DECOMPOSITION OF S

DISSE RTATI ON

PRESEN TE D IN PA RTIAL F%LFI L LM EN T O F TH E REQ %IREM ENTS FO R THE D EG REE O F DO C TO R O F PHI LO SO PH Y IN THE G RA D%A TE S C H O O L O F THE O HIO STATE %N I%ERSITY

BY JACOB CORNOG

1921

TABLE O F C ONTE NTS

R eview of th e Lit er atur e P ertin ent t o th e Form ation and f t t po sition o Di hiona es .

Aim s of th e Pr es ent Work

on of B ar i um Dithionate

a x e e t al of V riou s (E p rim n . )

G en eral C on sider ation s an d Proc edur e

T he D ecompo s ition of Dithion at e

of Some Other Dithionat es

th e Lit eratur e

P LYT H I O A T E I . T H E O N S H Dithionic acid , 2 8 2 0 6 , the first ember of this remarkable

1 - group of acids , was discovered in 9 by Welter and Gay Lus 1 5“ sacl H 1 842 Lan lo i s z ; trithionic acid , 2 S 3 0 6 , in , by g ; tetrathionic H 1 843 G elis 3 a acid , 2 8 4 0 6 , in , by Fordos and ; pent thionic acid , H 8 0 1 845 Wacken roder“ hexathi 2 5 6 , in , by ; finally potassium K 1 88 5 onate , Q S 6 , was discovered in 8 by D ebu s as a part of ’ roder his classic investigation of Wacken s solution . Dithionic acid was originally called hyp osulfu ri c acid (u n ters chw efelsau er in the German ) . The present nomenclature was suggested by ' 6 Fordos and Greli s in 1 847 to simplify the naming O f th e i n creas ing number of polythionic acids which were being discovered lfu ri oc about that time . However the name hyp osu c persists i o ll cas na y as late as 1 880. The Obviously outstanding feature of these acids is the piling ” up of sulfur atoms in the molecule , increasing in number one atom at a time , from dithionic acid with two to potassium hexa to thionate with six sulfur a ms to the molecule . This is a p rom ising field for investigation of valence and molecular structure . Indeed the molecular structure of the p olythi on ates has already f been the aim O much investigation , but apparently , thus far, results are more speculative than real . Without attempting a complete discussion of the results already attained in this field , O the following facts and bservations are mentioned . 5 ol hi on Debus experimentally found that all the p yt ates , save dithionate , are intermediate products between sulfide and , on the one hand , and free sulfur and o n the other , as represented by the equation

2

The sulfur in the sulfur dioxide represents a higher state of oxidation than does the sulfur in any of the polythi on ates save t O the dithiona e . S apparently the W hole series of p olythionates occurring between the first and last products of the above equa “ tion represents a running down proc ess in the degree of oxida tion of the sulfur . This opinion is in harmony with the findings 7 of Thomsen in the matter of heats of formation . He found for

5 kOle er 1 ol thi onates o the ew s i es 9 3p y , that the heats of formati n vary uniformly% and inversely as the number of sulfur atoms in e c o c s Of th respe tive m le ule . From the decreasing heats forma tion with increasing number of sulfur atoms in the molecule it would seem that there is an upp er limit to the number of sulfur I n atoms that may occur a single molecule , and further that the processes of formation and decomposition are not spontaneously reversible . A further characteristic action of the p olythi on ates occurs on their spontaneous decomposition in water solution under the influ ence of heat . Although in none of them is the sulfur found

' lf in a state of oxidation corresponding to that of su ates , yet all of them on spontaneous decomposition in water solution yield o n sulfates as e of the chief products , along with sulfur dioxide ol th i and in siome cases sulfur . This phenomenon in which a p y onate breaks down into products representing b oth a higher and a lower state of oxidation of the s ulfur th an is found in the “ parent substance is alluded to in the present work as autoxi da ” on e tion . Such in brief, in the opinion of the author, are or two o f the more salient aspects of the general subj ect of p olythi ol thi on ates on ates . Since the formation of one or more of the p y is a very frequent factor in actions involving sulfur dioxide and ’

in %iew of the wide importance of sulfur dioxide , it was thought desirable on the part of this l aboratory to attempt a series O f studies of this very interesting and important family of com pounds in the hope of amplifying present knowledge of the sub j ect and p erhaps ultimately formulating a rational theory of f mol ecular structure . In pursuit O this aim the following studies

have been completed . l Z The Action of on the S u fides of Iron , inc , and

Manganese . C Henderson and Weiser . Journal of the American hemical

5 2 39 . Society . 3 ,

’

Preparation and D ecomposition of Some Thiosulfates .

Henderson and Hummel . (In Preparation . )

a Preparation and Decomposition of Tetrathion tes .

Henderson and Scott . (In Preparation . )

The present work contemplates a study of the dithionates al ong

lines indicated in the title . It is hoped that other papers will be

forthcoming . 6 II I O F T H E LI T T TI T T O T H E . A REV EW E RA U RE PE R NE N

F ORMA TI ON A N D D E C O M PO SI TI ON O F D I T H I ONA T E S .

A survey of the literature shows that the preparation , analysis , crystallography , and determination of chemical and physical properties have been rather thoroughly though by no means exhaustively studied. Salts of nearly all the common and many of the rare metals have been prepared . Many double salts

e O . are known though , singularly , no acid salts have be n bserved i d In the resume of the literature which follows , there are nclu ed ,

as being pertinent to the present work , only those citations which bear on the formation or decomposition of dithionates . An ex tensive bibliography covering the entire field of dithionates is to be found in the files o f the C hemistry Department of Ohio State bibli University . The reason for this exclusion is that the ography is large and much of it without significance in the

- present work . Reference works such as Gmelin Kraut or

’ “ ” ’ “ ” Abegg s Handbuch or Hoffman s Lexikon con tain rather complete records of papers published on dithio nic acid and its

various salts . The partly accidental discovery of dithionic acid was recorded

1 by Welter and Gay - Lussac as occurring in the following man

ner . M . Welter , a manufacturer of bleach , in attempting to recover the that h ad been used in making

chlorine, treated the spent material with sulfur dioxide . As a “ ” result he Obtained a neutral bi sulfite which he b elieved to be a at the b se of manganese dioxide . At this point Welter con

s ult - ed Gay Lussac , with the ultimate result that dithionic acid n and the manganese , barium , calcium , stro tium , and potassium

