Magnesium chloride

Magnesium chloride

Names
IUPAC name Magnesium chloride
Systematic IUPAC name Magnesium chloride
Other names Nigari salt
Identifiers
Jmol-3D images	Image
SMILES [Mg+2].[Cl-].[Cl-]
Properties
Chemical formula	MgCl2
Molar mass	95.211 g/mol (anhydrous) 203.31 g/mol (hexahydrate)
Appearance	white or colorless crystalline solid
Density	2.32 g/cm3 (anhydrous) 1.569 g/cm3 (hexahydrate)
Melting point	714 °C (1,317 °F; 987 K) 117 °C (243 °F; 390 K) (hexahydrate)
Solubility in water	anhydrous 52.9 g/100 mL (0 °C) 54.3 g/100 mL (20 °C) 72.6 g/100 mL (100 °C) hexahydrate 167 g/100 mL (20 °C)
Solubility	slightly soluble in acetone, pyridine
Solubility in ethanol	7.4 g/100 mL (30 °C)
Thermochemistry
Std molar entropy (So298)	89.88 J/mol K
Std enthalpy of formation (ΔfHo298)	-641.1 kJ/mol
Hazards
Safety data sheet	ICSC 0764
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	2800 mg/kg (oral, rat)
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Magnesium chloride also known as Nigari is a chemical compounds with the formula MgCl₂.

Properties

Chemical

Magnesium chloride will react with calcium hydroxide to give magnesium hydroxide and calcium chloride:

MgCl_2(aq) + Ca(OH)₂ → Mg(OH)_2(pp) + CaCl_2(aq)

Physical

Magnesium chloride is a white hygroscopic solid, soluble in water but poorly soluble in organic solvents, such as ethanol.

Availability

Magnesium chloride is available as tofu coagulant, more exactly as "Nigari flakes" or "Nigari salt".

Magnesium chloride sometimes occurs naturally as the mineral bischofite.

Preparation

Magnesium chloride can be prepared by reacting hydrochloric acid with magnesium or magnesium carbonate.

A cheaper way involves the reaction of magnesium sulfate (Epsom salt) with calcium chloride. The resulting calcium sulfate is filtered off and the magnesium chloride solution is gently heated at 100 °C to remove the water. Since a small amount will hydrolyze, injecting dry hydrogen chloride gas will regenerate the magnesium chloride. Magnesium carbonate can also be used instead of Epsom salt, but since it's very poorly soluble, the reaction needs lengthy boiling under reflux (similarly to converting barium sulfate to carbonate).

Projects

• Make elemental magnesium (electrolysis of molten MgCl₂ at over 714 °C, or of an eutectic mixture of MgCl₂, KCl, NaCl at 475 °C)
• Home-made desiccator

Handling

Safety

Magnesium chloride is deliquescent and its anhydrous form may cause irritations on contact with skin, eyes or mouth.

Storage

Because of its hygroscopicity, magnesium chloride must be stored in an air-tight container.

Disposal

Magnesium chloride can be safely poured down the drain.

References

Relevant Sciencemadness threads

• failed attempt for magnesium chloride.
• Magnesium Chloride to Magnesium Metal