The HI-93754C-25 is a box of 25 reagent vials for COD, high range 0 to 15,000 mg/L (as O 2) *This method with chromium-sulphuric acid is officially recognised by EPA for wastewater analysis. Each box of 25 vials is supplied with a Hanna certificate of quality. The reagents are traceable to NIST SRM® 930.