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i recently purchased a meter and am wondering if anybody has one of their own and how they calibrate it. my instruction manual states to calibrate first in pH 6.86 a so-called standard phosphate buffer. this is the first part i dont understand seeing as the second Pka of phosphate is 7.2. then it says to calibrate in a pH of 4.01 or 9.18 the standard buffer of borax.
so after saying all that how do i calibrate my meter? cant i just use something simple like vinegar which if pure should be pH 4.76 and then maybe something else like bicarb?

Most meter manufacturers provide standards for their instruments. The standards are "set points" to align the readings. If you don't use the correct "set points", your meter will give you a reading but it will be the wrong reading.

For example, the instrument is to be calibrated with a 4.0 pH standard and a 9.2 pH standard. Instead, you calibrate the lower end in pure vinegar witha pH of 4.76. So, the meter assumes a pH of 4.76 is a pH of 4.1. Your readings are now understated by 0.66 pH.

Not too far off, unless it is a logarithmic scale! Each 1.0 change in pH is an increase or decrease of 10 in acidity. base is 7.0, therefore 6.0 is 10 times more acidic than base, 8.0 is 1/10th as acidic as base or 10 times more alkaline.

Use the calibration liquids or don't use the meter.

__________
"To steal ideas from one person is plagiarism; to steal from many is research."
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