Magnesium chlorate
IUPAC name
Magnesium dichlorate hexahydrate
Systematic IUPAC name
Magnesium dichlorate
Other names
  • Magnesium(II) chlorate
3D model (JSmol)
ECHA InfoCard 100.030.634 Edit this at Wikidata
EC Number
  • 233-711-1
UN number 2723
  • InChI=1S/2ClHO3.Mg/c2*2-1(3)4;/h2*(H,2,3,4);/q;;+2/p-2
  • (dihydrate): InChI=1S/2ClHO3.Mg.2H2O/c2*2-1(3)4;;;/h2*(H,2,3,4);;2*1H2/q;;+2;;/p-2
  • (hexahydrate): InChI=1S/2ClHO3.Mg.6H2O/c2*2-1(3)4;;;;;;;/h2*(H,2,3,4);;6*1H2/q;;+2;;;;;;/p-2
  • Cl(=O)(=O)[O-].Cl(=O)(=O)[O-].[Mg+2]
  • (dihydrate): O.O.[Mg+2].[O-]Cl(=O)=O.[O-]Cl(=O)=O
  • (hexahydrate): O.O.O.O.O.O.[O-]Cl(=O)=O.[O-]Cl(=O)=O.[Mg+2]
Molar mass 191.20 g/mol
Appearance White crystalline solid
Density 1.747 g/cm3 (hexahydrate)[1]
Melting point 35 °C (95 °F; 308 K)[2]
Boiling point 120 °C (248 °F; 393 K)[2] (decomposition)
114 g/100 ml (0 °C)
123 g/100 ml (10 °C)
135 g/100 ml (20 °C)
155 g/100 ml (30 °C)
178 g/100 ml (50 °C)
242 g/100 ml (60 °C)
268 g/100 ml (100 °C)[2]
Solubility in acetone Soluble
a = 6.39 Å, b = 6.51 Å, c = 13.90 Å
α = 90°, β = 100.3°, γ = 90°
590.1 Å3
GHS labelling:
GHS07: Exclamation mark
H302, H332
Lethal dose or concentration (LD, LC):
6348 mg/kg (rat, oral)
Related compounds
Other cations
Calcium chlorate
Strontium chlorate
Barium chlorate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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.[3]


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.[4] The magnesium chlorate can be purified by exploiting its solubility in acetone.[4]


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.[2]

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.[1]


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.[5]


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


  1. ^ a b c Kossev, K; Tsvetanova, L.; Dimowa, L.; Nikolova, R.; Shivachev, B. (2013). "Synthesis and Crystal Structure of Magnesium Chlorate Dihydrate and Magnesium Chlorate Hexahydrate". Bulgarian Chemical Communications. 45: 543–548.
  2. ^ a b c d Joseph William Mellor (1922). Supplement to Mellor's Comprehensive Treatise on Inorganic and Theoretical Chemistry: suppl. 3. K, Rb, Cs, Fr. Longmans, Green and Company.
  3. ^ Ojha, Lujendra; Wilhelm, Mary Beth; Murchie, Scott L.; McEwen, Alfred S.; Wray, James J.; Hanley, Jennifer; Massé, Marion; Chojnacki, Matt (2015). "Spectral evidence for hydrated salts in recurring slope lineae on Mars". Nature Geoscience. 8 (11): 829–832. Bibcode:2015NatGe...8..829O. doi:10.1038/ngeo2546.
  4. ^ a b Herbert Maxim (1948). The electrolytic production of magnesium chlorate and perchlorate. the Department of Chemical Engineering: University of Southern California.
  5. ^ "MAGNESIUM CHLORATE". National Center for Advancing Translational Sciences. U.S. Department of Health & Human Services. Retrieved 27 August 2021.