. "French patent application FR-A-2 764 211 describes the synthesis and use of heteropolyanions with formula MxAB11O40M???C(Z-2x) in which M is cobalt or nickel, A is phosphorus, silicon or boron and B is molybdenum or tungsten, M??? is cobalt, iron, nickel, copper or zinc, and C is an H+ ion or an alkylammonium cation, x takes the value 0 to 4.5 and z takes a value between 7 and 9." . . .