CHEMISTRY OF THE PROTEIDS CHAP. 



a precipitate made with phosphotungstic acid redissolves on being 

 washed, for some time, with water. The objections which v. Rhorer 

 has raised against Erb's estimations of hydrolysis by means of calcium 

 phosphotungstate are not valid because the phosphotungstates undergo 

 hydrolysis themselves. 



That firm or solid salts of albumin may be dissociated by water 

 should always be remembered when working with albumins. 



Precipitates of albumins contain usually large quantities of other 

 bodies, such as inorganic acids and bases, colouring matters, sugars, 

 glycogen, lecithin, other albumins, ferments, etc. These may be re- 

 moved more or less completely by prolonged washing, and therefore it 

 was supposed that they were simply carried down mechanically and 

 not bound chemically to the albumins. Jacoby 1 and others, who 

 have worked at the purification of ferments, show, however, that this 

 cannot be the case, as the admixtures are held by the albumins in 

 chemical union, which latter is loosened whenever hydrolysis takes 

 place. 



In addition to the salts mentioned up till now, others have been 

 described, in which the acid or the base is present in much smaller 

 amount, and in which the acid or base cannot be removed so 

 readily. Osborne 2 investigated the chlorides, dichlorides, sulphates, 

 and nitrates of edestin, and the sodium and potassium salts of 

 edestin. He estimates the equivalent weight of edestin at 14,300 

 to 7000, and states that the acid or base is very difficult to remove 

 even after great dilution and prolonged washing. Harnack 3 describes 

 similar salts of denaturalised egg-white with copper, Werigo 4 with 

 sodium, and both agree in giving the equivalent weight of albumin 

 as 4748. The equivalent weight of casein has been estimated, from 

 calcium 5 and ammonium salts, 6 to be approximately 5100 by 

 Hammarsten, 7 Soldner, 8 and Salkowski. 6 In the presence of an excess 

 of alkali the equivalent weight of casein, according to Spiro and 



1 M. Jacoby, Zeitschr. f. physiol. Chem. 30. 135, 166 (1900) ; Arch. f. experiment. 

 Path. u. Pharmakol. 46. 28 (1901) ; Hofmeister s Beitrdge, 1. 51 (1901). 



2 T. B. Osborne, Journ. Amer. Chem. Soc. 21. 486 (1899) ; Zeitschr. /. physiol. 

 Chem. 33. 241 (1901). 



3 E. Harnack, ibid. 5. 198 (1881) ; Ber. d. deutsch. chem. Ges. 23. 3745 (1890) ; 

 Zeitschr. f. physiol. Chem. 19. 299 (1894). 



4 B. Werigo, Pftuger's Arch. f. d. ges. Physiol. 48. 127 (1891). 



5 0. Hammarsten, Ges. d. Wiss. zu Upsala, 1877 ; F. Soldner, Dissertation, Erlangen, 

 1888. 6 E. Salkowski, Zeitschr. f. Biol. 37. 401 (1899). 



7 0. Hammarsten, Ges. d. Wiss. zu Upsala, 1877. 



8 F. Soldner, Dissertation, Erlangen, 1888. 



