbrunn and Sandell extracted osmium tetroxide from aqueous
solutions into chloroform or carbon tetrachloride. Ruthenium tetroxide was also extracted, but, by first reducing the osmium to a lower oxida tion state and then re-oxidizing, a separation could be effected.
Geilmann and Neeb*^ were able to complex ruthenium with either diphenyl- thiourea or 2 ,^-diphenylthiosemicarbazide and extract the complex into chloroform. The same authors also were able to separate osmium from ruthenium by a chloroform extraction of the complex formed by reacting tetraphenylarsonium chloride with hexachlorosmate.
Extraction of osmium and ruthenium as inorganic complexes has not been widely investigated. Boswell and Brooks^* investigated the
pseudo-countercurrent extraction of the chlorides of 31 elements with
U-methyl-2 -pentanone and found that osmium was about 80$ extracted from
6 M HCl. They gave no data for ruthenium because they observed two peaks
for it and stated that this was most probably due to the presence of
either different valence states or different complexes of low lability.
There are a number of spectrophotometric methods available for 7 the determination of osmium and ruthenium alone. Beamish has given an 2 excellent critical evaluation of many of these methods and Avtokratova
has compiled an extensive collection of analytical procedures for ruthenium.
4 Thiourea is one of the most widely used reagents for the spectro
photometric determination of osmium and ruthenium. The reaction between 1* osmium and thiourea was first reported by Chugaev J in 1925. Since that
time thiourea and substituted thioureas have been extensively studied as
reagents for osmium and ruthenium. 29 Ruthenium forms a blue complex with thiourea. Yaffe and Voight
reported this to be a neutral complex of the following formula: HN. 3
There is some doubt about this formulation, since we were unable to ex
tract the supposedly neutral complex into several organic solvents. The
same authors also reported that the complex is paramagnetic and there
fore the ruthenium is in the + 5 and not +4 state. it Ayres and Young studied the complex formed when ruthenium
chlorides in 6 M HC1 were reacted with thiourea. Their data showed the
absorption maximum to occur at 620 mx with a molar absorptivity of about
6 0 0 0 .
Aryes and Wells^ reported that the rose complex formed with
osmium (Vlll) and thiourea showed a sharp absorption at 1+80 mx and a lesser
band at 5^0 nix. pit Sauerbrunn and Sandell have studied the reaction between osmium
and thiourea in detail and report that the complex is Os(NH2C SNHa )|+ . They
also reported that in contrast to the rapid reaction between thiourea and
osmium tetroxide, the reaction between thiourea and hexachlorosmate is ex
ceedingly slow at room temperature. Even at 100°, with a large excess of
thiourea in the mixture approximately one-half hour is required for quanti
tative conversion of chlorosmate into the thiourea complex. Dwyer and llj- Gibson had determined osmium by reacting the hexabromosmate with thiourea
but this required heating at 100° for only 15 minutes. They apparently
did not look at the spectrum of the hexabromosmate alone.
Very little work has been done towards the development of a pro
cedure for the simultaneous determination of osmium and ruthenium despite 21 the obvious advantages of such a method. Philipenko and Sereda have re
ported a spectrophotometrlc method for the simultaneous determination of
osmium and ruthenium complexed with selenourea. The procedure requires
the measurement of absorbance at two different acid concentrations. The
ruthenium concentration is determined from a calibration curve and from If
another curve its absorbance at the osmium peak is determined. This is subtracted from the osmium absorbance and the osmium concentration is determined from another calibration curve. The procedure is asserted to be useful for 2-60 ppm of osmium and ruthenium, and only palladium among
the platinum metals interferes. This procedure is rather lengthy and re
quires three working curves.
The work reported here was first directed toward the separa
tion of bromo complexes of osmium and ruthenium by a solvent extraction
procedure. The bromo complexes of the metals were chosen for study be- 9 cause Berg and Sanders'^ had previously studied the solvent extraction of
the bromo complexes of palladium, platinum, rhodium, and iridium. It was
hoped that ultimately a procedure could be developed for the separation
and determination of mixtures of all six of the platinum metals using
countercurrent extraction as the separation technique.
