Activity coefficients and partition coefficients as parameters for the evaluation of biological activity. A linear relationship between log "gamma" and log P.

The activity coefficient (gamma) and the partition coefficient n-octanol/water (P) of various groups of substances of pharmaceutical and biological interest (anaesthetic gases, primary n-alcohols and barbiturates) were compared in order to obtain a linear relationship. Considering n-octanol as an ideal solvent, the curve of the behaviour of any real substance with the system n-octanol/water has an inclination of 45 degrees (delta log "gamma"/delta log P = 1). By means of the n-octanol/water partition coefficient the activity coefficient can be calculated in order to evaluate the biological activity of the groups of substance examined.