Anhydrous manganese sulfate is a nearly white orthorhombic crystal.
Manganese sulfate monohydrate is a light pink monoclinic crystal system with a density of 2.95g/mL (25°C), a melting point of 700°C, and a boiling point of 850°C. Unstable under normal temperature and pressure. It is easily soluble in water, with a solubility of 5-10g/100 mL (21°C), and insoluble in ethanol. It starts to lose crystal water when heated to above 200℃, loses most of crystal water at about 280℃, and becomes anhydrous salt melt at 700℃. It begins to decompose at 850°C, and releases sulfur trioxide, sulfur dioxide or oxygen due to different conditions. The remaining black insoluble trimanganese tetroxide is completely decomposed at about 1150°C.
Manganese sulfate tetrahydrate is a translucent light rose-red crystal with a density of 2.107g/mL (25°C), soluble in water.
It begins to decompose at 850°C. Due to different degrees of heating, it can release sulfur trioxide, sulfur dioxide or oxygen, and the residue is manganese dioxide or trimanganese tetroxide. Manganese sulfate can form hydrates containing 1, 2, 3, 4, 5, and 7 crystal waters. When heated to above 280°C, it can lose all of its crystal water and become anhydrous.