In order to follow the extraction of osmium and ruthenium a
means of determining the metals was needed. Since thiourea has been thorough
ly investigated as a spectophotometrie reagent, it was used. This did not
prove to be satisfactory- in the presence of the organic solvent so the
separation was followed by means of radioactive tracers. However, during
the attempt to determine osmium and ruthenium separately as the thiourea
complexes, a method was developed for the simultaneous determination of the
metals. This procedure was based upon the difference in reaction rates of
the bromo complexes of osmium and ruthenium with thiourea. II. EXPERIMENTAL
1. Simultaneous Determination of Osmium and Ruthenium.
A. Reagents. Osmium tetroxide obtained from A. D. Mackay, Inc. was dissolved in 100 ml. of 0.2 M NaOH in a 250 ml. Erlenmeyer flask. The solution was filtered into a one liter volumetric flask and diluted to the mark with water. The solution was standardized by means of the 1 ,2,5-benzotriazole 28 procedure of Wilson and Bye . The final osmium concentration was 780 ppm.
Ruthenium trichloride trihydrate from A. D. Mackay, Inc. was dis solved and diluted to one liter with 6 M HC1. The solution was standard ized by taking aliquots to dryness in Rose crucibles and igniting under hydrogen to reduce the ruthenium to the elemental state. The final ruth enium concentration was 820 ppm.
Bromides of osmium and ruthenium were formed by taking aliquots of the stock solutions, adding equal amounts of concentrated HBr and taking to dryness. This procedure was repeated with additional concentrated HBr.
The residue was then dissolved in 6 M HBr and brought back to its original volume. When necessary, further dilutions were made by taking aliquots of
the concentrated bromide solution and diluting with 6 M HBr.
A 10$ by weight solution of thiourea was prepared at least every
two weeks by dissolving 10 grams of thiourea in 90 ml. of distilled water.
Concentrated (48$) HBr was obtained from J. T. Baker Chemical Co.
Thiourea was obtained from J. T. Baker Chemical Co.
B. Apparatus.
A Beckman Model DB Spectrophotometer and matching 1 cm. silica cells
were used for absorbance measurements.
5 6
Spectra were recorded with an E. H. Sargent and Co. Model SKL
Recorder.
C. Procedure.
The following procedure Is recommended for the simultaneous deter mination of osmium and ruthenium. To an aliquot of a mixture of osmium and ruthenium bromides containing between 5 and 30 ppm of the elements, add 10 ml. of concentrated (^8$) HBr, then add two ml. of 10$ (w/w) thiourea and dilute to 25 ml. with 6 M HBr. After a 15 minute development time, measure the absorbance at 620 mx and mx in a 1 cm. cell against a blank
of 6 M HBr. The concentration of osmium and ruthenium may be obtained by
solving two simultaneous equations. (See Table 1.) TABLE X
Molar Absorptivities of Complexes of Ru-thiourea and Hexabromosmate kh6 mx 620 mx Os (bromo complex) 6.8l x 103 325”
Ru (Thiourea complex) 763 2.Vf x 103
Simultaneous Equations for Determination of Os and Ru
Absorbanceg^Q ■ 328 x (Os) + 2 .U7 x 103 x (Ru)
Absorbance)^g ■ 6.8l x 103 x (Os) + 7 6 3 x (Ru) 2. Separation of Osmium and Ruthenium by Solvent Extraction.
A. Reagents,
The preparation of solutions of osmium and ruthenium has been described earlier*
l+-methyl-2-pentanone was obtained from Matheson Coleman and Bell.
Osmium-191 was obtained from The Oak Ridge National Laboratory as a solution of sodium osmate. The garnaa ray spectrum of osmium-191 is shown in Figure I. The isotope has a half-life of fifteen days and emits a gamma ray having an energy of 0.128 Mev.
