Buffer Capsules will accurately produce 100 ml. of solution at pH 4.00, 7.00 and 10.00. Hydrion Buffers are free flowing soluble powders that prepare clear or color safe solutions in minutes. The set contains 1 vial of each buffer standard, with each vial containing 10 capsules.
You can get a solution with pH 4 manually as follows: Add 20g per liter of citric acid and then add KOH slowly to increase the pH up to 4.00. After preparation leave the buffers to rest for a few hours and measure the pH again to ensure that your solution pH remains stable.
Buffer solutions Specifications, Ph At 20 C 4,01 Uncertainty 0 01 Composition Per Litre Is 10,3G Potassium Hydrogen Phthalate.
Buffer Solution pH4.00 (Phthalate) NIST Standard Solution ready to use for pH measurement, Fisher Chemical™ 2.5L HDPE plastic bottle.
where water is specified for solution or dilution of test substances in pH determinations use carbon dioxide free water.