An Attempt at Simultaneous Observation by Polarizing Microscopy and by Differential Thermal Analysis

An apparatus for differential thermal analysis using a polarizing microscope has been developed. With this device it is possible to observe the state of a sample under the heating or cooling conditions with a polarizing microscope and to obtain the DTA curve simultaneously. The transformations of several substances—potassium laurate, ammonium nitrate and tripalmitin— were observed. The results are in agreement with those obtained by X-ray diffraction. The relation between the appearance of Phase III of NH4NO3 and the water content of the sample was considered on the basis of the microscopic observations. In the case of tripalmitin, two types of transformations were observed under cooling conditions. The relation between the DTA curve of tripalmitin and the heating rate has also been studied. The apparatus may be useful for the study of liquid crystals.