Studies on the gel—sol transition and some gel characteristics of photographic gelatine

Abstract

AbstractStudies have been made on gelatine gels containing inorganic salts and ionic surfactants, with the aim of learning about factors that influence the structural make‐up of hydrogels. Gel‐sol transition temperature, Tm, was studied by a micro capillary‐visco‐meter, gel‐elasticity, E, by applying unidirectional compression and gel‐hardness (rigidity), H, by using Röths micro penetrometer. An attempt was made to describe the results quantitatively. The equation lg Tm = k c + b was found to fit the data on gelation and analogous equations proved to be valid for both the E vs. c and the H vs. c relations. This is true for the different chlorides in the whole concentration‐range studied, but for sulphates over a limited concentration range only. The specific effect of the latter reveals itself mostly in the changes of Tm and H. As ΔH was not altered significantly by the cosolutes used it is concluded that ΔS plays the essential role in the described effects.