NATURE OF BOUND WATER IN COLLOIDAL SYSTEMS

Abstract

The state of water in colloidal systems was investigated to determine the causes for anomalous changes in activity which form the basis for so-called "bound" water phenomena, often considered to be related to cold resistance in plants and animals. Various artificial and natural colloidal and crystalloidal systems were investigated. Vapor pressure measurements of high accuracy were made at 1[degree] and 20[degree]C on relatively simple solns. and thermodynamic functions were calculated therefrom. Similar functions were calculated for systems at low water content. The activity of water in colloidal and true solns. of diverse complexity and moderate conc. was detd. by the freezing-point method, using 2 types of reference solutes. Entropy of the water component was not decreased by presence of the colloid in dilute soln. The activity of water in dilute solns., both colloidal and true, may deviate on either side of expected values, depending upon the nature of the solutes present, in accordance with known properties of electrolytes, and non-polar and dipolar non-electrolytes. Water relations in colloid systems are evidently of 2 kinds 1) a small amt. of water may be so intimately associated with the colloid at low water content that random orientation is limited, the phenomenon dominated by irreversible processes; 2) the water molecules in dilute colloidal soln. are not limited in their random orientation by the colloid particles. Anomalous changes in activity reflect the influence of all solutes present which tend to make the soln. non-ideal. This phenomenon is due to reversible processes.