294 M. Vauquelin on Sorbic Acid. [Oct. 



any degree, upon jelly mixed with it, but upon a substance more 

 analogous to vegetable gum. The juice of the sorbus, after 

 fermentation, still contains a red colouring matter, which passes 

 to a violet purple by the contact of tin, and which becomes a 

 greenish yellow by the action of alkalies. The juice also con- 

 tains a very acrid and hot principle, which has some analogy 

 with that which we meet with in Pyrethrum ; it is soluble both 

 in water and in alcohol, and is always accompanied by a brown 

 and bitter substance. The berries of the sorb, after being; bruised 

 and expressed, retain a yellow matter, which may be separated 

 by warm alcohol, or ether, and which seems to have some 

 resemblance to a resin ; it is principally attached to the paren- 

 chymatous part of the fruit. 



The recent juice of the sorb is of a red colour, and of a veiy 

 acid flavour, mixed with a degree of bitterness. When the 

 carbonate of lime is added to it, an effervescence is excited ; 

 but whatever quantity we employ, the fluid always continues 

 acid. If this solution of the super-sorbate of lime be poured off, 

 and the carbonate of potash added, a brisk effervescence takes 

 place, and a white powder is precipitated, which consists of 

 neutral sorbate of lime : 100 parts of the precipitated sorbate of 

 lime, when well dried, were decomposed by heat, and appeared 

 to consist of 



Acid 67 



Lime 33 



100 



When acetate of lead is poured into the juice of the sorb, a 

 precipitate is formed, which is white, thick, and bulky. By 

 standing a few hours, however, its bulk is much diminished, and 

 it assumes a brilliant, crystalline appearance, which begins at 

 the surface, and is gradually continued to the bottom of the 

 vessel ; the supernatant fluid also deposits crystals, which are 

 more white, more bulky, and more b*rilliant. If the precipitate 

 be collected in separate portions, the first is highly coloured ; the 

 second, less so ; and the last, nearly without colour. 



When the juice of the sorb is saturated by potash instead of 

 lime, and afterwards precipitated by acetate of lead, the preci- 

 pitate, instead of being rose-coloured, is greenish yellow ; in this 

 case it is much longer in acquiring the crystalline appearance. 

 Five grammes (77*22 grs.) of subcarbonate of potash will satu- 

 rate a decilitre (6*1 cubic inches) of the juice of the sorb. 



The sorbate of lead is nearly insoluble in cold water ; but a 

 little more so in boiling water : as it cools, it crystallizes in beau- 

 tiful needles, white, brilliant, and shining, which have a consi- 

 derable resemblance to sublimed, benzoic acid. A remarkable 

 phenomenon occurs when sorbate of lead is boiled in water. 

 Whilst one part of the salt saturates the water, the other part, 



