j. Colorreagent: Combine 1500 mL water, 200.0 mL conc phosphoric acid, H3PO4, 20.0 g sulfanilamide, and 1-0 g N-(1-naphthyl) –ethylenediamine dihydrochloride. Dilute to 2000 mL. add 2.0 mL polyoxyetylene 23 lauryl etther. Store at 4 0C in the dark. Prepare fresh reagent every 6 weeks. Alternatively, prepare proportionally smaller volumes to minimize waste.