Aqueous nonelectrolyte solutions. Part XIII. Ice and hydrate freezing points of aqueous ethylene oxide solutions and the formula of congruent ethylene oxide hydrate

Abstract

Ice freezing temperatures and hydrate formation temperatures have been measured by the dynamic cooling method for aqueous ethylene oxide (EO) solutions containing from 0 to 95 mol% EO. The ice and the congruent hydrate freezing temperatures exhibited standard errors on a single measurement of 0.004 °C and 0.013 °C, respectively. The ice–hydrate eutectic temperature was observed at −2.107 °C with standard error 0.001 °C and composition 1.991 mol% EO with standard error 0.008 mol% EO. The congruent hydrate was found to freeze at 11.083 °C with standard error 0.002 °C and composition 12.64 mol% EO with standard error 0.02 mol% EO. The formula of the congruent hydrate was EO•6.91H2O with standard error 0.013 mol water/mol EO. Only a single hydrate was found over the whole composition range down to −26 °C: the shoulder of the hydrate freezing curve above 40 mol% EO resulted from the high activity coefficients to dilute water in concentrated EO solutions. Equations and best values for the ice freezing temperatures and the hydrate formation temperatures together with their standard errors were evaluated by the method of least squares. Keywords: clathrate hydrate of ethylene oxide, freezing of water – ethylene oxide, ethylene oxide hydrate.