664 BOTANY AND PHARMACOGNOSY. 



Barbadoes Aloes is a hepatic variety of Curagao Aloes, which 

 is not obtained at the present time from Barbadoes, but from the 

 Dutch West Indies. It occurs in dark brown, dull, opaque masses, 

 giving a yellow powder that is colored red with nitric acid. About 

 72.4 per cent, of fresh and 62.8 per cent, of old Barbadoes aloes 

 is soluble in chloroform. It contains about 9 per cent, of moisture. 



3. Cape Aloes. — Of a reddish-brown or of an olive-black 

 color, transparent in thin pieces; fracture smooth and glassy; 

 powder greenish-yellow, becoming light brown and giving a 

 greenish color with nitric acid. 



About 65 per cent, of Cape aloes is soluble in cold water. 

 It is almost completely soluble in alcohol or boiling water; and 

 the latter solution gives a precipitate of 60 per cent, of " resin 

 of aloes." From 81 to 86.8 per cent, is soluble in chloroform, 

 and from 1.5 to 6.5 per cent, in ether. It contains about 9 per 

 cent, of moisture, and yields but a small percentage of ash. 



Uganda (or crown) Aloes is a hepatic variety of Cape 

 Aloes prepared by allowing the juice to stand and undergo a 

 partial fermentation, after which the clear liquor is decanted and 

 evaporated by exposure to the sun. It occurs in reddish-brown 

 masses, producing a powder, which is colored yellow to brown 

 with nitric acid. 



Constituents. — A crystalline, bitter principle, aloin, the per- 

 centage (4.5 to 30 per cent.) and composition of which vary in 

 the different varieties, and which is supposed to occur in largest 

 amount in old aloes; emodin (see Rhubarb) ; a pale yellow, vola- 

 tile oil, which is apparently not identical in the different varieties, 

 giving them their characteristic odors; 13 to 63 per cent, of res- 

 inous material, which consists chiefly of a resinotannol ester of 

 cinnamic acid (Curacao and Barbadoes Aloes) or of a resino- 

 tannol ester of paracumaric acid (Cape Aloes) ; and i to 4 per 

 cent, of ash. 



Aloin is a neutral, bitter principle, which on distillation with 

 zinc dust yields anthracene. It forms minute, lemon-yellow to 

 yellowish-brown acicular crystals, which are sparingly soluble in 

 water but more so in alcohol, the solutions becoming brown on 

 standing. Alkaline solutions of aloin have a deep red color and 

 exhibit a greenish-red fluorescence. Upon the addition of aloin 



