Read a thread about rinsing a thermos and clearing out residue and a comment referenced the 3 rinses in chemistry.
All us non-chemistry minded travel mug/bottle/thermos owning folks who’ve struggled with soapy tastes after washing would like to learn.
Thank you.
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More rinses is generally better than less rinses at removing contaminants but there’s no hard rule about the “correct” number of times you should rinse something.
The standard practice in a lab is to rinse three times, but there’s no reason why it has to be exactly three. It’s just standard because it’s a nice number that seems to give satisfactory results in most cases. The justification that you will often hear is that if each rinse is successful in removing 99% of the contamination, then after 3 rinses your contaminant will be diluted to 1 part per million. But that explanation isn’t really based on anything.
In practice you don’t know if your rinsing actually removed 99% of the contamination (could be more or less), and who is to say whether 1 part per million of contamination at the end is good or bad? For some purposes, you might be able to get away with significantly more contamination and be fine. For example, if I’m reusing a coffee cup to hold water, I’ll be willing to accept only a single rinse because if my water ends up tasting a little bit like coffee that’s not the end of the world. But if I’m trying to calibrate an extremely delicate sensor in an experiment I may want to rinse a piece of glassware 10+ times, because even contamination as small as 1 part per million is unacceptable, so I want to be on the safe side.
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