T A K 



TAR 



walff, and at leaft 120, or as others fay 60 parts of cold 

 water ; and hence a hot fatiirated folution begins to depofit 

 cryftals almofl: immediately after it begins to cool. So great 

 is the affinity between the tartareous acid and that propor- 

 tion of potadi which conftitutcs the fiipcr-t;irtrate, tliat the 

 acid of tartar will, partially or wholly, decompofe all the 

 neutral falts of potafh, even the fulphate. Neverthelefs, the 

 affinity between the fuper-tartrate and the additional quan- 

 tity of potaili neceflary for the complete faturatioii of this 

 acid is much weaker than that of moft other acids for pot- 

 alh ; and hence aiHfes a great number of dccompofitions, 

 when tartareous acid, potafti, and any other acid are mixed 

 in different ways. The property, which the tartareous acid 

 poffeiTes, of decompofmg the neutral falts with the bafis of 

 potafh, is very ufeful in analyfis, as it ferves to diftinguilTi 

 them at once from the correfponding falts of foda and am- 

 monia, which are not decompofable in the fame manner. 

 By faturating the excefs of acid in cream of tartar with the 

 feveral bafes (potafh excepted) various triple falts are pro- 

 duced. Although fome inconvenience attends the ufe of 

 borax in adding the folution of Cream o/"Taktar in water 

 (fee that article) ; yet fimple boracic acid has the power of 

 rendering foluble four times its weight of cream of tartar in 

 only five or fix parts of hot water, and, as it is fuggefted, 

 without decompofmg the tartar, fince the affinity of the 

 boracic acid for the leveral bales is remarkably weak. 



If a folution of cream of tartar in water is expofed to 

 the air for a length of time, it gradually becomes turbid, a 

 number of mucous flocculi are depofited, and in the courfe 

 of fome months it ceafes to be acidulous, after which it be- 

 comes fenfibly alkaline to the tafle and to chemical lefts, 

 and it is finally converted into a weak folution of carbonate 

 of potafh, the tartareous acid totally difappearing, and car- 

 bonic acid takir.g its place. Fire operates a more rapid 

 deftruftion of the tartareous acid, for if cream of tartar is 

 calcined in an open fire with a red heat, it firll foftens, 

 blackens, becomes of a pafty confiftence, the acid burns off 

 with flame and fmoke, and finally a white carbonate of pot- 

 afh is left. The alkali procured in this way is very pure, 

 and is often obtained for the laboratory by moiflening crude 

 tartar or cream of tartar to the confiftence of ftiff pafte, 

 wrapping up fmall parcels of it in brown paper, and arrang- 

 ing them in a grate or furnace of any kind with charcoal, 

 and kindling it. After the charcoal has burnt out, the 

 tartar is converted into lumps of carbonate of potafli, which 

 llill cohere, and may be readily picked out of the afhes of 

 the charcoal. A very pure carbonate of potafh may alfo 

 be made by deflagrating in a red-hot crucible equal parts of 

 nitre and cream of tartar. 



This fait is compofed, according to Thenard, of 57 /fr 

 ient. of tartareous acid, and 33 of potafti, the remaining 10 

 parts being chiefly water of cryftallization. Of thefe 57 

 parts of acid, 20 are in excefs, fo that the compofition of 

 the fait may be ftated, in a different manner, to be 70 per 

 cent, of tartrite of potafh, and 20 of tartareous acid. 



Cream of tartar is decompofed by lime and barytes, and 

 probably by ftrontian, and cauftic potafh is left in the folu- 

 tion. 



Tartrite of Potajh. See Solulle Tartar, and Tartrate 

 of Potajh under Salts. This fait, confifting of tartareous 

 acid and potafh in mutual faturation, is moft conveniently 

 prepared by adding cream of tartar to a hot folution of car- 

 bonate of potafh. During the effervefcence, the addition of 

 cream of tartar fhould be continued ; when this ceafes, the 

 folution fhould be boiled down till a pellicle appears on the 

 furface, and then left to cryftallize by cooling. The tar- 

 trite of potafh then feparates, generally in the form of pa- 



rallclopipeds, with dihedral fummits. When the fait is pre- 

 pared in a large way for medicinal purpofes, the evaporation 

 is continued nearly to drynefs, with frequent ftirring, by 

 which the fait is obtained in a fhapelefs granular mafs. This 

 fait is partially decompofed by the ftronger acids. Tar- 

 tareous acid dropped into a moderately (Irong folution of 

 tartrite of potafh caufes an immediate depofit of cream of 

 tartar. For other particulars, fee the articles above cited. 



