ON VEGETABLE ACIDS 269 



one hand, the results may be when different plants are 

 treated in the same manner, the products, on the other, 

 which are obtained from the same plant by different opera- 

 tions are as widely different. How different are the qualities 

 of sugar when it is dissolved in water, and left to ferment 

 under proper management till it is converted into vinegar, 

 when it is distilled dry by itself, 1 and when the acid of sugar 

 is obtained by means of nitrous acid ? 2 In order to be 

 thoroughly convinced of this, it is only necessary to com- 

 pare, in the two last cases, the experiments made by Mr. 

 Schrickel and Professor Bergmann on earths, alkalies, and 

 metals with one another. I intend to treat, on some other 

 occasion, of the causes of the different products that are 

 obtained from the same plant, treated in different ways. I 

 shall at present confine myself to the extrication of the same 

 constituent parts from different vegetables when the same 

 method is applied to each. 



The acid which passes over in dry distillation, along with 

 an empyreumatic oil, is scarce perceptible beforehand, though 

 it is procured from very various plants. All vegetables that 

 run into the acetous fermentation yield a vinegar which has 

 in all cases the same essential qualities. This gave rise, in 

 the minds of many chemists, to this very natural conjecture, 

 that the acid diffused through the whole vegetable kingdom 

 may be of the same kind, and the species may proceed only 

 from the different proportion of oily and mucilaginous 

 particles intermixed with it. Thus it is said by Mr. 

 Morveau, 3 among others, that the acid basis is probably 

 the same in all plants, and only modified by the various 

 constituent parts by which it is neutralised. Most chemists 



1 Schrickel, Diss. de salibus saccharin, vegetal}, ex sacch. albi anabjsi 

 acidoque hujus spiritu speciatim. Giessse, 1776. 



2 Bergmann, Opusc., vol. i. p. 251. 



3 Siemens de Chemie Theor. et Prat., t. ii. p. 9. 



