Just curious, but when we were doing a lab calculating Ksp of Ag2CrO4, we determined the concentration of chromate in solution with a spectrophotometer, and as such, we first had to make a calibration curve based on the absorbances of chromate solutions of known concentration.
When making our solutions of known concentration, we took incremental volumes of 0.0024M potassium chromate and diluted each with 0.25M sodium nitrate solution to reach 100ml of standardized samples of known concentration.
Why did we dilute the potassium chromate with sodium nitrate? Why not use distilled water?