Geochemist's Workbench Support Forum

# [OLD] Density of evaporated seawater

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From: Michael Lim

Subject: density of evaporated seawater

Could anyone please help me with finding a table containing details of partial Molal Volume of the various salt find in common seawater?

From: Michael Lim

Subject: density of evaporated seawater

The reason why I asked all these questions started with our calculation using seawater as our benchmark. The seawater Specific Gravity reported by Modelling Halite Formation and Brine Densities: Comparison of Non-Marine and Seawater Brines L.A. Chambers, M.W. Wadsley and G.J. Brereton Seventh Symposium on Salts Vol I, 533-538 (1993) was 1.23 (figure 5) at the point when Halite precipitates. But using the same set of inputs and crunched through Geochemists Workbench, we got 1.177. The ionic strength is the same in both cases, 7.266. Just wonder anyone has any idea what I have done wrong. Your help is much appreciated. Please see our input below.

h-m-w

TDS 35080

swap CO2(g) for H+

log f CO2(g) = -3.5

Cl- = 19350 mg/kg

Ca++ = 411 mg/kg

Mg++ = 1290 mg/kg

Na+ = 10760 mg/kg

K+ = 399 mg/kg

SO4-- = 2710 mg/kg

HCO3- = 142 mg/kg

fix fugacity of CO2(g)

react -996 grams of H2O

From: Craig Bethke

Subject: Re: density of evaporated seawater

Fluid density as reported by React is what we call a â€œsecondary variableâ€?, i.e., one not used internally in the calculations, but reported for the user's convenience. The calculation method is described by Phillips et al. (1981): Phillips, S. L., A. Igbene, J. A. Fair and H. Ozbek, 1981, A technical databook for geothermal energy utilization. Lawrence Berkeley Laboratory Report LBL-12810, 46 p. The method is a correlation function that gives the density of a NaCl solution from temperature and concentration. (For more info and a corrected coefficient, see the Basin2 Users' Guide, available for download from our web site.) Of necessity, React must treat the general case. But in working with a specific solution (e.g., evaporated seawater) or at a known temperature, it is sometimes possible to calculate density more precisely. Since the reference you cite considers just such a specific case, it likely gives a better estimate of fluid density than the Phillips et al. correlation. My guess is that this is the source of the discrepancy you cite.

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