Chemical Science, 181 



duced also not only by the spontaneous decomposition of hydrocyanic 

 acid, but by those of hydrocyanate of ammonia, of cyanogen dissolved 

 in water, by the action of cyanogen upon bases, and indeed whenever 

 compounds of this substance are experimented with. The action of 

 weak nitric acid on cast iron, or the carbon it contains, produces a 

 similar substance ; and as azulmic acid appears to combine with 

 concentrated nitric acid, there is reason to believe that artificial 

 tannins are only combinations of this body with nitric acid, or at 

 least that they contain an analogous substance*. 



15. ON GASEUM AND MILK. (Braconnot.) 



An excellent, because practical memoir on milk has been published 

 by M. Braconnot, in the Annales de Chimie, xliii. 337, which offers 

 many applications of a substance long but not thoroughly known, 

 not a few of which we anticipate will hereafter come into use. 

 This substance is caseous matter, or, as he has called it, caseum. 



Soluble Caseum, and its Applications. 2500 parts (grammes) of 

 the curd of new cheese, as sold in the market, were heated to 2 12 

 for some time : it contracted, and became a glutinous elastic mass, 

 swimming in much serum. Being washed in boiling water, to re- 

 move the acid serum, and dried, it weighed 469 parts. It was a 

 compound of caseum with acetic and lactic acids : being divided, put 

 into sufficient water with 12.5 parts of crystallized bicarbonate of 

 potassa, and heated, it dissolved with effervescence, producing a 

 mucilaginous liquor, distinctly reddening litmus paper. Being 

 evaporated carefully, with continual agitation, it left a soft portion, 

 which, as it cooled, acquired consistency, was drawn out between 

 the fingers into thin portions, and then dried in the air upon a sieve : 

 it weighed 300 parts. This soluble caseum is a surcaseate of po- 

 tassa, containing still butter and salts. It resembles isinglass, is of 

 a yellow-white colour, translucent, and of a stale taste : it is per- 

 fectly soluble in hot or cold water, producing a fluid rendered milky 

 by the presence of butter. 



In this impure state the substance is easily prepared : instead of 

 the bicarbonate, the potash or soda of commerce may be used. The 

 following are hints for its application. Like gelatine, it may be 

 preserved without alteration for any length of time, and may be 

 obtained in enormous quantities, if required. Associated in various 

 ways with food, it must prove of the greatest importance on board 

 vessels for long voyages. Its aqueous solution, sugared and fla- 

 voured with a little lemon-peel, makes an agreeable and nourishing 

 drink for invalids. It is a powerful cement : its solution, evapo- 

 rated on glass or porcelain to dryness, cannot be removed without 

 injury to the vessels ; its hot concentrated solution has been applied 

 with great success to join glass, porcelain, wood, and stone. The 

 same solution forms a brilliant varnish : being applied to paper, it 



Annales de Chimie, xliii. 273, 



