Magnesium perchlorate

Magnesium perchlorate
Magnesium perchlorate
3D model (JSmol)
ECHA InfoCard 100.030.086 Edit this at Wikidata
RTECS number
  • SC8925000
  • InChI=1S/2ClHO4.Mg/c2*2-1(3,4)5;/h2*(H,2,3,4,5);/q;;+2/p-2 checkY
  • InChI=1/2ClHO4.Mg/c2*2-1(3,4)5;/h2*(H,2,3,4,5);/q;;+2/p-2
  • [Mg+2].O=Cl(=O)(=O)[O-].[O-]Cl(=O)(=O)=O
Molar mass 223.206 g/mol
Appearance white powder,
Odor odorless
Density 2.21 g/cm3 (anhydrous)
1.98 g/cm3 (hexahydrate)
Melting point 251 °C (484 °F; 524 K) (anhydrous)
95-100 °C (hexahydrate)
Boiling point decomposition
99.3 g/100 mL
Solubility in ethanol 23.96 g/100 mL
Occupational safety and health (OHS/OSH):
Main hazards
GHS labelling:
GHS03: OxidizingGHS07: Exclamation mark
H272, H315, H319, H335
P220, P261, P305+P351+P338
NFPA 704 (fire diamond)
Safety data sheet (SDS) External MSDS
Related compounds
Other cations
Calcium perchlorate
Barium perchlorate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Magnesium perchlorate is a powerful oxidizing agent, with the formula Mg(ClO4)2. The salt is also a superior drying agent for gas analysis.

Magnesium perchlorate decomposes at 250 °C. The heat of formation is -568.90 kJ/mol.

The enthalpy of solution is quite high, so reactions are done in large amounts of water to dilute it.

It is sold under the trade name anhydrone. Manufacture of this product on a semi-industrial scale was first performed by G. Frederick Smith in his garage in Urbana Illinois, but later at a permanent facility in Columbus, OH called G. Frederick Smith Chemical Co. He sold the magnesium perchlorate to A. H. Thomas Co., now Thomas Scientific, under the trade name Dehydrite.


It is used as desiccant to dry gas or air samples, but is no longer advised, for use as a general desiccant, due to hazards inherent in perchlorates. It is dried by heating at 220 °C under vacuum.

Magnesium perchlorate and other perchlorates have been found on Mars. Being a drying agent, magnesium perchlorate retains water from the atmosphere and may release it when conditions are favorable and temperature is above 273 K. Briny solutions that contain salts such as magnesium perchlorate have a lower melting point than that of pure water. Therefore the abundance of magnesium and other perchlorate salts on Mars could support the theory that liquid aqueous solutions might exist on or below the surface, where temperature and pressure conditions would ordinarily cause the water to freeze.


Magnesium perchlorate is produced by the reaction of magnesium hydroxide and perchloric acid.

This page was last updated at 2024-04-17 21:25 UTC. Update now. View original page.

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