Potassium Compounds.

Potassium is a bluish-gray metal, soft, with such a strong affinity for oxygen that it must be preserved under naphtha, and capable of decomposing water with such avidity as to inflame the liberated hydrogen by the heat evolved. It is generally prepared by first calcining crude tartar, (tartrate of potassa,) mixing this with one-tenth its weight of charcoal in small pieces, and then distilling over the potassium, at a red heat, from a retort of hammered iron with an escape tube dipping into a receiver partly filled with naphtha and surrounded by ice. The metal is not used alone, nor often procured for the purpose of making compounds with it, as the majority of its compounds are obtained, by various processes, from the refined carbonate of potassa (pearl-ash) procured from the leaching of wood ashes.

CARBONATE OF POTASSA. KO, CO₂+2HO.This salt is a prominent constituent of all inland plants, as a corresponding salt of soda is of marine plants. It is prepared by evaporating the lye of wood ashes, calcining the coarse product to drive off organic matter, dissolving the remaining saleratus with its own weight of cold water, filtering, and again evaporating to dryness. It comes on the medical market as a snow-white, pearly, granular powder, which slowly absorbs moisture and becomes deliquescent, and is many times filled in orders for the more costly bicarbonate. It is a strong alkali, not often suited to inward use.

BICARBONATE OF POTASSA. KO, 2(CO₂,)+HO. This is prepared by passing a stream of carbonic acid gas through a cold solution of the above carbonate. The gas is rapidly absorbed to the extent of an additional equivalent, and a white crystalline compound falls. This is dissolved in three times its own weight of warm water; and, on cooling, the purified bicarbonate forms large, colorless, nearly transparent, rhomboidal crystals, whose size and hue distinguish them from the small and white crystals of carbonate. The bicarbonate does not deliquesce, is less soluble than the carbonate, and is a much milder alkali. Heat and boiling drive off the second equivalent of carbonic acid and leave the simple carbonate of potassa. The bicarbonate is far preferable to the carbonate for medical use, an equal weight of it will neutralize more acidity than will the bicarbonate of soda, and it is usually more acceptable to the stomach than most of the alkalies. The chief use made of it, is to relieve acidity of the stomach, especially in the form of Neutralizing Cordial; but it is also employed as the alkaline basis in various effervescing powders and draughts, and some have commended it in rheumatism (to little real advantage.) Like other alkalies, it may be used so freely as to neutralize the gastric juice as well as the morbid acidity of the stomach; whence three or four grains are usually a sufficient dose, though ten or more grains may be used on occasion.

POTASSA CAUSTICA, Hydrate of Potassa, Caustic Potash. KO, HO. Dissolve one part of carbonate of potassa in ten parts of distilled water, bring to the boiling point, add small portions of milk of lime at intervals of a few minutes, (boiling for two minutes after each such addition, and carefully replacing the water lost by evaporation.) The lime removes the carbonic acid from the potassa, and falls as a fine carbonate of lime, the clear liquor potassa remaining. This liquor is then to be drawn off carefully with a syphon, and rapidly evaporated to a solid consistence. This is then purified by being dissolved in alcohol, which takes out the pure hydrate, and leaves undissolved any carbonate of lime or potassa. The alcohol is then to be quickly evaporated, and the liquid poured into small cylindrical molds as it nears the solid consistence. It comes to market in small grayish-white sticks, four or five inches long, is intensely caustic, and has such an avidity for water as to soften into a dense liquid unless kept in very tight bottles. At present, it is seldom applied as a caustic, partly on account of the pain it often causes as it destroys both living and half-dead structures, and partly from its tendency to soften and spread beyond the parts where it is needed.

POTASSA CUM CALCE, Potassa with Lime, Milder Common Caustic. Equal quantities of caustic potash and unslaked lime are rubbed together, and kept in well-stoppered bottles. Or the potash may be heated to fusion in an iron spoon, the lime added in successive portions with stirring, and the mass poured into leaden molds. It is a milder caustic than the preceding, yet a potent one; and is not deliquescent, nor very liable to spread. The powder is moistened with alcohol, and is often called Vienna paste. A. strip of adhesive plaster around the part to be cauterized, will keep it from spreading.

