LILLICEA^, ■ 473 



of the resins, which seldom have a higher specific gravity than 

 1 00 to 1*10. In water, aloes dissolves completely only when 

 heated. On cooling the aqueous solution, whether concentrated 

 or dihite, becomes turbid by the separations of resinous drops, 

 which unite into a brown mass, the so-called resin of aloes. The 

 clear solution, after separation of this substance, has a slightly 



acid reaction ; it is coloured dark-brown by alkalies, black by 

 ferric chloride, and is precipitated yellowish- grey by neutral 

 lead acetate. Cold water dissolves about half its weight of 

 aloes, forming an acid liquid which exhibits similar reactions. 

 The solution of aloes in potash or ammonia is precipitated by 

 acids, but not by water. {P/iarmaco(/raphia, p. 686.) 



The most intei'csting constituents of aloes are the substances 

 \ known as Aloln. The Aloiu of Jafarabad Aloes has been 

 examined by AT. A, Shcnstone. About 1| lb. of the powdered 

 aloes was treated with enough proof-spirit to make a thin paste, 

 aud after stauding for a few hours was enveloped in folds of 

 stout calico and submitted to powerful pressure, by which means 

 about 28 per cent, of crude Aloin was obtained. This was 

 purified by twice crystallizing from water, then by crystallizing 

 several times from dilute spirit, and finally by crystallizing 

 twice or thrice from rectified spirit. Portions of the crops of 

 crystals thus obtained were burnt with the following results ; 



I- •1104 gram of aloin which had been once crystallixod 

 from rectified spirit and dried in vacuo over sulphuric acid ^^.i\c 

 '^138 gram of CO^ and -0561 gram of H'^0. 



II. "1380 gram of aloin which had been twice crystallized 

 from rectified spirit and dried in vacuo over sulphuric acid gave 

 '301:2 gram of CO^ and '0696 gram of II-O. Corresponding to 



Carbon. Hydrogen. Oxygen. 



1 6022 5-64 34-14 



II GOll 5-60 34-29 



The aloin therefore was evidently in a pure state. l'2'^7^} 

 gram of pure air-dried aloin dried over sulj)huric acid in a 

 vacuum lost '1987 gram of water, corresponding to lu-0 per 



cent. 



I1I.-60 



