Hydrogen Sulfates

acid salts of sulfuric acid, H₂S0₄—for example, NaHS0₄. Only hydrogen sulfates of alkaline metals are known. They are produced by moderate heating of sulfates with sulfuric acid: K₂S0₄ + H₂S0₄ = 2KHS0₄. Potassium and sodium hydrogen sulfates lose water upon melting, turning into pyrosulfates—for example, 2KHS0₄ = K₂S₂0₇ + H₂0. Upon further heating, the pyrosulfates break down: K₂S₂0₇ = K₂S0₄ + S0₃. This fact is used to make soluble the strongly annealed oxides of aluminum, chromium, and iron, which are insoluble in acids and which, when melted with hydrogen sulfates (or pyrosulfates), are transformed into sulfates—for example: A1₂0₃ + 3K₂S₂0₇ = A1₂(S0₄)₃ + 3K₂S0₄.