‘ salts were prepared and described . The mode of preparation ,

more fully discussed later , was by the passage of a stream of

sulfur dioxide through a water suspension of manganese dioxide ,

whereby manganese dithionate , along with manganes e sulfat e , o was formed . Barium dithi nate was prepared by doubl e de composition between and manganese dithi n i onate . Dithio ic acid was prepared by treating barium dith

onate with an equivalent of sulfuric acid . After removal Of the

resulting by filtration , the remaining Water s olu tion of dithionic acid was concentrated by evaporation under re duced pressure to a density of Attempts at further con centration resulted in the decomposition of dithionic acid into

sulfuric acid and sulfu r dioxide . 8 In 1 82 6, H eeren published the results of a rather ext ensive

work on dithionates . He found that high yields of manganese dithionate were promoted by the fineness of the m anganese di ox ide used in the suspension , the purity of the manganese dioxide

used , and b y th e maintenance of a low temperature during the

time in which the action occurred . Heeren prepared some i twenty salts , giving much attent on to crystalline structure . He Observed that dithionic acid an d many of its salts in water solu tion spontaneously decompose into sulfur dioxide and the cor

responding sulfate . Jacquelain 9 learn ed that a water solution of sulfur dioxide in a tightly stoppered bottle after standing two years at room

temperature contained sulfurous , sulfuric , and dithionic acids . Pean de Saint Gilles 1 0 found that dithionates in small quantities

were formed by the action of permanganate on sulfur dioxide , m ’ 1 1 also that dithionates are not oxidized by per anganate . Hauer prepared sodium dithionate by neutralizing a solution of sul f ro u u s acid with sodium carbonate . After this the solution was

heated with finely divided manganese dioxide . When the excess r o dithi manganese dioxide had been removed , c ystals of s dium eli 1 2 onate were obta ined by concentrating the solution . G s first completely described the action O f sulfur dioxide on ferric

hydroxide as a general method for preparation of dithionates . This is one of th e best methods for preparation on a laboratory Z 1 3 o scale . Rathke and schiesche p repared sodium dithi nate N 2 N a N a S e a S 0 . according to the equation , S O 3 Se , 2 2 6 Sokolow and M ultsch ew ski “ show that under proper conditions 2 N I o 2 N aH O I a O . the following action ccurs . S 3 2 H , S , 6 Kluss 1 5 studied the salts of m etals having more than one valence and of metals j ust above and below hydrogen in the o o electrochemical series . E xcept in the matter of the comp siti n n of the salts prepared he records no experime tal data . As bear ing on the present work it may be gathered from the work of Kluss:that

o e 1 . Heating solutions of dithi nic salts , xcept those of the e alkali and alkaline earth metals , causes spontaneous d composi

tion into sulfur dioxide and the corresponding sulfate . d 2 . The temperature at which ecomposition begins varies in a general way with the p osition of the m etal in the electroch em e ical series , i . . the higher the position in the series the higher o the temperature at which dec mposition occurs .

8 3 . Dithionates of the alkali and alkaline earth metals can be

boiled i ri s aturated solutions without decomposition .

4 . Of metals having more than one valence, the ous “ i ” decomposes as already outlined , while the c salt decomposes “ ” “ ” with the formation of both ous and ic sulfates along with s liberatio n of sulfur dioxide , and where possible a basic alt may

be formed . The sequence of these actions is not to be deduced

from the article . Berthelot 1 6 found that bromine water decomposes all the ol i n 1 7 p yth o ates into sulfates . Antony and Lucchesi found that ruthenium dithionate is formed when sulfur dioxide is led

re through a solution of ruthenium sulfate . They say that the sulting ruthenium dithionate is decomposed by potassium N O permanganate into sulfate . O other workers have bserved the o s 1 8 decomp ition of dithionates by this reagent . Nabl Obtained barium dithionate in small quantity by treating barium sulfite

with sulfur dioxide . The careful work of C arpenter1 9 shows that c obaltic hydroxide as well as manganic and ferric hydroxides can be used with sulfur o dioxide to form dithionates . He prepared ferrous dithi nate in quantities as required by the equation

2 F e OH 3 F e O S H O F e O ( ) 3 so , s2 6 , S

Obtaining 9 6% of theoretical yield along with a small quantity of 5 sulfate . With manganic hydroxide he obtained 7 % and with cobaltic hydroxide 35% of theoretical yield as required by equa

tions corresponding to the one j ust set forth for iron hydroxide .

The sulfur not found in the dithionate was recovered as sulfate . NO dithionate was Obtained with a similar action between nickelic

hydroxide and sulfur dioxide . C arpenter points out that the yields of dithionate with these metallic hydroxides varies di “ ” rectly as the heat absorbed in their reduction from the i c to “ ous hydroxide . For this reduction ferric hydroxide absorbs 546 44 o calories , manganic hydroxide 8 cal ries , cobaltic hydroxide 2 2 5 i ve calories , while nickelic hydroxide g s Off 1 3 calories in this

process .

2 0 2 Foerster and F ries sn er and F ri essn er 1 prepared s odium 2 2 dithionate by the electrolysis of sodium s ulfite. Baubigny de scribes the formation Of dithionates by boiling silver sodium sulfite and the same author 2 3 prepared dithionate by the action sulfite of sodium on copper sulfate .

9 Numerous theories have been advanced during the past centu ry seeking to explain the mechanics of the action of sulfur dioxide on manganese dioxide to form both dithionate and sulfate con a currently . Only few of the more recent ones are mentioned .

2 5 J . Meyer , from an investigation somewhat similar to that of

‘ r C arp enter , formulated a the o y that required that a molecule of

2 6 sulfate be formed for each molecule of dithionate . Marino demonstrated that the proportion of sulfate to dithionate varies

with temperature , thus rendering the theory of J . Meyer un

. o M n 2 tenabl e Marino thinks the chief reacti n is O2 + S O 2 M ni S 2 O6 and that the sul fates always found are to b e accounted

M n for by the secondary action S 2 0 6 In ’ ’ m H an db h Abegg s uc , the chemical induction theory of Luther chilow 2 8 i 2 9 and S and S ch lOW is applied to the action in question . ” The chemical induction theory supposes that two substances A (the actor) and B (the acceptor) , which under ordinary con diti on s reacts very slowly , may be caused to react rapidly when

h - a third substance C (t e inductor) , which reacts readily with A , is placed in the system along with A and B . That is , the actor A B n o and the acceptor , which ordinarily do t react , may be caused a to react by the presence of the inductor C , which itself re dily e and simultaneously acts on A . Abegg points out that this th ory

fits the case of manganes e dioxide and sulfur dioxide very nicely . t The actor is the oxidizing agent manganese dioxide , the induc or ” o is sulfur dioxide , and the acceptor the manganese dithi nate . The increasing amounts Of manganese sulfate formed with rising temperature are explained by saying that h eat accelerates the m induced action . While the foregoing theory is in har ony with u experimental facts , yet it s eems to the a thor that a simpler

m . explanation , which fits the facts equally well , may be for ulated Such an explanation will be attempted later when the exp eri mental facts Of the present work have been set forth .

