616

Alkalies and Neutral Salts.

PART III.

Owing to the great proportion of water of crystallizationthis salt contains, it readily undergoes the watery fusion, andis completely dried by continuing the heat; but its propertiesare not otherwise altered. The constituents of 100 parts, inthis state, according to the analysis of Kirwan, are 40* 14 ofacid, and 59*86 of soda ', which nearly accords with the analy-sis of Dulong and Dal ton.

Medical properties and uses. — The chief advantage obtainedfrom drying the subcarbonate of soda is the facility of exhibit-ing it in the form of pills; for when the crystallized salt isused for this purpose, the pill formed with it falls to pieces assoon as the salt effloresces. Dr. Beddoes* has extolled it, inthis form, as a remedy in calculous affections: and it certainlyaffords relief from the painful symptoms attending calculus inthe kidneys, and other urinary affections: but its effects are pal-liative only; and depend on its destroying the prevalent acidin the stomach. The dose is from grs. x. to grs. xv., giventhree times a day. Beddoes directed it to be combined withsoap and aromatics.

AQUA SUPER-CARBONATIS SOD/E, Edin. Waterof Supercarbonate of Soda.

" Take of water ten pounds ,• subcarbonate of soda, ticoounces,■ dissolve and subject the solution to a stream of caroo-nic acid gas procured from three ounces of carbonate of lime, andthe same quantity of sulphuric acid, with three pounds of wa-ter, gradually and cautiously mixed together. It may be con-veniently prepared in Nooth's apparatus. But if a largequantity of it be required, an apparatus capable of affordinga greater pressure will be requisite. The fluid must be pre-served in well-corked bottles.

This preparation is milder and pleasanter than the waterprepared with subcarbonate of potass. It is manufactured inlarge quantities on a great scale, of a much superior qualityto any which the apothecary can prepare ; and is in very gene-ral use as a cooling beverage. Half a pint of it poured overtwo table-spoonsful of lemon-juice, sweetened with a little sugar,forms an excellent and very agreeable effervescing draught;and the same quantity poured upon two ounces of boiling milkforms an excellent substitute for asses' milk.'

SO'DiE SUL'PHAS, Lond. Sulphate of Soda.

1 Nicholson's Journal, 4to. iii. 215.

,; Beddoes on the Nature and Cure of Calculus.

3 What are termed Sodaic Powders, are attempted to be passed upon the publicas capable of answering in every respect the purpose of soda water; but the saltformed by the solution of these ponders is a tartrate of soda, not a carbonate. Thepowders are packed in two distinct papers, the one blue and the other white ; theblue containing 5ss. of carbonate of soda, the white gr. xxv, of tartaric acid,