Possible Anomaly in the Surface Tension of Supercooled Water: New Experiments at Extreme Supercooling down to-31.4 °C

Abstract

The surface tension of water is suspected to show a substantial increase at low temperatures, which is considered to be one of the many anomalies of water. The second inflection point (SIP) anomaly, originally claimed to be at around -8 degrees C, was experimentally refuted down to -25 degrees C by HrubY et al. (J. Phys. Chem. Lett. 2014, 5, 425-428). Recent molecular simulations predict the SIP anomaly near or even below the homogeneous freezing limit of around -38 degrees C. To contribute to an ongoing discussion about the SIP anomaly, new experiments focused on extreme levels of supercooling were carried out in this study. Unique experimental data down to -31.4 degrees C were collected using two measuring techniques based on the capillary rise method. A significant deviation from the extrapolated IAPWS formulation R1-76(2014) for surface tension of ordinary water was detected below -20 degrees C. Contrary to previous data, new experiments provide room for an anomaly in the course of surface tension in the deeply supercooled region.