"Take of sulphur, an ounce; carbonate of potassa, four ounces. Rub them together, and place the mixture over the fire in a covered crucible until they unite."

Sulphuretum Potassae

Edin.

1 Phillips's Trans, of the Pharmacopoeia, p. 56. 1837.

2 Quoted by Brande, Manual of Pharm. p. 232.

3 Kali sulphuratum, P. L. 1787.

"Take of subcarbonate of potassa, two parts; sublimed sulphur, one part. Rub them together, and put them into a large, covered crucible, to which, having adapted a cover, apply the fire cautiously, until they melt. Preserve the mass in a well-closed vessel."

Sulphuretum Potassae, Dub. Sulphuret of Potassa.

" Take of carbonate of potassa, four parts; sublimed sulphur, one part. Having mixed them together, put them into a crucible, and having adapted to it a cover, expose it to a fire gradually raised until they unite."

Syn. Sulphure de Potasse(F.), Schwelflichtes Kali (G.), Solfuro di Potassa

This sulphuret cannot be properly formed by following the directions of any of the Colleges : for, to render the action complete, it is necessary to expose the carbonate in a crucible to a red heat, previously to its being rubbed with the sulphur, in order to dissipate the water of the carbonate, and to expel a portion of the carbonic acid. When the fusion is effected, the mixture is to be poured upon a marble slab, and as soon as it concretes, the mass must be broken in pieces and instantly put into a closely-stopped bottle. In this process the potassa, after the carbonic acid is expelled, is partly decomposed, and the oxygen of that portion combining with a portion of the sulphur forms sulphuric acid, which combines with the undecomposed portion of the potassa, and forms sulphate of potassa. The remainder of the sulphur combines with the potassium and forms a sulphuret: thus making the result of the process a compound of one eq. of sulphate of potassa and three eq. of sulphuret of potassium.1

Qualities.-Well-prepared sulphuret of potassium, is inodorous while; dry but when moistened or dissolved in water, a partial decomposition of both the water and the sulphuret is effected, and sulphureted hydrogen is formed. It has an acrid, bitter taste; changes the vegetable blues to green; is hard, brittle, breaking with a glassy fracture, of a liver-brown colour, and stains the skin brown.2 By exposure to the air it attracts moisture; its colour changes to a pale green; the foetid odour noticed above is emitted; and it is gradually converted into sulphate of potassa. It is also decomposed by all the acids which expel sulphureted hydrogen, and the sulphur is precipitated. In a violent heat the sulphur sublimes, leaving the potassa. The constituents of the sulphuret are 1 eq. of potassium = 39.15 + 1 of sulphur = 16.1; making the equivalent 55.25.

1 A simple or monosulphuret is formed by decomposing sulphate of potassa by means of a high temperature, in a crucible lined with a charcoal lute, the vacant space being filled with charcoal rammed hard, and the cover luted on. The oxygen of both the potassa and of the sulphuric acid is carried off by the carbon, whilst the sulphur and the potassium remain in combination as a sulphuret.

2 Hence its old name, hepar sulphuris.

Medical properties and uses. - Sulphuret of potassium is expectorant and diaphoretic. It has been frequently given in chronic asthma and bronchitis, and in pertussis, without much benefit; but it has been found useful in arthritic, rheumatic, and herpetic affections; and in combination with conium as a palliative in cancerous cases.1 It has also been employed in France, for the cure of scabies, in the form of a bath, or of an ointment made with one part of the sulphuret, sixteen of soap, and thirty-two of oil. From a theory founded on its chemical action on metallic salts out of the body, it has also been strongly recommended as an antidote against arsenical, saturnine, and mercurial preparations, when these have been taken in doses sufficient to produce deleterious effects; but as far as concerns arsenical poisons, it has been recommended on erroneous principles.

The usual dose is grs. v. or grs. viij., combined with soap, in the form of pills, for the first-mentioned cases; or from grs. v. to grs. x. as an adjunct to conium in cancer, given several times a day; or as an ointment, 3j. to j. of lard.