Viscosities of casein in dilute 0.1 mol/L NaOH solutions at different temperatures were carefully measured.The upward phenomena of the apparent viscosity of casein in NaOH solutions was attributed to the adsorption of the solute on the inner wall of the glass capillary, and a corrected viscosity equation was used to deal with the obtained viscosity data.Five viscosity parameters have been obtained to describe the state of casein molecules in the solution and on the interface.It seemed that the size of casein molecules in solution changed little with temperature, and the adsorption layer thickness varied regularly with the adsorption amount.
In order to investigate the property and concentration dependence of dissociation and hydrolysis of polyelectrolytes,acrylic acid-sodium acrylate copolymers with various degree of neutralization were prepared by adding calculated amounts of sodium hydroxide into the aqueous solutions of a poly(acrylic acid) sample,and the pH values of the solutions covering a wide concentration range were measured for each copolymer at 25℃.It was found that the pH values of the solutions of a copolymer with degree of neutralization of 0.96 kept constant and equaled to 9.80 as c>0.001 mol/L.For another copolymer with degree of neutralization of 0.30,the pH values of its solutions remained constant and equaled to 6.25 as c<0.001 mol/L.These two copolymers may serve as polymeric buffer reagents which couldn’t penetrate through semi-permeable membranes in the corresponding concentration regions.
