332 PROTEIN-COMPOUNDS. 



in water containing chloride of sodium or any alkaline salt. It is 

 insoluble in alcohol and ether. 



After being dried in vacuo, or at a temperature below 50, it 

 can be heated to 100 without passing into the insoluble condi- 

 tion ; the aqueous solution, however, becomes turbid at 60, coa- 

 gulates perfectly at 63, and separates in flakes at J5. When 

 excessively diluted, no turbidity can be perceived below 90, and 

 coagula will only separate after it has been boiled for a considerable 

 time. 



Albumen may be precipitated from an aqueous solution by 

 diluted alcohol; the precipitate, however, is not coagulated ; but 

 when a large quantity of strong alcohol is added, it is converted into 

 the insoluble or coagulated form. It behaves very differently 

 towards ether free from spirit; it is generally asserted that the 

 albumen of the serum of blood is not coagulated, while that of eggs, 

 on the other hand, is coagulated by ether ; but as this observation 

 is not constant, this supposed variation may be dependent on the 

 degree of concentration of the albuminous solution. 



Fatty and volatile oils neither dissolve nor coagulate albumen. 

 It is coagulated by creosote and aniline. 



Albumen is converted into the insoluble state by most acids, 

 but it is not precipitated by the mineral acids (except by tribasic 

 phosphoric acid) unless when they are added in excess. The 

 organic acids, with the exception of the tannic acids, do not pre- 

 cipitate albumen. 



Alkalies do not precipitate albumen, but they convert it into 

 the insoluble modification. 



The greater number of the metallic salts precipitate albumen ; 

 the precipitate containing either a combination of a basic salt with 

 albumen, or a mixture of two compounds, one of which consists of 

 the acid of the salt and albumen, and the other of the base of the 

 salt and albumen. The albumen generally passes into the inso- 

 luble state in these combinations. 



Albumen is not usually found isolated in solution in the normal 

 animal fluids, but in combination with a small proportion of alkali, 

 whose quantity does not admit of exact determination on account of 

 the salts which are also mixed with the albumen. In some experi- 

 ments conducted by myself on the albumen of hens 5 eggs, I found 

 that 1'58 parts of soda were directly combined with 1 00 parts of albu- 

 men, calculated as devoid of salts. This albumen has a slightly alkaline 

 reaction, is more readily soluble in water than pure albumen, from 

 which it differs mainly in the form in which it coagulates when the 



