PART III.

Alkalies and Neutral Salts.

£13

water at 60°. It is decomposed by the strong acids, muriateof baiytes, lime, and by a red heat. The constituents of 100parts of this salt, according to Schulze, are 41*3 of tartaricacid, 14-3 of potass, 13\3 of soda, and Sl'l of water 1 : but,according to Vauquelin, they are, tartrate of potass, 54 parts,tartrate of soda 46 parts.

Medical properties and uses. — Tartrate of potass and soda isa cooling and not very unpalatable cathartic. It was introducedinto practice by M. Seignette 2 , an apothecary of Rochelle, andthe preparation kept a secret until it was discovered and pub-lished by Boulduc and Geoffrey in 1731. It operates mode-rately, and without exciting much irritation ; hence it is wellsuited to nephritic and puerperal cases. The dose is from ^j.to ^jss., dissolved in any convenient vehicle.

SODiE CARBO'NAS, Lond. Carbonate of Soda." Take of subcarbonate of soda, a pound; subcarbonate ofammonia, three ounces; distilled water, a pint. To the solutionof the subcarbonate of soda in the water, add the ammonia;then expose the mixture in a sand-bath to a heat of 180° forthree hours, or until the ammonia be expelled; finally, set itapart to crystallize. The residuary liquor may be evaporatedin the same manner, and set apart again to crystallize."Carbonas SoDiE, Edin. Carbonate of Soda." Take of subcarbonate of soda, two parts; water, threeparts. Dissolve the salt in the water, and subject it to a streamof carbonic acid gas, until the acid be no longer absorbed.Then filter the fluid and evaporate it in a heat not exceeding180°, that it may crystallize. The carbonic acid is easilyobtained from equal weights of pulverized carbonate of limeand of sulphuric acid largely diluted with water.

Syn. Carbonate de Soude (F.), Kohlensaures Natrum ((?.), Caroonato diSoda (I.).

In these processes the subcarbonate of soda is nearly neu-tralized by the action of the same affinities as are exerted inthe formation of the carbonate of potass.

Mr. Phillips has remarked, that the proportion of the am-monia in the London formulae is too small by half an ounceto convert the subcarbonate of soda into bicarbonate ofsoda. 3 The soda is certainly not completely neutralized,as it still changes to green the vegetable blues; a defectwhich must be ascribed to the nature of the operation. Theconstituents of the neutral carbonate, according to Rose, arein 100 parts, 49 of acid, 29"85 of alkali, and 20-20 of water.

1 Gelden Journ- iv. 210. Thomson's Chemistry, 4th edit. iii. 96.8 Hence its appellations of Sal de Seignette, Sal Ruppellcnsis,3 Remarks on the Editio Altera, p. 27.

R R 3