pH 4.01 is a common low-range pH meter calibration point. All Environmental Express pH buffer solutions are manufactured under ISO 9000 quality guidelines and traceable to NIST standard (for meters with 0.01 resolution). A pH/temperature table is printed on the label for accurate calibrations.

pH 4.01 buffer solution is colored red for visual reference. It is sold in individual 1000-mL (1-L) bottles. If unopened, shelf life of pH 4.01 is 2 years.

Store buffers away from direct sunlight.