Vicinal water surface tension

Conventional water-based and non-aqueous inkjet inks are mixtures of several components, including volatile solvents, dissolved materials, and dispersed solids (for pigment inks). When the ink reaches the nozzles prior to jetting, the volatile components may evaporate from the nozzle. Therefore, the liquid in the vicinity of the nozzle can have a composition which differs from that of the bulk ink which is further back in the print head supply channels. This disparity causes differences in the physicochemical properties of the ink (e.g., an increase in viscosity or decrease in surface tension)... 

The irregularly shaped pores between soil particles contain both air and water (Fig. 9-9). The soil pores, or voids, vary from just under 40% to about 60% of the soil by volume. Thus a soil whose pores are completely filled with water contains 40to60% water by volume. In the vicinity of most roots, moist soil contains 8 to 30% water by volume the rest of the pore space is filled with air. Therefore, the pores provide many air-liquid interfaces (Fig. 9-9) where surface tension effects can lead to a negative hydrostatic pressure in the soil water (Chapter 2, Sections 2.2G and 2.4E). Such a negative P is generally the main contributor to the water potential in the soil, especially as the soil dries. The thermal properties of soil are discussed in Chapter 7 (Section 7.5), so here we focus on soil water relations. 

Before applying such models to vicinal water, they should be checked to account for the properties of bulk water (molar Internal energy, pressure, specific heat, singularity at 4°C, etc.), which is sometimes done l, and for the surface tension as a function of temperature, which is a more critical test but rarely done. ... 

Based on surface tension measurements using the rise height of water in narrow capillaries and then obtaining the entropy term by numerical differentiation of the data, Drost-Hansen (1965) found a large peak in entropy of surface formation near 30 C. This is taken to mean that vicinal water is disorganized at 30°C (see also Drost-Hansen, 1973). Another example is provided by the data of Wershun (1967), who studied the effects of temperature on chromosome aberration rate in the broad-leaf bean Viciafaba. As shown in Figure 7, a notable peak occurs at 30°C. 

The surface light scattering method has been used to show that the low interfaciai tensions in the Winsor I and II systems (O/W microemulsion in equilibrium with excess oil and W/O microemulsion in equilibrium with excess water, respectively) are due to the large surface pressure of the surfactant monolayer coating the interface, which almost balances the bare oil/water interfaciai tension [36,37]. Schulman and Montagne [38] proposed early that the low interfaciai tensions in microemulsion systems should be associated with these large surface pressures tt, i.e., 7 = 70 - tc 0. In other models, the origin of the low interfaciai tensions was attributed to the vicinity of critical points [39,40]. 

Water molecules of hydrophilic sols, in the vicinity of dispersed molecules of high molecular weight substances (proteins and polysaccharides), are relatively tightly associated by non-bonding interactions. They are usually in the state of thermodynamic equi-Hbrium and are therefore relatively stable. Their viscosity and surface tension are significantly different (higher) than the viscosity and surface tension of the pure dispersion medium (water). 

The absolute values of the interfacial tensions varied between different amphi-philes and solvents (Table 1). AOT, which is well known in the literature for the formation of microemulsions, showed the lowest surface tension at the interface of both solvents. The other nonionic snrfactants mentioned here. Span 80 and Brij 72 showed shghtly higher valnes. This was also observed for Lecithine, but this lipid precipitated partly during the spinning-drop measurements. Due to this phenomenon, it was not possible to measure accurate data for this emulsifying compound. The interfacial tension had also some influence on the mean size of the emulsion droplets and on the stability of the vesicles (Table 3). In addition to the stationary values of the surface tension, dynamic processes as the surfactant diffusion represented another important factor for the process of stimulated vesicle formation. If an aqueous droplet passed across the fluid interface it carried-over a thin layer of emulsifiers and thereby lowered the local surfactant concentration in the vicinity of the oil-water interface. In the short time span, before the next water droplet approached the interface, the surfactant films should entirely reform and this only occurred, if the surfactant diffusion was fast enough. 

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