If you're not doing a two-point calibration on your pH meter, then you wasted your money on the meter. Periodic calibration will make it obvious how much the cell in your meter can "wander", and you do need to be able to trust your meter. I keep three or four of of the 7.00 and 4.00 packets around to check my meter every cider pressing season.

This and the pH 4 solution is what i use to calibrate my electrode. The accuracy seems to wander so I need to recalibrate every time I use it.

I once had my electrode dry out and it was never the same after that. Now I keep it protected with this when not in use.

I need this to calibrate my pH meter. Without it the pH reading drifts over time._x000D_i also get the pH 4.01 package.

This is a great tool for calibrating PH meters. Make sure you pick this up if you buy a PH meter as it is highly valuable.