Let me begin this post by stating that I do not know basically anything about chemistry, which is why I am asking for your help. Please be kind :)

Today, I saw the following post on Twitter and Reddit and it somewhat scared me:

I had no idea that Isopropanol, stored for too long, can potentially turn into something quite dangerous (and according to the comments on Twitter / Reddit many people are in the same boat).

In the beginning of 2019, so over four years ago, I bought a 1 liter bottle of Isopropanol 99,9% on Amazon. The product page on Amazon explicitly stated that it contains no additives. I bought it for cleaning purposes, for example cleaning heat paste from CPUs and so on, but I don't do that too often, so it was not used a lot and there is still quite a lot of Isopropanol in it. I probably have not used it for several years now, but I thought that nothing would happen to it.

The bottle is a white, somewhat opaque, "soft" plastic bottle. This bottle is still stored on my shelf. One thing I have noticed with the bottle is that it somewhat compressed by itself, but I guess that does not indicate anything dangerous (?).

The room it is in usually does get some light, but not very bright light, and sun light is rare. That might have been slightly different in the years 2019 and 2020, I cannot remember for sure.

I am now worried that this might have happened to my bottle of Isopropanol, but other than the time that has passed since I opened it, I have no indication for it. I am not really sure how to assess the risk.

At the moment, I would not even move the bottle, but I might be overcautious here and fueled by unnecessary anxiety. Due to the opaqueness of the bottle, I probably would not even be able to tell for sure if there are crystals in the bottle, most likely I would also have to move it to be able to check it properly.

What is your risk assessment and what are your suggestions on how to deal with it? I would love to just get rid of it, but that would probably mean bringing it to a waste disposal site, and I assume that could already be dangerous, if something of that sort had happened.

Thank you all for your help, suggestions and comments.

  • $\begingroup$ Well, isopropyl is listed as a peroxide former. Up to you to decide what to do. I’ve had bottles last longer than that, but that is no guarantee yours isn’t going south. $\endgroup$
    – Jon Custer
    Jul 2, 2023 at 15:39

1 Answer 1


Since you state, "the bottle is... somewhat compressed," it indicates that the $\ce{(CH3)2CHOH)}$ solvent has slowly evaporated through the plastic container, but air has not entered. In essence, the plastic bottle is a semipermeable membrane. The pressure decrease is cause by by osmosis of a vapor. Not harmful, and since it indicates more air is not entering to form peroxides, likely the solvent is still safe, though it might be possible a small amount has formed on the bottle the cap thread.

Note that isopropanol is on this list. A similar question has also been asked.

Since this is a personal safety question, it probably does not belong on this site, but I felt this non-authoritative answer worth the effort, though it should soon be removed.

  • 2
    $\begingroup$ The document cited by DrMoishe Pippik is called "this list", The very first lines of this document are repeated here : Peroxide formation in solvents and reagents have been the cause of occasional accidents. Even the relatively innocuous solvent, isopropyl alcohol is capable of peroxide formation. This can occur upon exposure to air, heat, light, or simply with passage of time. . $\endgroup$
    – Maurice
    Jul 2, 2023 at 20:58
  • 1
    $\begingroup$ Thanks, @Maurice, I fixed that glaring error! $\endgroup$ Jul 2, 2023 at 21:17
  • $\begingroup$ It is a pity that solution of FeSO4 or Na2S2O5 cannot be used as they are for diethylether or diisopropylether. $\endgroup$
    – Poutnik
    Jul 3, 2023 at 8:44
  • $\begingroup$ What about the solid in the picture the OP posted. Is that fake? $\endgroup$
    – Karsten
    Jul 3, 2023 at 13:29
  • $\begingroup$ Don’t distill it: pubs.acs.org/doi/10.1021/acs.oprd.2c00112 $\endgroup$
    – Karsten
    Jul 3, 2023 at 13:36

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