422 



(lull the viscosity inc-reases with increasing; gelatin-content. As the 

 variations of the viscosity as a consequence of the heating in the 

 V2 " solution had not yet ceased at the moment of the dilution, 

 we must assume that the equilibrium between large and small particles 

 had not yet set in. The state for the cone, c^ (Vs 7o) i^i^st therefore 

 be represented by a point below the equilibrium line, e.g. a. At 

 the moment of the dilution from c, to c^ the number of large parti- 

 cles undergoes only a slight variation, so that for c, the state may 

 be represented by /;. This point lies above the equilibrium line ; a 

 gradual diminution of the viscosity is the consequence of this, which 

 does not cease until the state of equilibrium p is reached. 



That actually an approach to the equilibrium at the given tem- 

 perature and concentration takes place, may be proved by heating 

 part of the diluted (74 7o) solution at 70° for some minutes, and 

 then reducing it again to 20°. At this high temperature the equi- 

 librium ratio is quickly reached for the 74 7o solution, so that after 

 the cooling there are fewer large particles than at the equilibrium 

 (represented by d in fig. 2) ; now an increase of the viscosity must 

 be found. It appears from table 'J that a tendency really exists in 

 both cases to approach the same final value. 



TABLE 1. 



Variation of the viscosity with the time at 20° in a '/4O/0 



solution, prepared by dilution of a ^'2% solution (the 



viscosity of water at 20° taken as unity). 



Variation of the viscosity with the time at 20° in the same 

 solution after a heating at 70°. 



