Some notes on the use of filters in KMnO4analyses

✍ Scribed by Johannes Kjensmo

• Publisher: Springer
• Year: 1965
• Tongue: English
• Weight: 235 KB
• Volume: 26
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00045546

✦ Synopsis

Potassium-permanganate consumption has been widely used as a measure of the content of oxidizable matter in lake waters . Concerning humic influenced lakes especially, the KMnO 4 consumption often is used as one of the criteria for humosity. According to their humus content, these lakes as a rule are divided into the following three groups : oligo-, meso-and polyhumic . Border-line values of KMnO 4 consumption in such a division are given by NAUMANN (1921) and by ABERG & RODHE (1942) .

ABERG & RODHE point out that the border lines for KMnO 4 consumption naturally are only approximate and there are great fluctuations. JUDAY & BIRGE (1932) found that oxidation with KMnO4 for thirty minutes (i . e . thirty minutes boiling) destroys organic matter equivalent to 40% of the organic carbon present . The borderline values given by ABERG & RODHE are founded on a method including 10 minutes boiling under acid conditions . The fact that the organic matter present in the water does not all oxidize when boiled for 10 minutes, makes it clear that special care must be taken when carrying out the analyses if comparable results are to be obtained . Further, OHLE (1940) found that humic substances are oxidized more quickly and completely by boiling under alkaline conditions . The above facts indicate the importance of strict adherence to the appropriate method of analysis for the border-line system in question, when using such a system to classify a lake . In addition, corrections for reducing agents such as ferrous iron, divalent manganese or nitrites present in the water should be undertaken if the KMnO 4 consumption is to be considered as a measure of organic matter . Such a correction can be done by titration of the sample with KMnO 4 in the cold (MACKERETH 1963) .