O F O K I I I . S C O PE AND A I M S TH E PRE S EN T W R The general aim of this work is to attempt a contribution to l hi o a existing knowledge of po yt n tes , as a part of the general program of studies in this field being conducted in this labora decom osi tory . The specific aim is to study the formation and p f tion of the dithionates with the hope that such knowledge may l ead to fuller understanding of their mol ecular structure and

1 0 i chemical behav or . As the formation of dithionates has already a received considerable experiment l attention , the result of which is available, little attention is given to formation in the exp eri mental part of this work . On the other hand , while one frequently reads that dithionates in water solutio n decompose into sulfur dioxide and the corresponding sulfate , yet a search of the literatu re fails to reveal a single quantitative study of this matter . Indeed even qualitatively no greater substantiation is generally Offered than the bare statement of fact . C oncerning the alkali and alkaline earth dithionates Kluss 1 5 records that their o saturated s lutions are not decomposed on boiling , while Abegg under barium dithionate says that this s ubstance is decomposed 1 0 d at 55 into the sulfate and sulfur ioxide , giving a citation to r i D e eg b u s as authority for the statement . The citation to D eregibus is incorrectly recorded by Abegg and could not be Ob tain ed from other sources . In view of the foregoing , it is the purpose of the experimental part Of this study to attempt a quantitative study of the decomposition in water solution of a few o f th e characteristic dithionic salts , particularly those of the alkali and alkaline earth metals . The u ltimate aim is the fo rm u Of O f lation a reasonable theory of the course the decomposition . The decomposition of barium dithionate was first and m ost ex i e tens vely studied . All salts subs quently studied were found to decompose substantially as barium dithionate . Only minor dif feren ces were noted ; these are spec ifically mentioned with the work on individual salts .

Since , at the present time , dithionic salts are not obtainable from commercial sources , it was n ecessary to prepare all salts used . Barium dithionate is the parent substance from which all other dithionates are usually made , so mention is here made of the work done in its preparation .

R F IV . PRE PA A TI ON O BARI U M D I T HI ONA T E i Two methods of preparat on of barium dithionate were used , 1 the original method of Welter and Gay - Lussac and the method li ” G e s . of Only a brief outline here recorded of the processes , ‘ is which though somewhat long and tedious are not particularly difficult . A fuller description may be found in the literature al a . re dy me,ntioned The quantities of materials mentioned are about as large as can be conveniently manipulated with ordinary laboratory apparatus . 1 1 1 1 A - . METHOD OF WELTER AND G Y LUSSAC

a Prepar tion of Manganese D ioxide Suspension .

9 0 to 1 00 grams of potassium permanganate is dissolved in

00 - about 5 cc . of water contained in a two liter E rlenmeyer flask . The solution i s heated to boiling and a quantity of methyl alcohol sufficient completely to reduce the p erm anganate . to a more or less hydrated manganese dioxide is slowly added . The action is vigorous ; no trace Of pink color remains in the supernatant liquo r when reduction is complete . The physical condition of the a precipitate varies consider bly from time to time . In freeing the precipitate from impuriti es filtration by suction is undesi rabl e because of difficulty in again getting the precipitate in a sus d pended condition . Washing by ecantation when the precipitate th settles readily is satisfactory . O rdinarily e precipitate doeS not settle readily ; resort may b e had to the expedient Of diluting the suspension to the capacity of a large beaker and then separat ing the solid and liquid portions by filtration through filter paper R on an ordinary funnel . epeating the process six to ten times is usually sufficient . The manganese dioxide suspension thus prepared is slowly added to a well cooled saturated solution of s ulfur dioxide , through which a stream Of sulfur dioxide is slowly passed:The action is rapi d and i s accompanied by considerable evolution of heat . The solution is kept near air is excluded and a good excess of s ulfur dioxide is maintained until solution is compl ete . In practic e it was found to make no practicabl e difference in the final yield whether the above procedure was observed or the sus pension was first placed i n the flask and kept cool whil e sulfur o dioxide was bubbled through until solution was c mplete .

When the su s p en smn 1 s completely dissolved there is present . in the solution sulfur dioxide , manganese sulfate and manganese

con centrated . b ari um dithionate . The addition of a hydroxide soluti on precipitates everything but the dithionate , all dithionic

- salts being water soluble . The manganese dithionate is con verted into barium dithionate by the barium hydroxide . After filtratio n the excess barium hydroxide is precipitated by carbon

u re dioxide . When the barium carbonate th s formed has been moved by filtration the solution is boiled to remove any barium r bicarbonate which may be present . When thi s has been e mo ved the solution remaining is concentrated to a density of

1 2 ab out to and crystals are allowed to form . The con centration of the original barium dithionate solution may be ao i 0° celerated by boiling while very dilute , but concentrat on at 5

° to 60 until crystals j ust begin s to form on the bottom of the vessel is a safer procedure . If at this point the crusts which gen

“ ” erally form are washed down with a minimum quantity of hot water and the solution is then allowed to co ol overnight a good

r - Y 1 yield of well formed fi st crop crystals is obtained . ield , 5 to

2 5 grams . dithi Although , theoretically , a saturated solution of barium onate is not affected by temperatures up to yet in practice it frequently happen-s that an app reciable quantity of a very o i d finely divided white powder , pr bably barium sulfate , s forme when concentrated s olutions of barium dithionate are boiled or filtered under reduc ed pressure during the process of prepara tion . This may be partly accounted for by remembering that barium sulfate has an appreciable though slight solubility . When i the solut on is much reduced in volume precipitation results . o However, there is a high degree of pr bability that concentrated barium dithi onate solutions slightly decompos e at temp eratures below It was found in the present work that apparently over a considerable range of temperature decompos ition d o es not o i ccur consistently . There s evidently some factor ope rating with which we are not acquainted .

The barium sulfate fo rmed during concentration of barium a dithionate is usu lly too fine to be removed by filter paper . It may be removed by diluting the solution to less than saturation

a o - at room temper ture and all wing it to stand twenty four hours , o when all solids will settl e to the bott m . It may be fu rther Ob

i r - served that n water solution , fi st crop barium dithionate

- crystals yield a light straw yellow solution . After tw o or three recrystallizations of the barium dithionate the solution i s entirely transparent and colorless .

