Abstract:
Drying methods are the most widely used techniques. Drying techniques with
convective heating principle comprise ordinary oven drying and vacuum oven drying. It is
important to be aware that drying techniques do not measure the water content as such. The
result is a mass loss under the conditions applied or “moisture” is often used instead. These
conditions can principally be freely chosen and the results are, consequently, variable.
Drying to a constant mass is often required, but a real constancy is only achieved in rare
cases. The mass loss is not only caused by water but by all the substances volatile under the
drying conditions, either already contained in the original sample or produced by the
heating process. The application of low pressure in vacuum ovens reduces the danger of
producing volatile decomposition compounds but does not allow a distinction to be made
between water and other volatile substances already present in the product. To shorten the
long determination times, more intensive heating is used. The results can vary in a very
broad range depending on the drying parameters applied. Mass-loss results can, however,
be matched with the results of another method, particularly a reference method, by
adjusting the parameters in an appropriate way. In these cases the most suitable calibration
must be established for every type of product in a specific way [1].