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Re: Aquatic Plants Digest V3 #903

In a message dated 3/13/99 2:05:58 AM Mountain Standard Time, Aquatic-Plants-
Owner at actwin_com writes:

> You are rught about the amount of CaCO3 necessary to raise hardness. The
>  practical problem lies in the insolubility of CaCO3. It will just sit on
>  the bottom and NOT dissolve, because there is insufficient CO2 in the
>  water to drive the equation  2 CaCO3 + H2CO3 --> 2 CaHCO3  to the right. 
>  To complicate matters, to keep the bicarbonate in solution, an excess of
>  CO2 is needed, up to 5 times stoichiometric. That takes a lot of CO2.
>  Unless CO2 is supplied, CaCO3 will not dissolve in water. (That's why we
>  have lime caves -- they do not dissolve away completely, because the
>  water in them is CO2 limited.

Last year aas part of a Science fair project my daughter and I (mostly I )
filled a box filter with crushed dolomite and let it bubble in seven gallons
of water in a bare aquarium.  Non-carbonate hardness rose from 60ppm to 140
ppm in four days.  No additional CO2 was used.  I'm not debating what you're
saying, I just don't understand it in light of the fact that CaCO3 dissolves
with no more than atmoshperic CO2 interaction.

Bob Dixon