# Re: [APD] Interesting idea

```Scott,
for the math challenged, why do I keep getting 225ppm with your
(Roger's) equation?

15.969 x 5 (kH degrees) x 10^.45 (6.35-5.9)= 225.03

Vaughn's gives me 188.84ppm

Hmmm.....

Dennis

S. Hieber wrote:
> This [CO2=3*KH*10exp(7-pH)] is the formula that George Booth originally offered and, iirc, Karla Booth came up with it.
>
> The one I showed [CO2 ppm = 15.696*KH*10^(6.33-pH) for 31 degrees C]
>  comes closer to Roger's.
>
> sh
>
>
> ----- Original Message ----
> From: Vaughn Hopkins <hoppycalif at yahoo_com>
> To: stuart at stuarthalliday_com; aquatic plants digest <aquatic-plants at actwin_com>
> Sent: Tuesday, October 17, 2006 7:17:42 PM
> Subject: Re: [APD] Interesting idea
>
>
> The equation is:  ppm of CO2=3*KH*10exp(7-pH).  A spreadsheet almost
> writes itself!
>
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>

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