Glycerol as a Cryoprotectant: An Undergraduate Experiment Using Differential Scanning Calorimetry to Study Glycerol-Water Mixtures

This study describes a laboratory experiment performed with undergraduate physical chemistry students utilizing differential scanning calorimetry (DSC) to determine a eutectic phase diagram, measure solution glass transition temperatures (T g), and predict the glass transition temperature (T g) of water. The DSC techniques employed determine accurate equilibrium freezing temperatures (T f) of glycerol-water mixtures with glycerol mole fractions (x g) between 0 and 0.201. When x g >= 0.300, the slow rate of crystallization of glycerol inhibits crystallization, and solutions exhibit a T g rather than a T f. The T f's serve to discuss solid-liquid equilibria and estimate eutectic phase diagrams with varying levels of accuracy. The T g's serve to estimate the T g of water (135.3 +/- 1.2 K). Together, these behaviors allow for discussion of glycerol's effectiveness as a cryoprotectant.