ON ALOINE, THE CATHARTIC PRINCIPLE OF THE ALOES. 279 
rivals the other. When the liquid is slowly evaporated, tufts 
of long needle-shaped crystals of chrysammate of potash are 
produced. 
For an account of the chemical characters of aloin, we beg to 
refer to an article by our friend, Dr. Stenhouse, in the “London, 
Edinburgh, and Dublin Philosophical Magazine” for December 
last, from a consideration of which it will be quite obvious, that 
the substance we have obtained from the aloes is quite different 
from that described by Mr. Edmund Robiquet. 
Monthly Journal of Medical Science , Feb. 1851. 
ON ALOINE, THE CRYSTALLINE CATHARTIC PRIN- 
CIPLE OF BARBADOES ALOES*. 
By John Stenhouse, LL.D., F.R.S.L. and E. 
ABOUT two months ago I received from my friend, Mr. Tho- 
mas Smith, apothecary, Edinburgh, a quantity of a brownish- 
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 pres- 
sure between folds of blotting-paper, and then repeatedly crys- 
tallized 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 
* This is the article above referred to. — E d. Vet. 