Ruthenium-105 was prepared by neutron irradiation of ruthenium tribromide in the reactor at Georgia Institute of Technology. The gamma ray spectrum of ruthenium-105 is shown in Figure II. The isotope has a half-life of forty days and emits a gamma ray having an energy of O.I+89
Mev. The ruthenium sample was not pure; it contained an unknown amount of iridium-192 plus some unidentified impurities.
B. Apparatus.
Tagged samples were counted with a Technical Measurement Corpora
tion Pulse Height Analyzer, 1+00 channels, Model 1+01, in conjunction with a Technical Measurement Corporation Resolver Integrator, Model 522.
Detection was by means of a 2 inch well type Nal scintillation detector.
In the initial extraction studies 60 ml. separatory funnels were
used.
Four ounce narrow mouth screw cap polyethylene bottles were used
in the extraction studies with tagged samples.
A Burrell mechanical shaker, Model BB, was used in the isotope
studies. FIGURE I Gamma Ray Spectrum of Os-191
0-128 Mev
Channel Number FIGURE II Gamma Ray Spectrum of Ru-103 0.498 Mev
Channel Number IX
Samples taken for counting were placed in IT non. l.d. x 55 nan. snap top polyethylene vials.
C. Procedure.
The following procedure was finally adopted for the extraction separation. The osmium and ruthenium bromides, formed by taking a sample solution almost to dryness with concentrated HBr, are taken up in 10 ml. of 6 M HBr previously saturated with l4--methyl-2-pentanone. The sample size should be such that in the final volume there is not more than 300 ppm of each metal.. The HBr solution is placed in a 4 oz. narrow mouth screw cap polyethylene bottle. A sufficient quantity of radioactive iso topes are added to give an initial activity of about 2000 counts per minute for both osmium and ruthenium. A two ml. sample is taken for determining the initial activity. Sixteen ml, of h-methyl-2-pentanone previously saturated with 6 M HBr is added, and the mixture is shaken for two minutes on the Burrell shaker. The phases are allowed to separate, and two ml. samples of each phase are taken for counting. The gamma ray spectrometer is calibrated with a cesium-137 source. III. RESULTS AND DISCUSSION
1. Simultaneous Determination of Osmium and Ruthenium.
The absorption spectrum from TOO mx, to 400 mx of the complex form ed when ruthenium bromides are reacted with thiourea Is shown in Figure
III. It shows a single broad band centered at 620 mx with a molar ab
sorptivity of about 2500.
As mentioned previously, the slowness of the reaction of the hexa- 14 24 halo complexes of osmium with thiourea has been noted by several authors '
No one had apparently JLooked at the absorption spectra of the halo com
plexes alone to see if they would be analytically useful. The absorption
spectrum of the bromosmate complex shown in Figure IV reveals a strong
absorption at 446 mx and a less intense band at 492 mx. Absorption at 620
mx is very slight. This suggested that a simultaneous determination of
osmium and ruthenium might be possible if conditions could be found where
by the ruthenium-thiourea complex would be formed without causing the
osmium-thiourea complex to form.
Figure V shows the results of a time versus acidity study of bromo
smate in the presence of thiourea. At final acid concentrations below
6.7 M in HBr a definite reaction between bromosmate and thiourea occurs.
This is shown by a steady decrease in the bromosmate absorption at 446 mx.
At 6.7 M the bromosmate is stable at least four hours.
Figure VI shows the results of a time study of the development of
the ruthenium-thiourea complex at the acid concentration required to pre
vent the bromosmate-thiourea reaction. A 15 minute development time is re
quired, and the color is stable at least four hours.