2 . METHOD OF C ELIS

The ferric hydroxide suspension may be prepared by di ssolv ing 1 2 5 gram s of ferric sulfate in a liter of water and adding sufficient sodium carbonate to cause complete precipitation as ferric hydroxide . The ferric hydroxide may be purified in a

manner similar to that described for manganese dioxide . The

1 3 reaction between ferric hydroxide and sulfur dioxide in its gen eral aspects is similar to that described for manganese dio xide i and sulfu r d oxide . However , the reaction for ferric hydroxide

is not instantaneous , but is a matter of hours and days . This o pr cess has the advantages of using cheap er materials , giving

better yields , and being success fully conducted at room temperatures witho ut the use of artificial cooling The follow ing manipulation to bring about action between ferric hydroxide d e and sulfur ioxid has been employed with satisfaction . The ferric hydroxide suspension is placed in a la rge E rlenmeyer flask

- provided with a motor driven stirring device . The air is ex

cluded as much as possible , while th e sulfur dioxide is slowly o bubbled thr ugh the suspension . The stirring and passage Of sulfur dioxide may be discontinued overnight or for a few days d at a time with apparently no etrimental results . The stirring and passage of sulfur dioxide are maintained continuously or i n termittently until the s olution of ferric hydroxide is app roxi

mately complete . Following the solution of the ferric hydroxide the procedure is the same as that already described under the

n - o method of Welter a d Gay Lussac , except of c urse one must test for the complete removal Of iron and not manganese after the

d u 2 5 40 . barium hydroxi e precipitation . Us al yield to grams

C C 3 . PREPARATION OF DITH IONI A ID AND DITH IONIC SALTS FROM BARIUM DITH IONATE

With barium dithionate as a mother sub stance dithionic acid and the dithionic salts of metals having soluble sulfates are readily obtained by treating sulfuric acid or the sulfate with an of c equivalent barium dithionate . Dithioni salts of metals hav ing insoluble sulfates may be prepared by treating dithionic acid l th . with an excess of e meta lic carbonate , oxide , or hydroxide

E X P E R I M SI TI O F I O S I TH I T S . % . D E C O PO ON VAR U D ONA E (

M E NT A L . )

1 C C . GENERAL ONSIDERATIONS AND PRO EDURE

As a first approach to the experimental study of decomposi

' tion it was necessary to learn h ow decomposition could be i n an sured , whether it w as complete or incomplete , d if incomplete whether there existed a qu antitative relation between the prod u cts of decompos ition that would allow the formulation Of a

1 4 reasonable theory of th e mechanics of decomp o sition . In the earlier stages many results were apparently indeterminate and w as de inharmoniou s . In none of the salts studied complete ‘ ° composition secured at Some salts required ab out 1 80 at to insure complete decomposition . Working temperatures

° above 1 00 nec essitated working in closed systems under pres s sure . C onsiderable time was lo t finding glass containers that

° were sufficiently inso luble in water at 1 80 to prevent vitiation of

results from dissolved glass . Pyrex glass and Jena combustion

- s as tubing were the most resis tant o f glasses tried . Sealed tube

well as pressure bottles of various types were tried . Under the conditions of the experiments the glass in mo st commercially Ob tain ed pressure bottl es w as so soluble as to make them worthless . Bottles in which “ citrate of magnesia ” is usually sold at drug n stores were usually good for two or three b eati gs . A new type of pressure bottle was developed and found satisfacto ry under c e - onditions us d . The glass part was a straight sided cylinder of

heavy pyrex glass , sealed Off and flattened at the bottom and

a flared at the top . The top was ground down so as to m ake

o . tight j oint with a plate of thick glass , which was used as a c ver

More conveniently , where it will not interfere with results , a

rubber gasket may b e inserted between cover and pres- sure bot

a s tle . For making g skets that would withstand the condition o inv lved , it w as found that the inner tubes of autom obil e tires o were more suitable than any rdinary gasket material tried .

Leather gaskets are completely destroyed . For holding the cover on the press ure bottle du ring heating an iron frame with a clamp O ing device perated by a screw was used . It w as found expeditious to heat sealed tubes and pressure

bottles submerged in water in an autoclave . By slowly heating and cooling the autoclave the difference in pressure on the inside s and outside wall of the pressure bottle was never very great . By this expedient it was found practicable to use ordinary thin a 50 o f w lled cc . E rlenmeyer flasks pyrex glass as pressure bot s tles . They were succes fully subj ec ted to a temperature of 330 which corresponds to a pressure of pounds per square inch .

° 180° to 1 9 0 In the matter of rubber gaskets , is about the upper limit of temperature which can be employed without danger of

The usual procedure was to plac e the solution under investi ation r ‘ g in a pressure bottle . After the p essure bottle (or sealed 1 5 tube ) was closed it was placed in the a utoclave , then du ring two d about hours was slowly heate to the desired temperature .

This temperature was maintained about six hours , after which about an h our was usually consumed in slowly reducing the temperature to Then the source of heat w as removed and

o O the autoclave allowed to c ol overnight . On pening the bottles w r ere unifo mly found to have a negative pressure .

2 . DEC OM POSITION OF BARIUM DITHIONATE

C . A . IN PRESEN E OF AIR Fifty cubic centimeters of normal barium dithionate was placed in a pressure bottle of 380 cc . e 1 5 capacity and h ated at for an hour and a h alf . When the o O bottle was pened a white powder was bserved , which weighed s gram after being collected on an alundum crucible . Th ere was O Of h a strong dor sulfur dioxide in the b ottle . T e white powder was thought to be barium s ulfate , as would be inferred a s o f from the literature . An an ly is the powder in question Of yielded the following percentages barium and sulfur .

r Th eo .

N N r O . 1 . o . A v e a e. i n a . 2 g B S O A

From the foregoing it is evident that the solid formed in decom posing barium dithionate is too high in sulfur and too low in barium to b e pure barium sulfate . Further a . little computation sho ws that under the conditions of this experiment only about o f s one third the dissolved dithionate was decompo ed .

