C2 METHODS OF PREPARING SERUM-ALBUMIN. [BOOK I, 



When alcohol is added to serum in considerable excess, as in the 

 proportion of two volumes of absolute alcohol to one of serum, the 

 albumin is precipitated : at first the precipitate can be redissolved in 

 distilled water; by prolonged contact with the alcohol it becomes 

 almost absolutely insoluble. In order to secure the latter result as 

 perfectly as possible, as for instance in the preparation of solutions of 

 fibrin-ferment, the quantity of alcohol added must be much larger 

 than that indicated above, even 15 or 20 times as much alcohol as 

 serum being used, and the action of the former upon the latter 

 being continued for about three months. 



The albumin recently precipitated by alcohol from serum, when 

 it is redissolved in water, yields a faintly opalescent liquid. 



Prepara- Various methods have been suggested for the 



tion of Serum- preparation of pure serum-albumin; they all yield a 

 albumin. substance, which can only be regarded as approximately 



pure, inasmuch as they fail in separating inorganic salts which, more 

 or less, always continue to adhere to the substance and to modify 

 its physical properties. 



Hoppe-Seyler's method. 



Blood serum is treated with dilute acetic acid, as for the prepara- 

 tion of paraglobulin, and the clear liquid is filtered from the latter 

 body. The liquid is then concentrated by evaporation in shallow 

 basins at a temperature which must not exceed 40 C. 



The concentrated liquid is neutralized with sodium carbonate and 

 is then placed in a dialyser suspended in distilled water, which 

 must be very frequently renewed. The dialysate is tested from 

 time to time with solution of silver nitrate; when this reagent no 

 longer produces a marked opalescence it is concluded that all dif- 

 fusible impurities, of which sodium chloride is the chief, have been 

 removed; the contents of the dialyser are then emptied into a flat 

 capsule and evaporated at a temperature not exceeding 40 C. 



Prepared by this process, serum-albumin still contains from 

 0*5 to TO per cent, of salt, and is obtained in the form of a trans- 

 parent, yellowish, brittle solid, which breaks with a glassy fracture, 

 and which furnishes, when pulverised, a yellowish white powder. 

 It is soluble in distilled water, the solutions being slightly opalescent 

 and, when concentrated, viscous. Solutions of serum-albumin deviate 

 the plane of polarization to the left ; (A)j = 56. The specific 

 rotatory power is remarkably little affected by the presence of salts 

 or by the degree of dilution. 



When dry, solid, soluble albumin, prepared by the previously 

 described method, is heated to 100 C. it is, after a considerable time 

 has elapsed, rendered insoluble in water. 



Solutions of serum-albumin are not precipitated by carbon- 

 dioxide, by acetic or by orthophosphoric acid. They are precipi- 



