Sal Enixum of Commerce.
Qualities. Crystals, long hexangular prisms; Taste, sour and slightly bitter. Chemical Composition. It is a bi-sulphate, consisting of two proportionals of acid, and one proportional of base. Solubility. It is soluble in twice its weight of water, as well as in alcohol. Med. Uses. It affords a convenient mode of exhibiting sulphuric acid combined with a saline purgative, in a solid form; as it is more soluble, so is it more active than the sulphate. Dose, grs. x to ʒij. It forms a grateful adjunct to rhubarb. See Form. 85.
POTASSÆ SULPHURETUM. L.E.
Sulphuretum Kali. D.
Kali Sulphuretum, P.L. 1787. Hepar Sulphuris.
Qualities. Form, a hard brittle mass; Colour, liver brown, hence the old name of hepar; Taste, acrid and bitter; Odour, none when dry, but if moistened, it yields the stench of sulphuretted hydrogen. Chemical Composition. I consider this substance as a mixture of Sulphate of Potass, with variable quantities of Sulphuret and Bi-Sulphuret of Potassium.[[612]] Incompatible Substances. It is instantly decomposed by water, the oxygen of which forms Potass with the Potassium; while its hydrogen, combining with the sulphur, produces Sulphuretted hydrogen, part of which escapes, and another part forms, with the excess of Sulphur, Bi-Sulphuretted hydrogen; this latter body uniting with the base, produces what has been termed an Hydroguretted Sulphuret, but which might be more properly called an Hydro-bi-Sulphuret; upon adding an acid to the solution, a quantity of Sulphur is thrown down, Sulphuretted hydrogen is evolved, and a salt of Potass remains in solution. Metallic salts also decompose it, the metal falling down as a Sulphuret, or Hydro-sulphuret. Medicinal Uses. It presents us with a form in which sulphur is soluble in water; it is diaphoretic, and has been found advantageous in cutaneous affections, (Form. 118,) and in arthritic and rheumatic complaints; while, from its known chemical action on metallic salts, it has been proposed as an antidote to such poisons. Its solution has been lately recommended as a lotion for the itch of infants, and in some cases it has been known to succeed after the sulphur ointment had failed.[[613]]
POTASSÆ SUPER-TARTRAS. L.E.
Tartarum Crystalli. E.
Super-Tartrate of Potass. Crystals of Tartar.
Qualities. Form, small irregular brittle crystals, which when reduced to powder are termed cream of tartar. Taste, harsh and acid. Chemical Composition. It is a bi-tartrate, consisting of two proportionals of acid and one proportional of potass. Solubility. It requires 120 parts of water at 60°, and 30 parts at 212°, for its solution; it is slightly soluble in alcohol. The watery solution of this salt was first observed by Berthollet to undergo a spontaneous decomposition by keeping, during which a mucous matter is deposited, and there remains a solution of carbonate of potass coloured with a little oil. It has long been regarded a pharmaceutical desideratum to increase the solubility of cream of tartar; Vogel discovered that it might be accomplished by combining it with boracic acid, and accordingly a formula has been introduced into the Codex Medicamentarius of Paris, for preparing a “Tartras Acidulus Potassæ Solubilis, admixto Acido Boracico.” The following is the process. Let thirty parts of boracic acid, and twenty parts of distilled water be heated together in a silver dish; as soon as this has been effected, add, in divided portions, 120 parts of super-tartrate of potass, taking care to shake the mixture continually; the whole will soon liquefy, (“mire liquescent,”) and by continuing the heat, a pulverulent mass will result. As it is extremely deliquescent it must be carefully preserved from the contact of the air; it dissolves in its own weight of water at 55°, and in half its weight at 212°. It is probable that the result is a new salt, in which the boracic and tartaric acids exist in combination,[[614]] but grant even that the chemical identity of the super-tartrate is preserved inviolate in the compound, I would ask what medical advantage can possibly attend the discovery? The peculiar value of cream of tartar depends doubtless upon its comparative insolubility, as I have already stated at page 173; modify this, and you will instantly change the medicinal effects of the salt; for like the neutral tartrate it will act upon the bowels, and therefore cease to undergo those changes in transitu which are essential to its characteristic operation. Alum also has been observed by Berthollet to have in some measure the same effect in increasing the solubility of cream of tartar. Incompatible Substances. Alkalies and alkaline earths; the mineral acids, &c. Med. Uses. In doses of ʒiv to ʒvj, it acts as a hydragogue cathartic, producing a considerable discharge of serous fluid into the intestines; when however it is often repeated, it is liable to occasion debility of the digestive organs, and consequent emaciation: in smaller doses it acts as a diuretic. (Form. 112.) ʒj in oj of boiling water, flavoured with lemon peel and sugar, forms when cool an agreeable beverage well known by the name of Imperial. A Cream of Tartar Whey may be made, by adding to a pint of milk (when it begins to boil) ʒij of Cream of Tartar; the pan must then be removed from the fire, the whole suffered to cool, and the whey separated from the curd by straining; this whey, diluted with warm water, furnishes an excellent drink in Dropsy. As it decomposes the carbonate of potass, the union of these salts will afford a very pleasant purgative draught. (Form. 82.) Officinal Preparations. Pulv. Jalap. comp. E. (BM) Pulv. Scammon. E. Pulv. Sennæ comp. L. Ferrum Tartarizatum, L. (I) Antimonium Tartarizatum L.E. D. (I) Soda Tartarizata, L.E.D. (I) Adulterations. Super-sulphate of potass (Sal Enixum,) is the substance with which tartar is usually adulterated; it may be detected by its superior solubility, and by the solution affording with muriate of baryta a precipitate insoluble in muriatic acid.[[615]]