‘ It w as next desired to ascertain the nature of the products of d r decomp osition which , as above indicate , a e not solely sulfate a and sulfur dioxide . C onsequ ently gr ms of the solid residue , in nitric acid and bromine water , was digested overnight s an on a hot plate , the purpose being to di solve y free sulfur, sul o i fites , thiosulfates , or other sulfur comp unds convert ble to sul fates Or s ulfuric acid by this method . The residue lost of its weight in this proc ess . The addition of to the filtrate resulting from the digestion of the s olid residue in nitric acid and bromine water yielded a. precipitate of ba ri um sulfate which weighed grams , or almost exactly the same as the weight lost by the original solid res idue in the process of

1 6

Summarizing findings to this point, it may be stated that under the conditions o f the experiment the end products of deco mposi of u tion barium dithionate are bari m sulfate , barium s ulfite, sul furi c an d s 1 00 acid , ulfur dioxide . In decomposition at 8 the

quantity of sulfur dioxide found as an end product i s negligible . The figures in the table represent p erc entages of sulfur on the n a original weight of barium dithio ate t ken as the sample .

Barium dithionate contains sulfur . Hence it is intended

that on reading the figures etc . down the o Ba s n c lumn headed S as S O 4 the reader hould u derstand that the weight Of sulfur fo und in the end product barium sul fate i n the different determinations corresponds to t r e c . of the weights of the espective original samples . Kn owing that barium dithionate is sulfur it might b e correctly inferred that approximately half the sulfur in the original barium dithionate had been decompos ed into barium

sulfate . This same mode of setting forth results is employed

throughout the p aper .

T A BLE S E N D D XP D 1 . N o . DISTRIBUTION OF ULFUR AMONG PRO UCTS E RESSE K AS PERCENTAGE OF WEIGHT OF ORIGINAL SAM PLE DITHIONATE TA EN .

L en gth of T o ta l of of time of B aS gO s i n ori g T o ta l S dec o mp o aecom S as S as S as S a s tri a l s o lu r eco v

si ti on p o s ed B aS O i BaS O g S O H fi o i ti o n er ed

°

T t a w h e s t e . 1 50 C . e e e t , mp ra ur ich d compo i occurr d

1 % hr . 1 5 6 6

° 1 80 2 T emp er atur e at w hich d ecompo sition occurr ed 6 6 6 0

Observations on Foregoing Data .

of Of r a 1 . The constancy percentage sulfur ecovered s barium

sulfate is notable . It is Slightly less than half the sulfur

originally in the b arium dithionate . If to the percentages of sul fur in barium sulfate are added the percentages in the barium Of sulfite column the result , within the limits experimental error,

is exactly half the sulfur in the original sample .

1 8 o 2 . The elimination of sulfur dioxide as a significant fact r at the higher temperatures empl oyed and the corresponding in

is o crease in the quantity of s ulfuric acid formed worthy of n te .

B 2 H z 2 Ba 2 a 0 0 S O 2 H , S O . 3. SO The equation z 6 2 2 4 2 4

° fi o 1 80 H ts . 2 2 0 the results of decomp sition at fairly well f Thus , it appears that under the conditions O the exp eriment a four per cent solution of barium dithionate is decompos ed into

a equimolecular quantities of b rium sulfate and sulfuric acid . It is t o be recalled that no effort was made to exclude air from the pressure bo ttle when the sample was being prepared for decomp o

' iti n o s o . A s later devel pments Show , this is a factor in tracing the course of the reaction .

B . DEC OMPOSITION OF BARIUM DITHIONATE IN ABSENCE OF

A IR . It is pertinent to inquire as to the source of oxygen rep re a sented in the bove equation . Measurement of the volume of air held in the pressure b ottle during the time of decomposition sho wed there was present an excess of oxygen theoretically re quired by the equation for the quantities of dithionate decom posed . TO learn if the oxygen of the air present in the pressure bottle w as the source of the oxygen required by the above equa tion a second series of exp eriments , similar to the first , was per rm fo ed , with these differences . The container was very much smaller and the air contained therein was replaced with nitrogen .

The s tage in the experimental work immediately following was beset with som e trouble from breaking and soluble pressure bot

- tl es along with non concordant results . The work did not a with previous experience . The chief reason for this , % h rmonize af r i in i on e te el m at of p o or pr ssure bottles , was found to arise o from the fact that the exclusion of air introduced an entirely f vi a O s . new factor as one the end product , , free sulfur For e some time its presenc e was not suspect d . After it was known to be present some difficulty in the matter of separation and

estimation w as encountered , as ordinary methods of oxidation to s ulfu ric acid gave only pa rtial oxidation after prolonged di

gestion . The entire recital of exp eriences encountered in the course of discovering the presence of free sulfur and the evolution of the methodology for its separation and estimation need n ot e be recounted here , except in a very sk tchy way . The presence of free sulfur w as first established by noticing a flake of dark

1 9 colored substance in the solid residue c ollected on the alundum u cr cible . When this flake was placed on a foil and heated it Of an manifested the prop erties melting d burning sulfur. The earlier attempts at recovering free sulfur by oxidation meth o ds w as failing, resort had to ignition of the solid res idue and estima f h tion of free sulfur by di ference . T e s ulfuric acid present was i a as a est m ted lready indicated . By taking the values Of sulfur O fo r thus btained barium sulfate , sulfuric acid , and free sulfur and ignoring small quantities of barium s ulfite and sulfur dioxide the equation

B H 3 aS 0 . 2 0 eBaso 2 H o s 4H 2 6 2 , 2 s , , O

fits the facts fairly well . A comparison of the percentages . of sulfur theoretically required by the various m embers Of this equa tion , with the c orresponding percentages experimentally ob t in d a e , reveals the following . E ach quantity represents a p er centage of sulfur on the original weight of the dithionate s ample .

H : 3B QH 3B aS 2 0 6 . 2 2 0 aS 0 4 ZS O I S

e et l 1 9 2 9 6 40 3 2 Th or ica 3 60 . x e t l 2 2 2 E p erim n a 8 3 6 . 60

If the s ulfite sulfur is added to the sulfate sulfur the showing is still b etter . These first results , while not overly reli able , be cause they show a rather singular relation among the quantities of sulfur found in the products on the right side of rt a the above equation are retained . Fu her they harmonize f irly well with later results .

C ONFIRMATION OF FOREGOING RESULTS . All attempts at oxida tion of free sulfur found in the solid residue gave non - concordant Of e results . Indeed th e oxidation sulfur s ldom advanced beyond the stage where small pieces of free s ulfur were not vis ible to to the eye . The method finally employed was extract the free s ulfur from the solid residue with aceton e and weigh the extract o o as free sulfur , acc rding t the m ethod described for the deter u i rcu lar th minati on of free sulfur in r bber by C 38, of e U . S . s Bureau of Standard . The chief desideratum sought in the following series of experi ments w as to learn whether or not the decomposition of barium dith ionate in the absence o f air gives the three chief products s barium sulfate , sulfuric acid and free ulfur in the quantitative

20 relation represented in the last mentioned equation . The rela tively small quantities of barium sufite and sulfur dioxide were temporarily ignored .

