Some observations on the partition of Na+ and K+ into a lipid phase.

It is likely that sodium and potassium must traverse a lipid membrane surrounding cells and that this membrane has to do with intracellular cation selection. Electrolyte theory is inadequate to predict the partition of salts of these cations between water and a lipid phase. The data obtained here demonstrate the partition and the cation selection to be a function of the anion species (or ionized lipid), the solvent and the presence of the unionized form of the lipid. Specificity in lipid partition is not synonymous with the cation specificity in precipitation of ionic crystals.