The synthesis of silver(II) sulfate (AgSO4) with a divalent silver ion instead of a monovalent silver ion was first reported in 2010[9] by adding sulfuric acid to silver(II) fluoride (HF escapes). It is a black solid that decomposes exothermically at 120 °C with evolution of oxygen and the formation of the pyrosulfate. AgF2 + H2SO4 → AgSO4 + 2 HF 4 AgSO4 → 2 Ag2S2O7 + O2