VEGETABLE ACIDS. 
pots and placed in a cellar, without any other 
‘precaution than a covering of parchment. When 
you wish to use the vegetables, all that is ne- 
cessary is to let them steep some hours in water, 
their cooking taking no more time than that 
given to vegetables recently gathered, and their 
taste is as agreeable. M. Braconnot extended 
his trials to many sorts of vegetables, among 
others to sorrel, Roman lettuce, common lettuce, 
and asparagus; and they all afforded him satis- 
factory results. He found, however, that the 
sulphuric acid was usefully employed only when 
applied to tender vegetable substances, suscepti- 
ble of prompt cookery. 
VEGETABLE ACIDS. Compounds which 
possess the properties of an acid, and are derived 
from the vegetable kingdom. <A brief account 
of them has already been given in the article 
Actps. They are, for the most part, less liable 
to spontaneous decomposition than other vege- 
table principles; and they probably owe their 
comparative stability to the large proportion of 
oxygen which they contain. They constitute a 
highly important class of organic substances; 
and are nearly four times as numerous as the 
vegetable alkalies; and differ very widely from 
one another in transformative power and aggre- 
gate chemical behaviour ; and, in many instances, 
play a conspicuous part both in the organic che- 
mistry of nature and in the economical chemistry 
of art. About one half consist, in various pro- 
portions, of oxygen, carbon, and hydrogen; two, 
the oxalic and the croconic, consist only of oxy- 
gen and carbon; two, the indigotic and the 
carbazotic, consist of oxygen, carbon, and nitro- 
gen; five or six consist of oxygen, carbon, hydro- 
‘gen, and nitrogen; and the rest either have not 
been carefully analysed, or consist of some other 
powerful acid, such as the sulphuric, in combina- 
tion with alcohol, with ether, or with some other 
vegetable principle. One class, comprising be- 
tween one-sixth and one-seventh of the whole, are 
volatile acids, or may be volatilized without de- 
composition ; and the most interesting of these 
are the acetic, the lactic, the oxalic, the sebacic, 
the formic, the benzoic, and the hippuric. A 
second class, comprising about double the number 
of the preceding, are fixed acids, which cannot 
be volatilized or distilled over without decompo- 
sition, and which, when exposed to a sufficient 
degree of heat, are resolved into other acids called 
pyracids; and the most interesting of these are 
the malic, the citric, the racemic, the gallic, the 
meconic, the tannic, the ulmic, and the caffeic. 
A third class, comprising a rather greater num- 
ber than the first, are oily acids which result from 
the boiling of wax or fixed oils with potash or 
soda, and whose combination with the alkali 
constitutes soap; and the most interesting of 
these are the margaric, the stearic, and the enan- 
thic. A fourth class, about half as numerous as 
the first, are azotic, or have nitrogen in their 
Como ee and in consequence possess a nearer 
VEGETABLE CHEMISTRY. 561 
kindred than the rest to the proximate principles 
which distinguish the animal kingdom; and the 
most interesting of these are the carbazotic, the 
azulmic, and the cholesteric. A fifth class, nearly 
equal in number to the first, are imperfectly 
examined acids, whose constitution 1s obscurely 
known or is matter of dispute; and the most 
interesting of these are the pectic, the crenic, the 
apocrenic, and the gummic. And a sixth class, 
nearly half as numerous again as the first, are . 
compound acids, which consist of a vegetable 
principle in combination with a strong mineral 
or vegetable acid; and the most interesting of 
these are the xanthic, the tartrovinic, the sul- 
phocetic, stearin, and olein. 
VEGETABLE ALKALIES. See ALKanorps. 
VEGETABLE CHEMISTRY. Hither the che- 
mistry of vegetation, whether -with reference to 
the actions which take place in the interior of 
plants, or with reference to the agencies which 
affect and control and determine them from 
without; or the chemistry of vegetable princi- 
ples,—both those which are formed by living 
plants, and afterwards separated from them by 
artificial processes, and those which result from 
the excretion or death or decay of plants, or 
which are artificially formed out of portions of 
their substance by manipulation or chemical re- 
action. In the former sense, vegetable chemis- 
try, in its various parts and phases, is very abun- 
dantly treated in the articles ORGANIC CHEMISTRY, 
AgricunTuRAL Cuemistry, Manure, Foop or 
Puants, Farm-Yarp Manure, Sauts, ALKALIES, 
Arr, Execrriciry, Ammonta, Azotr, CARBONIC 
Actp, and many others; and in the latter sense, 
it is treated with sufficient fulness and frequency 
for all the purposes of the various classes of our 
readers, both in articles on entire classes of vege- 
table substances, such as ALKALOIDS, VEGETABLE 
Acrps, Orzs, Restns, Gums, Sauts, and Barsams, 
and in articles on each of the most important 
principles which are used either in medicine, in 
domestic economy, or in the arts, such as Sugar, 
Srarcu, AncoHon, Prorrrn, and all the chief 
oils, gums, resins, and salts, and all the chief 
artificial products of destructive distillation and 
artificial recombination. “The chemistry of 
vegetable principles,” says Dr. Thomson, “has 
made considerably greater progress than that of 
animal principles; chiefly because the former 
have a greater tendency to crystallize, and, in 
consequence of this property, can be more easily 
obtained in a state of purity than the latter. 
This is the case with most of the vegetable acids 
and alkaloids, with sugar and some other sub- 
stances not easily classified. Others are vola- 
tile, and are formed or driven off at particular 
temperatures. Alcchol, ethers, and volatile oils 
are in this predicament. Pretty frequently se- 
veral of these volatile bodies occur together ; and 
in such cases we have scarcely the means of ob- 
taining them in a state of purity, unless when 
they enter into definite and crystallizable com- 
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