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20-04-2003, 06:23 AM

tose (LeighMo) wrote in message ...
So introducing bicarbonate (CO2 dissolved in water at this pH mostly
takes the form of bicarbonic acid) into water will not increase
"carbonate hardness"? I'm not sure I understand.

Baking soda will increaase the KH. That's what I said. I was arguing with
someone who insisted you could increase your KH by injecting CO2 gas into the
water.

Okay, baking soda is sodium bicarbonate (Na^+ HCO3^-), so the addition
of that will increase KH as bicarbonate concentration has increased.

CO2 dissolves in water to form hydrogen bicarbonate (bicarbonic acid):

CO2 + H2O --- H^+ HCO3^-

(that simplies matters somewhat, HCO3^- forms equilibria with CO2 and
CO3^2- that depend on temperature, pH and other parameters, but by and
large you can consider the dissolution of CO2 in that way)

Dissolving CO2 in water increases bicarbonate concentration, so why
would it not increase KH?