- Potassae Aqua. Ed. - Potassae Causticae Liquor. Dub.

- Water of Potassa.

Preparation and Properties. The officinal solution of potassa is prepared by boiling caustic lime with a solution of bicarbonate of potassa. The lime takes the carbonic acid, and falls as an insoluble carbonate, and the liberated potassa remains dissolved in the water, which is decanted, when it has become clear after standing. The materials are used in definite quantities, and the resulting solution has consequently a definite strength. Prepared according to the directions of the U. S. Pharmacopoeia, it has the sp.gr. 1.065, and contains 5.8 per cent. of hydrate of potassa. The British preparation has the sp. gr. 1.058, and is therefore considerably weaker than ours.

It is perfectly colourless and inodorous, and has very strongly the peculiar acrid, very disagreeable, soapy taste of the alkalies. it is known to contain potassa by affording a yellow precipitate with chloride of platinum, and a copious white precipitate of bitartrate of potassa with an excess of tartaric acid. it is incompatible with all the acids, the acidulous salts, the soluble salts of the common metals, including their soluble chlorides and iodides, the salts of ammonia, and calomel. it dissolves resins and fixed oils, forming soaps with the latter. As it attracts carbonic acid from the air, it should be kept in well-stopped bottles.

Medical Effects and Uses

Solution of potassa has, in a high degree, all the characteristic properties of the alkalies. in relation, however, to the neutralizing or antacid power, both this preparation and the carbonates are much inferior, for equal weights of the pure alkali or earth, to any other of the medicines used as antacids; for, while the equivalent of soda, which is next in order, is 31.3, that of potassa is 47.2; that is, the quantity of acid which will require 31.3 parts of the former for neutralization, will require 47.2 of the latter. Hence, purely as antacids, potassa and its carbonates stand at the bottom of the scale.

In over-doses, the solution of potassa is capable of producing fatal inflammation or erosion of the stomach. in a case of poisoning, the proper antidote would be one of the vegetable acids, as vinegar, lemon-juice, or tartaric acid; and, if neither of these should be at hand, one of the mineral acids, much diluted.

The solution has been used for the antacid, antilithic, and antiphlogistic effects of the alkalies, but has no advantage whatever over the carbonates, while it is more unpleasant, and much more hazardous. It should, therefore, I think, be abandoned as an internal remedy. Externally, it is sometimes used as a rubefacient, but has no special virtues in this capacity. it is more important as a pharmaceutic than as a therapeutic agent. The dose for internal use is from ten to thirty minims, twice or three times a day. When given, it should be largely diluted either with water, one of the aromatic waters, or a bitter infusion.