The present invention relates to a process for separating at least one metal compound and/or a component thereof from a mixture, said process comprising contacting the said mixture with a heteropoly acid or heteropoly acid anion, thereby producing a precipitate comprising the heteropoly acid or heteropoly acid anion and the metal compound and/or a component thereof. The present invention further relates to a process for the purification of a mixture containing at least one metal compound, said process comprising contacting the said mixture with a heteropoly acid or heteropoly acid anion, thereby producing a precipitate that is substantially insoluble in the said reaction mixture and recovering the reaction mixture.