12 0.6 0.5 0.2 Absorbance 0.1 0 0 4 66pm Ru) ppm (656 Ru-Thiourea Complex Complex Ru-Thiourea Absorption Spectrum of of Spectrum Absorption 500 aeeghi mp in Wavelength FIGURE III 600 700 0.2 0.5
O.i Absorbance 0.4 0 600 400 bopin pcrm f Hexabromosmate of Spectrum Absorption aeegh n mp in Wavelength 500 ope (312Os} ppm Complex FIGURE IV 700 .32 .34 Absorbance .56 .39 vs Time for Hexabromosmate Hexabromosmate for Time vs at Absorbance aiu cd Concentrations Acid Various in Presence of Thiourea at at Thiourea of Presence in 10 4 4 6 mu mu 6 4 4 Time (minutes) Time 15
FIGURE V 20 25 30 HBr M J 6 O . HBr M 4.8 . HBr M 3.7 .32 .34 .31 .33
Absorbance .35 boac a 60m v Tm Fr uTiue Cmlx in Complex Ru-Thiourea For Time vs mp 620 at Absobance TO 13 Time (minutes)
I U E VI FIGURE . HBr M 6.7 20 25 30 35 CT\ 17
The data in Figures V and VI show then that a simultaneous deter mination of osmium and ruthenium is possible at an acid concentration of
6.7 M HBr. Under these conditions, the ruthenium bromides react readily
with thiourea while the bromosmate does not react with thiourea.
Molar absorptivity values for the osmium and ruthenium complexes
are given in Table I. Data for replicate determinations of mixtures of
osmium and ruthenium are shown in Table II. These data show an absolute
error of *1 ppm for osmium and ruthenium over the useable range. Percent
relative error is about 3$ at the upper range and about 1 6$ at the lower
range. Calculation of the 95$ confidence level shows it to be 'tl of the
mean for a set of five duplicate determinations.
Palladium and rhodium will interfere with the determination be
cause, under the experimental conditions of the determination, palladium
and platinum bromides absorb strongly at the analytical peak of osmium.
Iridium and platinum bromides do not interfere with the determination of
ruthenium but cause an absolute error of t 2 ppm in the osmium results.
This result would cause the relative error for the determination of osmium
to range from 6 to 35$ and would be unacceptable. In light of these inter
ferences, this method is only recommended for the determination of osmium
and ruthenium after separation from the other platinum metals. TABLE II
Replicate Determinations of Os and Ru Mixtures
ppm Os ppm Ru
absolute found error taken found
31 5 2 + 1 55 33 31 31 0 33 3^ 31 31 0 33 33 31 31 0 33 34 31 32 . + 1 33 33
31 31 0 7 6 31 3 0 - 1 T 7 31 3 0 - 1 7 7 31 31 0 7 7 31 31 0 7 7
6 7 + 1 33 33 6 6 0 33 33 6 6 0 33 33 6 7 + 1 33 33 6 7 + 1 33 33
6 6 0 7 6 6 5 - 1 7 7 6 5 - 1 7 7 6 6 0 7 7 6 6 0 7 7 19
2. Separation of Osmium and Ruthenium by Solvent Extraction.
The nature of the bromo complexes of osmium and ruthenium is not definitely known. Presumably osmium is present in solution as the hexa- bromosmate(lV) complex. As the hydrogen ion concentration is increased, the neutral species, HgOsBr6 , is more prevalent and may be extracted.
Ruthenium is known to form a variety of complex halides such as RuOHXg2 ,
RuHgOX52~, and RuXg2-.” The stock solution used in this study was supposed to contain ruthenium(lll) but it is quite possible that during the con- version to the bromides some ruthenium(iv) was formed. In any event, the ruthenium is assumed to be present as a charged complex because it could not be extracted with some common solvents. As was mentioned earlier, the bromo complexes of these metals were used in order to correlate this 9 work with the previous work by Berg and Sanders..
At first, it was thought that the course of the possible extrac tion could be followed spectrophotometrically by following the absorption of complexes formed with thiourea. An immediate problem arose; it was difficult to tell if the rose osmium-thiourea complex had formed in the presence of the reddish brown hexabromosmate solution. This problem was
never resolved, however, since it was discovered that the rate of forma
tion of the rose thiourea complex was so slow that it could be ignored.
