Molecular Interaction of Condensed Bodies

The constants and B can be determined by calculation, using Eqs. (II.9) and (11.44), and also on the basis of experimental data. In the latter case, it is necessary to measure the force of interaction of the bodies with a fixed gap between them, while observing conditions that will eliminate the effect of all components of adhesive interaction other than the molecular component. 

Let us examine the determination of the constant A in the case in which there is direct contact of the particle with the surface. The constant can be calculated in terms of X/ - in accordance with Eqs. (II.3) and (II. 8) if we know the chemical composition of the contiguous bodies and the surrounding medium, the coefficient of refraction, the dipole moment, and the density of the substance. De Boer [48] calculated the constant of dispersion interaction Xf y and the constant for NaCl molecules the respective values were 10 erg cm and 10 erg. 

The calculation of the constant 1 can be performed by a different method. The force of interaction of two plane surfaces with a small gap between the contiguous bodies, i.e., without accounting for electromagnetic lag, can be represented not only by Eq. (11.33), but also in a somewhat different form (the force as calculated for unit contact area)  

The quantity hv by analogy with the constant of molecular interaction, is 

The quantity characterizes the imaginary part of the complex permittivity of the contiguous bodies. This quantity is related to the product hv, which in turn determines the constant A by means of the following relationship hp = 

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Equation (11.32) characterizes the molecular interaction of condensed bodies, including the case of adhesion of particles to a surface. 

Then, by analogy with Eqs. (II.21) (II.26), we obtain formulas characterizing the molecular interaction of condensed bodies with allowance for electromagnetic lag [44,45] ... 

Determination of Constant of Molecular Interaction with Allowance for Electromagnetic Lag. In this case, we are speaking of the molecular interaction of condensed bodies that are separated by a gap of 100 A or more [44, 45]. 

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