The following are the ordinary tests for the potassium compounds: 1. Solution of tartaric acid added in excess to a moderately strong solution of a potassium salt, gives after some time a. white crystalline precipitate of cream-of-tartar. See TARTARIC ACID. The result is hastened by stirring or shaking. 2. Solution of bichloride of platinum gives a crystalline yellow precipitate, which is a double salt of bichloride of platinum and chloride of potassium. If not previously acid, the mixture to be tested should be acidulated wills hydrochloric acid. See PLATINUM. 3. The violet tint occurring in the presence of potassium in the outer flame of the blow-pipe, or in the flame of spirit, has been already noticed. 4. The spectrum of a flame containing potassium exhibits it characteristic bright line at the extreme limit of the red, and 'another one at the opposite violet limit of the spectrum. See SPECTRE:II ANALYSIS.
The British Pharmacopmia contains the following preparations of this metal: Caustic potash, or hydrate of potash. (10,110), which occurs in hard white pencils. From its being fused before being poured into the metlds which give it the form of pencils, it is often termed potassa fuse. From its power of dissolving the animal tissues, it is 'some times used as a caustic, although its great deliquescence renders it somewhat difficult to localize its action to the desired spot. In bites of venomous serpents, mad dogs, etc., it may be applied with advantage, and it is useful in destroying warts and fungoid growths of various kinds. It can be employed with greater safety than the lancet in opening certain abscesses, especially those of the liver. Solution of potash, commonly known us liquor potassce, is obtained by the process already given for the preparation of hydrate of potash—namely, by the action of slaked lime on a boiling solution of carbonate of potash. Its sp. gr. is 1.058, and hence the solution is somewhat weaker than that of the London pharmacopeia, whose sp. gr. is 1.063, and which, according to the experiments of Mr. Phillips, contains 6.7 grains of potash in 100 grains of the solution. ‘• One fluid ounce requires, for neutralization, 48.25 measures of the volumetric solution of oxalic acid." Liquor potasste, in combination with a tunic infusion, is of service in cases of dyspepsia which are accompanied with excessive acidity of the stomach, such, for example, as often occur in habitual spirit-drinkers. It is also frequently given with the view of rendering the urine alkaline, or of diminishing its acidity in cases in which that secretion is too acid. In chronic skin-diseases, especially those of a scaly nature, it often gives relief, if given in full doses, and for a sufficient time: and in chronic bronchitis it is given with advantage for the purpose of diminishing the viscidity of the bronchial mucus. The usual dose is ten drops, gradually increased to as much as a fluid dram. Infusion of orange-peel and table-beer are fluids which conceal its unpleasant taste. Veal-broth has also been recommended as a medicine in which to present it. Its too prolonged use renders the urine alkaline and sedimentary (from the deposit of phosphate of lime), and tends to impoverish the blood. Sulphurated potash, or potassa sulphurabt which is the new name for the sulphuret of potassium, or liver of sulphur (hcpar salplauris)—is obtained by fusing together carbonate of potash and sublimed sulphur. It occurs in solid greenish masses, which arc liver-brown when recently broken. It is
alkaline and acrid to the taste, readily forming with water a yellow solution, w hich has the odor of sulphureted hydrogen, and evolving that gas freely, on the addition of an excess of hydrochloric acid. It is sometimes given internally in doses of duet: grains (in the form of a pill made with soap), in obstinate skin-diseases; hut is chiefly used as a lotion, bath, or ointment for these diseases. It must be recollected that this compound is an energetic narcotico-acrid poison, its action being very like that of sulphureted hydrogen. Acetate of potash, (KO,C is obtained by the action of acetic acid on carbonate of potash, and occurs in white foliaceous satiny masses. In its passage through the system it is converted into carbonate, and thus renders the urine alkaline. In small doses, as from a scruple to a dram, it acts as a diuretic, and is of service in some forms of dropsy. Combined with other potass-salts, it is touch given in acute rheumatism. Carbonate of potash is employed in medicine in the same cases as those in which solution of potash is used. In large doses it acts, likes caustic potash, as an irritant poison. It is frequently employed in the preparation of efferves• cing draughts, 20 grains of this salt being neutralized by 17 grains of citric acid, or 18 grains of tartaric acid, or by half a fluid-ounce of lemon-juice. Bicarbonate of potash may be used in the same cases as the carbonate or solution of potash. It is chiefly used for the manufacture of effervescing draughts, 20 grains of the crystallized salt being neutralized by 14 of citric acid, 15 of tartaric acid, and 34- drams of lemon juice. 6'lilorate of potash is prescribed with advantage in diseases of a low type. such as scarlatina maligna, tantrum oris, diphtheria, scurvy, etc. As it is elhn inated unchanged by the kidneys, its modus operandi is unknown. It may be prescribed in doses of from 10 to 20 grains three times a day in solution. Citrate of potash is obtained by neutralizing a solution of citric acid with carbonate of potash, filtering and evaporating to dryness, when the salt is deposited as a white powder of a saline, feebly-acid taste, 'deliquescent, and very soluble in water. It is procured extempore in a state of solution in the effervescing draughts for which we have given prescriptions in our remarks on the carbonates of potash. It acts mildly on the skin, bowels, and kidneys, whose secretions it promotes, and is an excellent cooling dia phoretic in fevers with a hot and dry skin, being less liable to net on the bowels than the tartrate or acetate of potash. In irritability of the stomach, it is an excellent remedy, when given as an effervescing draught. It may be taken in doses of a scruple or half a dram in solution every few hours. The therapeutic uses of nitrate of potash are noticed in the article NITER. Sulphate of potash (KO,S03) is useful as a mild laxative, a scruple of this salt, especially if combined with ten grains of rhubarb, usually acting mildly and efficiently. It has considerable power in repressing the secretion of milk, and has be, a, much used for this purpose.
The uses of the tartrates of potash are noticed in the article TARTARIC ACm. Bromids of potassium (liTir) occurs in white, transparent, cubical crystals, and is occasionally employed in enlargement of the spleen and in certain forms of epilepsy. The uses of iodide of potassium are described in the article IoDENE.