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Comment on Why are there no flow batteries with symmetric ferrocyanide electrolytes?

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Cyanide batteries... hmm..

Ferrocyanide is not dangerous. Sodium ferrocyanide is used as an anti-caking agent in table salt. It's considered safe for this use in both the US and the EU, e.g.:

https://ec.europa.eu/food/food-feed-portal/screen/food-addit...

Yes, but as the article points out, the process likes to evolve free cynanide in operation.

Putting stuff in electric fields while thinking "well, it's stable" is a fool's errand.

(As the article says...)

*ferrocyanide Less toxic than cyanide.

Potassium ferrocyanide: 1.6g/kg LD50 Potassium cyanide: 5mg/kg

So cyanide is approx 320 times more toxic.

Exactly. Table salt has an LD50 of 0.5-1g/kg, 1.5-3x more toxic. I weigh ~85kg, I'd have to eat about 46 cubic centimeters of potassium ferrocyanide (on the conservative side) to consume an LD50 worth.

If you're talking about the chemicals in batteries we have today, the LD50 is probably way lower for most of them. If we're talking about batteries for consumer electronics, you'd have to eat (density wise) multiple batteries worth of potassium ferrocyanide to hit LD50.

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