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Re: Alkalinity and Phosphates



roger said, in part:
> I'm sorry if I gave you the impression that organics
> would
> interfere with the pH test.  As far as I know they don't.
> The presence of organics may cause the pH to change, but
> that isn't a false effect.  That's a real change and it
> doesn't hurt the test results.
> 
> Problems come up with the alkalinity (KH) test because
> the
> method assumes that all of the alkalinity is bicarbonate.
> When that isn't true -- as when there are organic acids 
> measured as part of the test -- then the assumption is
> wrong and the test results are bad.
> 
> Similarly, problems arise with the acidity (CO2) test
> because the method assumes that all of the acidity is
> CO2.
> When that isn't true -- as when there are organic acids
> contributing to the acidity -- then the assumption is 
> wrong and the test results are bad.

You didn't give the wrong impression.  You just caught me
being sloppy in my thinking and writing.  The issue isn't
whether organics make the pH test false but whether using
the pH value would give a false reading when applied to the
pH/KH/CO2 chart.  

But could that be the case?  With organic acids present you
could have no CO2 (or carbonic acid) and the table would
show that you did because of the organic acids effect on pH
-- I guess my question is, is that the same effect that
disturbs the KH reading or another phenomenon confounding
the use of the table?  (albeit a small confounding ;-)  ) 

If the organics can present acid that lowers the pH does it
then also reduce KH?  If so, does that counteract, somewhat
the effect of inflating the KH reading?

Scott H., for whom the art of the simple question, or
posing questions simply is illusive.

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