AbstractIt is to be expected that for the higher members of a homologous series the heat of formation at a given temperature and state of aggregation is a linear function of the number of C atoms in the normal alkyl group; the increment of the heat of formation per C atom is independent of the nature of the series.Assuming that this law remains true for infinitely diluted solutions, corollaries are derived for various thermodynamic equilibria in which a member of a homologous series occurs.It is found that the relations derived for the distribution equilibrium for two liquid phases at infinite dilution, the equilibrium constant for chemical reactions at infinite dilution, the vapour pressure of a homologous series at a given temperature, etc. contain eitherquantities independent of n (i.e. the number of C atoms in the normal alkyl group)quantities linearly related to n, orquantities whose logarithms are linearly related to n.