SOURCES OF ALBUMEN. 305 



Proximate Principles of Organic Nature. 



Albumen. Under the name of albumen has been long 

 known a substance of which the type is the white of eggs. 

 The albumen of the white of eggs differs somewhat from the 

 albumen obtained from the serum of the blood. Albumen is 

 distinguished from other proximate principles by its coagula- 

 bility. In begins to coagulate at 140 of Fahrenheit's thermo- 

 meter ; and if the solution is concentrated, it sets into a firm 

 mass such as a hard-boiled egg exhibits. Strong alcohol pre- 

 cipitates albumen from its solution ; but if the alcohol be 

 rendered slightly alkaline by potassa, no coagulation takes 

 place. Sulphuric ether, if free from alcohol, does not coagu- 

 late albumen, yet it renders a concentrated solution of albumen 

 viscid. Creosote instantly coagulates albumen. The concen- 

 trated mineral acids precipitate albumen in a coagulated form, 

 but gradually decompose it. Metaphosphoric acid coagulates 

 albumen ; the other varieties of phosphoric acid have no effect. 

 Acetic acid and the organic acids in general do not cause a 

 precipitate in solutions of albumen. The tannic acid in an 

 infusion of galls has, however, a coagulating effect. Solutions 

 of alum and salts of copper, lead, mercury, and silver, preci- 

 pitate solutions of albumen. Albumen forms definite com- 

 pounds with the alkalies and other metallic oxides. Coagu- 

 lated albumen is dissolved freely by solutions of the alkalies. 



The albumen from a hen's egg in 100 parts exhibits 53.5 of 

 carbon, 7.0 of hydrogen, 15.5 of nitrogen, 22.6 of oxygen, 1.6 

 of sulphur, and 0.4 of phosphorus. This ultimate constitution 

 differs very little from the ultimate constitution of fibrin e, and 

 also very little from the ultimate constitution of caseine, except 

 that in caseine no phosphorus has been detected. 



Of late it has been taught that the vegetable kingdom con- 



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