- The pressure bottl e used during decomposition w as a 60 cc . E e 4 rlenm yer flask of pyrex glass . In each instance a % solution ° of the dithionate in the presence of nitrogen w as heated at 1 80 o for six h urs . After removal from the autocl ave concentrated hydroc hloric acid was added to the contents of the press u re bot tle to insure the solution of any b arium sulfite which might be present . The s olid residu e, consisting of barium sulfate and free sulfur , was next collected , washed and dried on an alundum crucible . After this the free sulfur was separated from the barium sulfate by extraction with acetone . The sulfuric acid formed by the decomposition of the dithionate w as found in the filtrate arising from the coll ection of the original solid residue on the alundum crucible . The quantity of sulfuric acid pres ent was determined in the usual m anner by precipitation with barium chloride . The figures in Table 3 represent percentages of sulfur on the

e weight of the original s ample as in the preceding tables . Sinc barium dithionate contains s ulfur if decomposition into barium sulfate , sulfuric acid , and free sulfur represents the true facts of decomposition , the sum of their percentage sulfur in any 2 a roxi 3 . given analysi s should total 1 9 . %I It does this only pp mately .

T L F S W S A E N D AB E N O . 3. INAL HO ING OF DISTRIBUTION OF ULFUR MONG

PRODUCTS AFTER DECOM P OSITION IN ABSENCE OF AIR .

°

1 T r t n e t . 8 t 6 h s . 0 emp . of D ecompo si ion . Dura io of h a ing

T al v B ec v . t S B ec v B ec . S S o . S o o o

a s B aS O . as H 28 0 4 as fr ee S R ecover ed

* 1 83 8 . 98 .

7 9 9 8 49 7 9 1

T e t n Ba 2 H 3Ba S O 2 11 8 H e e e . 3 O . 0 0 S 0 . h ore . r quir d by q S g c 2 I 2 4 4 2

F e bt e b fe e e i gur s thu s marked w ere o ain d y dif r nc .

2 1 Obs er vati on s on r esu lts O btai n ed i n the for egoin g table 1 . There is a notable constancy in b arium sulfate Obtained . 2 . The variations in results Obta ined for sulfuric acid and free sulfur are too large to be cons idered as checking in fair analytical work . 3 . The results do not satisfactorily fit the hypothetical equa tion that has b een set up . 4 . Small but weighable quantities of barium sulfite have been ignored .

5. Sulfur dioxide also w as ignored ; yet on Opening the pres e sure bottl after heating in the autoclave , in some o f the above determinations a slight but appreciable odor of s ulfur dioxide O was bserved . In others none was perceptible .

In view of the foregoing observations and other variations in the products of decomposition previou sly encountered , it was thought that the equations thus far proposed were untenable . In attempting to fo rmulate a theory of decomposition h armon iz ing with obs erved experimental facts it w o uld appear probable ' ro ee i n that the reaction does not p c d one s tage . The following a ssumptions s eemed promising as a possibl e basis for the ex planation of observed facts . 1 i Assumption . In all cases the primary action s represented

B . 2 H Ba O 2 H by the equation aS 2 O G . , O S , S O 2 Z O

s ulfit i Assumption 2 . Barium e s formed by double decomposi tion between undecomposed barium dithionate and sulfurous acid .

re A s sumption 3. Under the con ditions of experiment the 3H S 2 H 0 action represented by the equation Z O 3 H 2 S O , S 2 s proceeds to an appreciabl e extent . R i ing temp erature woul d dis- place this reaction to the right in accordance with the prin i l h li r c p e of LeC ate e .

ob These ass umptions , if true , account for all the vagari es as sum served and indeterminate results obtained . Are these p tion s tru e % Assumption 1 seems reasonable on its face beside being in ha rmony with the findings of other investigators .

Assumption 2 s eems possible and probable . Only as sumption e o 3 app ears a bit unusual and p rhaps doubtful . H wever,

30 ‘ Jungfl ei sch and B runell found that this reaction proceeds at all

2 2 temperatures between 1 5° and while Lunge 3 1 further states n o that in the pre sence of Sufli ci e t xygen , sulfate is the sole prod

uet . Assumption 3 was experimentally verified for conditions most frequently used in the present work by s cali ng in a glass 1 0 0 . a . tube , of approximately 3 cc c pacity , cc of water saturated i r with sulfur dioxide . Previous to sealing , the a in the tube was replaced with gaseous sulfur dioxide . After sealing, the tube and

° contents were heated in the autoclave at 1 80 for six hours . On opening the tube globules of free sulfur were plainly visible and ob were found to weigh grams . In addition there were served copious quantities of sulfur dioxide al ong with decisive i quantities of sulfuric acid . The sulfur dioxide and sulfuric ac d re were determined only qualitatively . From the experimental sults j ust mentioned and from the findings of Jungflei sch and s ob ec Brunell it would eem that assumption 3 is tenable . The j tion might be raised that there is no assurance that the actions mentioned in assumptions 1 and 3 will proceed simultaneously in the same v essel without materially modifying one or both re

actions . In order to see if the barium s ulfate would modify the reaction

3H S O 2 — H z 3 H 2 S O 4 l S Q O , the following exp eriment was per O f formed . grams of barium sulfate suspended in 1 0 cc .

- a 60 . water was placed in cc pressure bottle . The air in the pres

sure bottle was replaced with sulfur dioxide , the bottl e closed and 1 0° heated at 8 for six hours . The nature o f the con tents of the pressure bottle after being heated is shown by the following

statement of materials recovered . Total solids recovered gram s ; the weight of sulfur recovered from sulfur dioxide : grams ; the weight of sulfur recovered from

2 sulfuric acid grams . The free sulfur recovered weighed

grams . Also it is to be mentioned that the solid residue

lost grams on hydrochloric acid digestion . In view of the ve ry minute quantity involved it is doubtful if this last figure has

any significance . So in a qualitative way it would appear that the presence of barium sulfate does not in any way interfere with the decomposition of sulfurous acid into sulfu ric acid and

free sulfur .

