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[APD] Re: pH at which CaCO3 dissolves
Jim Seidman wrote:
> I certainly think this is getting closer to accurate, but [Ca++] is a molar
> concentration, while ppm hardness is based on weight. You would have to
> divide by the molecular weight in order to make this equation work.
Actually, *multiply* by the molecular weight, otherwise you're right, Jim.
Fortunately, I did convert to ppm hardness by weight. The conversion is
imbedded in the second to last line of my letter. It goes like this:
[Ca+2] (in gram-moles/l)*100(grams CaCO3/gram-mole of Ca+2)
= Ca-hardness (in grams CaCO3/l)
Ca-hardness (grams CaCO3/l)*1000 = Ca-hardness (in mg/l or ppm)
The whole conversion is
[Ca+2]*100000 = Ca-hardness in ppm.
or as I said in the letter:
molarity Ca++ = Ca-hardness in ppm divided by 100000.
There are some kinetic data available on CaCO3 dissolution, but putting it to
use is a complicated process.
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