Consequently the osmium remained as the bromo complex whereas the blue
ruthenium-thiourea complex formed rapidly under the same conditions. On
this basis then, several solvents were surveyed as extractants for osmium
and ruthenium. The results are shown in Table III. The best solvent
seemed to be 4-methyl-2-pentanone. The ruthenium-thiourea complex did not
appear to be extracted while the bromosmate appeared to be extracted al
most completely. It was not possible to be sure that the latter extraction TABLE III
Extraction of Ru-thiourea and Bromosmate into Various Solvents solvent Ru -thiourea bromosmate n-pentyl acetate no extraction no extraction benzene
chloroform
4-methyl-2 pentanone complete extraction
tributyl phosphate slight " 21
was complete because a suitable procedure for the determination of osmium in the presence of U-methyl-2-pentanone could not be developed despite extensive investigation.
At one point it appeared that the bromosmate was actually only partially extracted in a single equilibration. This caused a rather
lengthy investigation to be undertaken on the possibility of separating
the metals by a continuous extraction technique. The only positive re
sults to come out of this study was the discovery that thiourea was not
needed to complex ruthenium since the ruthenium bromides themselves did
not appear to be extracted into U-methyl-2-pentanone. It was then de
cided that the separation could best be followed by measuring the activity
of tracer quantities of radioactive isotopes of osmium and ruthenium.
The effect of acidity upon the extraction of osmium and ruthenium
with 4-methyl-2-pentanone was studied by means of the tracer technique.
The results are given in Table IV. These data show that with equal volumes
of extractant and raffinate, about 78$ °f the osmium would be extracted
in a single equilibration at an acid concentration of 6 M HBr. However,
when both the extractant and raffinate are pre-saturated with each other
much better separation is obtained. The results are shown in Table V. With
phase equilibration essentially a quantitative extraction of osmium occurs
in a single two minute equilibration. The distribution coefficient cal
culated for ruthenium would indicate about 2$ extraction; however, it is
believed that the measured activity in the extractant after a single equili
bration is due to the presence of one of the impurities in the ruthenium
sample.
Figure VII, shows the gamma ray spectrum of a sample of mixed
osmium and ruthenium bromides before extraction, and Figures VIII and IX 22
TABLE IV
Distribution Coefficients of Bromo Complexes of Os and Ru as a Function of Acidity Using Phases that were not Pre-saturated.
Acid Concentration Kh (Ru ) K^fOs)
1 M 0.01 2.93
2 M 0.02 2.91
3 M 0.02 2.80
k M 0.02 3*20
5 M 0.03 3*25
6 M 0.07 3.51 TABLE V
Effect of Using Pre-saturated Phases Upon Extraction of Bromo Complexes of Os and Ru with ^-methyl-2-pentanone at an Acid Concentration of 6 M HBr.
l^Os KyRu phases not 5*51 0.07 saturated
phases pre 206.5 0.05 saturated Total Counts a pcrmo O pu R Bfr Extraction Before Ru plus Os of Spectrum Ray 18 hne Number Channel 0.128 Mev 0.128 IU E VIIFIGURE *10 70 498 Mev 8 9 .4 0 Total Counts 18 Channel Number Number Channel am Ry pcrm f Extractant of Spectrum Ray Gamma 0.128 Mev 0.128 IU E VIIIFIGURE *10 70 Total Counts *1 18 Channel Number Number Channel am Ry pcrm f Raffinate of Spectrum Ray Gamma FIGURE IX x10 70 498 Mev 8 9 .4 0 27
show the gamma ray spectra of the extractant and raffinate, respectively.
The osmium-191 peak in the extractant is not as intense as that in the initial sample because the extractant was twice the volume of the raf- finate. Notice that no osmium activity can be seen in the raffinate and no ruthenium activity is seen in the extractant. Six replicate deter minations gave the same result, namely quantitative extraction of bromo- osmate after a single two minute equilibration.