If the assumptions are true , the decomposition of barium dithion ate as measured by the quantity of solid barium sulfate

formed should be a monomolecular reaction . Some effort was

2 3 made to measure the s peed of decomp os iti on of barium dithi _ onate , but without success . It was attempted to carry on the action with a seri es of samples in seal ed tubes . Supposedly by subj ecting them all to the same conditions of heating, a uniform condition of decomposition would be obtained . Then by suc cessivel y removing one tube at a time , after various intervals , and analyzing its contents it should have been possible to arrive at the amount and rate of decomp osition . This was not realized in practice . %ery little c onsistent relation w as observed between the temperature , time of heating , and resulting degree of de composition . Apparently , as already mentioned under the preparation of dithionates , there is a factor or factors involved

in decomposition that has not been discovered . In connection with the matter of decomp osition is to be men

Q ‘ ti on ed the work of M uller 1 who s tudied the reactio n

N I 2 H o 2 N aH S 2 H I a , s, o , , , O, ,

and found i t to be monomolecular . This l ed Muller to think the

. : 1 action proceeded in three steps , viz ( ) Liberation of dithionic 2 o acid , ( ) its decomposition into sulfur us and sulfuric acids and h (3 ) the action of iodine on sulfurous acid . T e time for 1 and 3 2 is negligible compared with 2 , so that only is measured . He found that the velocity constant at 51 3 ° was and that velocity increased with rising temperature .

Y C . MODIF ING FAC TORS The purpose of these experiments was to see if the decomposi tion of barium dithionate was influenced by the presence of any of the products of decompo s ition that were likely to be present . In each instance the plan pursued was to place one gram of

( barium dithionate contained in 1 0% solution in a press ure bottle . The pressure bottle and contents were heated in the autoclave for one hour at This produced only partial decomposition .

By weighing the quantity o f barium sulfate formed , the extent to which decomposition had proceeded was ascertained . After it was learned to what extent decomposition had proceeded under these conditions , the effect produced on decomposition by the addition of s mall quantities of variou s substances to the solu c tion during heating was studied . The pro edure was the same as that employed for the pure barium dithionate solution al ready outlined , except that small quantities of sodium thiosulfate ,

2 4

The point in the foregoing arises from the fact that if the S olid thus fo rmed is barium s ulfite it may offer corroborative evidence as to the truth of the second assumption . After the study of the decomposition of the dithionic salts of some other metals the p robable truth of the three assumptions in the light of experimental data adduced will receive further dis i o cuss n .

3 T H E C F . DE OMPOSITION O SOME OTHER DITHIONATES

The other dithionic salts stu died were those of potassium , cadmium , and nickel . The first and third assumption s set up to account for the decomposition of bariumdithionate were

s ulfite t found applicabl e throughout . No s of metals were detec ed in this latter part of the work . The decomposition of cadmium and nickel dithionates yielded small quantities of the respective ulfite sulfides . It is possible that s s were present in small quan tity but escaped detection . The weight of the free sulfur and sulfide combined for the cadmium and nickel salts weighed from

ten to twenty milligrams .

A . POTASSIUM DITH IONATE

Free sulfur was the only insoluble product of decomposition .

° A five percent solution was heated to 1 80 during six hours . No l s u fit e nor thiosulfate could be detected .

W E N D TABLE 5. SHO ING DISTRIBUTION OF SULFUR AMONG PRODUCTS AFTER

DECOM P OSITION OF POTASSIUM DITHIONATE IN ABSENCE OF O XYGEN .

ta t l ss e 2 6 9 1 . Po ium dithiona . % Su fur

% S a s % S as % S as To ta l % s

H QS O I S 0 2 R ecov er ed 9 7 . 6

9 . 56

The mode of analysis was along lines similar to those employed for barium dithionate decomposition .

B . CADM IUM DITHIONATE

Abegg describes thi s salt as being effioresc ent an d having six molecules of water of crystallization . By an analysis for sulfur it was found that crystals of this s alt dried by exposure to the air at room temperature were without water of crystallization .

2 6 A saturated solution of cadmium dithionate decompo s es at In a pressure bottle a 1 0% solution was not completely nor even

extensively decomposed after heating three hours. at

In the analyt ical portion of this work , after decomposition had

s - been effected , the solid products thus ari ing were collected on th e an alundum crucible and weighed , after which cadmium sul

fide was dissolved by hydrochloric acid , and the remaining sulfur

weighed . The manipulation of liquid and gaseous products was similar to that already described for the decomposition products

of barium dithionate .

T S W T S A G E N D D ABLE 6 . HO ING DIS RIBUTION OF ULFUR MON PRO UCTS ARIS ING FROM DECOM P OSITION OF C ADMIUM DITHIONATE IN XY ABSENCE OF O GEN .

e t s l t se . C dS Q O o s ulfur . 5% C onc ntra ion of o u ion u d

T m o as as a s S as S as To ta l S e . S S S % p f % , % % % %

D ec am d H ee S C dS ec v er ed p . C S O 4 .8 0 4 S 0 2 fr r o

° 1 50 1 1 est est 3 42 9 . T T .

0 1 80 T est 1800 ° 1 2 00 3 . 30

K C . NIC EL DITHIONATE The nickel dithionate used was not crystallized from th e solu

tion in which it was formed . A S the exact concentration of nickel dithionate s olution suffering decomposition was not known the following figures represent the weights of sulfur found in the Of various products decompos ition .

DISTRIBUTION OF SULFUR AMONG PRODUCTS OF DECOM P OSITION ° i D ecompo sed at 1 80 for s x hour s .

m o .

g. g.

The chief obj ect in pu rs u I ng this phase of the work was to

learn whether the products of d ecompos ition of potas s ium ,

cadmium , and nickel dithionates were materially different in kind and quantity from those obtained by decompo s ition of

barium dithionate . Apparently the state of aggregation of the end products or the potential formation of insoluble sulfides plays no role in the general course of the reaction in the various

2 7 C C VI . D I S C U S SI ON AND ON LU SI ON S

The following comprises a consideration o f the foregoing ex p erimen tal work and to some extent the work of others in rela tion to (1 ) the formation of dithionates and (2 ) the decomposi

tion of dithionates .

