Magnesium perchlorate

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Magnesium perchlorate
Magnesium perchlorate
3D model (Jmol)
ECHA InfoCard 100.030.086
RTECS number SC8925000
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
Safety data sheet External MSDS
R-phrases R8, R36, R37, R38
S-phrases S17, S26, S27, S36, S37, S39
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
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. It is also a superior drying agent for gas analysis.

Magnesium perchlorate decomposes at 250 °C.[1] The heat of formation is -568.90 kJ mol−1.[2]

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,[3][4] but is no longer advised, for use as a general desiccant, due to hazards inherent in perchlorates.[5] It is dried by heating at 220 °C under vacuum.

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

In 2011, a study of the Georgia Institute of technology unveils the presence of magnesium perchlorate on Planet Mars. It would be a proof of the presence of water on the planet. Being a drying agent, magnesium perchlorate retains water of the atmosphere to release it when conditions are favorable and temparature is above 250K.


  1. ^ CRC Handbook
  2. ^ Lange's
  3. ^ H. H. Willard, G. F. Smith (1922). "The Preparation and Properties of Magnesium Perchlorate and its Use as a Drying Agent". Journal of the American Chemical Society. 44 (10): 2255–2259. doi:10.1021/ja01431a022. 
  4. ^ L. Wu, H. He (1994). "Preparation of perlite-based magnesium perchlorate desiccant with colour indicator". The Chemical Educator. 41 (5): 633–637. doi:10.1016/0039-9140(94)80041-3. 
  5. ^ W. L. F. Armarego and C. Chai (2003). Purification of laboratory chemicals. Oxford: Butterworth-Heinemann. ISBN 0-7506-7571-3.