414 ION SERIES AND PROTEINS. Ill 



SUMMARY. 



1. Ions with the opposite sign of charge as that of a protein ion 

 diminish the swelhng, osmotic pressure, and viscosity of the protein. 

 Ions with the same sign of charge as the protein ion (with the excep- 

 tion of H and OH ions) seem to have no effect on these properties as 

 long as the concentrations of electrolytes used are not too high. 



2, The relative depressing effect of different ions on the physical 

 properties of proteins is a function only of the valency and sign of 

 charge of the ion, ions of the same sign of charge and the same valency 

 having practically the same depressing effect on gelatin solutions of the 

 same pH while the depressing effect increases rapidly with an increase 

 in the valency of the ion. 



3. The Hofmeister series of ions are the result of an error due to the 

 failure to notice the influence of the addition of a salt upon the hydro- 

 gen ion concentration of the protein solution. As a consequence of 

 this failure, effects caused by a variation in the hydrogen ion concen- 

 tration of the solution were erroneously attributed to differences in 

 the nature of the ions of the salts used. 



4, It is not safe to draw conclusions concerning specific effects of 

 ions on the swelling, osmotic pressure, or viscosity of gelatin when 

 the concentration of electrolytes in the solution exceeds m/16, since 

 at that concentration the values of these properties are near the mini- 

 mum characteristic of the isoelectric point. 



Note. — The solutions of 1 per cent isoelectric gelatin were prepared by bringing 

 1 gm. of dry gelatin to the isoelectric point according to the method described 

 in previous papers. It was found that in this process about 20 per cent of the 

 gelatin was lost, so that the originally 1 per cent gelatin solution contained in 

 reality only about 0.8 per cent isoelectric gelatin. This does not a£fect the con- 

 tents of the paper or the conclusions since the gelatin concentration used was 

 always the same. 



