Those of sulphur sublimatum.

Preparation. - By digesting sulphur with dilute ammonia, thoroughly washing, drying at a gentle heat, and passing through a No. 30 sieve. In this process the ammonia not only neutralises any sulphurous or sulphuric acid, but dissolves out and removes sulphide of arsenic which may be present in the sulphur, and which is soluble in ammonia.

Tests. - Water agitated with it should not redden blue litmus paper (absence of free acid). If washed sulphur be digested with two parts of water of ammonia, and the mixture filtered, the filtrate, on being supersaturated with hydrochloric acid, should remain unaltered (absence of arsenious sulphide), nor should a precipitate make its appearance on passing hydro-sulphuric acid through the filtrate (absence of arsenious acid).

Officinal Preparations.

u.s.p.

Pulvis Glycyrrhizae Compositus.

(1 in 12 1/2.)

Sulphuris Iodidum.

Unguentum Sulphuris Alkalinum.

U.S.P. Unguentum Sulphuris Alkalinum. Alkaline Sulphur Ointment. Smlphur 20; carbonate of potassium 10; water 5; benzoated lard 65.