The Decomposition equilibria of platinum di- and mono-chlorides by the simultaneous torque-knudsen technique

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d e c o m p o s i t i o n of the p l a t i n u m c h l o r i d e s was f i r s t r e p o r t e d in 1909 and 1913 by W o h l e r , e t a l ~'~ who o b s e r v e d that p l a t i n u m t e t r a c h l o r i d e on h e a t i n g in a c h l o r i n e a t m o s p h e r e d i s s o c i a t e s with the l i b e r a t i o n of a c h l o r i n e m o l e c u l e a c c o r d i n g to the s t e p w i s e reaction PtC14 ~ PtC13 ~ PtC12 ~ P t C 1 - Pt.

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The t e m p e r a t u r e r a n g e s at which t h e s e compounds a r e s t a b l e n e a r a c h l o r i n e e q u i l i b r i u m p r e s s u r e of one a t m o s p h e r e w e r e also r e p o r t e d , K r u s t i n s o n s 3'4 obr a i n e d by s t a t i c method the d i s s o c i a t i o n p r e s s u r e of PtC12 b e t w e e n 839 to 850 K. K r u s t i n s o n s ' data gave a t e m p e r a t u r e of 849 K for a c h l o r i n e p r e s s u r e of 1 a t m in c l o s e a g r e e m e n t with that of W o h l e r who obrained 855 K. Shchukarev, e t al, S u s i n g a s t a t i c method, o b t a i n e d 862 K for a c h l o r i n e p r e s s u r e of 1 a r m . All of the above data w e r e obtained at r e l a t i v e l y high t e m p e r a t u r e s and for v e r y s m a l l t e m p e r a t u r e r a n g e s . A m o r e r e c e n t study of the e q u i l i b r i a b e t w e e n p l a t i n u m a n d c h l o r i n e by the flow method has b e e n r e p o r t e d by S c h a f e r and Wosiewitz 6 An e x p e r i m e n t a l value of 1163 K was o b t a i n e d for a c h l o r i n e p r e s s u r e of 1 arm. T h e i r t e m p e r a t u r e r a n g e d f r o m 973 K to 1373 K. F u r t h e r s t u d i e s on the d e c o m p o s i t i o n of PtC12 by o t h e r methods s u c h as m a s s s p e c t r o m e t r y and the s i m u l t a n e o u s t o r q u e - K n u d s e n t e c h n i q u e is n e c e s s a r y in o r d e r to b e t t e r e s t a b l i s h t h e i r d e c o m p o s i tion r e a c t i o n s and t h e r m o d y n a m i c p r o p e r t i e s . Mass s p e c t r o m e t r i c w o r k done on p l a t i n u m d i c h l o r i d e by Muenow and M a r g r a v e 7 has c o n f i r m e d the p r e s e n c e of p l a t i n u m i n the s o l i d p h a s e and c h l o r i n e m o l e c u l e s in the gas p h a s e . WILLIAM G. O'BRIEN, formerly Graduate Assistant, is now with Photo Products Division, DuPont, Towanda, PA. HARVEY J. JENSEN, is Senior Research Technician, Ames Laboratory-ERDA. ROBERT N. BENEDICT, formerly Undergraduate Research Helper, is now Graduate Student, Department of Chemical Engineering,University of California, Berkeley, CA. RENATO G. BAUTISTA,is Associate Professor of Chemical Engineering and Group Leader, Ames LaboratoryERDA, Iowa State University, Ames, IA 50011. Manuscript submitted July 14, 1975. METALLURGICAL TRANSACTIONSB

In this work, the s i m u l t a n e o u s t o r s i o n a l and m a s s effusion m e a s u r e m e n t t e c h n i q u e was u s e d to d e t e r m i n e the heat of d e c o m p o s i t i o n of the p l a t i n u m d i c h l o r i d