Barium perferrate, BaFeO₄

Barium perferrate, BaFeO₄.H₂O, is obtained as a purple precipitate on addition of barium chloride to a solution of the calcium salt or of barium chromate to a solution of sodium perferrate.

Barium perferrate is the most stable salt of the series. It is insoluble in water, and its suspension in water may be boiled without decomposition. It is practically unaffected by dilute sulphuric acid in the cold. Apart from this it is readily attacked by acids, even carbonic; dilute hydrochloric or nitric acid decomposes it instantly, yielding salts of barium and iron. When treated in the cold with very dilute hydrochloric acid, chlorine is evolved and the solution assumes a red colour, probably due to the presence of the FeO₄'' ion. Acetic acid reacts similarly. On boiling, the solution evolves oxygen, and becomes colourless.

The composition of barium perferrate is proved iodometrically by means of the reaction

2BaFeO₄ + 8KI + 16HCl = 2BaCl₂ + 2FeCl₂ + 8KCl + 8H₂O + 4I₄.