Sodae Potassio - Tartras. Lond. Potassio-tartrate of Soda

"Take of carbonate of soda, twelve ounces; bitartrate of potassa in powder, sixteen ounces; boiling water, four pints. Dissolve the carbonate of soda in the boiling water, and add gradually the bitartrate of potassa. Filter the solution; then apply a gentle heat until a pellicle floats, and set it aside to crystallize. Pour off the water from the crystals, and dry them. Evaporate the liquor again, that it may yield crystals."

Tartras Sodae Et Potassae. Edin. Tartrate of Soda and Potassa

"Take of subcarbonate of soda, one part; supertartrate of potassa, three parts, or a sufficient quantity; boiling water, fifteen parts. To the subcarbonate, dissolved in the water, gradually add the supertartrate rubbed to a fine powder, as long as effervescence is excited, which generally ceases before the whole of the three parts of the supertartrate are added: when the fluid is cold, filter it through paper, and after a proper degree of evaporation, set it aside that crystals may form."

Sodae Et Potassae Tartras

Dub. Tartrate of Soda and Potassa, paper; evaporate, and set it aside, that, as it slowly cools, crystals may form."

"Take of carbonate of soda, five parts; bitartrate of potassa, rubbed to a fine powder, seven parts; boiling water, fifty parts. Dissolve the carbonate of soda in the water, and gradually add the bitartrate of potassa; filter the solution through state; and that at ] 80° 5/8 of the salt take all the water, whilst 4/9 separate in the dry state. Journ. of Science, vol. xix. p. 153.

1 Nicholson's Journal, 4to. iii. 215. 2 Trans. of Pharm. 1837.

Syn. Tartrate de Soude et de Potasse (F.), Natrum-weinstein (G.), Tartrato di Potassa e di Soda (I.).

In these processes the superabundant acid of the bitartrate is saturated by the soda of the carbonate, the carbonic acid of which is dissipated in the gaseous form; and a triple salt is obtained by the evaporation, instead of two distinct salts being formed from the different alkaline bases.

Qualities. - This salt has a bitter, saline taste. Its crystals are large, regular, transparent, hard, rhomboidal prisms, but often in halves, as in the figure. They are slightly efflorescent, and soluble in five parts of water at 60°: are decomposed by the strong acids, chloride of barium, lime, and by a red heat. The constituents of 100 parts of this salt, according to Schulze, are, 41.3 of tartaric acid, 14.3 of potassa, 13.3 of soda, and 31.1 of water1: according to Vauquelin, they are, tartrate of potassa, 54 parts; tartrate of soda, 46 parts: and according to Mr. Phillips (Translation of the Pharmacopoeia), 40 parts of tartrate of potassa, 34.5 of tartrate of soda, and 25.5 of water, in 100 parts. In equivalents the crystals contain 1 eq. of tartrate of potassa = 113.63+ 1 of tartrate of sodar=97.8 + 8 of water=72; making the equivalent 283.43. It is incompatible with acids and acidulous salts, acetate and diacetate of lead, and chloride of calcium.

Medical properties and uses.-Tartrate of potassa and soda, or potassio-tartrate of soda, is a cooling and not very unpalatable cathartic. It was introduced into practice by M. Seig-nette2, an apothecary of Rochelle, and the preparation kept a secret until it was discovered and published by Boulduc and Geoffrey, in 1731. It operates"moderately, and without exciting much irritation; hence it is well suited to nephritic and puerperal cases. The dose is from 3ij. to j. dissolved in any convenient vehicle.