THE ACTION OF NEUTRAL SALTS 



101 



nearly 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 VI, which shows the results of the 



TABLE VI. CHANGES IN pH OF 0.8 PEE CENT GELATIN CHLORIDE OF 

 pH = 3.0 UPON ADDITION OF VARIOUS CONCENTRATIONS OF SALTS 



measurements of pH in these different gelatin solutions after 

 the addition of salts. The original gelatin chloride solution had 

 a pH of about 3.0 and the pH was not altered by the addition of 

 NaCl and only slightly by the addition of NaH 2 PO4 in con- 

 centrations below M/16. According to the valency rule the 

 curves for the depressing effect of NaCl and NaH 2 P04 should be 

 almost identical and Fig. 33 shows that this is the case. 



Table VI shows that NaCNS, monosodium tartrate, and mono- 

 sodium citrate raise the pH of the solution as soon as the con- 

 centration 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 monosodium tartrate is a little steeper 

 in concentrations of M/128 and above than the curve for the 

 depressing effect of NaCl. Figure 33 shows that the curves for 

 the depressing effect of these three salts are slightly lower than 

 the curve for NaCl or NaH 2 PO4. The greatest apparent 

 deviation from the valency rule occurs in the curve for Na acetate 

 whose depressing effect is of the order of that of Na 2 SO4. 



In the colloidal literature it is always stated that Na acetate 

 acts like Na 2 SO 4 and this is interpreted to mean that the acetate 



