Preparation

Acetate of potassa is prepared by treating bicarbonate of potassa (U. S.) or carbonate of potassa (Br.) with acetic acid more or less diluted, and evaporating the solution either to dryness, as directed in the U. S, Pharmacopoeia, or so that it shall upon cooling concrete into a crystalline mass, as ordered in the British. When crystallized, it consists of one equivalent of acetic acid, one of potassa, and two of water. it should be kept in well-stopped bottles.

Properties

it is a white salt, exhibiting a fibrous texture when its solution is evaporated to dryness, but foliated when it crystallizes. it is very soft to the touch, of a pungent, saline, disagreeable taste, very soluble in water and alcohol, and extremely deliquescent. By heat it is decomposed, and carbonate of potassa is left. It is known to be an acetate by exhaling the odour of vinegar, when treated with sulphuric acid, and to be a salt of potassa by giving, with an excess of tartaric acid, a precipitate of bitartrate of potassa. it is decomposed by almost all the acids.

Medical Effects and Uses

Acetate of potassa has been known since the thirteenth century. in small doses, frequently repeated, it operates as a diuretic, especially if taken dissolved in a large proportion of water, and the patient is kept cool. in larger doses it is cathartic.

It has been ascertained to render the urine alkaline; the acetic acid being decomposed in the system, and the salt converted into the carbonate; and it is probably mainly in this new form of combination that it produces its effects. The juices of various plants contain acetate of potassa, and have similar properties.

This salt has been long employed as a diuretic, and formerly had so much reputation as to have received the name of sal diureticus, by which it was generally designated. Very different opinions, however, have been entertained as to the degree in which it possesses the diuretic power; and it is certainly much less esteemed in this respect now than formerly. The statement of Cullen, that " though trying the exhibition of it in various ways, he could never render its diuretic effects remarkable, or fit to be depended on, when a large discharge of urine was required," probably contributed to the disgrace into which it generally fell. Yet there are some who still have a high opinion of its powers, and I have known it to be preferred even to the bitartrate. Having seldom used it, I am unable to decide between the conflicting opinions; but cannot help thinking that they who had formed an unfavourable estimate of its powers, have used it in doses either too small, or not often enough repeated. I know that many failures with cream of tartar have been owing to that cause; and, in consideration of the old reputation of the acetate, and the success obtained with it by some practitioners of the present time, it is very reasonable to suppose, that a want of similar success on the part of others may have depended on an inefficient method of administration.

Dropsy is the disease in which it has been most used; and it may be given under the same circumstances, in this affection, as the bitartrate and nitrate of potassa.

It has, moreover, been employed in several other complaints, in which it probably owes its efficacy mainly to its property of rendering the blood and urine alkaline. Thus, it has been found useful in various cutaneous eruptions, in which alkalies are among the most efficient remedies. With the same view, it has been used in acute rheumatism by some of the advocates of the alkaline method of treating that disease; and has been recommended in the uric acid lithiasis, in which alkalinity of the urine is always aimed at, in order that the urates may be held in solution, and their deposition prevented. Ambrosoli has obtained good effects from it in acute and subacute gonorrhoea. At least three ounces of it, however, must be taken altogether, before a favourable result can be expected. it is of no use in chronic urethritis. {Ann. de Thérap., 1863, p. 115.)

The dose with a view to the diuretic effect, or to alkalize the urine, is from half a drachm to a drachm, to be repeated three or four times a day, or more frequently; and it is probable that once every two or three hours will not be too frequent. The medicine should be given in solution. Two or three drachms of it are said to be aperient.

Carbonate And Bicarbonate Of Potassa have also been used as diuretics, and are not without considerable efficiency in this respect. They cannot, however, be depended on exclusively in the treatment of dropsy, but may be used in all cases in which there is a coincident indication for an antacid, either on account of an excess of acid in the primae viae, or the deposition of uric acid or the urates from the urine. The ashes of certain plants formerly had some reputation as diuretics, which they owed to the carbonate of potassa contained in them; and the sal absinthii or salt of wormwood, which was formerly highly esteemed, was nothing more than an impure carbonate of potassa obtained by lixiviating the ashes of that plant.

Carbonate And Bicarbonate Of Soda have, in some degree, the same disposition to excite the kidneys, but are less efficient than the corresponding salts of potassa. Castile soap, of which soda is the basis, has also been supposed to possess diuretic properties.

Of all these alkaline carbonates, as well as of caustic potassa, which also is diuretic in solution, more will be said when the class of antacids shall come under consideration.