The results of increasing concentration of osmium and ruthenium upon efficiency of extraction are shown in Table VI. It can be seen that
there is an appreciable increase in the distribution coefficient of ruth
enium and a decrease in the distribution coefficient of osmium as the con
centration of osmium and ruthenium increases. This result is probably due
to saturation of the extractant with osmium with increasing concentration
and a salting out effect with increasing amounts of ruthenium. Once the
extractant is saturated with osmium, it cannot remove any more osmium from
the raffinate. As the ruthenium concentration is increased in the raf
finate, some ruthenium may be driven into the extractant by a salting out
process.
Berg and Sanders had studied the countercurrent extraction of the
bromo complexes of platinum(lV), palladium(ll), rhodium(lll), and iridium(lV)
into lt-methyl-2-pentanone. The values they obtained for the distribution
coefficients of these metals together with the values obtained here for
osmium and ruthenium indicated that it might be possible to separate the
bromo complexes of osmium, palladium, and ruthenium. Palladium was chosen
because its distribution coefficient is low enough to permit resolution
of the three components if it is assumed that the ruthenium would not be
extracted. This separation was investigated with a 15 stage Craig apparatus. TABLE VI
Effect of Increasing Concentration of Metal Upon Extraction of Bromo Complexes of Os and Ru into V-methyl-2-pentanone at an Acid Concentration of 6 M HBr. 29
The same difficulties encountered earlier in the determination of osmium and ruthenium after solvent extraction occurred again and these difficulties were compounded by the presence of palladium. The presence of the solvent
Interferes with the determination of the metals. Removal of traces of the extractant with strongly oxidizing reagents is not possible because of the possibility of formation of the volatile tetroxides of osmium and ruthenium. As a result, it was possible only to confirm visually that a separation was taking place. Time did not permit the further work re quired to obtain quantitative data.
Berg and Sanders had also written a computer program for the Craig equation. This program was rewritten so that the results were printed out directly instead of being recorded on cards and the results were presented
in a better format. The revised program is shown in Table VII. The print out of data for a theoretical 15 stage countercurrent extraction of each of the six platinum metals is shown in Tables VIII, IX, and X. These re
sults indicate that it may be possible to separate with 15 stages mix
tures of ruthenium, palladium, and osmium or ruthenium, iridium, and osmium,
or ruthenium, rhodium, and osmium, but not ruthenium, platinum and osmium. : n I KEN S ICN FACT( 31 ) 2 CATA FACT/ 1- , 1., 2.* 6., 24., 120.» 720., 504u. , 1 0.4G32CCCQE 05, 0.362 88CCCE C6, 0.36288CCCE 07, 2 0.399168GOE 08, 0.479CJ16^£ C9, 0.62270208E 10, 3 C.8717 829GE'11, 0.13C76744E 13, G.2C92279CE 14, 4 0.25568742E 15, 0.64C23736E 16, 0.1216451LE 18,
5 L.24J2V:2jE 19, 0.51L9C941E 20, 0.11240C07E 22, Craig Equation Programthe forRevised Computer 6 C. 25852H6E 23, 0.62C44838E 24, 0.155112C9E 26, 7 C .~4w 225l44E 27, 0. 1C 8 8 8 869E >29 , C . 3C48 8 83 2 E 3 0 » 3 U.88417614E 31, 0.26525284E 33 / 7a* *EA|_ K , KO 4 INTEGER TUBE R t; le CCNT INUE 6 PRIM i: 7 7?C FCPPAT ( 1H1 ) 10 RE AC 1 , N , KD , X , RATIC . 11 1 FQRVAT ( 1 1 ’. , 3F1..5 ) 12 K = KC * RATIO 13 CC 2 I = 1 , N 1* PRIM 3 , KC , RATIO 15 3 FQRVAT { 1H- , IX , 9FTRANSFERS , 1CX , 6HTUBE R , 1CX , 1 18HFRACT IC\ CF SOLUTE , 5X , 7HPERCENT , 10X , 2 15F0IST. CUEFF. = , F10.4 , 1CX , BHRATIC = , Fe.3 // ) 16 i m = i - 1 17 EC 4 TUBE R = 1 , I 2t I M M = I - TIJRFR 21 T\P = ( FACTtIM+1) / ( FACT( TUBER ) * FACT{IM18T +1) ) ) 1 « ( ( 1. / { K+l.) ) •* IV1 ) * ( K »* ( TUBER - 1 ) ) 22 PERCM = TNR * Hi. 23 PRIM 5 , 181 , TLBE R , TNR , PERCNT 24 5 FCRPAT ( IH , IX , 16 , 1CX , 16 , 12X , F15.8 , 5X , F10. 1 ) 25 4 CCNTINUE 26 2 CCNT I \L f 27 CC TC 18 *5 w-*i 5 CO stcp 31 CNC fEN TKY
VJ4 o 31
TABLE VIII
Theoretical Data for Countercurrent Extraction of Bromo Complexes of Cs and Ru on a 15 Stage Craig Apparatus.
