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Re: Tap water mystery

Ed Hengel asks....

>While checking the water parameters on my discus grow out tank i decided
>to test for co2 on a hunch that it might be higher than normal (water
>changes would lower the pH which would then slowly go back up during the
>day).  What I did not expect was the greater than (I did not want to
>waist any more reagent than necessary) 50 ppm co2.  Thinking this was
>odd I checked the tap water and sure enough it was >50 ppm co2.  So I
>filled a glass with tap water, let it sit all day and checked it again
>this evening along with the pH and Kh. The co2 is still >50 ppm, the pH
>is 5.96 and the Kh is 3.36.  Now I'm no scientist, but shouldn't the co2
>have equalized with the atmosphere after the water sat all day?  And if
>it did, what could be causing the LaMott test kit to give a false
>reading that coincides with the pH, Kh, co2 chart?  And how come the
>tank pH would slowly rise again by the next morning(6.2 to 6.7)after the
>previous morning water change (50% of a 55 gal) if very little co2 was
>diffusing out. If my spring fed well water really does have so much
>stubborn co2 dissolved in it I think I'm going to bottle it and sell it
>as the latest natural, slightly carbonated, water fad.  For those who
>think it chic to drink naturally carbonated spring water but don't like
>the bubbles tickling their nose.  We could call it Sparkle Lite! <G>
>Next I going to let the water sit overnight and most of the next day and
>see what, if anything, is different tommorow evening. 

I'm unfamiliar with the LaMotte Test Kit but....

If the CO2 reading is obtained by titrating the water sample with
Na2CO3, then free mineral acid, if present, will be measured. Also,
heavy metals such as iron, chromium, and aluminum salts interfere.
This from the Betz Handbook of Industrial Water Conditioning.

Dave Whittaker
ac554 at FreeNet_Carleton.ca