Overview
EN ISO 8467:1995 (ISO 8467:1993) specifies a standardized chemical test for determining the permanganate index - a conventional measure of the oxidizability of water by potassium permanganate. The method is primarily intended for assessing water quality of drinking, well, spring and surface waters (including pool waters) and is equivalent to the referenced ISO edition. It provides a quick, simple screening test for organic and oxidizable inorganic contamination but is not a substitute for Chemical Oxygen Demand (COD) for heavily polluted or waste waters.
Key topics and technical requirements
- Test principle: Heat a defined volume of sample in a boiling water-bath with a known amount of potassium permanganate (KMnO4) and sulfuric acid for a fixed period (10 minutes). Oxidizable substances reduce part of the permanganate. After reaction, an excess of sodium oxalate is added and the remaining permanganate is back-titrated with KMnO4 to determine the consumed oxidant.
- Reagents & apparatus: Analytical-grade sulfuric acid, potassium permanganate solutions and sodium oxalate standard; water-bath, test tubes reserved for permanganate determinations, volumetric pipettes, burette (10 ml, 0.02 ml divisions) and volumetric flasks.
- Sample conditions:
- Applicable to waters with chloride < 300 mg/L.
- Samples with permanganate index > 10 mg/L must be pre-diluted.
- Optimum lower limit: 0.5 mg/L.
- Add acid at sampling or immediately on receipt; analyze promptly (within 2 days) and store at 0–5 °C if >6 hours.
- Quality control: Perform blank determinations in parallel and standardize titrant; typical blank volumes and reproducibility data are described in the standard.
- Limitations: The permanganate index measures partial oxidation and oxidizability only; it does not equal theoretical oxygen demand, COD, or total organic carbon. Some inorganic reducing agents (Fe(II), NO2–, H2S) contribute to the result.
Applications
- Rapid screening of drinking water and raw water sources for oxidizable contamination.
- Routine water monitoring in utilities, environmental labs and field laboratories for water quality surveillance.
- Preliminary assessment where a simple, low-cost test of oxidizability / permanganate index is sufficient.
- Not recommended as the primary method for industrial or municipal wastewater organics (use COD, ISO 6060).
Who uses this standard
- Water utilities and municipal laboratories
- Environmental testing laboratories
- Public health agencies and regulators
- Laboratories performing routine potable water compliance and source-water surveys
Related standards
- ISO 6060: Water quality - Determination of Chemical Oxygen Demand (COD) - recommended for wastewaters.
- ISO 385-1: Laboratory glassware - Burettes (referenced for burette requirements).
- EN ISO 8467:1995 is the CEN-adopted version of ISO 8467:1993.
Keywords: EN ISO 8467:1995, ISO 8467:1993, permanganate index, water quality, potassium permanganate, oxidizability, water testing, drinking water, water analysis.
