I want to give students the chance to gently waft and smell HCl.
What concentration would be considered safe for a once-off single waft and smell ?
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2$\begingroup$ Why would you want your students to smell HCl? $\endgroup$ – Nilay Ghosh Oct 11 '20 at 13:57
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3$\begingroup$ See this and this answer. Bottom line: Don't smell chemical compounds. They are not perfumes. $\endgroup$ – Nilay Ghosh Oct 11 '20 at 13:59
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2$\begingroup$ That's not really answerable, thing is highly dependent on how you do it and what this "safe" means. BTW @NilayGhosh It's not like you can smell anything but chemical compounds ;> $\endgroup$ – Mithoron Oct 11 '20 at 14:03
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$\begingroup$ @Mithoron It is late at night. I should catch some zzzs. $\endgroup$ – Nilay Ghosh Oct 11 '20 at 14:10
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$\begingroup$ That will naturally occur if they are supposed to be trained in practical chemistry. If they don't, there are better things to smell. $\endgroup$ – Alchimista Oct 11 '20 at 15:32
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I think it is enough to watch the Safety Data Sheet to understand. I found this one browsing on the internet:
Safety data sheet of a Chloridric acid manufacturer
On section 11 you can find: ATE US (gases): 1560.000 ppmV/4h. ATE means "Acute Toxicity Estimates".
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As a teacher, you should lead by example how to engage with chemicals respectfully, as a professional. Which neither is to be fearful, nor to be sloppy and negligent for their potential hazards. This includes to plan ahead, to limit exposure to dangerous goods (like concentrated HCl is), to use protective gear, safe manipulation of the chemicals in response to their possible action, and to have a rescue plan should something go wrong.
The students may already know the smell of acids from cuisine (e.g., balsamic vinegar, kimchi stew, choucroute garnie, etc.), but teach them early the right way chemists do:
(screen photo from here; it is not concentrated HCl)
Or would you trust a dentist as professional if forceps were not both clean and functional?
