The rate and extent of both physical and chemical processes can be monitored at elevated humidity by placing a saturated salt solution in the calorimeter cell with the sample.  Here the results showed that a suspected hydrate impurity formed more rapidly at smaller particle sizes.  However, since the three samples had the same total heat generated the extent of formation was not dependent upon particle size.  The entire particle formed the hydrate, not just the surface as was erroneously concluded from other methods such as reflectance FTIR.