Viscosity of aqueous solutions of some alkali cyclohexylsulfamates at 25.0 °C

The dynamic viscosity of aqueous solutions of cyclohexylsulfamic acid and of its lithium, sodium and potassium salts was measured in the concentration range from 0.02 to 0.70 mol dm−3 (the potasssium salt only up to 0.20 mol dm−3 because of its poor solubility) at a temperature of 25.0 °C. The data for relative viscosity, which were calculated from the dynamic viscosity, were analysed with the help of the extended Jones–Dole equation and the viscosity coefficients Aη, Bη and Dη were evaluated. The Bη coefficients of the salts were divided into their ionic contributions and the ionic Bη value for the cyclohexylsulphamic ion was determined. From the viscosity coefficient Bη the partial molar Gibbs energy of activation for viscous flow at infinite dilution was calculated for the investigated solutes and interpreted in terms of relative solute effects on the solvent in the ground and in the transition states. Additionally, the hydration number of the solute was determined and some correlation between the transport properties of solutions of cyclohexylsulphamates and their relative sweetness was found.