ABSTRACT
Natural waters are, as Lavoisier pointed out, the "rinsings of the earth", and during their interminable cycling they interact with the air, with the rocks, and with the biota to form solutions of great complexity and variability. The student of natural water chemistry must find ways of estimating activity coefficients in complex electrolyte mixtures. To determine speciation and other equilibrium properties, such as distribution between solid and aqueous phases in solution, it is necessary to calculate the osmotic coefficient and activity coefficients of the dissolved components. Where the equilibrium involve only trace species, in a solution dominated by strong electrolytes, then the activity coefficients of the trace species will be determined solely by interactions with the major ions present. In natural waters a number of effects might prevent the attainment of equilibrium. The pH of natural waters is buffered in the short term by equilibria involving weak acid-base reactions in solution.
