5. Condensers on an evaporator must provide sufficient cooling to condense the water vapour from the evaporator. Condenser calculations are based on the heat transfer equation.
6. Boiling-point elevation in evaporators can be estimated using Duhring's rule that the ratio of the temperatures at which two solutions exert the same pressure is constant.
7. Special provisions, including short residence times and low pressures to give low boiling points, are necessary if the maximum retention of volatile constituents is important, and to handle heat sensitive materials.