Anomalous Volume Properties of Vicinal Water and Some Recent Thermodynamic (DSC) Measurements Relevant to Cell-Physiology

Abstract

The properties of water and aqueous solutions adjacent to interfaces (particularly solid surfaces) differ from the corresponding properties of the bulk systems. The differences are ascribed to structural effects of the interface on the aqueous phase — the resulting interfacial water being referred to as vicinal water. Extensive reviews of the nature of vicinal water have been published (1, 2, 3, 4) over about a decade and will not be reviewed here; suffice it to mention that vicinal water appears to exist over notable distances from the interface namely of the order of 30 to 150 molecular diameters or in other words 0.01 to 0.05 microns (pm). Furthermore, vicinal water appears to differ energetically only slightly from bulk water (3, 5). Vicinal water undergoes abrupt changes in properties — and, hence, no doubt, in structure — near a number of discrete temperatures, namely near 15, 30, 45 and 60°C, referred to respectively as T₁, T₂, T₃, and T₄, or in general T_K. (An additional anomaly appears to occur near 74°C) (6). Previous measurements (7) of the thermal properties of vicinal water have suggested that the specific heat is approximately 25 percent larger than that of bulk water. It is of interest to note that in recent studies Angell and co-workers (8, 9) have observed notable increases in the specific heat of (bulk) water at very low temperatures (below say − 20°C) and at temperatures approaching the critical temperature.