Ph Buffer calibration solution Ph-4, Ph -7, Ph-10

Ph buffer solution, (calibration solution) Ph-4, Ph-7,Ph-10 used for making calibration for all type of PH-meter.
The calibration is very smple procedure. New fluid must be used for each calibration.
It's not recommended to reuse it.
Calibration should be performed once a month or when you uspect a devices display.