Production of amiphenazole

In a process for the preparation of 2,4-diamino-5-phenyl thiazole hydrochloride or hydro bromide an aqueous solution of 2,4-diamino-5-phenyl thiazole containing hydrochloric or hydrobromide is heated to a temperature not exceeding about 60 DEG C., contacting the said solution with an amount of an appropriate inorganic chloride or inorganic bromide such as will remain in solution in said solution but which will depress the solubility of the resultant 2,4-diamino-5-phenyl thiazole hydrochloride or hydro bromide sufficiently to cause crystallization of said 2,4-diamino-5-phenyl thiazole salt and recovering the said salt from the solution. Alternatively the benzene sulphonate or alkylated benzene sulphonate salt of 2,4-diamino-5-phenyl thiazole is reacted with an alkali metal hydroxide or carbonate or ammonia solution to yield the free base and the base is subjected to the foregoing process to yield the hydrohalide. U.S.A. Specification 2,709,172 is referred to.