500 
SECOND REPORT— 1832 . 
properties, we can have no evidence, but the simplicity of the 
process by which it is prepared, that it is not the result of the 
treatment to which the vegetable has been subjected. And 
even this is not conclusive evidence; for though the process 
for extracting oils by distilling the parts of plants with water 
is very simple, it has been shown that these oils do not always 
exist ready formed in the substance of the vegetable. Thus, 
from bitter almonds, alcohol or aether extract no oil, nor is any 
formed in them by the aid of heat until water is added. The 
same is the case, also, with the volatile oil of mustard-seed. 
Now what happens in these cases is likely to take place in 
many others, so that it will probably be long before we are 
able to determine in all cases what are and what are not real 
proximate principles. It will be still longer before we are able 
to refer each of them to its true place in a purely chemical 
arrangement, and to make them out to be so many determi¬ 
nate compounds of a series of organic radicals. The first step 
towards such an arrangement has been made by the discovery 
of the relation between benzoic acid and oil of bitter almonds; 
and we may hope that similar discoveries will gradually dimi¬ 
nish the confusion and obscurity which at present prevail in 
animal as well as in vegetable chemistry. 
Vegetable acids—Tartaric and Paratartaric acids. —One of 
the most interesting results lately arrived at regarding the ve¬ 
getable acids, is that obtained by Berzelius from his analysis 
of the racemic (paratartaric) and tartaric acids. The former 
acid had been found by John to be different from the tartaric 
acid; and Gay-Lussac had determined that their atomic weights 
were as nearly as possible the same. Berzelius discovered, 
further, that they have the same elementary composition 
=4C+2H+50; and was led by this discovery into a train of 
reasoning in regard to isomeric bodies, which has been already 
adverted to when treating of that interesting subject. 
Th e para- is distinguished from the common tartaric acid, by 
its inferior solubility in water; by its containing two atoms of 
water of crystallization, one of which is given off at a moderate 
heat; by the insolubility of its salt with lime ; and by its giving 
no double salt with soda and potash. This last property may 
be taken advantage of to separate the two acids. The crude 
tartar, or other mixture containing them in the state of acid 
salts, is saturated with soda; the Rochelle salt allowed to cry¬ 
stallize, and separated ; the mother liquor precipitated by a lead 
salt, and the precipitate afterwards decomposed by sulphuric 
acid. 
Modification of tartaric acid. —When tartaric acid is fused 
