On the Tariareoui Sails. 269^ 



itattrafls the humidity of the air and becomes vifcid by heat. Pot-afll feparates the mag- 

 nefia, which proves contrary to the opinion of Bergmann, that this alkali has a ftronger 

 attraftion for the tartareous acid, than for that earth. It is more eafily prepared by,- 

 . heating magiiefia, recently precipitated from its folution, by a cauftic alkali and {till in the 

 humid (late, with the folution of cream of tartar. 



A, From the union of alumen with the acidulous tartrite of pot-afli, a faline fubftance 

 refults which is not cryftallizable, nor precipitated by the alkalies, whether pure or carbo- 

 nated. To afcertain the caufe of this fingular effe£l:, Citizen Thenard combined, by means 

 of a gentle heat, gelatinous alumen to tartrite of pot-a(h, and though a confiderable quan- 

 tity of the earth was diffolved, there was not any trace of pot-afh having feparated. 



This experiment {hews the reafon why pot a{h does not occafion a depofition in the 

 tartrite of alumen in combination with pot-afti, namely, that in this cafe the vegetable fait 

 which is formed retains in folution the alumen feparated from the tartareous acid. 



The fait of Seignette prcfented the fame properties. 



5. He alfo mentions the ammoniacal tartrite of pot-afli, which cryftallizes in fine tranf- 

 parent cryftals, decompofable after a time by expofure to the air j this fait is already known.. 



Concerning the Alkaline, Earthy, and Metallic Acidulous Tartrites. 



Citizen Thenard in this feflion fliews, that the tartrites of foda, of magneGa, and of 

 copper, unite with a fuper-abundance of their acid, and by that means produce acidulous 

 falts, lefs foluble than the neutral tartrites. This property was before obferved in the tarr- 

 trites of pot-afli, of foda, and of ammonia. 



If to a folution of tartrite of copper, which is very foluble, and difficultly cryftallizable, 

 there be poured a fuffieicnt quantity of pure tartareous acid, a new combination is cfFedled 

 of fparing folubility, and of which almoft the whole falls down under the form of a white 

 blueilh powder, which foda, pot-afh, and the carbonate of pot-a(h diflblve completely, 

 without any feparation of the copper. 



The water in which the acidulous tartrite of copper has been precipitated, does not ber 

 come blue by ammonia, which proves that no part of the fait has remained fufpeflded, and 

 confequently that it is of very fparing folubility. 



Order of AttraElions of Earthy and Alkaline Subjlances, nuith Regard to the Tartareous Acid. 

 After having compofed the triple falts here fpoken of, and exhibited their principal pro- 

 perties, Citizen Thenard determines by comparative experiments, the degrees of affinity 

 which, the alkalies and the earths have for the tartareous acid. According to him lime 

 muft occupy the firft rank, and barites the fecond, and the others in the following order,, 

 ftrontian, pot-afh, foda, ammonia, magncfia, and alumen. 



Metallic Alkaline Tartrites. 

 Citizen Thenard then pafles to the examination of the metallic alkaline tartrites, among 

 which he principally diftinguiflies thofe of manganefe, zinc, tin, copper, lead, mercury, 

 8 and 



