THE KINETICS OF THE SULFtJR(IV) - suLFuR(vI) ISOTOPIC EXCHANGE REACTION IN AQUEOUS AND CONCTRATED ACID )LUTIONS by RAY LOCKE McDONALD A THESIS submitted to OHEGON STATE COLLEGE In parti1 fulfillment of the requirements for the degree of DOCTOR 0F PHW)SOPHY June 196]. flIiY1i$IT Redacted for Privacy Professor of Chemistry In Charge of Major Red acted f or P rivacy Chairman of Department of Cnemistry Redacted for Privacy Chairman of School Graduate Committee Redacted for Privacy Dean of Graduate School nate thesis is presented Typed by LeAnna kiarris tffi*ffimffi Fcar rdsrmo ad mflss. dte rU egestr d lilt rretc Mlr1 tb lutEm'rprm [ilr;r* dffi tldr te EufUe ?. E. I*1ill. TABLE OF CONTENTS Page I. INTRODUCTION ...................... i II. E(PERIMENTAL ...................... 7 A. General Procedure ................. 7 B. Radioactivity Analysis ............... 9 C. Chemical Analysis ................ il D, Preparation of Materials and Reactant Solutions 13 1. General ................. 13 2. Sulfur Dioxide ................ 1.3 3. Labeled Aqueous Sulfuric Acid ......... i1 )4. Labeled Concentrated Sulfuric cid ....... 15 ;. Labeled 100% Sulfuric Acid ........... 16 6. Labeled Fuming Sulfuric Acid .......... 16 7. Labeled Aqueous Sodium Bisulfate ........ 16 8. Lat.ed Sodium Bisulfate in Aqueous Sulfuric Acid .................. 17 9. Labeled Sodium Bisulfate in Concentrated . Sulfuric Acid .................. 17 10. Labeled Sodium Sulfate ............. 17 li. Labeled Sodium Sulfate in Aqueous Sodium Bisulfate ................ 18 12. Labeled Elemental Sulfur ............ 18 III. RUN PROCEDURE AND DATA ................ 19 A. Sulfur(IV) - Sulfur(VI) Exchange in Basic Media . 19 B, - Sulfur(IV) Sulfur(VI) Exchange in Acidic Media . .23 1. Radiosulfur Ecchsuge Experiments Between Sulfur Dioxìe and Aqueous Sulfuric Acid of High Specific Activity ............ 23 2. Radiosulfur Exchange Experiments Setween Sulfur Dioxide arid Aqueous Sulfuric Acid of Low Specific Activity ............ 3.1 3. Radiosulfur Exchange Experiments Between Sulfur Dioxide and Concentrated Sulfuric Acid 32 14. Radiosulfur Exchange Ecperiments Between Sulfur Dioxide and Aqueous Sodium Bisulfate and Between Sulfur Dioxide arid Aqueous Sulfuric Acid - Sodium Bisu.l.fate - Sodium Sulfate Mixtures ................ 3Li 5. Radiosulfur Exchange Experint Between Sulfur Dioxide and Aqueous Sodium Sulfate of High Specific Activity ............ 36 Pag! 6. Radiosulfur Exchange ExperinEnts Between Sulfur Dioxide and Sodium Bisulfate - Concentrated Sulfuric Acid 9ixtures. , 36 7. Radiosulfur Exchange Experiment Between Sulfur Dioxide ar*i Oleum. 8. Radiosulfur Exchange Experiments Between Sulfur Dioxide and Aqueous Sulfuric Acid with Added Electrolyte . L2 9. Radiosulfur Exchange Experiments Between Elemental Sulfur and Sulfur Djjde in the Presence of Sulfuric Acid or Hydrochloric Acid. .W4 Iv.?!E1HODSOFCALCULATIDN...... .. A ........L8 Stable Systems . B. ..... Unstable . Systems. 1. - Sulfur(TV) Sulfur(VI) Exchange. 2. Sulfur(J) - Sulfur(IV) Exchange . .57 C. Volume . s . Corrections . I s 57 D. ..... Solubility of Sulfur Dioxide . 60 V . RESULTS . 63 A. Sulfur(IV) - Sulfur(VI) Exchange in Basic 4edia. 63 B. Sulfur(TV) - Sulfur(VI) i Exchange in Acidic Media . 6Li General . 6L 2. Sulfur . , Diaxide Concentration Dependency . .66 3. Sulfuric Acid Concentration Dependency . 