Diffusion coefficients and effective charge numbers of lignosulphonate. Influence of temperature

Abstract

The effect of temperature on the diffusion coefficients and effective charge numbers of a polydisperse polyelectrolyte, lignosulphonate, has been studied. The measurements were carried out in 1.0 g dm^–3 sodium lignosulphonate dissolved in 0.1 mol dm^–3 NaCl. The temperatures studied were 10, 20, 29, 38 and 53 °C. The diffusion coefficients increase with increasing temperature and the molecules behave as compact spheres in the temperature range studied. The effective charge number of the lignosulphonate molecules decreases slightly in the temperature range 10–29 °C, but drops suddenly to zero at ca. 38 °C, which means that the molecules are neutral at this temperature.