SULPHUKET OF POTASSIUM.

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sulphuric acid gas and the precipitation of sulphur; the solution ofthe sulphuret in water produces a reddish or black precipitate with asolution of lead. That it contains potassium may be determined thus :—Add excess of hydrochloric acid to a solution of it; boil, and filter.The before-mentioned tests for potash may be then applied.

Composition. —-According to Berzelius this preparation consists oftersulphuret of potassium, sulphate of potash, and carbonate of potash.

Physiological Effects, {a.) On plants. —There can be no doubtbut that this compound is a powerful poison to plants, though I am notacquainted with any experiments made with it.

{b.) On animals generally. —From the experiments of Orfila ( Toxicol.Generate ) on dogs, sulphuret of potassium appears to be a powerful nar-cotico-acrid poison. Six drachms and a half, dissolved in water, andintroduced into the stomach, caused convulsions and death in sevenminutes.

(c.) On man. —In small doses (as from four to ten grains) it acts as ageneral stimulant, increasing the frequency of the pulse, augmenting theheat of the body, promoting the different secretions, more especially thoseof the mucous membranes, and sometimes exciting local irritation, markedby pain, vomiting, and purging. By continued use it acts as a resolventor alterative, and on this account is employed in certain forms of inflam-mation.

In large doses it is an energetic narcotico-acrid poison. In twoinstances it proved fatal in fifteen minutes: the symptoms were, acridtaste, slight vomiting, mortal faintness, and convulsions, with an impor-tant chemical sign, the tainting of the air of the chamber with the odourof hydrosulphuric acid (Christison, p. 228).

Its local action is that of a powerful irritant: hence the acrid taste,burning pain, and constriction in the throat, gullet, and stomach, withvomiting and purging. But the nervous system also becomes affected,as is proved by the faintness, the almost imperceptible pulse, the, con-vulsions, and (in some cases) sopor. These symptoms are analogous tothose caused by the hydrosulphuric acid ; which, in fact, is copiouslydeveloped in the stomach.

Uses. —Internally it has been administered in very obstinate skin dis-eases, such as lepra and psoriasis, which have resisted all the ordinarymeans of cure. It has also been employed as a resolvent in inflamma-tions attended with lymphatic exudation, as croup, and in glandularenlargements. In chronic rheumatism, gout, hooping-cough, and variousother diseases, against which it was formerly employed, it is now rarelyif ever administered. It ought not to be given as an antidote for metallicpoisoning, since it is itself a powerful poison.

Externally it is applied in the form of lotions, baths, or ointment. Inchronic skin diseases, such as eczema, scabies, lepra, &c. it is employedas a bath, in the proportion of four ounces to thirty gallons of water.These baths are said to be particularly useful in the treatment of scabiesin children, but twenty at least are requisite to effect a cure. (Rayer,Treatise on Diseases of the Skin, p. 346.) Lotions are sometimes madefor local cutaneous affections, containing a larger quantity of the sulphuret(as an ounce to two quarts of water).

Administration. —Internally it may be administered in the dose of

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