TITRIMETRIC DETERMINATION OF CIS-3,6-ENDOMETHYLENE-1,2,3,6-TETRAHYDROPHTHALIC (ENDIC) ANHYDRIDE AND THE IMPURITY OF THE CORRESPONDING ACID

A titrimetric procedure is proposed for the determination of endic anh ydride by its reaction with piperidine (anhydride and acid groups) and triethylamine (acid groups) in acetonitrile. The procedure makes it p ossible to eliminate time-consuming stages of the hydrolysis of anhydr ide in the presence of pyridine and the dissolution of anhydride in an iline. It is demonstrated that the results of visual titration in the presence of indicators should be normalized with the inclusion of the indicator error in the determination of the total of anhydride and aci d groups.