Coal process, alcoholic potassium

The crude coal gas is washed with ferrous sulphate solution, whereby the latter is converted into a suspension of ferrous sulphide in ammonium sulphate solution. This reacts with the ammonium cyanide, yielding ferrous ferrocyanide, Fe2[Fe(CN)6], or ammonium ferrous ferrocyanide, (NH4)2Fe[Fe(CN)6], according to circumstances. Potassium ferrocyanide may be obtained from these by treatment with lime, as m the spent oxide process. By repeatedly dissolving in water and precipitating with alcohol, the salt can be obtained in a very pure state.1... 

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