CHEMICAL BASIS OF THE ANIMAL BODY. 11 



from which the salts have been removed by dialysis 1 . When precipitated 

 from solution by excess of alcohol it is readily coagulated by the pre- 

 cipitant, so that it is now usually insoluble in water. In this respect 

 it differs somewhat characteristically from serum-albumin which is not 

 so immediately though it is ultimately coagulated by the action of 

 alcohol. 



According to Corin and Berard 2 , by applying the method of fractional heat- 

 coagulation to filtered white of egg, coagula may be obtained at 57*5, 67, 72, 76, 

 and 82, the first two being due to globulins, the others to albumins. 



Strong acids, especially nitric acid, cause a coagulation similar to 

 that produced by heat or by the prolonged action of alcohol ; the 

 albumin becomes profoundly changed by the action of the acid and 

 does not dissolve upon removal of the acid. Mercuric chloride, nitrate 

 of silver and lead acetate, precipitate the albumin, forming with it' 

 insoluble compounds of variable composition. 



Strong acetic acid in excess gives no precipitate, but when the 

 solution is concentrated the albumin is transformed into a transparent 

 jelly. A similar jelly is produced when strong caustic potash is added 

 to a concentrated solution of egg-albumin. In both these cases the 

 substance is profoundly altered, becoming in the one case acid- in the 

 other alkali-albumin. 



The specific rotatory power, which is stated to be independent of 

 the concentration, is variously given as (a) D = 35'5 (Hoppe-Seyler) 

 or 37*79 (Starke). The latter agrees closely with Haas' determina- 

 tion 3 (a) D = 38-1 and is probably the most correct of the three values. 



Preparation. The fibrous network in white of egg is broken up with 

 scissors and violently agitated in a flask till a thick froth is formed. 

 The flask is then inverted, whereupon the foam rises to the top carrying 

 the larger part of the fibrous debris with it. The clear subnatant 

 fluid is now carefully drawn off and filtered through fine muslin ; to 

 this an equal volume of water is added, and the whole is finally filtered 

 through coarse paper. From this point onwards two methods may be 

 employed. 



1. For ordinary purposes the fluid may be very carefully and 

 faintly acidulated with acetic acid, filtered and the filtrate purified by 

 dialysis. 



2. To obtain the purest albumin proceed as follows 4 . Saturate the 

 fluid with magnesium sulphate at 20, filter and saturate the filtrate 



1 Laptschinsky, Sitzb. d. Wien Akad. Bd. LXXVI. 1877. Juli-Hfl. 



2 Travaux du Lab. de Leon Fredericq, Liege. T. n. (1888), p. 170. 



3 Pfliiger's Arch. Bd. xn. (1876), S. 378. 



4 Starke, loc. cit. 



