The distribution coefficient, log D, is the ratio of the sum of the concentrations of all forms of the compound (ionized plus un-ionized) in each of the two phases, one essentially always aqueous; as such, it depends on the pH of the aqueous phase, and log D = log P for non-ionizable compounds at any pH. For measurements of distribution coefficients, the pH of the aqueous phase is buffe. Overview In the, a partition coefficient (P) or distribution coefficient (D) is the ratio of of a in a mixture of two solvents at. This ratio is therefore a compariso. Despite formal recommendation to the contrary, the term partition coefficient remains the predominantly used term in the scientific literature. In contrast, the recommends that the title term n. The partition coefficient, abbreviated P, is defined as a particular ratio of the of a between the two solvents (a biphase of liquid phases), specifically for un- solutes, and the of.