124 PREPARATION OF CITRIC AND TARTARIC ACIDS. 
ART. XXXIV. — ON THE PREPARATION OF CITRIC AND TAR- 
TARIC ACIDS. 
BY THE EDITOR OF 11 THE DUBLIN HOSPITAL GAZETTE. ;? 
In the preparation of citric and tartaric acids it is necessary 
to employ a precaution similar to that just described in the 
preparation of phosphate of soda. If cold lemon-juice be 
poured upon chalk, the carbonic acid liberated by the union 
of the citric acid with the lime, will not entirely escape, but 
will in part unite with a portion of the chalk, forming bicar- 
bonate of lime, which will dissolve in the washings. Now, in 
this case, the inconvenience will result from the whole of the 
lime used not being present in the precipitate, for the quantity 
of dilute sulphuric acid used for the decomposition of the ci- 
trate of lime formed, is measured by the quantity of chalk em- 
ployed. You are to use eight times the weight of dilute sul- 
phuric acid, as of the carbonate of lime added to the lemon- 
juice, because it is calculated, that in this proportion there is 
just the amount of real acid necessary for saturating the earth. 
But if a part of the lime be carried off in the supernatant liquid, 
under the form of bicarbonate, it is evident that enough will 
not remain to neutralize the given quantity of sulphuric acid. 
So that when this acid has decomposed the citrate of lime, 
and freed the citric acid, the liquid which will dissolve the lat- 
ter, will likewise contain a notable quantity of sulphuric acid, 
sufficient, upon evaporation, to char the crystals of citric acid, 
and render them discolored. It is necessary, therefore, for the 
success of this preparation, that the whole of the lime employ- 
ed, should exist in the precipitate either as citrate, or carbonate? 
if an excess of the latter be used ; to gain this end, all the car- 
bonic acid liberated by the lemon-juice should be expelled, and 
to force its expulsion, the lemon-juice should be added to the 
chalk at a boiling temperature. 
The necessity for the employment of a boiling heat is equal- 
