# Make KCN from ferrocyanide, K2CO3, and carbon

$$\ce{2K4Fe(CN)6 + 2K2CO3 + 1C -> 12KCN + 2Fe + 3CO2}$$ This reaction seems very logical. Does it actually occur? What temperature should be used for the reaction? $\pu{640^\circ C}$?

...Dry fusion of pure $\ce{K4Fe(CN)6}$ is a bit tricky, if you will try to do this on air contact you will end with with cyanate and cyanogen beeing evolved. To prevent (this) oxidation process, $\ce{K2CO3}$ and carbon works the best - you don't need protecting atmosphere you just must cover reaction vessel with lid to reduce free air flow, reaction products CO and CO2 will form protecting buffer of gas under the cover and prevent oxidation of product to cyanate, remember you don't need completely airtight vessel (reaction gases must evolve freely) just cover crucible with ceramic lid and heat it up in electric furnace. I made $\ce{K4Fe(CN)6 + K2CO3 + C}$ process for many times now and produced a lots of cyanide using this method, temperature program i've used ~30 min to 600C, then 1 hour at this temp, rise to 650 in 30 minutes, and one more hour at 650. If your crucible is high and you sit it long enough cyanide separates from Fe and carbon particles and solidifies as shiny snow white layer at the top layer, however if this has't happened and resulting mass is black and feromagnetic this is fine too, you can separate cyanide by dissolving and filtering.
$$\ce{K4Fe(CN)6 + K2CO3 -> 5KCN + KCNO + CO2 ^ + Fe}$$ $$\ce{K2CO3 + C + NH3 -> 3KCN + H2O}$$