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"Lye, sulfuric acid, and hydrochloric acid aren't toxic per se. You can safely add unlimited quantities of them to your food if they're dilute enough." Right.

"Lye, sulfuric acid, and hydrochloric acid aren't toxic per se. You can safely add unlimited quantities of them to your food if they're dilute enough." Right. Decades ago when I was in highschool and learning chemistry the chem teacher brought out reagent bottles of HCl, HNO3, H2SO4 and NaOH (in soln.) which he intended us students to smell and taste. He also had boxes of brand new test tubes and he issued everyone with four thereof for the demonstration/experiment which he insisted that we wash thoroughly under running water despite them being brand new. His stated reasons were that as chemists that (a) we needed to become familiar with these common reagents as they were ubiquitous in chemistry labs and industry, and (b) we needed to know and experience the acidity of acids and to clearly distinguish them from the soapy character of the alkali. He also had a more important motive that I'll come to in a moment. He then diluted the reagents to a safe level (I think it was about 1/40 Normal but I can't remember for sure). Then we students all lined up and he poured a few ml of each of the reagents into our test tubes for us to first smell then taste, which we all did. Afterwards when we were all back in the tiered seats of the demonstration lab he made a statement in the sternest tone that shocked the wits out of lot of us: "You're all dead!" —long silent pause— "Don't you ever do that again. You don't know whether the reagents are true to label, for all you know I could have given you poison and you'd be none the wiser until it was too late. And even if the bottles are true to label then you've still no idea how pure they are—they may contain impurities that are highly toxic." He then went on to point out that these bottles of reagents were new and that he'd unsealed them in front of us and asked if anyone of us had noticed that. He then pointed to print on the label that said BP—British Pharmacopeia grade and then to the assay list of impurities which were many decimal places below one percent (the minutest of a trace). This chemistry lesson was by far the most important one we ever learned—nothing at university was ever the equal of it. It's a great tragedy that these days health and safety rules preclude students from ever participating in such a demonstration. Students must be taught not to fear chemicals but nevertheless to treat them with care and great respect lest they bite. These days much of society has an almost irrational fear of chemicals despite the widespread teaching of chemistry. That tells me there's something terribly wrong with the way we teach the subject—a matter that I've covered on HN previously.

kragen 2y ago
I agree. (Nitric acid is somewhat toxic as well aside from its corrosivity; accidental fatal poisonings with neutralized nitrates are well known in the literature.) Essential oils are generally not at high risk of deadly impurities, for three reasons. First, they are mostly intended for human consumption (whether BP grade or not), except for turpentine; second, their production process is just steam distillation and so doesn't normally involve any highly-toxic impurities; third, because the essential oils themselves are sufficiently deadly that most potential impurities would have to be present at very high levels before they were a concern.
- hilbert42 2y ago
  "Nitric acid is somewhat toxic…" Agreed. Whilst the lesson played out almost to the letter as I described it (I well remember the experience) some of the fine minutiae/details may be a bit unclear (after all, that lesson was in the 1960s). Thus, it's possible the 'odd-man-out' in the lineup wasn't HNO3 but rather H3PO4, but don't think so. Remember, the amount the teacher put in the test tubes was at most only a couple of ml and most just barely tasted the samples (you can imagine, there was much ooing and arring at the bitter taste) so the amount tasted was actually minuscule). Incidentally, there was general agreement that the most objectionable reagent to the taste was NaOH, 'yucky' was the most common description. Whilst I said the dilutions were about 1/40 N. that was almost certainly so for HCl but not necessarily so for the others which may have been more highly diluted (HCl's dilution specifically comes to mind because the teacher mentioned it in connection with stomach acid). The reason I don't think it was H3PO4 is that we didn't do much chemistry with it although I do remember it being discussed in connection with Coca-Cola in that we shined up pennies with it. I'd also point out there were other 'safety' lessons of a similar nature. Ones that come to mind Immediately include the need to take great care when handling aqua regia and H2SO4, especially so if heated in a retort, another was the preparation of H2S in a Kipp's generator/apparatus—the mandatory use of the ventiated fume cupboard and that H2S is particularly dangerous as it desensitizes one's sense of smell in even quite small concentrations. Then there were the strict rules surrounding the use of Hg (of which the lab had many litres thereof). It's interesting you mention turpentine as an exception. I occasionally do a bit of woodworking and I know others who are more avid woodworkers than I am. One thing that characterizes a small subset of them is that they insist on using real oil/spirit of turpentine rather than the mineral (white spirit) variety for no other reason than it's 'natural' whereas the mineral stuff is 'unnatural' as it comes from the petroleum industry. Frankly this horrifies me. As you'd know oil of turpentine is a catch-all name for any number of terpenes—of which there are hundreds if not thousands—all mixed in ill-defined ratios, what you get depends on where it's sourced. There's no telling these guys that many terpenes are both irritating to the skin and quite toxic—and that some are known carcinogens. What surprises me is that woodworking suppliers are actually allowed to stock and sell the stuff. If I had my way I'd ban it for that purpose (there might be some excuse for its availability if mineral turpentine was actually inferior in this application but that's not the case).

