202 



SOLUTION AND PRECIPITATION OF PROTEINS 



of Na2S04 is above m/32, a further increase in the concentration of 

 Na2S04 diminishes the solubility of gelatin, and the more so, the 

 higher the concentration of Na2S04. (NH4)2 SO4 acts in the same 

 way. We now understand why it is that we cannot precipitate 

 solutions of isoelectric gelatin with KCl or MgCl2 in concentrations 



130 



120 



110 



100 



90 



80 



70 



60 



50 



40 



30 



20 



10 



8 



■I 



c 



•r-t 



I 



to 



^ n n N ri n n 



^ 1024 512 256 128 64 32 



Concentration of salts 



Fig. 4. Influence of salts on the time required to completely dissolve 0.8 gm. 

 of powdered isoelectric gelatin in 100 cc. of salt solution of different concentra- 

 tions at 35°C. Abscissae are the concentrations of the salt; ordinates, the time 

 required for complete solution. 



up to 3 M (see Table III) while we can precipitate such solutions 

 with sulfates but only at concentrations above m/2 ; since our curve 

 shows that at such high concentrations of sulfates the solubility of 

 isoelectric gelatin in Na2S04 becomes less than in pure water. 



While isoelectric gelatin is only sparingly soluble, gelatin salts 



