REAGENTS AND SOLVENTS – Reagent grade or better chemicals must be used. Unless otherwise indicated, it is intended that all reagents will conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society (ACS), where such specifications are available. Other grades may be used if the reagent is demonstrated to be free of Cr(VI) and other interferences, and all requirements of the IDC are met when using these reagents.