Vanadium Pentoxide: Mottramite Sandstone Digested in Hydrochloric Acid, through Ammonium Metavanadate (Roscoe 1913)

The Cheshire Keuper sandstone carries a film of mottramite on its grains. Strong hydrochloric acid takes the vanadium off; ammonium chloride throws it down as ammonium metavanadate, and roasting that leaves vanadium pentoxide. Dissolving in ammonia and recrystallising cleans it. Result: vanadium pentoxide free from phosphorus, the start of the vanadium chain. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), p. 913. Not given: amounts, times, temperatures. Picture drawn by Youblob.