APR] CHEMICAL BASIS OF THE ANIMAL BODY. 703 



if subjected to lengthier action a coagulation occurs, and the albumin is 

 then no longer thus soluble. 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, argentic nitrate, and lead acetate, precipitate the 

 albumin, forming insoluble compounds of variable composition with it,: 

 the precipitant may be removed by means of sulphuretted hydrogen and 

 the albumin again obtained, apparently unaltered, in solution. 



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 of egg-albumin in aqueous solution is, 

 for yellow light, - 35 -5. Hydrochloric acid, added until the reaction is 

 strongly acid, increases this rotation to -37 '7. The formation of the 

 gelatinous compound with caustic potash is at first accompanied with an 

 increase, but this is followed by a decrease of rotation. 



Preparation. White of hen's egg is broken up with scissors into 

 small pieces, diluted with an equal bulk of water, and the mixture 

 shaken strongly in a flask till quite frothy ; on standing, the foam rises 

 to the top, and carries all the fibres in whose meshwork the albumin 

 was contained. The fluid, from which the foam has been removed, is 

 strained, and treated carefully with dilute acetic acid as long as any 

 precipitate is formed; the precipitate is then filtered off, and the filtrate 

 after neutralisation concentrated at 40 to its original bulk. 



2. Serum -albumin. 



This form of albumin resembles, to a great extent, the one previously 

 described. The following may suffice as distinguishing features. 



1. The specific rotation of serum-albumin is 5G; that of egg- 

 albumin is - 35'5, both measured for yellow light. 



2. Serum-albumin is not coagulated by being shaken up with ether, 

 egg-albumin is. 



3. Serum-albumin is not very readily precipitated by strong hydro- 

 chloric acid, and such precipitate as does occur is readily redissolved on 

 further addition of the acid ; the exact reverse of these two features 

 holds good for egg-albumin. 



4. Precipitated or coagulated serum-albumin is readily soluble, 

 egg-albumin is with difficulty soluble, in strong nitric acid. 



