Overview
ISO 8467:1993 specifies a standardized laboratory method to determine the permanganate index - a conventional measure of oxidizable organic and some inorganic matter in water. The method is widely used for assessing water quality of drinking, well, mineral and other raw waters (including swimming pool water). It is simple, rapid and intended for routine water testing and oxidizability surveys rather than for detailed organic load analysis.
Key topics and requirements
- Principle: Heat a measured water sample in a boiling water-bath with a known amount of potassium permanganate and sulfuric acid for a fixed time (10 minutes). The portion of permanganate reduced by oxidizable material is quantified by adding excess sodium oxalate and back-titrating with permanganate.
- Analytical limits: Applicable to waters with chloride < 300 mg/L. Samples with permanganate index > 10 mg/L must be diluted; the lower optimum range is 0.5 mg/L.
- Sample handling: Acidify samples (add 5 mL of specified sulfuric acid per litre) at reception if not acidified in the field. Analyze as soon as possible and within 2 days; store in the dark at 0–5 °C if storage exceeds 6 hours.
- Procedure details: Run a blank in parallel; titrate until a faint pink persists for ~30 seconds. Standardize the permanganate volumetric solution using the retained blank titrated solution and sodium oxalate.
- Reagents & apparatus: Uses standardized sulfuric acid strengths, potassium permanganate stock and volumetric solutions, sodium oxalate standard, and specified test tubes and a boiling water-bath. Use only reagents of analytical grade and distilled or equivalently pure water.
- Interpretation limits: The permanganate index is a conventional indicator of oxidizability, not a substitute for Chemical Oxygen Demand (COD); oxidation is often incomplete and volatile organics lost before permanganate addition are excluded.
Applications and users
- Environmental and public health laboratories performing routine drinking water quality monitoring.
- Water utilities, well and mineral water producers, and pool operators for quick assessment of oxidizable contaminants.
- Regulatory agencies and field survey teams needing a standardized test for comparing water samples.
- Note: For wastewaters or detailed organic load determination, ISO 8467 recommends the COD method (see ISO 6060).
Related standards
- ISO 6060:1989 - Water quality - Determination of Chemical Oxygen Demand (COD)
- ISO 385‑1 - Laboratory glassware (burette requirements)
Keywords: ISO 8467, permanganate index, water quality, potassium permanganate, water testing, oxidizability, drinking water testing.
