I read online that when you use regular household rubbing alcohol to soak something for sterilization purposes, you're then supposed to toss it out. I'm just curious why.

Like, as long as there's a lot of liquid still left, why is it not re-usable? Is it because there's bacteria or other stuff that transferred from whatever you were sterilizing into the alcohol, therefore reducing its effective % of alcohol, and that's what's important to sterilize, so once you're below a certain % concentration it's worthless. Or is it because the alcohol has actually evaporated off and what's left is just liquid (water)?

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    You discard alcohol from the same reason you discard washing water. Alcohol collects dirt - whatever this means, so you discard alcohol with dirt. But it's your choice. In 30 minutes, for example, no significant amount of alcohol should evaporate. – Jan Sep 24 '19 at 6:45
  • Got it, so the reason is because as dirt collects, it reduces the % of the alcohol, making it less effective at sterilizing other stuff, is that right? – james Sep 24 '19 at 16:46
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    The dirt does not necessary make alcohol less effective, but you transfer the dirt with alcohol to the next thing you want to sterilize. So, the question is if you want to use slightly dirty alcohol again. I'm not saying yes or no. – Jan Sep 24 '19 at 16:48
  • ok so this may be a stupid question, sorry. but honestly curious - whatever dirt is in the alcohol has been "sterilized"? so... it's like clean? or that's not how it works? – james Sep 24 '19 at 21:02
  • Yes, used alcohol will be sterile (free of live microbes), but it will not be exactly clean, because it will contain some "dirt" (dust or other particles). When you use such alcohol again, you will not pass the microbes to the new item, but you can pass some dirt, which may or may not be an issue... – Jan Sep 25 '19 at 8:48

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