Beryllium Oxyhalides

The perchlorate, BeClO₄.4H₂O, seems to be the only oxyhalide definitely known. Atterberg mentions the decomposition of the chlorate on evaporating its solution. He describes the perchlorate as needle-shaped, deliquescent crystals, with 4 molecules of water of crystallisation.7 Marignac says it is very deliquescent, and only crystallises on concentrating its solution to a thick syrup. It is prepared by dissolving beryllium hydroxide in excess of perchloric acid and concentrating the solution.

Atterberg refers to a "gummy mass " of beryllium iodate and to a periodate, 3BeO.I₂O₇ + 11 or 13H₂O, which is nearly insoluble in pure water.