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Re: Aquatic Plants Digest V3 #404

In a message dated 98-07-23 16:26:40 EDT, you write:

<< I finally got my pH controller yesterday and it came with 7.0 and 4.0
 solutions that are used to calibrate the unit.  The directions say to first
 calibrate with 7.0 then adjust slope with 4.0.  The directions say to repeat
 these steps until you get 7.0 and 4.0 without having to adjust the
 calibration and slope, but I couldn't get that to happen.  When I adjusted
 the slope to 4.0 and re-tested for 7.0, the pH always went back up to 7.12 -
 7.13.  I'd adjust the pH back and re-test for 4.0 and it would be
 3.8something.  Now I've used up my 7.0 and 4.0 calibration fluids (I saved
 them anyway) and Amer. Marine only bothered to put one of each in with the
 controller. >>

I had a similar problem with my pH meter and probe (American Marine) - but
this was after 5 months of use (I had no problem with the first calibration
procedure).  I called the company and they were very prompt in returning the
phone call.  They suggested that 1)  within .1 or so was adequate for CO2 use;
2)  putting the probe in a 1:2 solution of muramic acid would reset the probe
by cleaning any impurities from it.  I am not sure what you mean by "using up
the 7 and 4 pH fluids".  You should be letting the probe sit in the fluids and
then calibrating and then putting the probe in tap or deionized water for
cleaning between fluids.  Then putting the probe in the slope solution.  They
should never really be used up.  Simply shake the probe gently between
solutions, or carefully dab with a kleenex (not wipe dry) after cleaning in
deionized water before immediately placing back into another solution.  I did
find that by leaving the probe in the deionize water overnight, that the probe
came very close to calibrating without the muramic acid.  I also found that
air in the probe area had a major impact on the readings.

Good luck and let me know if they give any more info.