Chemistry - How do I extract cyanide from apple seeds?
Solution 1:
- Forget about the apple seeds, they contain about 1 to 4 mg amygdalin per gramm seeds (DOI).
- 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).
- It is probably advantagenous to break the husk with a nut cracker, a plier, etc. and cut the softer inner material to smaller pieces.
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 ;)
Solution 2:
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.