THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



SUPPLEMENT to VOL. XXXVII. THIRD SERIES. 



L X VI I . On Aloine , the Crystalline Cathartic Principle of Bar- 

 badoes Aloes. By John Stenhouse, LL.D,, F.R.S.L. fy E* 



A BOUT two months ago I received from my friend Mr. 

 -*•*- Thomas Smith, apothecary, Edinburgh, a quantity of a 

 brownish-yellow crystalline substance which he had obtained 

 fromBarbadoes aloes. Mr. Smith's process consisted in pound- 

 ing the previously dried aloes with a quantity of sand, so as to 

 prevent 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 

 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 



sweetish, 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, 



* Communicated by the Author. 



Phil. Mag. S. 3. No. 253. SuppL Vol 37. 2 I 



