Crystallization of ionic salts for calibration of differential scanning calorimeters

• Typical melting point standards supercool during crystallization.
• Calibration of DSC on cooling requires process that show minimal supercooling.
• Very small supercooling can be accomplished in crystallization of inorganic salts.

This study explores the possibility of using inorganic salts for temperature calibration of Differential Scanning Calorimeters (DSC) on cooling. The crystallization and melting of sodium nitrate, potassium nitrate, and rubidium nitrate has been studied at several cooling and heating rates. It has been found that these salts crystallize at almost the same temperature, at which they melt, meaning that they do not practically supercool. The DSC data have indicated that the median value of the supercooling is around 0.4–0.8 °C. The study suggests that the process of crystallization of these and possibly other inorganic salts can be considered for developing new standards to calibrate DSC on cooling.