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Chemistry
At 03:48 AM 11/16/98 -0500, Bob Dixon wrote:
> I wasn't about to just dump something like muriatic acid into a tank full of
>living things.
Good thinking.
> My objective was to find a way to reduce alkalinity (aka
>carbonate hardness) . At Dave Gomberg's suggestion, I started with HCl....
> the pH of the solution
>was 1.7 or 1.8. ... When I got the lid sealed tighter, the pH rise
>slowed down. Alkalinity dropped to 40ppm, and that was all I could get it to
>drop.
I am still not understanding the data. Pure water changes pH with the
addition of a strong acid in a pretty predictable way. Alkalinity measures
the presence of other molecular species (mostly carbonate and phosphate
complexes in "chemically" tainted water, mostly humic acids and their
relatives in "black", "organically" tainted water) which retards the drop
in pH as a strong acid is added. Basically (no pun intended), alkalinity
is most cleanly measured with a high-resolution pH meter and titration with
a strong acid (not necessarily a strong (concentrated) solution of acid,
but an acid that does not affect alkalinity itself, such as HCl, HNO3,
H2SO4). If the only weak base present is carbonate, you can use
alkalinity to find the level of CO2 in the water. That is just about the
end of the significance of alkalinity. So why you would be desperate to
drop it is a bit confusing to me.
Leaving all that aside, I don't understand what you measured. Near as I
can figure, you measured initial pH and alkalinity, added a dose of HCl,
then plotted pH and alkalinity as a function of time and found ????? It
sounds like the pH had an initial drop, then rose again, right? And the
alkalinity???
Please advise.
--
Dave Gomberg, San Francisco mailto:gomberg at wcf_com
http://www.wcf.com/wcf
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