Can I create carbon monoxide gas by just mixing formic acid and sulphuric acid together? Or do they have to be heated?

  • 5
    $\begingroup$ If you have pure, relatively concentrated formic acid, and pure, very concentrated sulfuric acid, then I don't think you need to do any heating. BTW, creating CO gas is very very dangerous! Please don't do it. ncbi.nlm.nih.gov/pubmed/18363119 $\endgroup$
    – Curt F.
    Jul 18, 2015 at 3:31

1 Answer 1


The formation of carbon monoxide already takes place when mixing formic acid and sulfuric acid at room temperature, but the reaction is relatively slow. Since the temperature of the mixture may significantly increase during the course of the reaction, the reaction rate may increase, which makes the reaction difficult to control.

For laboratory applications, concentrated sulfuric acid (or phosphoric acid) is usually heated to about 80 °C. Formic acid is added slowly, drop by drop. The formation of gas should start upon addition of the first drop, otherwise the temperature should be increased.

The generated gas contains various impurities, which can be removed using gas washing bottles. Usually, the gas is passed first through $\ce{KOH}$ solution; however, you should take care to prevent any backflow of $\ce{KOH}$ solution to the sulfuric acid.

  • $\begingroup$ And remember Curt’s comment from above: Carbon monoxide is dangerous; do not meddle with it unless you know exactly what you are doing. $\endgroup$
    – Jan
    Oct 24, 2015 at 23:23

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