DETERMINATION OF THE PARTIAL SPECIFIC VOLUMES OF THERMOREVERSIBLE GELATIN WATER AND KAPPA-CARRAGEENAN WATER GELS

In this paper systematic density measurements of gelatin/water and kap pa-carrageenan/water gels are presented in a wide range of concentrati ons and temperatures. From about 600 measurements for gelatin/water an d about 500 measurements for the system kappa-carrageenan/water empiri cal relations for both systems have been derived which allow to calcul ate the densities of these gels in a limited concentration range if th e temperatures and the polymer weight fractions are known. The calcula ted densities have an accuracy of better than 0,001 g/cm-3 compared wi th the directly measured densities. If the extrapolated partial specif ic volumes of the pure polymer are plotted against the temperature, a jump with an inflexion point can be detected at about 23-24-degrees-C for both systems. These data indicate a LAMBDA-type transition of the expansion coefficient alpha for both systems at 23-24-degrees-C althou gh there are still too few data to make clear conclusions.