Tartrite of Potajh and Soda, a triple cryftallizablc fait, 

 prepared by throwing into boiling water about a fifth of its 

 weight of cream of tartar, and adding gradually a quantity 

 of carbonate of foda, whilft any effervefcence is excited ; 

 then evaporating the whole to the confiftence of fyrup. As 

 it cools, the triple fait will be obtained in large beautiful 

 tranfparent cryftals, generally of the form of eight-fided 

 prifms, and often divided longitudinally through the axis. 

 This fait, which is perfectly neutral, dilfolves in about five 

 parts of water, and fomewhat efflorefces by being expofed 

 to the air. Barytes and lime totally decompofc it, and the 

 fupernatant liquor contains a mixture of potafh and foda. 

 According to Vauquehn, it is compofed of about 54 per 

 cent, of tartrite of potafh and 46 of tartrite of foda. It is 

 decompofed by the flronger acids, and yields cream of tar- 

 tar. See RuPELLENsis Sal, and Soda. 



Tartrite of Potajh and Ammonia, a triple fait prepared, 

 in the fame general manner as the preceding, by faturat- 

 ing cream of tartar with carbonate of ammonia, evaporating 

 and coohng. Expofed to the air it efllorefces, lofes its am- 

 monia, and returns to the ftate of fimple cream of tartar. 



Tartrite of Potajli and Lime, Barytes, &c. Between 

 tartrite of potafh and lime there exifts a certain affinity, 

 which tends to the formation of a triple fait, though hme 

 will completely decompofe any alkaline tartrite. Thus though 

 fimple tai-trite of lime is infoluble in cold water, no precipi- 

 tate is produced by the affufion of a fmall quantity of lime- 

 water into a cold folution of tartrite of potafli, which muft 

 therefore be owing to the tartrite of lime, then formed, 

 being rendered foluble by the remaining tartrite or rather 

 fubtartrite of potafh. Even when cream of tartar is as 

 completely as poffible decompofed by lime in fubftancc, in 

 the proceis of obtaining the acid, the cauftic alkaline hquor, 

 fupernatant over the precipitated tartrite of lime, ftill holds 

 a fmall quantity of the latter in folution, as has been re- 

 marked by Vauquelin, which may be confidered as a triple 

 fait of tartareous acid, lime, and potafli, the latter being in 

 very large excefs. 



The fame appHes to barj'tes and ftrontian, the folutions 

 of which do not immediately give a precipitate with tartrite 

 of potafli ; and even if tartrite of barytes or of ftrontian 

 recently formed and ftill wet be put into a folution of tar- 

 trite of potafh, it is foon diffolved ; though the mere quan- 

 tity of hquid prefent would be entirely unable to effeft a fo- 

 lution. There is therefore fuch a ilrong affinity between 

 tartrite of potafh and thefe earthy tartrites, as may perhaps 

 entitle us to confider thefe compound folutions as triple falts, 

 though they have not been obtained in a cryftallizcd form 

 like the triple tartrite of potafh and foda. 



Alumine unites with ftill greater cafe with tartrite of pot- 

 afh : for when this earth, recently precipitated from alum 

 by a cauftic or carbonated alkali, and ftill wet, is transferred 

 to a folution of tartrite of potafh, it readily diffolves therein, 

 and forms an uncryftalli/.able compound, which is not ren- 

 dered turbid by any addition of potafh or its carbonate. The 

 Rochelle fait has the fame habitude with alumine as the 

 fimple tartrite of potafh, which therefore forms a quadruple 

 compound of tartareous acid, potafh, foda and alumine. 

 See Alumu^e. 



Tar- 



