ESSAY XXV. 



UPON THE RESEMBLANCE WHICH VEGETABLE ACIDS 

 BEAR TO ONE ANOTHER, PARTICULARLY THOSE OF 

 MUST AND SUGAR, i BY DR. CRELL. 



THE acids that exist in the vegetable kingdom differ in many 

 respects from one another. They may be divided into the 

 Essential, the Fermented, and the Empyreumatic. 



The essential are almost entirely pure, as those of lemons, 

 sorrel, and sorrel-dock ; or but little altered by the admixture 

 of other matters, as the acids of cherries, barberries, apples, 

 unripe grapes, gooseberries, currants, tamarinds, etc. They 

 are so much covered as to be hardly distinguishable in many 

 sweet fruits when they are ripe, in grapes, in various roots, 

 as carrots, parsnips, in sugar, etc. These latent acids become 

 more evident, partly in consequence of fermentation, by 

 which almost all plants (a few, particularly those which 

 bear cruciform flowers, excepted) are made to yield vinegar, 

 and partly by dry distillation. In the two last operations, 

 all vegetables, however different from one another in taste 

 and other sensible qualities, seem to yield products very 

 nearly resembling one another. But however alike, on the 



1 Chemische Annalen, St. vii. p. 89. 



The obscurity and importance of this subject would alone justify me, 

 in the eyes of the intelligent chemist, for adding this and the two follow- 

 ing papers ; but Mr. Scheele has had so great a share in the discovery of 

 the new acids, that they form a peculiarly proper addition to his Essays. 

 It was another strong inducement with me to subjoin them, as they form 

 an excellent supplement to what is said, both by Bergmann himself in 

 his Essay on Attractions, and in the notes, p. 334. T. 



