Oxidation-Reduction Potential (ORP) is measured using an inert (usually Platinum) electrode and a suitable reference electrode. The measured ORP depends on the choice of reference electrode. RICCA CHEMICAL COMPANY uses a redox electrode incorporating a Silver-Silver Chloride reference electrode with 4 M KCl saturated with AgCl filling solution. This electrode pair gives a potential 200 mV lower than that obtained using a Platinum electrode versus the Standard Hydrogen Electrode.
Other ORP standards available from RICCA CHEMICAL COMPANY are Light’s Solution (Group No. 4330) and ZoBell’s Solution (Group No. 9880). These standards are labeled with the ORP versus several commonly used reference electrodes.
See Technical Reference Document TRD19, available at www.riccachemical.com, for more information on ORP.