310 NEWTON BALDWIN GREEN 



When the NaCl and CaCl2 solutions are mixed in the pro- 

 portions of 1000 to 15 and the rate of penetration into colloid 

 III measured, a curve is obtained as shown in figure 4. Along 

 with this curve is plotted a curve showing the effect of NaCl 

 alone, making the conclusion obvious. This experiment was 

 repeated using other proportions and in every case the curve 

 followed a course between that obtained for either salt alone, 

 the preponderant salt having the greater effect. Apparently 

 the inhibitive effect of the adsorbed Ca ions is no greater for ions 

 of one salt than for another. 



Summary of Part I 



Cylinders of colloidal gel such as gelatine, or mixtures of 

 gelatine, agar and whole wheat flour, are readily penetrated by 

 ions of NaCl and CaCU, the initial rate of penetration is not 

 the same for both salts; after several hours the rates become 

 identical. At the beginning the NaCl diffuses more rapidly than 

 the CaCl2, the ratio of the two rates being approximately 

 10:8. Because of the greater adsorption of the cations in the 

 case of CaCl2 the diffusion of ions is hindered to some extent. 

 This occurs at the surface of the colloid and may help to account 

 for Osterhout's decrease in permeabihty using calcium salts. 



When one salt is allowed to penetrate the colloid for a time 

 and then a second salt substituted, the rate of penetration of the 

 ions of the latter seems to be unaffected by presence of the former. 



A mixed solution of NaCl and CaCl2 gives a curve of resistance 

 fall similar to that of either of the constituents alone. It ap- 

 proaches in value more nearly the curve of the predominant 

 salt. 



The ions of NaCl and CaClo do not antagonize one another as 

 regards their penetration into certain colloidal gels, notably 

 gelatine, and mixtures of gelatine, agar and whole wheat flour. 



PART II 



The electrical determination of the penetration of ions into 

 gelatine is valuable as an index of the rate of diffusion of those 

 ions, but it does not show (except very indirectly) the actual 



