JACQUES LOEB 



405 



NaCNS, NaH tartrate, NaH2 citrate, and Na acetate. The curve 

 for Na2S04 is added for comparison. The monosodium salts of weak 

 dibasic and tribasic acids dissociate electrolytically into a Na ion and 

 a monovalent anion, H2PO4, H tartrate. Ho citrate, etc. All the salts 

 mentioned in Fig. 8 are therefore salts with monovalent anion with 

 the exception of Na2S04. Our valency rule demands that the rela- 

 tive depressing effect of these salts (with the exception of Na2S04) 

 should be the same and that deviations from this rule should find their 

 explanation in corresponding deviations of the pH due to the influence 

 of certain of the salts. We will first consider this latter influence as 

 given in Table I, which shows the results of the measurements of pH 



TABLE I. 



Changes in pH of 1 Per Cent Gelatin Chloride of pH = 3.0 upon Addition of Various 



Concentrations of Salts. 



NaCl 



Na2S04 



NaH2P04.... 



NaCNS 



NaH tartrate 

 NaH2 citrate . 

 Na acetate . . 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 



Molecular concentrations of salts used. 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.05 



s 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.1 



3.0 

 3.0 

 3.0 

 3.0 

 3.0 

 3.1 

 3.Z 



3.0 

 3.0 

 3.0 

 3.1 

 3.1 

 3.2 

 3.7 



3.0 

 3.0 

 3.1 

 3.2 

 i.3 

 3.4 

 4.3 



3.0 



3.05 



3.2 



3.45 



3.6 



4.6 



3.0 

 3.1 



3.6 

 3.5 

 3.7 



s 



3.0 



3.2 



3.4 



3.9 



3.55 



3.75 



3.0 

 3.3 



3.45 

 4.2 



3.0 



3.35 



3.5 



4.4 



in these different gelatin solutions after the addition of salts. The orig- 

 inal gelatin chloride solution had a pH of about 3.0 and this was not 

 altered by the addition of NaCl and only slightly by the addition of 

 NaH2P04 in concentrations below m/16. According to the valency 

 rule the curves for the depressing effect of NaCl and NaH2P04 should 

 be almost identical and Fig. 8 shows that this is the case. 



Table I shows that NaCNS, monosodium tartrate, and monosodium 

 citrate raise the pH of the solution as soon as the concentration reaches 

 m/128 or more. If we consider this effect, we must expect to find that 

 the drop in the curves for NaCNS, monosodium citrate, and mono- 

 sodium tartrate is a little steeper in concentrations of m/128 and 



