The Oakton WD3585012 pH Buffer Capsules, 4 pH (Pack of 10) require 100 mL of deionized or distilled water to produce a clear pH calibration solution accurate to ±0.02 pH (at 25°C) with traceability to NIST standards. These capsules are easier to store and transport than prepared aqueous buffer solutions. The WD-35850-12 capsules are color-coded for easy identification if mixed.

Store buffer solutions in an airtight container at room temperature for three weeks. Unused capsules have a five-year shelf life. Each vial contains 10 capsules.