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Re: Adjusting pH
On Thu, 31 Jan 2002, Jerry Baker wrote:
> Do KH test kits measure "effective" KH, or "real" KH?. I mean, when you
> add buffers you are changing the effective KH, but not the actual KH. Do
> the test kits pick this up? And if they do, does the chart still hold?
It's questions like this that make me hate the term "KH".
The KH tests measure alkalinity aka buffer capacity. Using the alkalinity
measurement in a CO2 determination assumes that the alkalinity is created
by bicarbonate. That is usually a good assumption -- so good that it is
the standard lab method for determining bicarb. There are other ions that
can interfere with the determination and if there is a significant
interference then the alkalinity measurement can cause the charts to give
you an incorrect CO2 determination .
To the best of my knowledge the only interference common in planted tanks
comes from some unidentified organic acids and it can sometimes be
significant. Phosphate is a potential interference, but huge phosphate
concentrations are necessary to cause a significant effect.
This has been discussed ad nauseum.