The Bluelab pH 4.0 Calibration Solution is used for calibrating your pH probe.
This solution is recommended for use when you expect a reading below pH 7.0. In such cases, you should use both the pH 7.0 and pH 4.0 calibration solutions.
When using the solution, always place the lid back onto the bottle after use to prevent evaporation. Do not measure directly into the bottle; instead, pour a small amount into a clean container and discard after use. Never add water to the solution, and store it in a cool place.
