288
ELEMENTS OF MATERIA MEDICA.
as an emmenagogue, and against hypertrophy of the ventricles. Prieger(quoted by Dierbach, die neuesten Entdeck. in d. Mat. Med. 1837) appliedit externally in the form of ointment in tinea capitis.
Administration. —It is exhibited in the form of pill or solution indoses of from four to ten grains three times a day. An ointment ofthis salt is made by mixing an ounce of lard with from a scruple to twodrachms of the bromide. To this some persons add free bronie.
Antidotes. —In a case of poisoning by this salt the treatment will bethe same as for iodide of potassium.
Potas'sii Sulphure'turn. — Sul’phuret of Potas'sium.
History. —Geber ( Invention of Verity, ch. vi.) was acquainted withthe solubility of sulphur in an alkaline solution; but Albertus Magnustaught the method of procuring sulphuret of potassium by fusion. Thepreparation kept in the shops is a mixture of the sulphuret of potassiumand sulphate of potash, and was formerly called sulphuret of potash, orliver of sulphur.
Preparation. —It is ordered to be prepared by rubbing one ounce ofsulphur with four ounces of carbonate of potash, and heating them in acovered crucible until they have united.
In this process the water and carbonic acid of the carbonate of potashare expelled. The oxygen and potassium of a portion of the potashunite with separate portions of sulphur to form sulphuric acid and asulphuret of potassium respectively. The sulphuric acid combines wdthsome undecomposed potash to form sulphate of potash. Supposingthe carbonate of potash to be anhydrous, and the sulphuret of potassiumto consist of one equivalent of each of its constituents, the followingdiagram will explain the changes :—
REAGENTS.
RESULTS.
efj, SW/y/i r .
4 eq. Cavb. Acid 88leq.Su!ph e .Pot h . 88
1 eq. Sulph 1 . Pot m .168
Berzelius ( Traite de Chim. t. 2 me . p. 301) says that if 100 parts ofcommon anhydrous carbonate of potash be heated with 58'22 of sulphur,the products are tersulphuret of potassium and sulphate of potash. Ifless than this quantity of sulphur be employed, a portion of carbonateremains undecomposed.
Properties. —When fresh prepared, it has a liver-brown colour; andhence its name hepar sulphuris. Its taste is acrid, bitter, and alkaline.If quite dry it is inodorous, but when moistened it acquires the odour ofliydrosulphuric acid. Exposed to the air, it undergoes decomposition,from the action of the aqueous vapour and oxygen. It becomes greenand moist, and ultimately whitish. This change depends on the abs rp-tion of oxygen, in consequence of which part of the sulphur is deposited,while a portion of the sulphuret of potassium is converted into hypo-sulphite, afterwards into sulphite, and ultimately into sulphate of potash.Sulphuret of potassium is soluble in water.
Characteristics.- Hydrochloric acid causes the evolution of hydro-