I recently looked at a reaction where CO is synthesized using formic acid and sulfuric acid, which seems to be one of the easier to control reactions for this, and obviously ventilation etc is necessary.

However I was wondering, is ventilation only necessary because of the dangerous nature of CO, or also because of the vapors or formic and sulfuric acid? I was quite into chemistry in school and after, but I do not remember that much, so I feel like I should know this but I cannot recall anymore. So at room temperature, if you would take a small amount of each of these acids and keep them either separately or mixed together, how fast/how much would evaporate and create dangerous acid vapor?

  • $\begingroup$ So the labels / other warnings cautioning of vapors are exaggerated? Or to use a concrete example, formic acid is also used by beekeepers against certain pests, and I read a report of one beekeeper losing his sense of smell because a bottle of formic acid (it didn't say which concentration) tipped over in his truck. How long would it take for this to happen or under what conditions? $\endgroup$
    – step21
    Jun 4, 2018 at 23:01
  • $\begingroup$ Lets put it more precisely, H2SO4 has no vapor pressure to speak of in r.t. but HCOOH does. Still, corrosiveness of conc. formic and toxicity of CO are more important IMO. There is some danger of HCOOH vapor, then again it's hardly as volatile as, say, NH3. $\endgroup$
    – Mithoron
    Jun 4, 2018 at 23:55
  • $\begingroup$ Formic acid is pretty pungent. Though fumes are toxic, the odor should be an initial warning. See chemical data safety sheets, e.g.basf.com/documents/corp/en/sustainability/employees-and-society/… $\endgroup$ Jun 5, 2018 at 21:10
  • $\begingroup$ Related: Making carbon monoxide gas from formic acid and sulfuric acid? $\endgroup$
    – user7951
    Aug 4, 2018 at 18:08

1 Answer 1


I might sound like a kill joy but I strongly suggest that you do not attempt to make carbon monoxide. The reaction you describe is a not one for the faint hearted. I would like to point out that aerosols of sulfuric acid are very harmful to the lungs, eyes and the rest of your body.

I think that any work done in the lab with concentrated sulfuric acid should be done in a fume hood to protect you against aerosols of the acid. The fumes from the formic acid are going to be corrosive.

In my youth we used to work on the open bench with glacial acetic acid, this is not a good thing to do as the whole lab soon becomes like a viniger factory. I fear that with formic acid being handled outside the hood the lab will soon become rather unpleasnent.

  • $\begingroup$ Thanks for the answer! I do not want to attempt anything, just to understand/learn and know what is theoretically possible with relatively little effort/equipment. And seeing as formic acid is used by beekeepers (my uncle had bees once, but cannot remember if he used it), it seems readily available and so it shouldn't be that difficult to handle if I was so inclined. Compared to Mithoron above, so you would say that there is actually vapor pressure from the aerosols, or are we talking about different things here? $\endgroup$
    – step21
    Jun 5, 2018 at 23:27

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