Standard preparations— Pipet 10 mL of the Manganese stock solution into a 500-mL volumetric flask, dilute with water to volume, and mix. Transfer 4.0, 5.0, and 6.0 mL, respectively, of this solution to separate 50-mL volumetric flasks, containing 10 mL of Sodium chloride solution, dilute the contents of each flask with water to volume, and mix.