Abstract
An experimental apparatus originally developed for the measurement of surface tension of supercooled water was modified such that it allows for measurement of binary aqueous mixtures. The measuring principle based on the capillary rise technique is similar to that employed in the previous measurements with pure water [J. Hrubý et al., J. Phys. Chem. Lett. 5 (2014) 425 and V. Vinš et al., J. Phys. Chem. B 119 (2015) 5567]. The temperature dependence of the surface tension is determined from the measured height of the liquid column elevated in a vertical capillary tube with an inner diameter of 0.32 mm. The aqueous liquid rises to a height of 60 mm to 95 mm depending on the solute concentration and the temperature. Preliminary tests performed with the binary mixtures of water with methanol, ethanol, and n-propanol at various concentrations and temperatures down to –28 °C approved functionality of the measuring technique. Some difficulties, such as influence of impurities on the liquid column elevation or formation of bubbles in the liquid column, were observed. The experimental apparatus is further being modified in order to obtain more accurate data for various aqueous mixtures.
Highlights
This study is part of a long-term research of our group focussing on the experimental investigation of thermophysical properties of water and aqueous systems under the supercooled conditions, i.e. on the properties of the metastable liquid aqueous phase at temperatures below the equilibrium freezing temperature
The experimental apparatus and the measuring technique used for the measurement of the surface tension of pure supercooled water [3-7] was modified such that it allows for investigation of aqueous binary mixtures
The water–lower alcohol model combines the surface tension of pure water obtained from the IAPWS correlation [11] and the surface tension of pure alcohols predicted using correlations by Mulero et al [16]
Summary
This study is part of a long-term research of our group focussing on the experimental investigation of thermophysical properties of water and aqueous systems under the supercooled conditions, i.e. on the properties of the metastable liquid aqueous phase at temperatures below the equilibrium freezing temperature. The experimental apparatus and the measuring technique used for the measurement of the surface tension of pure supercooled water [3-7] was modified such that it allows for investigation of aqueous binary mixtures. The new accurate data for the surface tension of aqueous systems, such as mixtures with alcohols or salts, under the supercooled conditions are important for scientific communities focused on the atmospheric and oceanographic research [8,9] and on the investigation of anomalous behaviour of water systems at low temperatures [1,2]. Functionality of the new measuring technique was successfully tested by initial measurements of water mixed with several short-chain alcohols; namely with methanol, ethanol, and n-propanol
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