Temperature and enthalpy of fusion calibration of Calvet calorimeter from-150C to 156C

To calibrate a commercial Calvet calorimeter and promote accurate measurement for an unknown sample, a calibration method using reference materials was studied within a wide temperature range of -150 similar to 156 degrees C. We present the results of two experiments that we conducted to calibrate the calorimeter for temperature and enthalpy of fusion measurements. The calibration materials included cyclopentane and n-heptane in the low-temperature region, in addition to water, gallium, and indium, which are fixed-point realisation materials specified in ITS-90 at temperatures above 0 degrees C. We determined the onset temperature and enthalpy of fusion at a heating rate of 0.1-0.4 K/min by analysing the heat flow signal and calculating the area under the corresponding curve. For each material, we obtained calibrated temperatures that showed a valid range with a maximum deviation of 0.17 degrees C from the fitted line. We successfully calibrated enthalpies of fusion with relative uncertainties ranging from 0.38% for water to 3.56% for gallium. We found that the overall uncertainty of the Calvet calorimeter was within 5.3%. Future research efforts will aim to further reduce the uncertainty by using a heating cell with Joule heating to enable continuous data collection over the entire temperature range.