Magnesium chlorate

Magnesium chlorate refers to inorganic compounds with the chemical formula Mg(ClO3)2(H2O)x. The anhydrous (x = 0), dihydrate (x = 2), and hexahydrate (x = 6) are known. These are thermally labile white solids. The hexahydrate has been identified on the Martian surface.

Production
Samples of magnesium chlorate were first claimed in 1920 as the result of treating magnesium oxide with chlorine. A more modern method involves electrolysis of magnesium chloride. The magnesium chlorate can be purified by exploiting its solubility in acetone.

Properties
The hexahydrate Mg(ClO3)2·6H2O decomposes to the tetrahydrate at 35 °C. At 65 °C, it dehydrates to the dihydrate, then at 80 °C forms a basic salt. If further heated to 120 °C it decomposes to water, oxygen, chlorine, and magnesium oxide.

As confirmed by X-ray crystallography, the di- and hexahydrates feature octahedral Mg2+ centers. The other ligands are water, exclusively in the hexahydrate. In the dihydrate, chlorate is also coordinated and functions as a bridging ligand.

Uses
Magnesium(II) chlorate is used as a powerful desiccant and a defoliant for cotton, potato, and rice. It is also found as a lubricant in eye drops as an inactive ingredient.

Hazards
Magnesium chlorate is an oxidizer and can in principle form explosive mixtures.