Boiling point elevation and water activity coefficient of technical (impure) sucrose solutions

Derived from measurement data, a method of calculating the boiling point elevation of pure and impure sucrose solutions is proposed. Depending on the proportion (mol fraction) of dry substance, the water activity coefficient is calculated via an equalizing function. For technical sucrose solutions with nonsucrose components, the apparent dry substance fraction in the solution is calculated. A function for the apparent molar mass of the nonsucrose components is presented. Solutions with up to about 70% dry substance content show a quadratic dependence of the logarithmic water activity coefficient from the dry substance fraction; in higher concentrations, the dependence approaches a fourth-order polynomial. The proposed method of calculation can be used for pure and technical sucrose solutions in a wide temperature and dry substance range.