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Re: Stoichiometry Anyone?



Todd H <toddhed at yahoo_com> wrote:

> Subject: Stoichiometry Anyone?
> A search of the archives turned up the following formula which seems
> to be the basis for the CO2 charts on The Krib:
> CO2 (mg/L) = 12.839 * KH * 10^(6.37 - pH)
> If my understanding of the definition of KH is correct, then this
> formula seems to have an incorrect conversion of KH to moles HCO3-.
> Is it correct that:
> 1 GH = 1 KH = 10 mg/L CaO = .3566 meq/L = .3566 mmoles/L HCO3-?
> For the result to indicate dissolved CO2 in mg/L, shouldn't the
> constant
> be:
> .3566 * 44.01 mg/mmole = 15.694 rather than 12.839?
> Assuming pK1 for carbonic acid = 6.37 at 25C to be reasonably accurate
> (reported values do vary somewhat), shouldn't the values for CO2 in the
> Krib charts be about 22% higher?

Todd, can't remember where I found it, but I've had it on my 
calculation sheet for a while:

CO2 = 3 x dK x 10^(7.00-pH), where dK equals degrees alkalinity.


Jamie    <"\\\><  Aquatic plants, water chemistry, and cichlids
                  http://www.ais-gwd.com/~jjirons