ALBUMINS OR PROTEINS. 



127 



nor even the system of crystallization itself, as a guarantee of the purity 

 of the individual substance. The only advantage that crystallization 

 possesses is that it gives us a means of separating one product from the 

 mixture, and possibly increasing its purity. 



The fact that we have so far not succeeded in obtaining a single abso- 

 lutely pure, individual, albuminous body, places the whole subject of 

 albumin investigation in a very uncertain light. At every turn we meet 

 this same unfortunate condition. We emphasize this point because a very 

 large number of investigations in the domain of albumin chemistry have 

 but little value for this reason. 



This is especially true of the molecular weight determinations of albu- 

 min. 1 These have been carried out in various ways. The elementary 

 composition has been investigated to see if this would establish anything, 

 considerable attention having been given to the sulphur content. If 

 albumin considered as " pure/' contains one per cent of sulphur, then 

 the molecular weight of the substance must be at least 3200 times that of 

 hydrogen. This method gives us only the minimum value, as we have no 

 means of knowing that only one atom of sulphur is present in the molecule. 

 The amount of sulphur in the various albumins differs greatly. The 

 following calculations have been made: 2 



Taking into consideration the fact that the albumin may contain more 

 than one atom of sulphur, Fr. N. Schulz 3 has estimated the molecular 

 weight of serum-albumin to be 5100, egg-albumin 4900, oxyhemoglobin 

 14,800, globulin 4,600, edestin 7,300. 



The substituted albumins, especially hemoglobin, give us another method 

 for estimating the molecular weight. Oxyhemoglobin contains, besides 

 the albumin globin, a substance containing iron, called hematin. About 

 . 4-0 . 5 per cent iron is present in oxyhemoglobin. Every hematin mole- 

 cule contains one atom of iron. It is generally considered that oxy- 



1 Cf. Fr. N. Schulz: Die Grosse d. Eiweissmolekiils, G. Fischer, Jena, 1903. 



2 Fr. N. Schulz: loc. tit. p. 17. 



3 Fr. N. Schulz: loc. cit. p. 29. 



