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139-EN, General section

Alternative to potassium dichromate in water analysis


Potassium dichromate is used in standardized method to determine the chemical oxygen demand (COD), an indicator of the content of oxidizable chemicals in waters. Alternatives to the hazardous potassium dichromate are available, but there are limitations to some of them, like the range of applicability and/or the content of equally hazardous substances.

Substituted substance(s)

  1. Potassium dichromate

    CAS No. 7778-50-9 EC No. 231-906-6 Index No. 024-002-00-6

Alternative substance(s)

  1. Potassium permanganate

    CAS No. 7722-64-7 EC No. 231-760-3 Index No. 025-002-00-9

Other type of alternative

IR detection method

Hazard assessment

Potassium permanganate has some of the hazards of the potassium dichromate that it substitutes but unlike the chromate, it is not classified as EU carcinogenic 1B, mutagenic 1B and skin sensitizer.

» Check the Substance Database according to SUBSPORT Screening Criteria (SDSC)

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Substitution description

In France a required standardised method for COD measurement uses potassium dichromate, a CMR 1B and a respiratory and skin sensitizer. Conditions of use include direct manipulation and 2 hour boiling of the sample.
Alternative methods exist, but have their limitations.

The use of potassium permanganate is also part of a standardised method and is a safer option. It is however applicable to levels of COD specific to water for human consumption, below 10mg/l, generally much lower than the level in polluted waters.

Another alternative is determination of COD by vaporising minute quantities of sample under conditions that transform organic matter in carbon oxide, measured by infrared (IR)) adsorption. This method is applicable to broad range of organic matter content in the sample as well as for samples containing high levels of chlorine. This method needs more expensive devices than the one it substitutes.

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Case/substitution evaluation

Replacement of potassium dichromate in COD measurement is possible if  the limitations of the alternatives , like lower measuring range or higher price,s are not a major inconvenient. The problem is of interest not only in France since many other countries have standardised methods using hazardous potassium dichromate.

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Other solutions

Further information

Further languages available

Original document only in French

Who provided the information

Type of information supplier


INSTITUT NATIONAL DE RECHERCHE ET DE SÉCURITÉ pour la prévention des accidents du travail et des maladies professionnelle ), France,,

Publication source

The Fact sheet was developed by CNAMTS and INRS , France and published by INRS on its website  in 20o7.

Type of publication and availability 

Fact shhet freely available on internet, in French

Original document: click here
Archived copy: click here

Comments from SUBSPORT users

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Publication or last update: 30.03.2012