DSC temperature calibration over the range −125 °C to 50 °C

The lack of Nationally Certified Reference Materials for the calibration of DSC equipment in the sub-ambient range has been addressed by the introduction of a Certified Reference Material of purified cyclohexane by the National Metrology Institute of Japan. This sample, in conjunction with the CRM material phenyl salicylate and the ITS-90 fixed point material mercury, has enable a DSC-thermomicroscopy system to be accurately calibrated over the temperature range −90 °C to 50 °C. The DSC has then been used to measure values for the solid-solid transitions in the potential Certified Reference Materials ammonium sulphate, adamantane and ammonium dihydrogen phosphate, which have the advantage of being thermally stable and easy to handle, and for the melting point of diphenyl ether. In addition, the effect of temperature cycling on these materials has been investigated.