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[OLD] Osmotic coefficients (again)


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From: James Cleverley

Subject: osmotic coefficients (again)

I am having trouble locating the exact reference source for the equation used to calculate the osmotic coefficient for NaCl salt solutions and used in GWB to calculate water activity. The equations and some regression coefficients are reproduced in Bethke (1996) as eq. 7.8, 7.9 and the table on page 114, however where in the literature are these defined and reproduced? The reason I ask is that I am having trouble reproducing the graph in Figure 7.5 of Bethke (1996) using the data on page 114 and equation 7.8, 7.9 and 7.7 (plus the A parameter from the GWB datafile) I am calculating much lower water activities at high Is. Any pointers to the original source of the regression data and those equations would be really appreciated.


From: Craig Bethke

Subject: Re: osmotic coefficients (again)

Bill Bourcier and Tom Wolery provide the following information: The oiginal literature reference is Helgeson, Brown, Nigrini, and Jones (1970) GCA 34:569. The actual parameters in the regression were taken from the PATH code, developed in the 1960s; it may (or may not) take some digging in the literature to find precisely how the parameter values were derived.

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