Diesella Buffer Solution powder for PH meter

Set of 3 letters with pH solution powder for mixing. Contains: pH 4.01 + pH 6.86 + pH 9.18 Directions for use: Completely empty the powder into a clean 250 ml glass beaker. Add 250 ml of deionized water. Stir untill the powder has completely dissolved. pH solution accuracy is 0.01 pH