Journal of Crystal Growth, Vol.226, No.1, 158-167, 2001
An examination of the solution phase and nucleation properties of sodium, potassium and rubidium dodecyl sulphates
The nucleation of sodium, rubidium and potassium dodecyl sulphates art: examined using temperature programmed milli-scale batch crystallisation experiments using optical turbidometry detection. As sodium dodecyl sulphate (SDS) crystallises as a hydrated system from aqueous solution, studies have also been carried out in the presence of sodium citrate, which causes the anhydrous phase to crystallise. The meta-stable zone widths (MSZW) and solution properties (the enthalpies and entropies of dissolution) as well as the nucleation reaction orders, are measured. The temperature of dissolution decreases with the decrease in cooling/heating rate whilst the temperature of crystallisation increases for all the systems, resulting in a decrease in the meta-stable zone width with decreasing temperature change rate. The enthalpies and entropies of dissolution of sodium, potassium and rubidium dodecyl sulphate increased with increasing alkali metal ionic radii. Very large values of MSZW for sodium citrate containing solutions occur. Extremely high reaction orders occur with SDS, at high concentrations when pure and at low concentrations when with sodium citrate.
Keywords:nucleation;surfactants