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Re: [APD] Re: NaHC03 and salinity

CaCO3 doesn't bogey things up but it plays a key role in KH
and pH.

 When added to water, the carbonate (CO3) in CaCO3 (calcium
carbonate) will raise the KH (ie., the alkalinity or the
ability of a solution to resist a pH change with an
addition of an acid). The calcium (Ca) in CaCO3 will raise
the GH (so-called general hardness or cations of calcium
and magnesium). But it does so only up to the a point, and
that's the pH point at which it will no longer dissolve
and/or precipates, which is way above pH 8.

Since KH is one of the things one measures when using the
pH/KH/CO2 table to determine CO2 levels, one takes the
affect on KH into account when one measures the KH to use
the table. So it doesn't *throw*  anything off, but it
raises the KH, the reading one gets when testing for KH,
and if no acid is added, then added CaCO3 will also
increase the pH.

Otoh, NaHCO3 (sodium bicarbonate or sodium hydrogen
carbonate) has raised the carbonate level (KH) but hasn't
the salts (calcium, magnesium) that account for GH, so it
doesn't raise the so-called general hardness.

Scott H.
--- Chris Hotte <ecwh at cogeco_ca> wrote:

> Rachel Sandage wrote:
> >CaCO3 doesn't "throw off" KH readings, but it will
> change them - it raises both GH and KH, and works nicely
> with MgSO4 if you have very soft water. One thing about
> it is that it is barely soluble, so you need to kind of
> hide it when you dump it in.
> >
> Yes, I knew I would get this reply after posting that
> message. I meant 
> to say that CaCO3 won't affect KH/PH = C02 readings.

Christel Kasselmann, 
author of the best current authoritative text on aquatic plants 
will be a featured speaker at 
The Northeast Council of Aquarium Societies 30th Annual Convention.
March 18-20, 2005 at the Marriott Hotel, Farmington, CT
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