The first α-Keggin anion, ammonium phosphomolybdate ((NH4)3was first reported by Berzelius in 1826. In 1892, Blomstrand proposed the structure of phosphomolybdic acid and other poly-acids as a chain or ring configuration. Alfred Werner, using the coordination compounds ideas of Copaux, attempted to explain the structure of silicotungstic acid. He assumed a central group, [SiO44− ion, enclosed by four where R is a unipositive ion. The [RW2O6+ are linked to the central group by primary valences. Two more R2W2O7 groups were linked to the central group by secondary valences. This proposal accounted for the characteristics of most poly-acids, but not all.