ANALYSIS OF ONIONS. Q()$ 



nic-9 it. Fioai these experiments they infer, that the crys- This substance 

 tulline matter of onion juice is nothing- but manna. 



It remained now to determine, whether the manna were formed by the 

 ready formed in the juice, or developed by fermentation. fenBematteQ * 

 To solve this question, they treated onion juice concen- 

 trated by evaporation in several ways, and obtained only 

 fermentable sugar, instead of the manna which the fer- 

 mented juice had furnished. It appears then, that the 

 manna obtained from onion juice is the product of fermen- 

 tation-, and this opinion is tiie more probable, as a scru- 

 pulous examination of the fermented juice exhibited to 

 them all the principles it contained before, except sugar*. 



From the preceding experiments Messrs. Fourcroy and. 

 Yauquelin conclude, that sugar, either when its solution is 

 too dilute, or when it contains a different ferment from yeast, 

 constantly undergoes a kind of alteration by acetiti cation, 

 which divides it into two new cornpouuds, unequal In 

 quantity, and differing in the proportion of their principles: 

 one vinegar, which contains fewer radicals than sugar; the 

 other manna, which contains more radicals than sugar. 

 In fact, all the chemical knowledge we have of these three 

 substances confirms this result. 



Perhaps, add the authors, there is no improbability in Natural form- 

 . . .. 1-tp -i i • ' i ation oi man " 



supposing, that, in the trees which furnish manna, this sub- na , 



stance is formed in their saccharine juice by the acetous 

 fermentation of sugar, assisted by the glutinous matter that 

 exists in all vegetables. It is natural to suppose, that the 

 saccharine juice of the ash and the birch, once escaped from 

 its vessels, runs into the acetous fermentation ; and that the 

 results are manna and vinegar, the latter of which after- 

 ward evaporates. This no doubt is the reason, why new 

 manna is acid, and smells of vinegar. This opinion may 

 be confirmed by examining the kind of sap or liquor, that 

 flows from trees apt to furnish manna, when the stem is 

 , tapped. 



The examination, that Messrs. Fourcroy and Vauquelin Examination 

 made of manna, convinced them, that beside the crystalli- manna , 

 zable matter analogous to what they obtained from the fer- 



* The fact mentioned in the preceding note tends to Cortina this. C. 



nicnted 