kragen 2y ago

I agree. (Nitric acid is somewhat toxic as well aside from its corrosivity; accidental fatal poisonings with neutralized nitrates are well known in the literature.) Essential oils are generally not at high risk of deadly impurities, for three reasons. First, they are mostly intended for human consumption (whether BP grade or not), except for turpentine; second, their production process is just steam distillation and so doesn't normally involve any highly-toxic impurities; third, because the essential oils themselves are sufficiently deadly that most potential impurities would have to be present at very high levels before they were a concern.

hilbert42 2y ago
"Nitric acid is somewhat toxic…" Agreed. Whilst the lesson played out almost to the letter as I described it (I well remember the experience) some of the fine minutiae/details may be a bit unclear (after all, that lesson was in the 1960s). Thus, it's possible the 'odd-man-out' in the lineup wasn't HNO3 but rather H3PO4, but don't think so. Remember, the amount the teacher put in the test tubes was at most only a couple of ml and most just barely tasted the samples (you can imagine, there was much ooing and arring at the bitter taste) so the amount tasted was actually minuscule). Incidentally, there was general agreement that the most objectionable reagent to the taste was NaOH, 'yucky' was the most common description. Whilst I said the dilutions were about 1/40 N. that was almost certainly so for HCl but not necessarily so for the others which may have been more highly diluted (HCl's dilution specifically comes to mind because the teacher mentioned it in connection with stomach acid). The reason I don't think it was H3PO4 is that we didn't do much chemistry with it although I do remember it being discussed in connection with Coca-Cola in that we shined up pennies with it. I'd also point out there were other 'safety' lessons of a similar nature. Ones that come to mind Immediately include the need to take great care when handling aqua regia and H2SO4, especially so if heated in a retort, another was the preparation of H2S in a Kipp's generator/apparatus—the mandatory use of the ventiated fume cupboard and that H2S is particularly dangerous as it desensitizes one's sense of smell in even quite small concentrations. Then there were the strict rules surrounding the use of Hg (of which the lab had many litres thereof). It's interesting you mention turpentine as an exception. I occasionally do a bit of woodworking and I know others who are more avid woodworkers than I am. One thing that characterizes a small subset of them is that they insist on using real oil/spirit of turpentine rather than the mineral (white spirit) variety for no other reason than it's 'natural' whereas the mineral stuff is 'unnatural' as it comes from the petroleum industry. Frankly this horrifies me. As you'd know oil of turpentine is a catch-all name for any number of terpenes—of which there are hundreds if not thousands—all mixed in ill-defined ratios, what you get depends on where it's sourced. There's no telling these guys that many terpenes are both irritating to the skin and quite toxic—and that some are known carcinogens. What surprises me is that woodworking suppliers are actually allowed to stock and sell the stuff. If I had my way I'd ban it for that purpose (there might be some excuse for its availability if mineral turpentine was actually inferior in this application but that's not the case).