270 ESSAY XXV. 



maintain that vinegar is the basis of the essential vegetable 

 acids. Others, as Mr. Westrumb, 1 suppose that the acid 

 of sugar, or rather, 2 as Mr. Hermbstaedt, that the acid of 

 tartar constitutes the essence of the other vegetable acids. 

 We have not, I believe, facts enough to ascertain this matter ; 

 neither do I think that, as yet, the case of two specifically 

 different acids, coexisting in one plant, has been considered ; 

 but their properties have been constantly deduced from one 

 single acid. This, however, seems frequently to take place. 

 Thus Mr. Scheele was not able to convert the crystallised 

 acid of lemons into acid of sugar by means of nitrous acid ; 

 though he perfectly succeeded in effecting this with the 

 saponaceous extract, which accompanied the acid before it 

 was crystallised. Mr. Hermbstaedt, in analysing the juice 

 of four cherries, obtained acid of sugar with a middle salt 

 containing an excess of acid, which was probably tartar. 

 In order to answer this question, it would be proper to 

 inquire, Whether the constituent parts and the products of 

 sugar, and the constituent parts of wine, the purest source 

 of vinegar, are in reality so very much alike (as is takei 

 for granted, and commonly supposed to be proved by 

 few circumstances) ? or, Wherein they differ ? 



The first question then would be, Whether sugar can be 

 extracted from the expressed must, in the same way as 

 Margraaf obtained it from various roots ? This admits of 

 but little doubt, since the same chemist asserts that he has 

 obtained sugar from very fine raisins. It is, moreover, 

 necessary to submit this sugar of wine, or at least the must, 

 after it has been properly purified and evaporated, to a dry 

 distillation, in order to see whether these substances would 



1 Neu. EntdecL, Th. xi. S. 109. 



2 Others hold the acid of sugar to be an artificial product, and not a 

 natural salt. See Mr. Wiegleb, Chem. Ann., Th. vii. S. 12 ; and Mr. 

 Hermbstaedt, N. EntdecL, Th. ix. S. 17. 



