pH meter calibration

[agregory]

Hi all,

Just wanting some advice. Biology soil testing EEI starts tomorrow. Brand new and hardly used pH meters were put in buffer solution 4 & 7 today. We had readings of 4.01-4.10 and 7.01-7.08. Is this acceptable? We (labbies) think so, but HOD thinks they need calibrating so that they all read the same and are spot on 4.0 and 7.0.

Opinions?

[fibreweb]

It's High School biology!
In my estimation these calibration figures are quite adequate
The process is what is important and as part of the evaluation the possible sources of errors are discussed.
From my use of pH meters trying to calibrate closer can turn into a real headache.

[lada]

Definitely good enough. How much closer does he want pH4 to be to 4.01?
Even after re-calibrating, you would be lucky to get it any closer.
Anyway, all students need to know, if the soil is acidic, basic or neutral
Lada

[Jazz]

We do not use "proper" pH meter for the soil. I bought this one in Bunning’s, cheap as chips. Measure; pH, moisture and light l. Less than 10 bucks

[smiley]

Same here Jazz. I'm not taking my precious pH meters and junking up the glass membranes with dirt!

In the same vein, I use a brick wall moisture meter (also from Bunnings) to test the soil, and that gives a workable reading too.