A spectrophotometric method is a alternative method for the determination of sulfate.
1. Weight a portion of sample and dissolve in water.
2. Filter the insoluble and collect the filtrate.
3. Transfer the filtrate to a volumetric flask and top up with water.
4. Take a known portion (~25mL) of dissolved sample and add 5 mL acidified 10% BaCl2 solution.
5. Measure the absorbance against the reagent blank @450nm.