Barium Iridicyanide, Ba₃(IrC₆N₆)₂

Barium Iridicyanide, Ba₃(IrC₆N₆)₂.18H₂O, was obtained by Martius as the result of treating the copper salt with excess of barium hydroxide solution. The excess of barium is removed by passage of carbon dioxide through the liquid, and upon slow evaporation the salt separates out in large trimetric crystals. Exposed to dry air the crystals effloresce, still, however, containing six molecules of water, which are completely expelled at 100° C.