T A K 



tious, and the effect only of the fluid in which it was pre- 

 cipitated : it cannot but have feme of the falts of that fluid 

 hanging about it, when firil made ; but tliefc may, by re- 

 peated wartings, be carried wluilly ofl', and tlie magiftery 

 will then remain a pure iimple earth, and (hew itfelt to be 

 no other than that earth, which may be properly called the 

 earth of all fixed falts ; and which, though neceffary to give 

 the fait of tartar its form as a lixivial fait, yet being not 

 neceffary to it in its new form of a neutral fait, is depofited 

 ill the making it into that form. It yet remains to be 

 proved by more numerous experiments, that the fixed falts 

 of plants owe that form only to a fixing earth, combining 

 their two original volatile principles into a fixed mafs ; for 

 if this be truly the cafe, there then needs no more to the 

 volatilizing thorn again, but the divelling them of this earth. 

 Phil. Tranf. N= 90. 



TARTAREOUS or Tartaric -^«</, was firft fepa- 

 rated from cream of tartar, and obtained in a folid cryftal- 

 iine fonn, by a nutiiod which was difcovered by Scheele, 

 and whicii, with little variation, is as follows : it very 

 much refimbles the mode ufed by the fame ingenious 

 chemift in obtaining the citj-ic acid : Having analyfed cream 

 of tartar (fee Swedifh Tranfaftions, part iii. for 1770.), he 

 found that this is not a pure acid, but a compound fait, 

 containing the fixed vegetable alkali, united with a fuper- 

 abundance of the tartareous acid, and therefore, that it 

 differs from foluble tartar only in the proportion of acid 

 which it contains. For obtaining this acid, he diflblved any 

 given quantity of the cream of tartai- in boiling water, and 

 whilft boiling, added gradually fome clean powdered chalk. 

 Upon this a copious effervcfcence will arife, and the addition of 

 chalk niufl be continued till this ceafes, when the mixture may 

 be fet by to cool. It then contains a white denfe fediment, 

 which confifts of the lime of the chalk, united with the ex- 

 cefs only of the acid of the cream of tartar ; and the fuper- 

 natant liquor is, therefore, a folution of the cream of tar- 

 tar deprived of its excefs of acid, or neutral tartrite of 

 potajh, or foluble tartar, as it is alfo called, and which may 

 be obtained cryftallized by fubfequent evaporation. Wafh 

 the precipitated tartrite of lime repeatedly with cold water, 

 then put it into a glafs veffel, and add to it a diluted ful- 

 phuric acid, compofed of as much concentrated acid, as is 

 equal to the weight of chalk employed in faturating the cream 

 of tartar, mixed with four or five times its weight of water. 



The fulphuric acid having a ftronger affinity for the 

 lime than the tartareous acid has, totally decompofes the 

 tartrite of Lme, during a digeftion of two or three days (or 

 in a fliorter time if aflifled by a gentle heat,) and the white 

 fediment, though it does not alter its appearance, is changed 

 to fulphate of lime, whilft the fupernatant liquor contains 

 naked acid of tartar. Then pour off the clear liquor, wafti 

 the fulphate of lime to extraft all the adhering acid, and add 

 the wafliings to the former liquor, and evaporate the whole, 

 (at firft with a boihng heat, and as it concentrates, with a 

 much gentler warmth, ) till it is of a thick fyrupy confift- 

 cnce, and then fet it by for fome hours, that all the fele- 

 nite, which it may hold in folution, may be depofited. 

 Then again dilute the mixture with cold water fufiicient to 

 rediifolve every thing but the felenite, and flowly evaporate 

 the folution to a f)Tupy confiftence, and after fome hours it 

 will depofit the pure tartareous acid in cryftals, which are 

 generally pretty large irregular hexahedrons. Cream of 

 tartar decompofed in this way by chalk (and therefore only 

 partially) will yield about a third of its weight of the cryf- 

 taUized acid. This quantity however muft not be taken as 

 the proportion of the acid in cream of tartar, for much of 

 the weight of the cryftallized acid is water of cryftalli- 



T A R 



zation, whereas the cream of tartar contains very little 

 water. 



