The investigation of protolytic equilibria in aqueous solution

These difficulties will be illustrated by reference to some individual systems. Although the value K = 24 derived for nitric acid by both n.m.r. and Raman measurements still appears to be unassailed, the agreement reported in 1957 for a number of other acids is not confirmed by later work. Thus, although perchloric acid was originally assigned K = 38, i.e., little stronger than nitric acid, more recent Raman and n.m.r. work indicates complete dissociation at least up to concentrations of 

The use of optical properties is of course restricted to a limited selection of acid-base systems, and methods of more general applicability are based on the properties of the hydronium ion, in particular the e.m.f. of cells 

Conductivity measurements do not lead directly either to K, or to but by making an allowance for the variation of ionic mobilities with 

If a small quantity of an uncharged base B (e.g., an indicator) is added to an acid solution, we can define an experimentally measurable function Hq by the equation 

Since we are now dealing with concentrated solutions, the choice of concentration scale becomes of importance [H ] can be expressed in either molarities or molalities, with corresponding changes in the values of the activity coefficients. 

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