THE ACTION OF NEUTRAL SALTS 103 



concentration (and not the alleged influence of the acetate anion) 

 explains the excessive depressing effect of Na acetate. That 

 this interpretation is correct can be proved in the following way: 

 0.8 per cent solutions of gelatin acetate of pH 3.3 and gelatin 

 chloride also of pH 3.3 were prepared. The relative viscosity 

 of these two solutions was practically the same (both were 0.8 

 per cent solutions in regard to originally isoelectric gelatin). 

 The solution of gelatin acetate of pH 3.3 was made up in various 

 concentrations of Na acetate of pH 3.3. The Na acetate solu- 

 tion of pH 3.3 was obtained by dissolving M/16 Na acetate in 

 IJ^J M acetic acid and the various degrees of dilution of this 

 M/16 Na acetate solution of pH 3.3 were brought about by 

 dilution with pure acetic acid of pH 3.3. The non-dissociated 

 molecules of acetic acid have no more depressing influence on 

 the physical properties of proteins than have the molecules of 

 any non-electrolyte. Figure 34 gives the curve representing the 

 depressing effect of Na acetate on gelatin acetate of pH 3.3, when 

 the pH is kept constant. 



The gelatin chloride solution of pH 3.3 was made up in different 

 concentrations of NaCl and the depressing effect of NaCl on the 

 viscosity of gelatin chloride is also plotted in Fig. 34. It is 

 obvious from Fig. 34 that the depressing effects of Na acetate 

 and NaCl are identical when the pH is kept constant and identical 

 in both cases. 



The same fact was confirmed in a somewhat different way. 

 A 1.6 per cent solution of gelatin chloride of pH 3.0 was made up 

 in various concentrations of Na acetate also of pH 3.0. In 

 order to prepare Na acetate solutions of pH 3.0, M/4 Na acetate 

 was dissolved in M/4 HC1 and the various dilutions required for 

 the experiment were obtained by diluting the mixture of equal 

 parts of M/4 HC1 and M/4 Na acetate with M/1,000 HC1. 



The 1.6 per cent gelatin chloride solution of pH 3.0 was diluted 

 with 50 c.c. of this mixture so that the resulting 0.8 per cent 

 gelatin chloride solution of pH 3.0 contained various concentra- 

 tions of Na acetate (or more correctly of NaCl and Na acetate). 

 The curve representing the depressing effect of this salt is given 

 in Fig. 35, and is shown to be identical with the curve representing 

 the depressing effect of the addition of NaCl to gelatin chloride 

 of pH 3.0. 



