220 
ON CITRATE OF MAGNESIA. 
Berzelius, in the eighth and ninth volumes of his Traitd 
de Chimie, which treat of the salts of magnesia, mention 
the oxalate, the acetate, and the tartrate, but not the citrate. 
In his theory of chemical proportions he gives the following 
composition for the citrate: — Magnesia, 26.12 ; citric acids 
73.88; but no account is here taken of the water of crystal- 
lization, which the salt contains. 
Citrate of magnesia may be obtained in two different 
ways. It may be made by double decomposition from 
sulphate of magnesia and citrate of soda, or by saturating a 
solution of citric acid with magnesia or the basic carbonate. 
If it be prepared by saturating a solution, somewhat concen- 
irated, of the acid, the liquor which is at first liquid and 
transparent, becomes in an instant a hard mass, adhering 
strongly to the sides of the vessel in which the combination 
is effected. This arises, probably, from the water which at 
first holds the salt in solution, passing to the state of water 
of hydration. 
The neutral citrate of magnesia, prepared by either of the 
processes above described, is a white pulverulent insipid salt, 
soft to the touch, heavier than magnesia, and soluble in 
water aided by the addition of a slight excess of the acid. 
This solution has a slightly acid taste, but is in no way dis- 
agreeable. 
A small quantity of the citrate of magnesia having been 
put into a glass tube and heated over the flame of a-lamp, 
aqueous vapour was disengaged and condensed at the other 
end of the tube. On further heating the tube, white inflam- 
mable vapours were given off, in which carbonic oxide and 
acetic acid were distinguished. 
One gramme of citrate of magnesia, dried in vacuo, and 
then strongly calcined in a porcelain capsule, left a white 
residue, consisting of pure magnesia, and the weight of 
which was 0.170. 