Ru
Transfers Tube R Fraction of Solute Percent Dist. 15 1 0.50506788 50.5 Coeff. 0.05 14 2 0.35354751 35 A 14 3 0.11490294 11.5 Ratio 1.00 14 4 0.02298059 2.3 14 5 0.00315983 0.3 14 6 0.00031598 0.0 14 7 0.00002370 0.0 14 8 O.OOOOOI35 0.0 14 9 0.00000000 0.0 14 10 0.00000000 0.0 14 11 0.00000000 0.0 14 12 0.00000000 0.0 14 13 0.00000000 0.0 14 14 0.00000000 0.0 14 15 0.00000000 0.0
0s
14 1 0.00000000 0.0 Dist. 14 2 0.00000000 0.0 Coeff. 200 14 3 0.00000000 0.0 14 4 0.00000000 0.0 Ratio 1.00 14 5 0 .00000000 0.0 14 6 0.00000000 0.0 14 7 0.00000000 0.0 14 8 0.00000000 0.0 14 9 0.00000000 0.0 14 10 0.00000001 0.0 14 11 0.00000058 0.0 14 12 0.00004243 0.0 14 15 0.00212157 0.2 14 14 0.06527893 6.5 14 15 0.93255622 93.3 32
TABLE IX
Theoretical Data for Countercurrent Extraction of Bromo Complexes of Pd and Pt on a 15 Stage Craig Apparatus.
Pd
Transfers Tube R Fraction of Solute Percent Dist. 14 1 0.00001607 _ 0.0 Coeff. 1.20 14 2 0.00027002 0.0 14 3 0 .00210614 0.2 Ratio 1.00 14 4 0.01010945 1.0 14 5 0.03336119 3.3 14 6 0.08006685 8.0 14 7 0.14412033 14.4 14 8 0.19765074 19.8 14 9 0.20753328 20.8 14 10 0.16602662 16.6 14 11 0.09961597 10.0 14 12 0.04346879 4 .3 14 13 0.01304064 1.3 14 14 0.00240750 0.3 14 15 0.00020636 0.0
Pt
14 1 0.00000000 0.0 Dist. 14 2 0.00000004 0.0 Coeff. 3.50 14 3 0.00000080 0.0 14 4 0.00001118 0.0 Ratio 1.00 14 5 0.00010758 0.0 14 6 0.00075306 0.1 14 7 0.00395356 0 .4 14 8 0.01581424 1.6 14 9 0.04843111 4 .8 14 10 0.11300593 11.3 14 11 0.19776038 19.8 14 12 0.25169503 25.2 14 13 0.22023315 22.0 14 14 0.11858708 11.9 14 15 0.02964677 3.0 33
TABLE X
Theoretical Data for Countercurrent Extraction of Bromo Complexes of Ir and Rh on a 15 Stage Craig Apparatus.
