285 
ON ALOINE, THE CRYSTALLINE CATHARTIC 
PRINCIPLE OF BARBADOES ALOES. 
By John Stenhouse, LL.D., F.R.S.L. & E. 
ABOUT two months ago, I received from my friend, Mr. 
Thomas Smith, apothecary, Edinburgh, a quantity of brown¬ 
ish-yellow crystalline substance which he had obtained from 
Barbadoes aloes. Mr. Smith’s process consisted in pounding 
the previously dried aloes with a quantity of sand, so as to pre¬ 
vent its agglutinating, macerating the mass repeatedly with 
cold water, and then concentrating the liquors in vacuo to the 
consistence of a syrup. On remaining at rest in a cool place 
for two or three days, the concentrated extract became filled 
with a mass of small granular crystals of a brownish-yellow 
colour. This is the crude substance to which Mr. Smith has 
given the name of aloine, and which appears to constitute the 
cathartic principle of aloes. The brownish-yellow crystals 
obtained in this way are contaminated with a greenish-brown 
substance, which changes to brownish-black on exposure to the 
air, and still more rapidly when it is boiled. In order to purify 
the crystals of aloine, therefore, they must first be dried by 
pressure between folds of blotting-paper, and then repeatedly 
crystallized out of hot water till they have only a pale sulphur- 
yellow colour. The aqueous solutions of aloine must on no 
account be boiled, but simply heated to about 150° F., as at 
212° F. aloine is rapidly oxidized and decomposed. By dis¬ 
solving the purified crystals of aloine in hot spirits of wine, they 
are deposited, on the cooling of the solution, in small prismatic 
needles arranged in stars. When these crystals have a pale 
yellow colour, which does not change when they are dried in the 
air, they may be regarded as pure aloine. 
Aloine is quite neutral to test-paper. Its taste is at first sweet¬ 
ish, but soon becomes intensely bitter. Aloine is not very 
soluble either in cold water or in cold spirits of wine ; but if 
the water or the spirits of wine are even slightly warmed, the 
solubility of the aloine is exceedingly increased : the colour of 
these solutions is pale yellow. Aloine is also very readdy dis¬ 
solved by the carbonated and caustic fixed alkalies in the cold, 
forming a deep orange-yellow solution, which rapidly grows 
darker, owing to the oxidation which ensues. The effects of 
ammonia and its carbonate are precisely similar. When 
aloine is boiled either with alkalies or strong acids, it is rapidly 
changed into dark brown resins. A solution of bleaching pow¬ 
der likewise gives aloine a deep orange colour, which soon 
changes to dark brown. Aloine produces no precipitate in solu- 
VOL. XXV. Q q 
