Contempt
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How do I calibrate a pH metre
I have a pH metre and i want to be sure of how to calibrate it properly. I have a solution with a pH of 4 and another with a pH of around 7-9 (not
sure exactly of the second). But i know that these two solutions come standard when one purchases a pH metre. Any help would be greatly appreciated.
Thanks
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Darkblade48
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If the second solution is a calibration solution, it should say somewhere what pH it is (7-9 is not suitable for calibrating your pH meter, obviously
 )
In general, to calibrate a pH meter, stick your pH meter into a solution of the calibration fluid, and then adjust the pH meter until it reads the pH
of the calibration solution. I think on most pH meters, there is a screw (or some other mechanical means) of adjusting the pH manually until it reads
the pH of the (known) calibration solution.
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Contempt
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thanks very much. the help is appreciated
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mick
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Try distilling water off from a dilute solution of NaCl. Discard the first portion. The pH should be about 7.
mick
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neutrino
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What is the purpose of the NaCl? Something having to do with carbonic acid no doubt, but I just don't see what it would do.
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unionised
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The water will pick up CO2 from the air and have a pH of about 5, unless it disolves some of the silicates from the glassware and ends up with a pH
near 8 or 9.
Distilled water is one of the worse ideas for a known pH- it has no buffering capacity.
A glass of fresh milk (pH 6.3 to 6.6) is probably a better bet.
A saturated solution of potassium hydrogen tartrate (cream of tartar) is a very good place to start for "calibrating my pH meter at home". pH 3.557 at
25C
M/100 borax is one of the easier alkaline ones to get hold of pH9.18 at 25 C
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