CHLORATE OF POTASSA. KO, C₁₀. The common method of preparing this salt, is that of passing a stream of washed chlorine over a damp mixture of seven parts carbonate of potassa and sixteen parts slacked lime, with continuous stirring. Boiling water dissolves out the chloride of potassium and chlorate of potassa thus formed, leaving the carbonate of lime; and by evaporation, the chlorate crystallizes while the chloride remains in solution. It forms thin, white, tabular crystals, of a slightly saline taste. Used internally, it has acquired much celebrity in the treatment of diphtheria, scarlatina, and other cynancheal affections; but I am fully convinced that it is a feeble article in such maladies, and much less antiseptic than the chloride of sodium, (common salt.) It is also commended highly, by Allopathists, as a cure for salivation; and probably they are prepared to judge on this matter. Some are of the opinion that it is a poison; but there seems to be no good ground for this belief, beyond the fact that even innocuous mineral compounds are not well received in large quantities. From ten to even thirty grains have been given, at intervals of three or four hours. Gum water is the best medium for its exhibition, using enough to dissolve the salt.

BITARTRATE OF POTASSA, Cream of Tartar. The tart wines slowly deposit a whitish crystalline substance, during the slow fermentation they undergo after having been racked off and stored in casks. This is called crude tartar, or argol. This is purified by melting in as little boiling water as will dissolve it, allowed to cool and crystallize, and redissolved and crystallized. The second crystals are bleached to pure whiteness on linen stretchers, and then pulverized. It is white, somewhat gritty, of a rather pleasant and quite mild acid taste, insoluble in alcohol, soluble in eighteen parts of boiling and nearly two hundred parts of cold water. It is classed among the cooling diuretics and cathartics, in large doses procuring rather watery stools. Dissolved in cold water, and sweetened, it is used as a grateful drink in fevers, and to promote the action of the kidneys. Combined with senna, jalap, podophyllum, and some other physics, it seems to increase their activity. To move the bowels, a drachm or more may be given, in water. Ten to fifteen grains may be dissolved in a tumblerfull of water, the desired quantity of sugar added, and a tablespoonful or more allowed at intervals. To the Physio-Medicalist, it is not an attractive remedy.

SULPHURET OF POTASSIUM, Hepar Sulphuris, Liver of Sulphur. KS. This is prepared by mixing intimately one ounce of fine sulphur with two ounces of carbonate of potassa, and slowly bringing them into fusion in a covered crucible. The resultant mass is really a bisulphide of potassium. It is a dense, brittle, greenish mass, with a nauseous and alkaline taste, and a filthy smell not unlike rotten eggs. It must not be confounded with the white salt, sulphate of potassa. During the reign of the first Napoleon, this article came into great repute as a specific for croup, owing to an essay on it having received a prize offered by the Emperor–another instance of the folly of heeding titled "authority" in preference to obeying Nature. The only medical use it is fit for, is as a wash for itch; and there it is a specific. A good method of employing it, is first to wash the patient thoroughly with soap and water, then with half an ounce of this sulphuret dissolved in twelve ounces of water and four ounces of rose water. Entirely fresh clothing should then be put on; and if the wash have been made to penetrate the sores, one application is usually sufficient.

Most of the other compounds of potassium, as well as some of the above, are more or less poisonous, though many of them are in use by Allopathic and Eclectic physicians. Among these may be enumerated: Nitrate of potassa, or saltpeter; acetate of potassa; cyanuret of potassium; and iodide of potassium. However highly these may be praised, they came into use only as agents capable of "producing another disease," (§66,) and the testimony as to their destructive powers is ample.

The Physiomedical Dispensatory, 1869, was written by William Cook, M.D.
It was scanned by Paul Bergner at http://medherb.com