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Calculation of amorphous silica solubilities at 25° to 300°C and apparent cation hydration numbers in aqueous salt solutions using the concept of effective density of water

Geochimica et Cosmochimica Acta

By:
and
DOI: 10.1016/0016-7037(83)90280-6

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Abstract

The solubility of amorphous silica in aqueous salt solutions at 25° to 300°C can be calculated using information on its solubility in pure water and a model in which the activity of water in the salt solution is defined to equal the effective density. pe, of “free” water in that solution. At temperatures of 100°C and above, pe closely equals the product of the density of the solution times the weight fraction of water in the solution. At 25°C, a correction parameter must be applied to pe that incorporates a term called the apparent cation hydration number, h. Because of the many assumptions and other uncertainties involved in determining values of h, by the model used here, the reported numbers are not necessarily real hydration numbers even though they do agree with some published values determined by activity and diffusion methods. Whether or not h is a real hydration number, it would appear to be useful in its inclusion within a more extensive activity coefficient term that describes the departure of silica solubilities in concentrated salt solutions from expected behavior according to the model presented here. Values of h can be calculated from measured amorphous silica solubilities in salt solutions at 25°C provided there is no complexing of dissolved silica with the dissolved salt, or if the degree of complexing is known. The previously postulated aqueous silica-sulfate complexing in aqueous Na2SO4 solutions is supported by results of the present effective density of water model

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Calculation of amorphous silica solubilities at 25° to 300°C and apparent cation hydration numbers in aqueous salt solutions using the concept of effective density of water
Series title:
Geochimica et Cosmochimica Acta
DOI:
10.1016/0016-7037(83)90280-6
Volume
47
Issue:
3
Year Published:
1983
Language:
English
Publisher:
Elsevier
Description:
10 p.
First page:
587
Last page:
596
Online Only (Y/N):
N
Additional Online Files(Y/N):
N