280 



THEORY OF COLLOIDAL BEHAVIOR 



outflow through a viscometer is measured immediately at 15C. 

 As a control the time of outflow at 15C. of identical water- 

 alcohol mixtures but containing no gelatin is also measured. The 

 ratio of the time of outflow of the gelatin-water-alcohol mixture 

 to that of the water-alcohol mixture without gelatin, i.e., 

 the relative viscosity of the gelatin solution, is given in Table 

 LIII. The upper horizontal row gives the relative amount of 

 alcohol in per cent, the second row the appearance of the solution, 

 the third the time of outflow of the gelatin solution in seconds, 

 the fourth row the time of outflow of the alcohol-water mixture 

 without gelatin, and the last row the relative viscosity of the 



TABLE LIII. INFLUENCE OF INCREASING QUANTITIES OF ALCOHOL ON THE 



VISCOSITY OF A 1 PER CENT SOLUTION OF GELATIN CHLORIDE OF 



ORIGINALLY pH 3.0 



gelatin solution. It is obvious that the viscosity drops sharply 

 between 80 per cent and 85 per cent of alcohol, and that at 85 

 per cent, where the solution is already opalescent, the relative 

 viscosity is only 1.286 and only 1.1 for 87.5 per cent alcohol. 



In a second experiment the same solutions were prepared but 

 the solutions were kept for 2 days in a thermostat at 9C., the 

 mixtures were then rapidly brought to 15C., and the viscosities 

 determined. The solution containing 60 per cent of alcohol or 

 less had set to a jelly; the solution containing 70 per cent was 

 almost solid, but the solutions containing 80 per cent or more were 

 all completely liquid. Their relative viscosity was measured 

 (Table LIV) and was found to be only slightly larger than at 

 the beginning, when the solution contained 85 per cent or more 



