OOO ON TANIN AND ITS SPECIES. 



Thetanin that &• Boiling water cannot totally dilTolve it. Its folution no 



is feparated is longer precipitates glue; it has neither the harfli tafle nor the 



not totally folu- , . . . . 



ble in boiling odour of tanin. With the red fulphate of iron it affords only 



waterj neither a whitifh grey precipitate, and laflly it does not afford a 

 does it precip.tate ..? .f • . c .. .. . ... . , , . 



glue, nor has it ma groa with the muriate or tin; it is precipitated merely in 



the tafte or fmell the manner of extracts, to the tafle of which it in fome meafure 

 It refembles'ex- a PP roacnes though it does not poflefs their bittemefs. Thefe 

 traces. are the alterations to which the taning principle is fubject 



when combined as before mentioned with tin oxided to the 



maximum. 

 It was fufpecled 7. From thefe changes he fufpecled that the tin might have 



Silken ox\%n }' ieldecl t0 lt that P ortion °^ oxi g en which conflitutes the 

 from the oxide ; difference between the oxide at the maximum and the oxide 

 but experiments at tne minimum, as happens with the oxide of iron in ink, 

 nor feem toindi- hermetically clofed. In order to afcertain this he diffolved in 

 cate this lofs. muriatic acid the oxide what had been deprived of tanin by 

 potafh ; but he difcovered no indication of that kind. The 

 folution produced no change in that of gold, nor in corrolive 

 fublimate. It was at the maximum* It is true that with re- 

 fpedt to the oxide of tin at the minimum, as well as that of 

 iron, warning and'expofing to the air fpeedily bring it to the 

 maximum. 

 Theory of this Whether by oxidation or by whatever other procefs, the 

 converfion y et tanin principle did at length pafs to the flate of ordinary ex- 

 tract. Tanin precipitates glue, but extra6t does not; this is 

 the difference between them, The influence of fome affinity, 

 which the author has not fufficiently developed, muff have 

 changed its radicals in their primordial arrangements or in 

 their proportions ; and it may be fuppofed that the gallic acid 

 like wife after having been fubje&ed to thefe changes became 

 aflimilated in trie fame Hate and by the fame caufes. 



Concerning the Varieties of Tanin. 



The genus tan'm If in the feries of immediate principles which compofe the 

 compofed of wno le of vegetable matter we confider the tanin of galls as a 

 genus, becaufethis in fact poffeffes the qualities in the higheft 

 degree, it is eaiv o form a notion that this genus may have its 

 fpecies, and may, as well as fugar, gum, ftarch, &c. affect 

 different modifications. There are various fjecies of fugar, 

 refin, gum &c, and there may be alfo various fpecies of 

 tanin. Mr. Prouft thinks that he has found this to be the 

 cafe. 



Cachou 



