4-29 



111 tlie second place a line G — (7 (sol-gel limit) is indicated. It 

 intersects the equilibrium line in a point wliere the number of large 

 particles has the above mentioned limiting-values. 



It has further been assumed that a solution which consists exclusively 

 of small particles is already a sol with very slight water-content. 

 and one in which exclusively large particles occur, is only a sol in 

 very great dilntion. Hence a state denoted by a point on the left 

 side of this line is a gel, and on its right a sol. 



Finally there is still a line L — L, on which the ditferent maxima 

 of imbibition lie. The occurrence of maxima of imbibition though 

 there exists a tendency to a uniform distributed of all the gelatin 

 and water present in the system, leads to the supposition that 

 the gelatin i)articles exert a force on each other, which opposes 

 the segregation of the parts when water is imbibed. As the 

 maxima of imbibition lie the higher as the imbibing gel contains 

 less gelatin, and a small number of large particles goes together 

 with slight concentration of gelatin, this line has been traced so 

 that only little watei is absorbed for a great number of large 

 particles, whereas with decreasing number of large particles the 

 water-content augments. The maximum of imbibition becoming identical 

 to a state of uniform distribution at the limiting value, the line 

 L — -L must gradually approach to the sol-gel limit G — G, and 

 linally coincide with it. If, the equilibrium being denoted by j), the 

 state is represented by a point of the line L — L, e.g. a\ this means 

 that so much water has been absorbed by the gelatin as the place of 

 a' indicates, the rest of the water being present in free condition. 



If by means of drying, water is extracted from a gelatin 

 solution, whose state isrepresented by p, the concentration increases 

 slowly and the number of large particles augments. The change can 

 take place along the line p — a, which lies wholly on the right of 

 the equilibrium line, so that in anhydrous state a number of large 

 particles exist as indicated by a. 



If this dried gelatin is suddenly .brought into contact with so much 

 water that the equilibrium in the system is again represented by p, 

 there exists in the first place a tendency to absorption of water, 

 and moreover a tendency to a diminution of the number of large 

 particles. As a result of both the change of a will take place in the 

 direction a — a'; it will be along time before the distance a — a' is covered; 

 every quantity of absorbed water causes large particles to disappear, 

 and this renders the absorption of more water possible; this goes 

 on till the line of the maxima of imbibition is reached. A further 

 absorption of water would have to take place along the line L — L, 



