Prep. By passing a stream of sulphuretted hydrogen gas into one fluid ounce of solution of ammonia as long as the gas continues to be absorbed.

Use. The solution of hydrosulphuret of ammonia is used to precipitate various metals from solution. It is employed to determine the presence of zinc in the salts of that metal; it gives with them a white precipitate of sulphide of zinc, which is very characteristic. Hydrosulphuret of ammonia gives rise to no precipitate in neutral solutions containing arsenious and arsenic acid, but an orange-red precipitate with neutral solutions of antimony, soluble in excess of the reagent.

Salts of mercury, silver, lead, copper, bismuth, tin, gold, and platinum, are precipitated as brown or black sulphides by the solution of hydrosulphuret of ammonia. The precipitates formed with the protoxide of tin, and the peroxides of gold and platinum, are soluble in excess of the reagent; the sulphide of tin requires a large excess.