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Re: Sodium bicarbonate/Sodium carbonate

> From: Ed Hengel <hengel at computer_net>
> Subject: sodium bicarbonate/sodium carbonate
> What are the pros and cons of using sodium bicarbonate (NaHCO3) vs.
> sodium carbonate (Na2CO3) to regulate carbonate hardness?  Does it
> matter one way or the other?  Does either one affect the efficacy of the
> system?

	Whichever you add, you will end up with bicarbonate ions in solution,
because, at the sort of pH that interests us, the ratio of HCO3- to CO3--
is large.  If you use the bicarbonate, you will go directly to the new 
HCO3- concentration, but if you use the carbonate, it must react with the CO2
in the water:

		CO3--  +  CO2  +  H2O  ->  2 HCO3-

	If you add enough sodium carbonate to wipe out the CO2 in solution,
and do it quickly enough that more CO2 can't come in to make up, you will
get a _huge_ pH spike.  It would not be at all difficult to reach pH 10.
I would use the bicarbonate.

Paul Sears        Ottawa, Canada