B.P. Sulphide of antimony, Sb2S3; 336; with a small and variable amount of oxide of antimony, Sb203.

U.S.P. Chiefly antimonious sulphide, Sb2S3; 340; with a very small amount of antimonious oxide.

Characters. - B.P. An orange-red powder. U.S.P. A reddish-brown, amorphous powder, odourless and tasteless.

Solubility. - It is insoluble in water and in alcohol.

Reactions. - B.P. It is readily dissolved by caustic soda, also by hydrochloric acid with the evolution of sulphuretted hydrogen and the separation of sulphur. Sixty grains, moistened and warmed with successive portions of nitric acid until red fumes cease to be evolved, and then dried and heated to redness, give a white residue weighing about 40 grains. U.S.P. When heated with twelve parts of hydrochloric acid, it is nearly all dissolved, with evolution of sulphuric acid. The residue, after having been washed and dried, burns, on the application of a flame, with the characteristic odour of sulphur, and should leave not more than a scanty ash. On dropping a solution of sulphurated antimony in hydrochloric acid into water, a white precipitate is produced, which, after washing and drying, should weigh not less than 85 per cent. of the sulphide. The liquid filtered from this precipitate yields an orange-red precipitate with hydrosulphuric acid.

Distilled water boiled with sulphurated antimony, filtered and acidulated with hydrochloric acid, should be rendered not more than slightly opalescent by test solution of chloride of barium (limit of sulphate).

Preparation. - By boiling black antimony with caustic soda and sulphur, the sulphide is partly converted into oxide and partly unites with sodium, forming sulphantimonite and antimonite of sodium.

Sulphide of Antimony

Soda

Sulphantimonite of Sodium

Antimonious Oxide

2Sb2S3 +

6NaHO

= 2Na3SbS3 +

Sb2O3 +

3H2O,

and

Antimonious Oxide

Soda

Antimonite of Sodium

Sb2O3 +

6NaHO

= 2Na3SbO3 +

3H2O.

Owing to the presence of free sulphur, sulphantimoniate, and antimoniate of sodium are also formed.

Sulphide of Antimony

Soda

Sulphantimoniate of Sodium

Antimonic Oxide

2Sb2S3 + 2S2 +

6NaHO

= 2Na3SbS4 +

Sb2O5 +

3H2O,

and

Antimonic Oxide

Soda

Antimoniate of Sodium

Sb2O5 +

6NaHO

= 2Na3SbO4 +

3H2O.

The sulphides and oxides of antimony are soluble in the solutions of the salts of antimony just mentioned. The addition of sulphuric acid decomposes the salts, with the formation and precipitation of the oxides and sulphides. In order to ensure uniformity of the product the acid is added while the solution is hot.

These antimony compounds are soluble in caustic soda, but when this is neutralised they are precipitated, the greater part of them being decomposed and the Sb2O3 reconverted into Sb2S3.

Sulphantimonite of Sodium

Sulphuric Acid

Sodium Sulphate

Antimonious Sulphide

sulphuretted Hydrogen

2Na3SbS3 +

3H2SO4

= 3Na2SO4

+ Sb2S3 +

3H2S.

Antimonite of Sodium

Antimonious Oxide

Water

2Na3SbS3 +

3H2SO4

= 3Na2SO4

+ Sb2O3 +

3H2O.

Sulphantimoniate of Sodium

Antimonic Sulphide

2Na3SbS4 +

3H2SO4

= 3Na2SO4

+ Sb2S5 +

3H2S.

Antimoniate of Sodium

Antimonic Oxide

3Na3SbO4 +

3H2SO4

= 3NaSO4

+ Sb2O5 +

3H2O.

Dose. - 1 to 5 grains.

Preparations

B.P.

Dose.

Pilula Hydrargyri Sufcchloridi Composita (Plummer's pill)

(p. 522) .................................1 part in 5...................................................................

5-10 gr.

U.S.P.

Pilulae Antimonii Compositae (Plummer's pill) (p. 523)....1 part in 4.....

1 or 2 pills.

The oxide it contains is probably the active part, and as this is variable the action is rather uncertain.