Aqueous nonelectrolyte solutions. Part XIV. D-ice and D-hydrate freezing points of deuterium oxide – ethylene oxide solutions and the formula of congruent ethylene oxide D-hydrate

Abstract

D-ice freezing temperatures and D-hydrate formation temperatures have been measured by the dynamic cooling method for deuterium oxide – ethylene oxide (EO) solutions containing from 0 to 95.5 mol% EO. The D-ice and the congruent EO D-hydrate freezing temperatures exhibited standard errors (SEs) on a single measurement of 0.004 °C and 0.017 °C, respectively. The D-ice–D-hydrate eutectic temperature was observed at 1.500 °C with standard error (SE) 0.002 °C and at composition 2.207 mol% EO with SE 0.010 mol% EO. The congruent EO D-hydrate was found to freeze at 13.242 °C with SE 0.007 °C and at composition 12.60 mol% EO with SE 0.07 mol% EO. The formula of the congruent EO D-hydrate was EO•6.93D2O with SE 0.045 mol D2O/mol EO. Only one type of D-hydrate was found over the whole composition range down to −23 °C: the shoulder of the D-hydrate freezing curve above 40 mol% EO resulted from the high activity coefficients of dilute deuterium oxide in concentrated EO solutions. Equations and best values for the D-ice freezing temperatures and the D-hydrate formation temperatures together with their SEs were evaluated by the method of least squares. Properties of EO D-hydrate are compared with those of EO hydrate. Key words: clathrate D-hydrate of ethylene oxide, freezing of deuterium oxide – ethylene oxide, ethylene oxide D-hydrate, formula of ethylene oxide D-hydrate.