66 )3. The Exchange Rate Law in Aqueous Acid . 72 5. The Effect of Ionic Strength . 78 6. The Effect of Hydrogen Ion Concentration . 83 7. The Effect of !ater and Bisulfate Ion in Concentrated Acid . , . 8!& 8. Rate Dependence on Sulfur Dioxide in . Concentrated Acid , . 88 9. The Rate Law in Concentrated Acid . 90 10. The Hydration Constant of Sulfur Dioxide . 100 i1. Summation . 101 12. Aqueous Exchange Results with Bisu1'ate and . .. Sulf3teInns. .. ..102 13. Temperature Coefficient of the Exchange Rate. 107 l4. Experiments with Elemental Sulfur arri with )lei.iri . 113 VI. DISCUSSION . ....... 115 'VI I SUMMARY . ............. 131 VIII. Bibliography.......... ........... 13!4 tIffi Sr fsmes Paga 1. Redtoaulfur Erchangc Expartncnt Bohmm I$agffi3 {d I$eZSffO; LB O.I S SSS* * * r t.* r.t i r r * *ll *. BadtasE3.f,er Bx&*nw e*rtw* s$M Negffi3 erd &g$fuh r,.s iIeS * . r * r r, I, r r i * r . *s 3. R*dloculfrr Erohrrqgg Ecpsrt.a{str Batre ,SA ard Aryaour He6*0b of, lirgh $coUno *ctlvl,ty. 8y l+. Badfoetrlfur Exe[ange &lporfnmtl Bahrcw SO2 ad Agrrcoue HgS*OL of Lfi gpoet-f,i.c Aotlvltf . r . 33 L RdtseuLf\r Erchngo Er$lgrlnenta Betrrosr 3s 6" Radfosra1:ftrr Ecohm6r EryGrr-eet! Bstysrn BOe and Aqu*ona mrrffi6 of, HlSh Srculc .aetirlEy . 3? ?. Bsdi.oeuHur &ctunge Sqporfnaotg Ecblwa S02 enil {Try}o ttA{fr0t - t{alE*GL - I{aES*oh Htxhlres-of 3s I' RadI"am}Sur Exslgugs Hrysrr.@t Seturum $Sg sd Sqtrwuu HtgS*O;*. * r r . r * * r r * *. ! * * * r s 3S 9. Radtogulfhr Exehange nrpertrmntc Behtgil SOI ard Coneentrat d lt2ffi[ Btth [c]I6#OU Addsd . : t ., . r lrl XS. ed*ssugtkr trreHrrga gqesr*ffit S*&an S*g$d0lgm* * r * * * * * i * . r * ' r * * * * * r,.# 11". Rdtosulfirr Exclun6e Srporltrmts Bsbraen $Oo erd AqueoutH2St0lrrithHs0rL04Addad. r r..I... r .. LS 1"2. Bdloeulfur-fuchengo Hrpertrmnte Batill+ea $Oa rnd Aquaws H*ffoh rtth t{nfiL or JffiL sddd* : * .,r r r . i, 116 13. Redloaulfir Exehangc &rperimta tsetnoan SOe und S*dt$tg0*.v* ffitwntr$ Sq3^fw r 'o . I t, . ., W 1lr. Acld Dmsltlse ard Caleul"stad 0meaatrctt@s Stth*k$&ng*Strymtlrm r | ! " 1r.. * * * r r i 5p tr'$. *e&ependwesffiBwbYolwr. r. r r r r r * * r. 6S Page 16. Radiosulfur Exchange Ratea Between Sulfur Dioxide and Sulfuric Acid.. 6 17. Radiosulfur Exchange Rates Between and VariousS(VI)Mixtures. .71 18. A Tabulation of RP Values at Constant (S32)f 76 19. Radiosulfur Exchange Rates Between SD2 and H2SO with NaC1 or UC1 added. , . 81 20. Radiosulfur Exchange Rates Between 302 Concentrated H2SO - NaHSO Mixtures. 21. Rate Dependence on SO2 in Concentrated H2S0. 89 22. Summary of k(HS3j) and R/(S32) Values. 93 23. Summary of K values in Aqueous Solution . .101 2)4. Radiosulfur Exchange Rates Between 502 and Acueou NaHS*0j - Na2S*0 Mixtures . .103 2. Radiosulfur Exchange Rates Between and Sul..fur(0). ........ .1114 26. Radiosulfur Exchange H2S*014 Rate Between so2 and ith Sulfur(0) Added. ...... .1114 27. Radiosulfur Exchange Rate Between S02 and Qleum . .UL LIST OF FIGURES Page i. Exchange Bombs . 20 2. Separation System for 3reak-Tip Bombs . 22 3. Separation System for "Sealed-Tube" Bombs . 28 14, Typical Plot of Log(l - F) vs. Time . se Typical Plot of F v. Time in Unstable System . 6. Rate Dependence on (so2) . 67 7. Rate Dependence on (H2SO) , , , . , 68 8. Plot of Log 'i . RP (HSO). 