A random contact point model for second virial coefficients in dilute solutions

A simple latticelike random contact point model is presented to correlate and predict second virial (or pair interaction) coefficients of thermodynamic quantities in dilute solutions. With this model it is possible to correlate pair interaction coefficients in different solvents with one equation and a single set of group interaction parameters. Enthalpic pair interaction coefficients of alkanes and alkanols dissolved in ten different alkan‐1‐ols and water, and of amides dissolved in N,N‐dimethylformamide, N‐methylformamide, and water are discussed in terms of the model. Corresponding group interaction parameters in water, alkan‐1‐ols, and amides are found to be equal within experimental error. When applied to aqueous solutions, the model yields the empirical equations of Savage and Wood, which are thus given some theoretical basis. The model also provides values of the higher interaction coefficients on the basis of the pair terms.