Sodae Carbonas Exsiccata. Lond. Dried Carbonate of Soda

" Take of carbonate of soda, a pound. Expose the carbonate of soda to proper heat in a vessel, until it is dry, and afterwards to redness. Lastly, rub it into a powder."

Sodae Carbonas Siccatum. Dub. Dried Carbonate of Soda

" Liquefy the crystals of carbonate of soda in a silver crucible over the fire: then, in an augmented heat, stir the dissolved salt until, by the evaporation of the water, it become dry. Reduce it to a fine powder, and preserve it in stopped phials."

Syn. Soucarbonate de Soude sec (F.), Getrocknetes Kohlensaures Natrum (G.), Sotto-carbonato di Soda secco (I.), Unvollmaakte Koolenstoffzuure Soda (Dutch).

Owing to the great proportion of water of crystallization which the carbonate of soda contains, it readily undergoes the watery fusion, and is completely dried by continuing the heat; but its properties are not otherwise altered. The constituents of 100 parts, in this state, are 40.7 of acid, and 59.3 of soda2, which nearly accords with the analysis of Dulong and Dalton; or 1 eq. of acid = 22.12+ 1 of sodas 31.3; making the equivalent = 53.42.

Medical properties and uses. - The chief advantage obtained from drying the carbonate of soda is the facility of exhibiting it in the form of pills; for when the crystallized salt is used for this purpose, the pill formed with it falls to pieces as soon as the salt effloresces. Dr. Beddoes3 has extolled it, in this form, as a remedy in calculous affections; and it certainly affords relief from the painful symptoms attending calculus in the kidneys, and other urinary affections: but its effects are palliative only, and depend on its neutralizing the excess of acid in the stomach. The dose is from grs. x. to grs. xv., given three times a day. Beddoes directed it to be combined with soap and aromatics.

1 Bib. Univer.xxvii. 146, 2 Nicholson's Journal, 4t iii. 215.

3 Beddoes on the Nature and Cure of Calculus.

Sodae Carbonatis Aqua. Dub. Water of Carbonate of Soda

"Take of carbonate of soda, any quantity; dissolve it in distilled water, and let the sp. gr. of the solution be to distilled water as 1024 to 1000.

"A solution of this specific gravity is made by dissolving an ounce of carbonate of soda in one pound of distilled water."

The only object of this process is to obtain a solution of a determinate strength.

Liquor Sodae Effervescens. Lond. Effervescing Solution of Soda

"Take of sesquicarbonate of soda, a drachm; distilled water, one pint Dissolve the sesquicarbonate of soda in the water; and pass into it, under pressure, more carbonic acid than is sufficient to saturate it. Preserve the solution in a well-stopped vessel."

Aqua Supercarbonatts Sodae, Edin. Water of Super-carbonate of Soda.

"Take of water, ten pounds; subcarbonate of soda, two ounces; dissolve, and subject the solution to a stream of carbonic acid gas procured from three ounces of carbonate of lime, and the same quantity of sulphuric acid, with three pounds of water, gradually and cautiously mixed together. It may be conveniently prepared in Nooth's apparatus; but if a large quantity of it be required, an apparatus capable of affording a greater pressure will be requisite. The fluid must be preserved in well-corked bottles."

Aqua Carbonatis SODAe acidula, Dub. Acidulous Solution of Carbonate of Soda.

"Take of carbonate of soda any quantity. Dissolve it in water so that each pound by measure contain one drachm of soda: then in a proper apparatus pass through a stream of carbonic acid gas, extricated from white marble by means of muriatic acid diluted with six times its weight of water, until the carbonic acid is in excess in the fluid."

This preparation is manufactured on a great scale, of a much superior quality to any which the apothecary can prepare; and it is in very general use as a cooling beverage. Half a pint of it poured over two table-spoonfuls 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 milk forms an excellent substitute for asses' milk.1

1 What are termed sodaic powders are attempted to be passed upon the public as capable of answering in every respect the purpose of soda water; but the salt