Re: [APD] CO2 and pH control

[gbooth at frii_com]

> Date: Tue, 13 Dec 2005 07:54:34 -0800
> From: Jerry Baker <jerry at bakerweb_biz>
> Subject: Re: [APD] CO2 and pH control
> To: aquatic plants digest <aquatic-plants at actwin_com>
>
> Gordon and Susan Watkins wrote:
>> Nope, after 20+ hours it still shows 8.6
>
> If your pH test is correct, and there are no other buffers in your water
> aside from carbonates, then your KH is around 40, not 9. I would be more
> inclined to believe that there are additional buffers, but I'm not sure
> what other buffers would increase the pH like that.

There are two equilibrium dissociation constants when carbonates are in he
water, around pH 6.4 (bicarbonates) and around 10.2 (carbonates). My guess
is that Gordon's water has lots of carbonates and that the "normal"
pH/KH/CO2 table does not apply.

See http://faq.thekrib.com/Annex/oldfaq-hardness.txt for details but don't
ask me to explain it even though I authored it.

George B.

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