Power of Crystalline Ovalbumin and Serum Albumin. 31 



sation can be repeated without much loss of material if care is used in adding 

 the (NH 4 ) 2 S04 with sufficient slowness. This operation is more difficult than 

 the correspnnding one with ovalbumin in that to produce a permanent 

 precipitate would be quite fatal to crystal formation. (NH^SC^ as a 

 saturated solution must be added to a point when the precipitate, which first 

 forms temporarily, redissolves slowly. From this on it is safest to add only a 

 few cubic centimetres every 20 or 30 minutes (1 c.c. per 100 c.c. fluid). By 

 this method I have obtained 82 per cent, of the total albumin in crystalline 

 form. I have crystallised serum which had remained for six months at —4° C, 

 so that the factor of staleness would not appear to affect the crystallisation 

 of serum albumin to the extent that it does that of ovalbumin. 



Again, I would emphasise that, as in the case of ovalbumin, we are 

 obviously treating an equilibrium reaction which is difficult to force to 

 completion. The albumin remaining in solution need not of necessity be 

 looked upon as non-crystallisable or as essentially different from the 

 crystalline. It may be that, if it were possible to control physically all 

 the constituents of the reaction, and to alter these as they were changed by 

 the deposition of crystals, then the albumin obtained in crystalline form 

 would amount to nearly 100 per cent. The physical difficulties, however, 

 become greater as the concentration of albumin in solution becomes less. 

 The fraction of total albumin crystallised, viz., 82 per cent., is somewhat 

 higher by this method than that obtained by the first method, viz., 70 per 

 cent. In the first method, however, the concentration of albumin was much 

 lower, owing to the small amount of material available. It was thus more 

 difficult to control the distribution of water between remaining albumin, 

 (NH4) 2 S0 4 , and free acid, while maintaining the latter at its optimum 

 concentration. 



By the above method, it has been possible to carry through a series of 

 crystallisations with determinations of rotatory power. Table XI summarises 

 the results obtained : — 



Table XL 



Crystallisation. 



Temperature. 



Concentration. 





OK. 



Mb. 





° C. 



per cent. 





o 



O 



First 



20 



5 -00 





-3-73 



- 74 -78 



Second 



17 



5 -41 





-4-09 



-75 -71 



Third 



15 



6 -08 



-62 -98 



— 4 - 77 



-78 -60 



Fourth 



20 



2 -34 



-62-70 



-3-08 



-78 -24 







_ 



-62-84 





-78 -42 



