494 AMPHOTERIC COLLOIDS. IV 



ratio of 1 : 3 particles in solution. This would account for the differ- 

 ence in the ratio of osmotic pressures but would leave unexplained 

 the identity of conductivity of the two solutions. It would there- 

 fore be necessary to make a second assumption; namely, that the 

 lower viscosity of a 1 per cent Ca gelatinate solution would raise the 

 conductivity of a Ca gelatinate solution enough to compensate for 

 the smaller degree of electrolytic dissociation. 



In order to account for the ratio of 1 : 3 in osmotic pressure of the 

 solutions of the two types of salts we have to assume that only about 

 20 to 25 per cent of the Ca gelatinate molecules are dissociated, while 

 the dissociation of the sodium gelatinate is complete (five molecules 

 of Ca gelatinate, one of which dissociates, would yield seven particles 

 while the same amount of gelatin would form ten molecules of sodium 

 gelatinate, yielding with- complete dissociation twenty particles; this 

 would result in a ratio of 7 : 20 for the relative number of particles in 

 solution) . The four electric charges of the one dissociated Ca gelat- 

 inate molecule would have to give the same conductivity as the 

 twenty electric charges of the sodium gelatinate. 



Our present knowledge speaks against such an influence of the vis- 

 cosity of gelatin solutions upon conductivity. We prepared 1 per 

 cent solutions of sodium, potassium, magnesium, and calcium gelat- 

 inate, of pH = 7.0, by putting 1 gm. of finely pulverized commercial 

 Cooper's gelatin (probably mostly calcium gelatinate) for 1 hour at 

 20°C. into 100 cc. of m/4 NaCl or KCl, or MgCla or CaCla, and allowed 

 the excess of salt solution to drain off by putting the gelatin on a 

 filter. We then washed the gelatin on each filter six times in succes- 

 sion with 25 cc. of H2O, melted the gelatin by heating to about 50°C., 

 and added enough water to make a 1 per cent gelatin solution. The 

 solution was cooled to 24°C. and the time of outflow through a vis- 

 cometer, as well as the conductivity of each solution, was measured 

 immediately, at 24°C. (Table I). We found the usual typical dif- 

 ference in viscosity between Ca and Mg gelatinate on the one hand, 

 and Na and K gelatinate on the other. It is well known that the 

 viscosity of a gelatin solution prepared by melting will increase on 

 standing, especially at a low temperature. The gelatin solutions 

 were kept at about 2°C. for 2 hours and were then heated to 24°, 

 and their viscosity and conductivity were again measured. All the 



