text: * Definition of the K or P-value
  : The K or P-value always only refers to a single species or substance:
  : with:
  :* concentration of species i of a substance in the octanol-rich phase
  :* concentration of species i of a substance in the water-rich phase
  : If different species occur in the octanol-water system by dissociation or association, several P-values and one D-value exist for the system. If, on the other hand, the substance is only present in a single species, the P and D values are identical.
  : P is usually expressed as a common logarithm, i.e. Log P (also Log P or, less frequently, Log pOW):
  : Log P is positive for lipophilic and negative for hydrophilic substances or species.
  * Definition of the D-value
  : The P-value only correctly refers to the concentration ratio of a single substance distributed between the octanol and water phases. In the case of a substance that occurs as multiple species, it can therefore be calculated by summing the concentrations of all n species in the octanol phase and the concentrations of all n species in the aqueous phase:
  : with:
  :*  concentration of the substance in the octanol-rich phase
  :*  concentration of the substance in the water-rich phase
  : D values are also usually given in the form of the common logarithm as Log D:
  : Like Log P, Log D is positive for lipophilic and negative for hydrophilic substances. While P values are largely independent of the pH value of the aqueous phase due to their restriction to only one species, D values are often strongly dependent on the pH value of the aqueous phase.