While at work during the past session in the Berlin Laboratory, it was suggested to me by Professor Hofmann, that I should examine the behaviour of thioformanilid when submitted to various degrees of heat. The thioformanilid employed was prepared by heating formanilid with penta-sulphide of phosphorus, the resulting mass was treated with dilute caustic soda, and the alkaline solution of thioformanilid thus obtained was mixed with excess of hydrochloric acid, when impure thioformanilid separated out; this was purified by crystallisation from hot dilute alcohoL The crystals thus prepared melted at 137°–138° C., the melting-point of pure thioformanilid being 137.5° C. (Hofmann).