Potassium dichromate (K₂Cr₂O₇), commonly known as potassium bichromate or red vitriol potassium, is an orange-red triclinic or acicular crystal. It has a melting point of 398°C and a boiling point of 500°C (with decomposition). It is soluble in water, forming an acidic solution that is corrosive, toxic, and strongly oxidizing.
Sodium dichromate (Na₂Cr₂O₇·2H₂O), commonly known as sodium bichromate or red vitriol sodium, is a red monoclinic prismatic or acicular crystal. It has a melting point of 320°C and a boiling point of 600°C (with decomposition). At 100°C, it loses its crystal water to form the anhydrous form. The anhydrous form has a melting point of 356.7°C and decomposes at 400°C to release oxygen. It is highly hygroscopic and readily soluble in water, forming a corrosive and toxic acidic solution that is strongly oxidizing.
