CIT 
tie obtained pure and crystallized by mere 
evaporation of the lemon juice, and that 
even the addition of alcohol did not sepa- 
rate completely the foreign matter. The 
process lie followed is to saturate the ex- 
pressed juice of the lemon, by the addition 
of chalk. The citric acid, combining with 
the lime, forms an insoluble compound, 
which of course precipitates. This is well 
washed with w'arm water, until the water 
pass off colourless; and in this way the mu- 
cilage and extractive matter are abstracted. 
The citrate of lime is then subjected to the 
action of as much sulphuric acid, previously 
diluted, as is sufficient to saturate the lime 
of the quantity of chalk that has been em- 
ployed. The citric acid is disengaged and 
dissolved by the water ; the mixture is boil- 
ed for a few minutes, to facilitate the preci- 
pitation of the sulphate of lime, and is then 
filtered. The filtered liquor is evaporated 
to the consistence of syrup, any sulphate of 
lime separated during the evaporation be- 
ing withdrawn ; and, on cooling and stand- 
ing for some time, the citric acid is obtain- 
ed in needle-like crystals. 
Citric acid exists in a number of other 
fruits, from which it may be extracted, and 
much, it is said, of what is at present found 
in the shops, is prepared from the juice of 
the lime. From Vauquelin’s analysis of tlie 
pulp of the tamarind, it appears to be the 
chief acid constituent of that fruit; one 
pound of the common prepared pulp of the 
shops containing an ounce and a half, witli 
smaller quantities of malic and tartaric acids. 
This acid is very soluble in water. At a 
moderate temperature, too parts of water 
dissolve 75 parts, cold being produced dur- 
ing the solution ; at 212° it dissolves twice 
its weight of it. Like the other vegetable 
acids, its solution undergoes spontaneous 
decomposition, though not very readily. 
The more powerful acids decompose if, 
though with some difficulty. Concentrated 
sulphuric acid converts it into acetic acid. 
Scheele remarked, that nitric acid did not 
convert it, as it did some of the other vege- 
table acids, into oxalic acid ; but Fourcroy 
and Vauquelin have found, that when acted 
on by a large quantity of nitric acid for a 
long time, it affords a small portion of oxa- 
lic, with a larger portion of acetic acid. 
Citric acid combines with the alkalies and 
earths, forming salts denominated citrates. 
The citrate of potass is very soluble, and 
does not crj'stallize but with difficulty, and 
is deliquescent: its taste is purely saline, 
and rather mild. It contains 55.55 of acid. 
CIT 
and 44.45 of alkali. Citrate of soda is like- 
wise very soluble, requiring little more than 
its weight of water for its solution : it cry- 
stallizes in six-sided prisms, and the crystals 
are slightly efflorescent. Their taste is 
faintly saline ; the proportions of the solid 
salt are 60.7 of acid, and 39.3 of soda. Ci- 
trate of ammonia is equally or even more 
soluble than tlie others, and does not crys- 
tallize but when its solution is much con- 
centrated : the forni of its crystals is an 
elongated prism. It consists of 62 of acid, 
and .38 of ammonia. The earthy citrates 
are iu general less soluble. Wlien the solu- 
tion of barytes is poured into the acid, a 
precipitate, soluble in the liquid by agita- 
tion, is formed; when the whole is satu- 
rated, the salt is deposited at first in the 
form of a powder, which is covered after- 
wards with a kind of crystalline efflores. 
cence, and which a large quantity of water 
dissolves. It consists of 50 of acid, and 50 of 
base. When the citric acid is saturated by 
lime, small crystals are deposited, which are 
very sparingly soluble : 100 parts contain 
62 66 of acid, and 37,34 of lime. When satu- 
rated by magnesia, the concentrated solution 
does not easily crystallize regidarly, but ra- 
ther assumes the state of a white, opaque, 
and somewhat spongy salt. The propor- 
tions of the salt, are 66.66 of acid, and 
33.34 of base. 
Vauquelin has likewise examined the ac- 
tion of citric acid on the metals. It does 
not dissolve silver; but it combines with 
its oxide, and forms a salt insoluble, of a 
harsh and strong metallic taste, and which, 
like the other salts of silver, is blackened 
by light : it is also decomposed by heat, 
sometimes leaving metallic silver intermixed 
with charcoal. It consists of 36 of acid, and 
64 of oxide. 
, Citric acid, in its crystallized state, can 
he preserved for any length of time without 
decomposition; and a grateful lemonade 
may be prepared from it, by dissolving 30 
or 40 grains in a pint of water, with the ad- 
dition of a little sugar; and to communi- 
cate flavour, a little lemon peel, or powder, 
formed by rubbing sugar on the fresh le- 
mon. The lemon juice may be regarded 
as a specific in scurvy, and there is every 
probability that the crystallized citric acid 
may be equally effectual, 
CITRUS, in botany, a genus of the Po- 
lyadelphia Icosandria class and order. Na- 
tural order of Bicornes. Aurantia, Jussieu, 
Essential character: calyx five-cleft; pe- 
tals five, oblong ; anthers twenty ; filaments 
