One Question per Day: Methanol and Purification Technology Forum Edition 20191102

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Regarding the control criteria for the potassium permanganate test in the quality specifications for pure methanol. In organic compounds, certain impurities are prone to oxidation due to the presence of carbon-carbon double bonds and carbon-oxygen double bonds; if they end up in refined methanol products, they affect their stability and reduce their quality and utility. An important indicator for measuring the stability of pure methanol is the potassium permanganate test: a certain concentration and amount of potassium permanganate is added to a specific volume of pure methanol, and the time it takes for the solution to change color is measured at a particular temperature. The longer it takes for a color change to occur, the better the stability; this indicates that there are few oxidizable impurities in the pure methanol. It also allows one to determine whether other impurities have been completely removed ； If the time is short, the opposite is true. The substances prone to oxidation in pure methanol are mainly isobutyl alcohol, diisopropylmethane, and formic acid.