Zirconium Carbonates

The existence of several carbonates of zirconium serves to emphasise the electropositive character of this element. Berzelius and Hermann obtained hydrated carbonates by precipitation, and Mandl prepared a precipitated carbonate by passing carbon dioxide through a mixture of zirconium nitrate and ammonium carbonate solutions. Chauvenet has reinvestigated the subject and finds that when a zirconium salt is precipitated by sodium carbonate of any concentration the compound ZrCO₄.ZrO₂.8H₂O is formed as a gelatinous, microcrystalline mass which becomes ZrCO₄.ZrO₂.2H₂O in an exhausted desiccator; ZrCO₄ may be regarded as an ortho-carbonate or a basic carbonate ZrO.CO₃. When the above salt is heated beyond 60° C. it loses carbon dioxide and water, forming 2ZrCO₄.3ZrO₂.3H₂O, which at 250° C. yields a product of the composition ZrCO₄.3ZrO₂.H₂O, and at 400° C. is converted into zirconium dioxide. No anhydrous carbonate appears to exist, but when the dehydrated basic carbonate is exposed to a pressure of 30-40 atmospheres of carbon dioxide it is converted into the hydrated ortho-carbonate ZrCO₄.2H₂O.