The problem is discussed of providing a theoretical explanation for the empirical equation of Laurent, Bjork, Pietruszkiewicz & Persson (1963) which relates the relative retardation of the sedimentation of compact particles in solutions of hyaluronic acid to the radius of the particle and the concentration of hyaluronic acid. From published and original data, the same relation is shown to apply also to sedimentation and diffusion in solutions of a number of linear and branched chain-polymers. Of several approaches to the problem, only one, based on the stochastic model of diffusional migration, yields the empirical relationship, and predicts a value of the numerical constant close to that observed. This treatment is shown to apply to other forms of migration, including the case where the chain-polymer is itself migrating. The theory is tested by calculation, from migration data, of the effective radii of the polymer chains. The results are consistent and comparable with values deduced from equilibrium experiments.

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The adsorption of Cd(II) onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. As the pH was increased, adsorption onto goethite occurred mainly in the pH range 5.5-8, whereas adsorption onto kaolinite occurred in two stages, separated by a plateau in the pH region 5.5 to 7. Adsorption onto illite increased steadily as the pH was increased, with far less Cd(II) adsorbing onto illite than onto goethite or kaolinite per m(2) of mineral surface area. Potentiometric titrations of suspensions of each mineral, with and without Cd(II) present, were also completed. Results from all three types of experiments were modeled using an extended constant- capacitance surface complexation model. The reactions [Formula: see text] [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto goethite, while [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto kaolinite. A combination of the first, second, and fourth of these reactions best fitted the data for Cd(II) adsorption onto illite. In each case the model fitted all experimental data well. The results suggest that adsorption onto the variable charge (SOH) sites on illite more closely resembles adsorption onto goethite than onto kaolinite.

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The solubilities of three estrogenic hormonessestrone, 17β-estradiol, and 17R-ethynylestradiolsand the industrial pollutant bisphenol A were measured in water, dilute acid and alkali (pH 4 and 10, respectively), and aqueous KNO 3 (0.01 mol‚L -1 and 0.1 mol‚L -1 ). The concentrations of saturated solutions, after equilibration at (25.0 ( 0.5) °C with excess solid for 4 days, were determined by HPLC. Six replicate results were obtained for each solute-solvent pair: the coefficient of variation was in most cases < 5 %. The solubilities in pure water with standard deviations were estrone (1.30 ( 0.08) mg‚L -1 , 17β-estradiol (1.51 ( 0.04) mg‚L -1 , 17R-ethynylestradiol (9.20 ( 0.09) mg‚L -1 , and bisphenol A (300 ( 5) mg‚L -1 . The solubility of each of the hormones was unchanged between pH 4 and pH 7 but was greater at pH 10. At pH 7, the hormones became progressively less soluble as the ionic strength increased from 0.0 to 0.1 mol‚L -1 . By contrast the solubility of bisphenol A was essentially the same under all of the experimental conditions tested.