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My isopropyl alcohol is expired. What happens when it expires? Does it break down into something else? Can I still use it to clean or sanitize?

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    $\begingroup$ Nothing, unless the container has been opened. If opened, it could slowly absorb water from air and/or evaporate isopropanol, but would still be useful. $\endgroup$ Aug 4 '20 at 2:06
  • $\begingroup$ Isopropyl alcohol is a fairly stable compound, so it probably won't break down. Instead, past the expiration, even if you've not opened the container, some of the alcohol might escape (thus lowering the percentage of alcohol*) and, in addition, some plastic might leach from the container into the alcohol. *You can tell whether this has happened significantly by comparing the level of liquid in your container with that in new containers; note that there is typically variation in the levels even in new samples, so this will only tell you if there's been significant loss. $\endgroup$
    – theorist
    Aug 4 '20 at 3:09
  • $\begingroup$ Expiration of stable compounds like isopropyl alcohol has nothing to do with their stability. It is rather commercial requirement. $\endgroup$
    – Poutnik
    Aug 4 '20 at 4:29
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    $\begingroup$ @Karl PE containers aren't typically 100% pure PE.The plastic often contains additives as well as impurities. And these compounds can leach into the isopropanol. Here's just one example (it discusses extraction with EtOH, which is close to isopropanol): ncbi.nlm.nih.gov/pmc/articles/PMC3222987 And here's a genl. discussion about leaching from HDPE pipe. It's discussing leaching of organics into water, but most water-soluble organics will be as soluble, or more so, in isopropanol: pprc.org/2015/p2-rapid/… $\endgroup$
    – theorist
    Aug 4 '20 at 7:42
  • $\begingroup$ That latter article states: "a 2003 study by Skjevrak, identified a wide variety of leachates from HDPE pipe. Odors associated with these leachates were above acceptable levels set by USEPA’s non-mandatory quality standards. Skjevrak found that the dominant source of contamination was likely due to breakdown-products of common polymer antioxidants. While these contaminants are not of remarkable toxicity, a host of other minor contaminants were identified, including benzene and xylene." [I'll add that, when I look at the bottoms of my isopropanol containers, they say they are made with HDPE.] $\endgroup$
    – theorist
    Aug 4 '20 at 7:46

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