Re: [APD] Solenoids & Needle Valves

[Paul M Wallace <pwallace at u_washington.edu>]

Almost, thanks to the Henderson-Hasselbalch equation, the change can be approximated as linear for small movements about the pKa (Bicarb, 6.4).  Get further than about 1 pH unit (acid to base etc of about 1000:1) away (also low KH) and the buffer loses the ability to well, buffer and the pH can crash (below 4) very quickly.

Controler reasons cont:
D) for runing PPM CO2 very high, E) after WC to bring ppm up quickly F) others...

-Paul


On Wed, 28 Sep 2005, S. Hieber wrote:

> The higher the pH level, the bigger the diff in levels for
> a given change in pH. Which is one reason some us recommend
> 25pp as a target. If you hit around 20-30, you should do
> fine.
>
> Just for argument's sake, if you had, say, 120 ppm, a rise
> of pH 0.2 would mean a climb to about 150 ppm. In actual
> cases, it would be hard to push things to 120 ppm and much
> harder still to psuh it up another 0.2 pH. At more
> reasonable targets, which are more easily achieved, the
> changes in CO2 are more moderate ;-)
>
> sh
>
>
> --- Paul M Wallace <pwallace at u_washington.edu> wrote:
>
>> . . .Now with a controler and solenoid, if you KH is 6
>> degrees, a change of .2 would result in:
>> pH 6.5  -->  57 ppm CO2
>> pH 6.7  -->  36 ppm CO2
>
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