^4 J^^' f'f^^^l on the Origin of the 



From thcfe experiments on cream of tartar, 

 the following conclufions refult : " That this 

 fubftance is not, as has been commonly fuppofed, 

 a pecoliar acid, joined with impurities, but that 

 it is really a compound fait, containing an al- 

 kali joined with an acid ; and further, that the 

 alkaline fait, obtained from tartar by incinera- 

 tion, is not generated in the fire, but was adually 

 pre-exiflent in the tartar." * 



might be quite fufncient to detach all the alkali. By 

 future trials, the proportion might be fo nicely adjufted, 

 as exadly to anfwer thi.^ intention, and thereby the acid 

 of tartar might be left, after the cr^ftallization, perfedly 

 pure and diflinft. 



I evaporated the fluid remaining after the cryftallization 

 flill farther, and endeavoured, by the fame mode of treat- 

 ment, to obtain more cryllals, but without fuccefs. The 

 evaporation was carried on, until the mafs became thick 

 and tenacious. When fet in the cool, it did not deliqui- 

 atc, or attraft any moifture, though I kept it a fortnight 

 in very damp weather. By this circumftancc, and by the 

 tafte, I judged to be princijialiy, almoft entirely, a pure 

 concrete acid of tartar, rendered a little more (harp and 

 penetrating by t!ie adhefjon of a little of the acid of nitre, 

 which prohably a longer continuance, and a little increafe 

 of the heat, would have diffipated. May not thefe experir 

 IJients, in conjunftion with thofe of Mr. Scheele, (who has 

 alfo fhewn that the acid of tartar may be obtained pure in a 

 concrete (late) lead to an improvement in the preparation of 

 tartar emetic? — But as this fubjed is not within the plan 

 prefcribed for difiertations of this kind, I Ihall trouble the 

 Jipciety with only this flight hint. 



* IVJed. Comment, ut. fupr, 



III. The 



