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Least-squares analysis of osmotic coefficient data at 25°C according to Pitzer's equation. 1. 1:1 Electrolytes
Journal article   Peer reviewed

Least-squares analysis of osmotic coefficient data at 25°C according to Pitzer's equation. 1. 1:1 Electrolytes

S.L. Marshall, P.M. May and G.T. Hefter
Journal of Chemical and Engineering Data, Vol.40(5), pp.1041-1052
1995
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Abstract

Pitzer ion-interaction parameters for 93 1:1 electrolytes have been calculated by least-squares analysis of published experimental osmotic coefficient data at 25°C. The quality of the resulting fit of these data, expressed as the sum of squared residuals, the standard errors in the least-squares estimates, and the variation of the residuals with electrolyte concentration, is shown to be consistently superior to that obtained with the use of parameters taken from previous publications. The discrepancies between the present estimates of the Pitzer parameters and the published values are mainly concentrated in β(1). The relative standard error in this parameter depends strongly on the maximum molality represented in the data and is typically at least 1 order of magnitude greater than the relative standard errors in the other parameters. This observation is interpreted by examining the contours of the sum of squared residuals in parameter space. Trends in the quality of fit for different classes of electrolytes are also described.

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