In the above detailed method of obtaining tartareous acid, 

 chalk, or carbonate of lime, is ufed to decompofe the cream 

 of tartar, which it docs merely by engaging the excefs of 

 acid, and leaving the remainder of the fait in the ftate of 

 tartrite of potafh. But if quick-lime be fubftituted to the 

 chalk, the whole of the cream of tartai- is decompofed, a 

 much larger quantity of tartrite of lime, and confcquently 

 of tartareous acid, is obtained, and the fupernatant liquor 

 is a folution of cauftic potafh. It has been found however 

 by Vauquehn, that the potafh retains a fmall quantity of 

 tartrite of lime in folution, fo that when the alkiiline liquor 

 is evaporated nearly to drynefs it gelatinizes by cooling, 

 owing to the feparation of this calcareous fait. It may be 

 decompofed by carbonate of potafii or foda, which pro- 

 duces carbonate of hme and tartrite of the alkali employed : 

 or the tartareous acid may be deilroyed by calcination, and 

 the lime, carbonated in the procefs, will remain. 



Calculating from the obferved proportions of acid in the 

 tartar, and of chalk required in the firft-mentioned procefs, 

 and of pure lime in chalk, we may eftimate that all tlie acid 

 in 100 parts of cream of tartar (which Thenard reckons 

 sX. ^"j per cent.) will require full 42 parts of pure lime for 

 its faturation, and fomewhat more lime fliould perhaps be 

 added to enfure the complete decompofition of the tartar. 

 The hme fliould be previoufly flaked and mixed with fuf- 

 ficient water to bring it to the confiftence of pafte. 



Lowitz has propofed another method, which is perhaps 

 preferable in every refpeft, except that it is fomewhat more 

 expenfive, and that no cauftic alkaU is obtained. It con« 

 fifts firft in decompofing the cream of tartar by chalk in the 

 ufual way, added as long as any effervcfcence takes place ; 

 and then pouring into the filtered fupernatant liquor muriate 

 of lime, as long as any precipitate falls down. By this 

 means the tartrite of potafh in liquor is totally decom- 

 pofed, muriate of potafh remains in folution, and the 

 precipitated tartrite of lime is added to that produced by 

 the chalk ; and both are afterwards decompofed by fulphuric 

 acid in the ufual way. The fame chemift alfo advifes to 

 add to the folution of tartareous acid in the laft part of the 

 procefs a quantity of charcoal powder, (the depurating 

 power of which has been mentioned under Carbon.) 

 This, however, is certainly not effential to the obtaining a 

 perfeftly fine colourlefs cryftallized acid, and, we beheve, 

 is feldom, if ever, ufed. 



The tartareous acid has a ftrong acid tafte, and is foluble 

 in five or fix parts of water, and in a much lefs quantity of 

 boihng water. The cryftals are permanent in the air. 



When heated per fe in a retort with a receiver, this acid 

 melts, boils up, and exhales a four pungent vapour, which 

 condenfes in the receiver into a red acid empyreumatic 

 liquor, equal to about a quarter of the weight of the tar- 

 tareous acid. 



This liquor has a pungent, acid, and empyreumatic tafle, 

 ftrongly reddens litmus, and effervefces with the alkaline 

 carbonates. It is called the Pyrotartareous acid, which has 

 not been much examined. The other produfts from the 

 diftillation of tartareous acid, are a large quantity of car- 

 buretted hydrogen and carbonic acid gas, and a foft fpongy 

 coal is left in the retort, which, heated in the open air, 

 burns with fcarcely any refidue. 



The tartareous acid, befides being found native in fome 

 vegetable juices, and in the depofit from wine during and 

 after fermentation, is alfo produced by the aftion of nitric 

 acid on alcohol. A further digeilion of tartareous with 

 nitric acid converts the former into oxalic acid, and a ftill 

 3 further 



