"Take of carbonate of potassa, a pound; of acetic acid, twenty-six fluid ounces; distilled water, twelve fluid ounces. Mix the acid with the water, and add to it the carbonate of potassa to saturation: then filter. Evaporate the solution on a sand bath, the heat being gradually applied until the salt is dried."

Acetas Potassae, Edin. Acetate of Potassa.

"Take of very pure carbonate of potassa, one pound; weak acetic acid, a sufficient quantity. Boil the subcarbonate in five pounds of the acid; and add more acid at different times, until, the watery part of the former portion being nearly dissipated by evaporation, the acid newly added occasion no effervescence, which will be the case when about twenty pounds of it have been consumed; then evaporate slowly to dryness. Liquefy this impure salt with a gentle heat for a short time; then let it be dissolved in water, and filter it through paper. If the liquefaction have been properly performed, the filtered fluid will be limpid; but, otherwise, of a brown colour. Afterwards evaporate this fluid in a shallow glass vessel, so that when removed from the fire it may pass into a crystalline mass. Finally, the acetate of potassa ought to be preserved in closely shut vessels."

Potassae Acetas, Dub. Acetate of Potassa.

"Take of carbonate of potassa from crystal of tartar, any quantity. Add to it gradually about five times its weight of distilled vinegar moderately heated. When the effervescence shall have ceased, and the fluid is somewhat evaporated, add, at intervals, more distilled vinegar, until the mixtures entirely cease to effervesce; then evaporate to dryness, and having raised the fire a little, cautiously liquefy the mass. Dissolve the salt in water, after it is cold: filter the solution, and let it be boiled, until, on being removed from the fire, it concrete into a crystalline mass, which should be very white. Put this mass, at the moment, into closely stopped bottles."

Syn. Kali acetatum, P. L. 1787. Acetate de Potasse (F.), Easigsaures Kali (G), Azynzuure Potasch (Dutch), Acetato di Potassa (I.).

In these processes, the acetic acid combines with the potassa of the carbonate, and expels the carbonic acid in a gaseous form, exciting effervescence. Owing to the largely diluted state of the acid in distilled vinegar, a very considerable quantity is required to saturate the potassa: the London College, therefore, now order the acetic acid, diluted with less than half its measure of water, to be used. Towards the point of saturation, when distilled vinegar is employed, the solution acquires a reddish-brown colour, and during the evaporation a small quantity of carbonaceous matter is deposited; or if the liquor be evaporated to dryness, a brownish coloured salt is obtained : but it is not coloured if the acetic acid be employed. The filtering the evaporated fluid, or fusing the salt, or keeping it for a little time fluid, then dissolving it in water, and filtering it, frees it almost entirely from colour, and a light carbonaceous matter remains on the filter. The filtered solution is nearly limpid and colourless; and when again evaporated it forms a nearly colourless salt.1 It is rendered still more colourless, if a portion of animal charcoal be added to the solution.2 The salt of the present Pharmacopoeia is free from odour.3

Qualities, - Acetate of potassa has a slight, peculiar odour, and a warm, sharp taste. It is usually in white masses, of a foliated, soft texture, shining, and becoming soon moist if exposed to the air. Exposure to a red heat converts it into carbonate of potassa. One fluid ounce of distilled water at 60° dissolves 504 grains; or 100 parts of it are soluble in 102 parts of water, and in twice its weight of alcohol. It is sometimes adulterated with tartrate of potassa, which may be detected by adding to a solution of the salt a solution of acidulated acetate of lead: a precipitate will fall soluble in acetic acid. Sulphates are detected by adding a solution of acetate of baryta; and hydrochlorates, by adding nitrate of silver. In the watery solution it is spontaneously decomposed; and is also decomposed by the strong acids; by a decoction of tamarinds; the sulphates of soda and of magnesia; the hy-drochlorate of ammonia; the tartrate of potassa and soda; and by solutions of bichloride of mercury, and of the nitrate of silver; which consequently cannot enter into formulae with it.

1 A very pure and beautiful salt, but too expensive for common use, may be prepared by adding to a solution of two parts of acetate of lead, a solution of one part of carbonate of potassa, and after filtering the liquor, adding to it a small portion of sulphate of potassa, and filtering again before evaporation. Vide Journ. de Pharm. Mai, 1818. p. 203,

3 Ann. de Chim. vol. lxxxvi. p. 44.

3 This salt was first described by Raym. Lully, and has been known by a great variety of names; as, for instance, arcanum tartari, secret foliated earth of tartar, essential salt of wine, regenerated tartar, diuretic salt, and digestive salt of Silvius.

Its constituents are 51.5 of acetic acid + 48.5 of potassa in 100 parts; or 1 eq. of acetic acid - 51.48 + 1 potassa = 47.15; 2 eq. of water, makes the equivalent = 116.63.

Medical properties and uses.-Acetate of potassa is mildly cathartic and diuretic. It is found to be occasionally beneficial in febrile affections and jaundice; but its principle use is in dropsies, and other diseases in which a copious discharge of urine is required. The manner in which this is effected is endeavoured to be explained by Dr. Paris, by assuming as a fact, that the stomach possesses "the power of readily decomposing all saline compounds, into which vegetable acids enter as ingredients, and of eliminating their alkaline base, which being in the course of the circulation carried to the kidneys, excites them into action, and promotes the excretion of urine."l But there are many objections to this theory. To produce its diuretic effect, the dose is from Эj. to 3j., given every three or four hours, in any bland fluid, or united with infusions of any of the lighter vegetable bitters, such as quassia or gentian. Doses of 3ij. or 3iij. open the bowels.

Officinal preparations. - Acetas Hydrargyri, E. D. Tinctura Acetatis Ferri, D. Acidum Aceticum, D. E.