There is a story about a scientist who wanted to know what Hydrogen Cyanide (HCN, Prussic Acid) tasted like, but couldn't because he died before he could write it out.

But it requires at least 25-30 seconds even in large doses, according to most resources.

Also, if I were to put a tiny bit of cyanide on my tongue and spit it out, would I die?

(Reference)

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    Please do not try and let us know. Also, it is a gas at room temperature and pressure. – picakhu Jan 21 '13 at 13:29
  • Welcome to Skeptics. Please provide some references to places where this story is being told. – Oddthinking Jan 21 '13 at 14:46
  • @Oddthinking I just found this. smh.com.au/news/world/suicide-note-reveals-taste-of-cyanide/…. It says it resolved the "long unanswered question". I find it hard to believe it was unknown for so long! – Anirudh Ramanathan Jan 21 '13 at 15:22
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    Yes, it is hard to believe that article at all. In any case, that was Potassium Cyanide, not Hydrogen Cyanide. – Oddthinking Jan 21 '13 at 15:39
  • @Cthulhu: You are asking about the taste of hydrogen cyanide. The article you link to refers to potassium cyanide. – Tor-Einar Jarnbjo Jan 21 '13 at 15:42
up vote 14 down vote accepted

Hydrogen Cyanide (HCN) has the odor/taste of bitter almonds. Exposure to 10-30 ppm HCN in air can result in a metallic taste being reported.

Source: Clinical Environmental Health and Toxic Exposures, by John Burke Sullivan and Gary R. Kreiger, page 711.

HCN can be detected at levels from as low as 1ppm and the fatal dose, depending on the time of exposure, is much higher.

Some people can detect hydrogen cyanide by odor or taste sensation at a concentration of 1 ppm in air while most people can detect 5 ppm. OSHA has set 4.7 ppm as the maximum, average safe exposure limit for a 15 min period. [...] A small concentration of cyanide always exists in a person's body, and the body has a mechanism to continuously remove small amounts of cyanide.

Source: Riegel's Handbook of Industrial Chemistry by von Emil Raymond Riegel, James Albert Kent, page 1221.

Here is a toxicological overview.

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    Cyanide tastes of almonds because they contain small amounts of cyanide-releasing compounds. So almond eaters do know the taste. – matt_black Jan 21 '13 at 19:25
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    'Fun' fact not everyone can actually smell Cyanide. 1 2 – Stefan Jan 22 '13 at 20:15
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    I find this discussion of the relation between the smell of cyanide and that of bitter almonds very misleading for several reasons: smell perception varies widely between humans (see the refs behind @Stefan's link). Amygdalin not only releases HCN but also benzaldehyde which has a very strong smell. I can actually smell HCN, and can distinguish HCN from benzaldehyde. Yet I perceive benzaldehyde as the predominant smell in bitter almonds (skeptics.stackexchange.com/a/15375/8865). This is backed by the fact that almond aroma is benzaldehyde without cyanide. (-1: potentially serious) – anonymized Mar 14 '13 at 20:09
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    @matt_black: Do you actually and personally know the smell of HCN and/or the taste/smell of raw bitter almonds? I doubt that almond eaters know the taste: almonds for eating are sweet almonds. Bitter almonds are usually only eaten after baking, and then there's basically no cyanide left, only the benzaldehyde. – anonymized Mar 14 '13 at 20:12
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    @matt_black: I still work as a chemist... I once held a workshop on the human sense of smelling, and for that we actually bought bitter almonds and mashed a bit with water + a drop of H2SO4 - that way the HCN smell comes first, then the benzaldehyde. That plus "reference substances", and most people were able to smell the components, though not all. Most were not able to describe the smells, though they recognized the benzaldehyde. Neither can I positively describe the smell other than naming it cyanide - though I've smelt HCN only in low concentrations, so I cannot comment on the "metallic". – anonymized Mar 14 '13 at 22:40

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