a c i d i n aqueous sodium p o r c h l o r a t e s o l u t i o n s of i o n i c s t r e n g t h 1 and 3.A potontiometric study is made a t 25'C of t h e d i s s o c i a t i o n of c i t r a c o n i c IWTRODUCTION I n foregoing pap.rsLfZ1' on t h e p o t e n t i m e t r i c study of t h e d i s s o c i at i o n of mono-and d i p r o t i c a c i d s s p e c i a l a t t e n t i o n was paid t o an a n a l y s i s of t h e emf e f f e c t s caused by s e l f -a s s o c i a t i o n of t h e a c i d and by compositional c h~n g e s during experiment. tormine experimentally ~1 1 c o n t r
i b u t i o n s of compositional changes t o t h e emf s h i f t . A f t e r c o r r e c t i o n f o r t h e s e e f f e c t s t h e E-[Ll curve# no longer showed signs of s e l f -a s s o c i a t i o n . acids, (H2L),on condition t h e two d i s s o c i a t i o n s t e p s are s u f f i c i e n t l y separated to study t h e i n d i v i d u a l influence of HL-and Lon t h e mean a c t i v i t y c o e f f ic i e n t o f t h e measuring e l e c t r o l y t e . However, as A g e n e r a l technique, it is b e t t e r only t o analyse t h e emf s h i f t when t h e presence of s e l f -a s s o c i a t i o n is c e r t a i n . Therefore, i n this paper, t h e experimental i n v e s t
i g a t i o n of an a c i d w i t h w e l l spread d i s s o c i a t i o n s t a g e s is described. C i t r a c o n i c a c i d (Kc1/Kc2
>
) was s t u d i e d a t two i o n i c s t r e n g t h s i n o r d e r t o f a c i l i t a t e t h e d i s t i n c t i o n botween s e l f -a s s o c i a t i o n of t h e a c i d and v a r i a t i o n of t h e a c t i v i t y c o e f f i c i e n t s .For indoed a higher I w i l l reduce t h e i n f l u e n c e of compositional changes on t h e .mf-signal.The lower d i e l e c t r i c u m of such s o l u t i o n s however promotes assoc i a t i o n of i o n i c substances.
EXPERIMENTAL
T i t r a t i o n technique and apparatusFormation curves w e r e determined by t i t r a t i n g c i t r a c o n i c a c i d s o l u t i o n s with di-#a-citraconato s o l u t i o n s and v i c e versa; d i l u t i o n curves by t i t r a t i n g buffor solution. with sodium p o r c h l o r a t e s o l u t i o n s and v i c e versa. A l l t i t r at i o n s were performed i n a cell without t r a n s p o r t while n i t r o g e n was bubbling through the s o l u t i o n .