1 . THE FORMATION OF DITH IONATES The survey of the literature already recounted shows that the course of the action or action s resulting in the formation of manganese dithionate and manganese sulfate , in variable pro portions , by the action of s ulfur dioxide on manganese dioxide has been the subj ect of considerabl e investigation and specula “ tion . With most writers the crux of the question has been Are the dithionate and sulfate fo rmed consecutively or simultan ” s % eou ly That is , is the dithionate intermediate between the sulfite and sulfate %

i - To the present wr ter it seems that , probably , the actions are consecutive and that the dithionate is an intermediate product

ul - between the s fite and the sulfate , that the primary action is °6 M n 2 M n that mentioned by Marino , O 2 S O2 S z OG , and that the sulfate is formed by the decompo s ition of the manganese dithionate into manganese sulfate and sulfur dioxide . Support ing this view iS the fact experimentally a dduced that sulfur o dioxide accelerates the decompositi n of dithionates . Some doubt i s cast upon the findings of Antony and Lucchesi 1 7 which conflict with the idea s j u st advanced by the internal evidence o of their own work . These auth rs thought they had obtained ruthenium dithionate by the action of sulfur dioxide on ruthen ium s ulfate . Later they state that the ruthenium dithionate thus fo rmed was decomp osed by the action of potassium per c manganate . Others have unsu cessfully attempted to decompose r dithionates with pe manganate . So in the absence of corrobora o tive evidence the w rk of Antony and Lucchesi , in this connec tion , is to be acc epted with reservation . The findings of J .

2 ” z f‘ 5 M arin o Meyer , C arpenter , and , already mentioned , may be interpreted by supposing that the manganese sulfate which these authors found occurring with manganese dithionate when sulfur dioxide and manganese dioxide are brought together is the result of decompositi on of manganese dithionate into manganese sulfate and sulfur dioxide . The higher the tempera

2 8 ture of the reactions the more the decomp o sition is p romoted s and consequently the more mangane e sulfate there i s formed . In view of the simplicity of this viewpoint as well as its harmony with experimental evidence it appears to be a. better theory than the inductor theory , though it is quite possible that both theories

o are c rrect .

Summarizing this part of the study it may be said , in %iew of the findings of others and the present experimental results , that the following conclusions m ay b e fairly drawn concerning the fo rmation of manganese dithionate and manganese sulfate simultaneously by the action of sulfur dioxide on manganese a dioxide in w ter suspens ion .

O A . C ONC LUSIONS N FORMATION

1 e2 6 re re . The first action , as suggested by Marin is that p sented by the equation

2 M n M n O . o , S O , S , ,

2 . Simultaneously a portion of the manganese dithionate de

composes into manganese sulfate and sulfur dioxide .

3 . The variation in the proportion between the quantities of ' sulfate an d dithi on ate fo rmed is to b e accounted for by the effect of variation in temperature on the action mentioned in the second concl u sion .

2 . THE DEC OMPOSITION OF DITHIONATES It is believed that a perusal of the experimental part of this work demonstrates t h e following fac ts with respect to the spontaneous. decomposition of dithionates in water solutions in C losed systems at the temperatures mentioned .

1 . . The final products are chiefly m etallic sulfates along with sulfur dioxide , sulfuric acid , and free sulfur in variable pro

- portions . In addition are found minute quantities of sulfites and sulfides on decomposing th e dithio nates of metals capable of r ulfi fo ming insoluble s tes and sulfides .

‘ i n 2 . ufiic e When s t oxygen is present , sulfur is n ot found as an end product but is converted to sulfate . 3 . Rising temperatures diminish the quantity of sulfur dioxide found as an end pro duct and cause a corresponding in in crease the sulfuric acid formed .

2 9 4 i i . Sulfur dioxide accelerates the decomposition of d th

on ates .

i n 5. S ii ect g a mixture of a saturated solution of sulfur dioxide in water and gas eou s sulfur dioxide to conditions of m ost of the experimental work results in the formation of appreciable quantities of sulfuric acid and free sulfur . From these experimental facts the following conclusions seem warranted as explaining the mechanics of the decomposition of u s the dithionates studied . These concl sion are partly contained in the first and third assumptions mentioned in connection with b the work on arium dithionate .

C C C A . C ON LUSIONS RESPE TING DE OM POSITION OF DITHIONATES 1 t . In all cases the p rimary decomposition resul s in the formation of metallic sulfate and sulfur dioxide . 2 d . All other pro ucts experimentally obtained arise from the

subsequent action or interaction of the three substances , unde

composed dithionate , sulfur dioxide , and metallic sulfate . Under conclusion 2 and arising from considerations there men

i on f t ed may be appended the ollowing corollaries .

or 1 . C . The action represented by the equation

3 2 O S O, S 3 S

under the conditions of this w ork proceeds sufficiently to account .

for the free s ulfu rI c acid and free sulfur found as end products . r 2 l o . fite m C . The s u s found were for ed by double decomposi

tion between undecomposed dithionate and sulfurous acid . or l de C . 3 . S u fi s found were formed by direct union between nascent sulfur arising from the action mentioned in corollary 1 i and the Of the metal n question . Just why s ulfites and sulfides mentioned in corollaries 2 and 3 should exist in the presence of sulfuric acid of concentratio ns

found is not apparent . However , that unusual conditions of temperature and p ressure as well as the presence of extraneous

subs tances sometimes greatly modify solubilities is well known .

The following results , not obtained experimentally , might be expected to arise from the Operation of well known chemical principles in the decompositio n of dithionates under the condi o tions bserved . ul e 1 . Thiosulfates should arise from heating s fit s in the n prese ce of free sulfur . 30 2 ulfites e e t I ll a Of . S should be formed to som ext n n c ses a “

‘ s c u e G r r d decompo sition of dithionates , but for variou a ses ar S w L

fi ed as to escape detection . It m ay be here observed that an action similar t o that men tioned in corollary 1 should convert sulfites to sulfates and free

sulfur .

In the matter of structure the author, at present , has no con tributi on to offer in addition to what is already afforded in the ackn o l literature . That the present status is unsatisfactory is w edged but apparently not to be helped until a more intimate

knowledge of atomic and molecular structure is forthcoming .

“ ” C onc erning the phenomenon termed autoxidation spoken of

in the earlier part of the paper , it may be mentioned that the de composition Of dithionates where one of the sulfur atoms in the

dithionate molecule forms sulfate with a sulfur valence of six , while the other sulfur atom of the same dithionate molecule forms s ulfur dioxide with a sulfu r valence of four is a

phenomenon of this kind . Here also is included the splitting of an sulfur dioxide into sulfur trioxide d free sulfur . Here is an

inviting and little explored field .

I I K L M T S V . A C NOW E D G E N

The author Wi shes to express his thanks and appreciation for all the suggestions and assistance received at the hands of p ra o tically every member of the C hemistry Department of Ohio State

but . University , particularly to Prof . W E . Henderson not only f or suggesting the p robl em and for much help in its solution but also for the example of h i s intellectual integrity and high

scientific idealism .

Thanks are due also to Prof . H . H . Willard of the University o f i f Michigan for the g ft o a supply of sodium dithionate .

T O VI I I . RE F E REN C E S TH E LI T E RA T U RE

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