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Benzoic acid may be procured from several re- 
sinous substances by distillation ; from benzoin, 
storax, and balsam of Tolu. It is distinguished 
from the other acids by its aromatic odour, and by 
its extreme volatility. 
Malic acid may be obtained from the juice of 
apples, barberries, plums, elderberries, currants, 
strawberries, and raspberries. It forms a soluble 
salt with lime ; and is easily distinguished by this 
test from the acids already named. 
Acetic acid, or vinegar, may be obtained from 
the sap of different trees. It is distinguished from 
malic acid by its peculiar odour ; and from the 
other vegetable acids by forming soluble salts with 
the alkalies and earths. 
Gallic acid may be obtained by gently and gra- 
dually heating powdered gall-nuts, and receiving 
the volatile matter in a cool vessel. A number of 
white crystals will appear which are distinguished 
by their property of rendering solutions of iron 
deep purple. 
The vegetable prussic acid is procured by dis- 
tilling laurel leaves, or the kernels of the peach, 
and cherry, or bitter almonds. It is characterised 
by its property of forming a blueish green preci- 
pitate, when a little alkali is added to it, and it is 
poured into solutions containing iron. It is very 
analogous in its properties to the prussic acid ob- 
tained from animal substances ; or by passing am- 
monia over heated charcoal ; but this last body 
forms, with the red oxide of iron, the deep bright 
blue substance, called Prussian blue. 
Some other vegetable acids have been found in 
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