Ir
Transfers Tube R Fraction of Solute Percent Dist. 1 0.00000575 0 .0 Coeff. 1.50 15 2 0.00009515 0 .0 15 5 0.00085789 0.1 Ratio 1.00 15 5 0.00575819 0.5 15 5 0.01828055 1.8 15 6 0.05118558 5.1 15 7 0.10758951 10.7 15 8 O .17198522 17.2 15 9 0.21067955 21.1 15 10 0.19665515 19.7 15 11 0.15765590 15.8 15 12 0.07007526 7-0 15 15 0.02552565 2.5 15 11+ 0.00528255 0.5 15 15 0.00052825 0.1
Rh
15 1 0.00026680 0.0 Dist. 15 2 0.00298815 0.3 Coeff. 0.80 15 3 0.01553850 1.6 15 5 0.05972287 5 .0 Ratio 1.00 15 5 O.IO959031 10.9 15 6 0.17502550 17.5 15 7 0.21002939 21.0 15 8 0.19202687 19.2 15 9 0.13551881 13.5 15 10 0.07169003 7.2 15 11 0.02867601 2.9 15 12 0.00835211 0.8 15 13 0.00166852 0.2 15 15 0.00020535 0.0 l5 15 0.00001173 0.0 IV. CONCLUSIONS AND SUGGESTIONS FOR FUTURE WORK
The simultaneous determination procedure described here should be suitable for the analysis of receiving solutions after the distilla
tion of osmium and ruthenium as tetroxides. Since the other platinum metals, particularly palladium and rhodium, interfere, some preliminary
separation such as the above mentioned distillation is required before
this method may be used.
The molar absorptivity of the complex formed between ruthenium
bromides and thiourea is rather low compared with the value reported by 1^ Ayres and Young . This decreases the sensitivity of the method. Further
work may reveal conditions which would increase the intensity of the ruth
enium color without adversely affecting the determination of osmium. It
also would be interesting to see if some thiourea derivative could be used
for a simultaneous determination of osmium and ruthenium.
The solvent extraction procedure appears to be an excellent and
rapid method for the separation of osmium and ruthenium. What is needed
to make this method more useable is a suitable method for the determination
of osmium and ruthenium in the presence of 4-methyl-2-pentanone.
The ease of separation of osmium and ruthenium by solvent extraction
makes the possibility of separation of mixtures of osmium and ruthenium
with other platinum metals look attractive. Further work on the counter-
current extraction of bromo complexes of the platinum metals is recommend
ed. Mixtures containing osmium, iridium, and ruthenium, or osmium,
palladium, and ruthenium, or osmium, rhodium, and ruthenium might be
readily separated in a 15 or 20 stage Craig apparatus. With additional
stages, perhaps mixtures of four or more platinum metals may be separated.
3^ V. BIBLIOGRAPHY
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35 36
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Harry Edward Moseley was born in New Iberia, Louisiana, on
October 18, 1929* He received his elementary and secondary school education at various schools in the Philippine Islands and the United
States.
In September, 19^6, he entered Louisiana State University, where he was awarded a Bachelor of Science in Chemistry in February,
1951 end a Master of Science in Chemistry in August, 1952.
In 1952 he entered the United States Air Force as a second lieutenant and was discharged in 195^- with the rank of first lieutenant.
His service time was spent at Wright-Patterson Air Force Base, Dayton,
Ohio. In 195^ he was employed by the Lion Oil Company in El Dorado,
Arkansas. He remained with the company when it was merged with the
Monsanto Chemical Company. He married Joyce Sinclair Goldstein of El
Dorado, Arkansas in 1955 and has two children, Elinor and Edward. In
I9 6 I he resigned from Monsanto to join the faculty of Louisiana Poly technic Institute in Ruston, Louisiana. At present he is on sabbatical leave from that institution. He is a member of Alpha Chi Sigma, Phi
Lambda Upsilon, and Sigma Xi. EXAMINATION AND THESIS REPORT
Candidate: Harry Edward Moseley
Major Field: Chemi s try
Title of Thesis: The Separation and Determination of Osmium and Ruthenium
Approved:
Manr Professor and/Chairman U3 Dean of the Graduate School
EXAMINING COMMITTEE:
Date of Examination:
September 50, 1968