uiih Animal and Vvgetal/le Sulstances. 448 



be obtained from it by destructive distillation,) is formed 

 of an esscnlial oil and vegetable acid alone. These views, 

 as they are louuded on facts, at least deserve some atteiT- 

 ticn, and, itcontirined by experience, may probably be of 

 great advanlau:e. 



I have likewise formed the combiniations of the essence 

 of lemon and of lavender with ninriatie acid. 39 ^rammea 

 of the essence of lavender require 22 of acid ; the resulting 

 compound is blackish, acid and liquid. 26 Lnanunes of the- 

 essence of lemon absorb 22 gramme^ oi acid ; the essence 

 is of a brownish line and solid. Neither of these essences 

 had been purified ; but both were used in the state they are 

 generally found in commerce. 



The essential arc not the only oils capable of combining 

 with acids. It has long been remarked ih.U the fat oils 

 form with different acids peculiar kinds of soap. The sul- 

 phuric acid when concentrated has this cfi'eci upon all of 

 them ; it produces with the oil of olives in particular a soapy 

 matter, of a thick and ^.Tceuish appearance, which gradu- 

 ally acquires consistence; when washed with water it be- 

 comes white ; it is acid, but less so than if the acid was 

 uncoinbined, and it may be brought into the neutral state 

 by a proper quantity of potash. 



Tannin be^ides, which is a vegetable matter, contracts, 

 as is well known, a strong union with acids ; for the con- 

 centrated sul))huric acid suddenly precipitates it from its 

 solution in water, and I am convniced that, however often 

 the precipitate may be wasiied, it is always acid. Nature 

 itself has offered us a compound of this species. In fact, I 

 have treated 10 tirammts of gallnuts with 2 litres of boil- 

 ing; water, and although the re-idue had been washed with 

 two litres more of very waim water, it still stronivly reddened 

 tincture of turnsole : in the gallnuts therefore Uic gallic acid 

 is retained by a true affinity. But as the quantity of gallic 

 acid abstracted liy a spontaneous decomposition far ex- 

 ceeds the quantity of free acid existing in its natural slate, 

 we must conclude that the greatest part of the acid is cer- 

 tainly neutralized bv the tannin. It is observed to»), that 

 if a decoction of gallnuts be allowed to follow its own 

 course, as the tannin is destroyed, the liquor bccoiries more 

 and more acid. One may, indeed, attribute this phceno- 

 iiienon to the transformation of the tannin itself into gallic 

 acid ; but numberless observations authorize us to believe 

 that this i« not the case. 



1. That vegetable substances during their dccomposili«ii 

 form no other acid but the acetic. 



0. That 



