The pH Buffer Capsule Kit, order code PH-BUFCAP, $29 (formerly order code PHB) contains two of the three items you'll need to prepare the electrode storage solution for our pH Sensors.
To prepare the proper solution to use as the storage solution for our pH Sensors, add the contents of one orange (pH 4) powder capsule, 3 drops of preservative, and 10 grams of solid potassium chloride (KCl) to 100 mL of distilled water. Stir the mixture thoroughly.
Note that the preservative also contains a universal indicator, thus your mixture will not be clear. This color will not harm your sensor.