This paper re-examines work on inorganic materials and oxalates, but combines differential scanning calorimetry (DSC) measurements with simultaneous observation and recording of the reflected light intensity to obtain more detailed information about the physical and chemical changes occurring. The method indicates the nature of the changes recorded by the DSC, both physical and chemical and gives additional confirmation of the nature of complex and overlapping DSC peaks for ammonium salts, copper carbonate and the potassium oxalato-complexes of aluminium, copper, iron and chromium.