358 CHEMISTRY OF THE PROTEIDS CHAP. 



crepancies are too great to be attributed to experimental error. Bond- 

 zynsky and Zoja 1 explain the discrepancies by assuming the existence 

 of several crystalline albumins, while Hofmeister, 2 Hopkins, 3 Osborne 

 and Campbell 4 maintain that in addition to the crystalline albumin 

 there is present in egg-white a second non-cry stallisable albumin, which 

 Osborne and Campbell and Langstein 5 call con-albumin. This con- 

 albumin is characterised by a higher nitrogen- and sulphur-content, 

 and in this it resembles the older non-crystallisable preparations of 

 Hammarsten. 6 As, further, the ovo-mucoid which can only be 

 separated with great difficulty from the ov-albumin contains still more 

 sulphur but less C and N than the con-albumin, it is readily seen how 

 by its admixture great discrepancies in the analytical numbers may be 

 induced. Schulz and Zsigmondy 7 have shown by means of the gold 

 number (see p. 333) that it is exceedingly difficult to free egg-albumin 

 from colloidal impurities, even sixfold recrystallisation not being 

 sufficient in some cases, and they found in addition to the ovo-mucoid 

 a "contaminating substance " which may not be an albumin at all and 

 which may possess an entirely different chemical constitution. It is 

 this impurity which adheres so strongly to egg-albumin. Under these 

 conditions the analytical differences may readily be attributed to con- 

 taminating substances, and there is no necessity to assume a multiplicity 

 of albumins. According to Spiro 8 the precipitation and crystallisation 

 of albumins by means of ammonium sulphate is never complete, and 

 therefore the non-crystallisable fraction or con-albumin need not be a 

 separate substance. 



The precipitation-limits for pure egg-albumin by means of ammonium 

 sulphate lie, according to Langstein, 5 between 6'2 and 6'S (see p. 292); 

 the limits are therefore very narrow, a fact which also supports the 

 view that egg-albumin is a uniform substance. It is precipitated by 

 sodium chloride in acid solutions, provided the solution is really satur- 

 ated with sodium chloride, according to Hopkins. 3 



The coagulation-temperature has been determined by Starke 9 as 



1 St. Bondzynsky and L. Zoja, Zeitschrift f. physiol. Chem. 19. 1. (1893). 



2 F. Hofmeister, ibid. 16. 187 (1891) ; 24. 159 (1897) ; F. N. Schulz, ibid. 25, 

 16 (1898). 



3 F. G-. Hopkins, Journ. of Physiol. 25. 306 (1900). 



4 T. B. Osborne and F. G. Campbell, Journ. Amer. Chem. Soc. 21. 477 (1899) ; 22. 

 422 (1900). 



5 L. Langstein, Hofmeister' 's Beitrage, 1. 83 (1901). 



6 0. Hammarsten, Zeitschr. f. physiol. Chem. 9. 273 (1885) ; K. V. Starke, Maty's 

 Jahresber. 11. 17 (1881). 



7 F. N. Schulz and R. Zsigmondy, Hofmeister' 's Eeitrage, 3. 137 (1902). 



8 K. Spiro, ibid. 4. 300 (1903). 



9 K. V. Starke, Maly's Jahresber. 11. 17 (1881). 



