A concentrated solution of tetraiodo-o-sulfobenzoic acid was prepared by boiling 22.4 g. of the corresponding anhydride with 50 cc. of water. Fifty cc. of concentrated aqueous ammonia was then added (causing the neutral ammonium salt to precipitate partially), the solution was saturated with hydrogen sulfide and allowed to stand for twenty-four hours. The white precipitate thus obtained in a yield of 11.5 g. was the neutral ammonium salt of ...
