Chlormolybdic Acids

The compound MoOCl₂(OH)₂, molybdenum hydroxy chloride or dichlormolybdic acid, is readily obtained by passing hydrogen chloride over any heated oxygenated compound of molybdenum. Fine white unstable needles are obtained, the aqueous solution of which deposits on evaporation amorphous molybdic anhydride. The substance is also soluble in ether, with which it forms a crystalline compound. An alternative method of preparation of dichlormolybdic acid consists in cooling a solution of molybdic acid saturated with hydrochloric acid.

Trichlormolybdic acid, MoOCl₃.OH.7H₂O, is obtained by the action of fuming hydrochloric acid on the hydroxydichloride.

Caesium, rubidium, ammonium, and certain organic trichlormolybdates have been prepared.

The hydroxychlorides Mo₃Cl₄(OH)₂.2H₂O and Mo₃Cl₄(OH)₂.8H₂O, or [Mo₃Cl₄.2H₂O](OH)₂.6H₂O, are obtained by precipitation with acetic acid, before or after saturation with carbon dioxide respectively, of a solution of molybdenum dichloride in potassium hydroxide.