In all measurements it is desirable that quantities like the charge and the capacity be related to unit, true, surface area of the @I03082@. While this is relatively simple for a liquid-liquid @I03082@, there are great difficulties when one phase is solid. In any report of these quantities it is essential to give a clear statement as to whether they refer to the true or the apparent (geometric) area and, especially if the former is used, precisely how it was measured.