A pH calibration buffer solution has a known and fixed pH-value and is used for calibrating pH electrodes this should be done reguarly to ensure the meter keeps its accuracy.
Just fill some of the fluid in a clean measuring cup and use it to calibrate your pH meter.
The specific instruction on how to calibrate is to find in the manual of your pH tester.
After a calibration please discard the used solution. Do NOT pour it back into the bottle as this may contaminate the whole bottle and make the solution inaccurate.
Bottle of 300ml
more
less