I'm working on a crime story about cyanide poisoning from apple seeds. I just would like to have an idea of what processes and extraction techniques might be involved in getting cyanide from the seeds. The character is supposed to have access to a high school chemistry lab; so I was thinking equipment and tools that can be found in a typical HS lab. I prefer a detailed answer, step by step, if possible. If not then just generalized terminologies would work.

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    $\begingroup$ "I'm working on a crime story" is the new "I'm asking for a friend who's trying to murder people." :) $\endgroup$
    – Jaydles
    Feb 2, 2015 at 21:34
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    $\begingroup$ I have a strange feeling that this question will be used as evidence in an upcoming murder trial... $\endgroup$
    – Coomie
    Feb 3, 2015 at 2:10
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    $\begingroup$ Plot twist: OP is someone you know. $\endgroup$ Feb 3, 2015 at 3:45
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    $\begingroup$ There are "better" ways, even on a budget and with limited equipment ;) $\endgroup$ Feb 4, 2015 at 9:46
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    $\begingroup$ Sorry, I couldn't ask my chemistry teacher - he will be the victim. $\endgroup$
    – Greg
    Jun 19, 2015 at 1:54

2 Answers 2

  1. Forget about the apple seeds, they contain about 1 to 4 mg amygdalin per gramm seeds (DOI).
  2. Instead, collect apricot seeds during the right season, the amygdalin content varies though the year and can be as high as 5% of the dry weight of the seed (DOI).
  3. It is probably advantagenous to break the husk with a nut cracker, a plier, etc. and cut the softer inner material to smaller pieces.
  4. Extraction of amygdalin can be performed by

    • immersing the material in methanol and subsequent ultrasonification
    • Soxhlet extraction with methanol
    • reflux extraction in water in the presence of citric acid

A comparison of the extraction methods is given here.

Removal of the solvent in vacuum will yield a crude material with significant amounts of amygdalin. You might want to have a look at this article from the Western Journal of Medicine on the toxicity. Here, an $\mathrm{LD_{50}}$ of 522 mg amygdalin per kg body weight was estimated for the oral application to rats. The online resource of the U.S. National Library of Medicine gives a value of 405 mg/kg.

Further information on the health risk of apricot kernels are provided by of the German Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment) and the British Committee on Toxicity.

A note in the a German medical journal, Deutsche Ärzteblatt, (PDF) describes a case where boy of four years (110 cm, 18 kg body weight) was given apricot kernels during an alternative cancer treatment. Upon additional treatment with a single dose of 500 mg amygdalin, the kid showed agitation, spasms and the eyes started to roll.

I'll leave it up to your fantasy as a writer on how to apply the poison, but spicing some marzipan with it might help ;)

  • $\begingroup$ Weird that the NFPA health rating is 1 if amygdalin is a potential murder toxic. How much do you need to ingest to become severely ill? $\endgroup$
    – Jori
    Feb 2, 2015 at 17:09
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    $\begingroup$ @Jori Unless I'm completely off, the blue NFPA ratings are for acute intoxications and health risks upon direct exposure. Release of cyanide from amygdalin takes place in the smaller intestine (Dünndarm). Anyway, I've added some more information to my answer. $\endgroup$ Feb 2, 2015 at 18:27
  • $\begingroup$ There is bitter almonds and "normal" almonds, the same seems to be the case for apricot. Of course only the bitter variants contain amygdalin. $\endgroup$
    – Georg
    Feb 2, 2015 at 18:34
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    $\begingroup$ @Georg To my knowledge, this is true for the sweet and bitter variants of the almonds, but not for the apricots (Prunus armeniaca). $\endgroup$ Feb 2, 2015 at 18:49
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    $\begingroup$ The leaves of many Prunus species contain high concentrations of amygdalin and prunasin, both of which are cyanogenic glucosides capable of doing the "job". There are better common garden plants for poisoning people, but I could see that there is something poetic about apples. $\endgroup$ Feb 7, 2017 at 9:10

Honestly, you probably wouldn't be able to get this done with just a highschool chem lab, at least not to a high purity (whether or not this is needed is debatable; in fact it could be interesting in the story because it would give a clue as to how it was produced, whereas pure cyanide wouldn't really tell the detective much).

Having said that, apples don't contain the harmful version of cyanide (hydrogen cyanide) in and of themselves. They do however contain amygdalin, which can be metabolized to hydrogen cyanide. A quick search ends up with wikipedia giving a brief overview of how it is isolated:

Amygdalin is extracted from almonds or apricot kernels by boiling in ethanol; on evaporation of the solution and the addition of diethyl ether, amygdalin is precipitated as white minute crystals.

In case your orgo isn't all that great (mine is a little rusty too), what you should read from the above quote is that ethanol is used to oxydize the primary alcohol group to an aldehyde or a carboxylic acid (depending on how long you let it boil for) making it polar and so non-soluble the diethyl ether (an organic solvent) which leads it to precipitating out as a white crystal. Once it precipitates out the easiest way to isolate it is just to use a paper filter, since it should be the only solid present. Suction filtration would be optimal but that's generally not available in high schools. Lastly you could use sublimation to get a really pure final product, but again this isn't normally available in high school labs.

If you're writing a novel I recommend you take the time to read up on it and how it is metabolized within the body. The more you understand the process the more authentic it'll feel, imo. Best of luck.

EDIT: You may want to consider switching to apricot kernels as opposed to apple seeds. The process is effectively the same but it's more realistic, since you'd need a LOT of apple seeds to get a decent amount of cyanide. Also, like I said my orgo is a bit rusty so if someone else could look over this that would be nice.

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    $\begingroup$ Ethanol can oxidize another alcohol? $\endgroup$
    – Dissenter
    Dec 27, 2015 at 8:31

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