Two-parameter debye-hückel approximation for the evaluation of mean activity coefficients of 109 electrolytes

Among the published formulae for the calculation of mean activity coefficients, the most trustworthy and comprehensive are those recently recommended by the National Bureau of Standards. In many applications, the ionic strength does not exceed ca. 1 M, and the NBS functions can then be approximated by a two-parameter Debye-Hückel model. The limits of applicability (e.g., 1% deviation from the corresponding NBS model) are listed. The procedure makes efficient use of calculator memory.