Barium carbonyl ferrocyanide, Ba3[Fe(CN)5.CO]2.11H2O, is readily prepared by decomposing the copper salt with a soluble barium salt, or by neutralising the free acid with barium hydroxide. It loses 10 molecules of water at 19° C. in vacuo, and becomes anhydrous at 130° C. The heats of solution are: -
[Ba3[Fe(CN)5CO]2] + Aq. = Ba3[Fe(CN)5CO]2Aq. + 16,900 calories,
[Ba3[Fe(CN)5CO]2.11H2O] + Aq. = Ba3[Fe(CN)5CO]2Aq.- 6,900 calories,
whence the heat of hydration of the anhydrous salt is 23,800 calories at 17.5° C. |