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Potas’sce Antimo'nio-Tar'tras. — Antimony-Tar’tr ate of Pot’ash .
History. —This salt was first publicly noticed in 1631, by Adriande Mynsicht ( Thesaurus Medico-Chymicus.) It has been known byvarious appellations, as tartarized antimony (antimonium tartarizatum ),emetic tartar (tartarus emeticus), stibiated tartar (tartarus stibiatus), andpotassio-tartrate of antimony (antimonii potassio-tartras, Ph . L.)
Preparation. —Antimony-tartrate of potash is prepared by boilingbitartrate of potash and sesquioxide of antimony (or some antimonialpreparation which contains it, as the oxychloride or an oxysulphuret)with water: the sesquioxide combines with the bitartrate to form anti-mony-tartrate of potash.
Antimony-ash (cinis antimonii), procured by roasting the sesquisulphu-ret, is employed to yield the sesquioxide in a manufactory in London .As already stated (p. 398), this compound is a mixture of sesquioxide,antimonious acid, and some undecomposed sesquisulphuret. The pro-portions of ash and bitartrate used vary according to the quality of theformer: the average being equal parts. This is the cheapest method ofobtaining emetic tartar.
In the Dublin and United States Pharmacopoeias the oxychloride(oxydum antimonii nitro-muriaticum, Ph . Dub.), commonly called Alga-roth’s powder, is employed. This is procured by pouring the sesquichlo-ride (common butter of antimony, vide p. 399) into a large quantity ofwater, and washing the precipitate. In the preparation of the sesqui-chloride a small quantity of nitric acid should he employed to decomposethe hydro-sulphuric acid remaining in the liquor, and which wouldimpair the colour of the precipitate.
In the London Pharmacopoeia an oxysulphuret, very similar in compo-sition to the old saffron of antimony (crocus antimonii) is used. It is thusprepared : two pounds of powdered sesquisulphuret of antimony are to beaccurately mixed with the like quantity of powdered nitrate of potash :four fluidounces of hydrochloric acid are then to be added, and the pow-der, ignited, spread out on an iron plate. The residue is to be rubbed toa very fine powder, and, when cold, washed with boiling water until it isvoid of taste.
It is then to be boiled for half an hour with fourteen ounces of bitar-trate of potash in a gallon of distilled water. The liquor is to bestrained while hot, and set aside to form crystals.
The theory of the process is this : part of the sulphur and of the anti-mony are oxidized at the expense of the oxygen of the acid of the nitrate,by which sulphuric acid and sesquioxide of antimony are formed, whilenitrogen and binoxide of nitrogen escape. The sulphuric acid uniteswith part of the potash of the nitrate. The hydrochloric acid reacts onanother portion of potash, and produces water and chloride of potassium.If no hydrochloric acid had been employed, the potash would react onsome undecomposed sesquisulphuret, and generate antimonio-sesqui-sulphuret of potassium and sesquioxide of antimony. The residuum ofthis operation is, then, sulphate of potash, chloride of potassium, sesqui-oxide of antimony, and some undecomposed sesquisulphuret. By wash-ing, the sulphate and chloride are got rid of. The following diagram,