544 
RESEARCHES ON ALOETINE. 
wax, and rapidly turning brown, in contact with nitric acid, 
and even, in damp air. To purify them completely, they 
must be washed in alcohol of 56 centesimal degrees (22° 
Beaume), until this liquid takes a straw-coloured tint, without 
any red in it, and then crystallized five or six different times 
in alcohol of 86 per cent. (36° B.) 
Dr. Pereira has described, with much care, a new variety 
of Socotrine aloes, recently imported into England, and which 
is no other than the natural juice of the plant which has un- 
dergone no manipulation. It is a chestnut brown liquid, with 
a powerful odour of black currant, in which float a great num- 
ber of silky crystals of aloetine. 
It would appear, at first sight, that nothing is easier than 
to prepare aloetine from this natural juice : simple pressure 
between folds of bibulous paper, and several crystallizations 
in alcohol, ought to be sufficient. But this is not the case, 
and the portion of this juice which has become altered in the 
air, suffices for preventing the crystallization of the aloetine 
from remaining intact ; at any rate, a large portion is lost. 
The process which is the least disadvantageous, is the fol- 
lowing: — the liquid juice of Socotrine aloes is diluted with 
distilled water, to which JO or 12 drops of liquid ammonia 
have been added per litre. The resinous portion of the juice 
is first dissolved by the alkali, and, if we operate very quickly, 
the portion still unaltered may be separated by filtration. Two 
or three crystallizations in alcohol are then sufficient for 
arriving at complete purification. Still, this method, however 
rapidly we may operate, never gives more than 4 or 5 per 
cent, of aloetine. 
Pure aloetine occurs under the form of prismatic needles, 
of a fine sulphur yellow. At the temperature of 10° C. 
(50° F.), 1 part of aloetine requires, for its solution, 10 parts 
of water, 2 parts of alcohol, of 36° B., and 8 parts of ether of 
66° B. It is impossible to determine, exactly, its solubility 
at the boiling points of these liquids, because heat alters it 
more or less profoundly. 
Owing to its sparing solubility in water, aloetine has 
scarcely any taste, but its characteristic bitterness is speedily 
developed. 
The mucilaginous pulp of the leaves of aloes contains a 
peculiar matter, which is colourless in the plant, but which 
rapidly acquires a violet red colour in contact with the air. 
This may easily be perceived by suddenly tearing one of these 
leaves, when the central part rapidly becomes coloured. This 
substance, whatever may be its nature, accompanies aloetine 
in its last purifications; I have ascertained that to it was due 
