Average Polarity of Solids

The Rating of Solid Surfaces by Immersional Heats in Organic Liquids 

Average Electrostatic Field Strengths for Solid Adsorbents and Commercial Pigments from Heals of Immersion 

The influence of the surface polarity of powders on their adsorption and dispersion properties can be profound, as is discussed in Sec. VIII,A. The values of F are likely to be put to many uses as more of them are measured. The electrostatic surface fields are doubtless involved in the phenomena of chemisorption and catalysis, capable of inducing polarization or electron shift of adsorbing molecules. For silica-alumina catalysts, the production of active M-O-M surface groups must be considered the most important factor responsible for chemisorption and catalj ic activity. 

For simplicity, a systematic classification of solid surfaces by heat of immersion values in a single liquid is desirable. Il in (53) predicted on theoretical grounds a decrease in the heat of wetting with increase in the size of the cation in salts or oxides. However, Il in and Kiselev (54) found that the decrease in the heat of immersion from SrSO to PbS04 to BaS04 predicted by theory is not observed. Heat data for the immersion of a variety of solids in water are listed in Table VII. Here, too, the changes in heat values are not systematic. 

Solid Activation temp., °C. ergs/cm. Crystal structure Oo 

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This commentary on the current status of research on heats of immersion begins where our review written in 1958 concludes [6]. The classification of heats of immersion of solids into liquids as a function of precoverage is expanded to include two new types of curves. Several difficulties in heat of immersion research are discussed. Then, current applications of heats of immersion to determine the average polarity of solid surfaces, heterogeneities on solid surfaces, wetting by surfactants, hydrophilicity of solid surfaces, and thermodynamics of the specific interaction of molecules from solution onto solid surfaces are described. 

The average polarity of solid surfaces can be estimated from heats of immersion into selected liquids, usually n-butyl derivatives possessing... 

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