77 9. Rate Dependence on 86 10. R/(S02) vs. (i3)))calc for One Term Rate Law . , . 9L U. Plot Resulting From Two Term Rate Law . 99 12. Rate Dependence on (NaHSOb) 106 13. Apparent Activation Energy . 109 1L. Exchange Between Na2303 Na230j4 - at 19°C . 130 TE KINETICS OF THE SULFUR(IV) - suLFm(vI) ISOTOPIC EXCHANGE REACTION IN AQUEOUS AND CONCENTRATED ACID SOLUTIONS I. INTRODUCTION The exchange of oxygen 2toms between sulfur(IV) ax suifur(VT) compourid3 was first investigated by Voge (!3,p.1O32-1O3), using radioactive sulfur. He observed no exchange in 36 hours at 1000C between aqueous sulfite and sulfate in either basic or 0,1 N acid solution. He also reported no exchange between sulfur dioxide and sulfur trioxide gases in 17 hours at 280°C, the addition of water vapor leading to only about 10% exchange tmder these conditions. At 33°C, however, he did find a slow exchange between these gases, the rate being accelerated by the presence of water or of platinized asbestos, Since this is about the temperature where the dis- sociation of sulfur trioxide first becomes appreciable, Voge postulated the rate determining step to be S3 + (1) !Juston (2L) later studied in detail the kinetics of tliis gas phase exchange, and ob8erved the rate to be conveniently measurable in the range 1.iOO - 0°C with a norma]. temperature coefficient. He found the reaction to be heterogeneous arxi, as Voge had indiccted, strongly catalyzed by water, but his date were irreproducible and involved. He did conclude, however, that the rate determining step seemed not to be that given by 2 (1), iluston (22,p.30S0) has i1so investigated the liquid phase e:chnge f sulfur between these two conounds, and has reported hat no exchange takes place at room temperature when sulfur trioxide is dissolved in liquid sulfur dioxide or vice versa. ¡le observed only very slow exchange (less than 2 in 62) hours) for sulfur dioxide dissolved in liquid sulfur trioxide at 1320C. Voge's results led :larnmon (19,p.].0) to speculate that perhaps the concentrations of both sulfur trioxide and water in hot concentrated sulfuric acid might be sufficiently high to lead to a more rapid exchange with sulfur dioxide than that observed between sulfur dioxide and sulfur trioxide in the gas phase. His results, while somewhat lacking in internal eon- sistency, indicated roughly: (1) at room temperature, rio ex- change in L8 hours; (2) at 1000C, % exchange in !8 hours; (3) at 280°C, complete exchange in less than S hours. This last result, when compared with all of the preceding work was evidently of considerable isxterest. Norris (37) further ives- tigated this exchange between sulfur dioxide and concentrated sulfuric acid. He found it to proceed it a conveniently measurable rate in the range 160 - 210°C, with an aparent activation energy of about 28.8 kcal.mole1. Continuing the investigation, Doherty, esters and Norris (11) found the reaction to be first order in sulfur dioxide and one-half order in water concentration in the range 85 - 98 sulfuric acid. 3 It is clear fron the preceding that, although the exchange appears to be faster in hot concentrated sulfuric acid than in the systems previously studied, in no case does rapid exchange of radiosulfur occur between sulfur(IV) and sulfur- (VI) species at room temperature.