Chemical Composition of Human Blood. 123 



-specific gravity I found to be 1-0262. It coagulates at 159° 

 according to Dr. Thomson, and after being cut into small 

 pieces, if it is allowed to stand, a liquid gradually appears 

 which is termed the serosity. By digesting the coagulated 

 serum in alcohol and water the albumen is obtained nearly 

 pure. 



The sulphuric, muriatic and nitric acids coagulate the 

 serum as well as heat. It is precipitated also bymetaphos- 

 phoric acid, but not at all by phosphoric or pyrophosphoric 

 acids. Acetic acid occasions no precipitate whatever. 



The alkalies seem to occasion no change when poured 

 into the serum. 



None of the earths form insoluble compounds with the 

 albumen of the serum. 



Tannin occasions a very copious yellow precipitate, which, 

 when dry, is very brittle. 



The metallic salts are remarkable for precipitating 

 albumen. The most delicate of all is the chloride of mer- 

 cury, which, according to Bostock, occasions a milky mass, 

 even when the albumen is diluted with 2000 parts of water.=* 



When albumen is coagulated, either by alcohol, ether, 

 heat, or acids, it becomes an opaque substance of a pearl 

 white colour and possesses rather a sweetish taste. In this 

 state it may be said to be totally insoluble in water, since 

 Chevreul found that water did not dissolve xoVo 1^- ^^ i^^ 

 weight. When perfectly dry it possesses an amber colour, 

 is very hard and brittle and semi-transparent like horn. 



1. I found that it dissolves very easily in common nitric 

 acid, the solution possessing a lemon colour. Evaporated 

 to dryness the mass has the appearance of gelatine, and is 

 soluble in water. Tincture of nut-galls occasions no pre- 

 cipitate but merely a slight opalescence in the solution. 

 Acetate of lead throws down a dense flocky orange coloured 

 precipitate. Prussiate of potash and chloride of calcium 

 produce no change. It would, therefore, appear that this 

 substance is quite different from that which Mr. Hatchett 

 obtained, which was so similar to gelatine in its characters. 



2. Sulphuric acid, appears at first to have no action upon 

 the albumen, but on the application of heat a solution is 

 effected with considerable effervescence. The solution at 



* See F. Rose's experiments on this subject, Records, i. p. 213. 



