Synonym. Potassii Sulphuretum. Lond.

Prep. By mixing together sulphur and carbonate of potash, and afterwards heating in a crucible till they have combined.

Prop. & Comp. A brown liver-coloured mass, which is brittle, slightly deliquescent, having a strong odour of sulphuretted hydrogen, especially when moist, and an acrid disagreeable taste; soluble in water, forming a yellow solution; the solution is precipitated by acids, with the deposition of sulphur, and strikes black with the salts of lead. The acid fluid when boiled and filtered is precipitated yellow by bichloride of platinum, and white by chloride of barium. It consists chiefly of tersulphuret of potassium (Ks3), with some sulphate of potash; about three-fourths of its weight (sulphuret of potassium) should be dissolved by rectified spirit.

Therapeutics. In small doses it acts as a stimulant diaphoretic and expectorant, and is sometimes employed in the treatment of chronic skin diseases, as scabies and psoriasis; also in chronic rheumatism, and certain cases of bronchitis. Externally in the form of ointment, bath, or lotion, in the above-named affections. It is poisonous in very large doses.

Dose. 3 gr. to 6 gr., in pill; in ointment, about 60 gr. to 1 oz. of lard.

Adulteration. When exposed, this compound becomes pale from oxidation and the formation of sulphate of potash.