Manganese(II) chloride

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Manganese(II) chloride
Names
IUPAC name
Manganese(II) chloride
Other names
Manganese bichloride
Manganese dichloride
Manganous chloride
Scacchite
Properties
MnCl2
Molar mass 125.844 g/mol (anhydrous)
161.874 g/mol (dihydrate)
197.91 g/mol (tetrahydrate)
Appearance Off-white solid (anhydrous)
Pink solid (hydrated)
Odor Odorless
Density 2.977 g/cm3 (anhydrous)
2.27 g/cm3 (dihydrate)
2.01 g/cm3 (tetrahydrate)
Melting point anhydrous
654 °C (1,209 °F; 927 K)
dihydrate
135 °C (275 °F; 408 K) (decomposes)
tetrahydrate
58 °C (136 °F; 331 K) (decomposes)
Boiling point 1,225 °C (2,237 °F; 1,498 K)
63.4 g/100 ml (0 °C)
73.9 g/100 ml (20 °C)
88.5 g/100 ml (40 °C)
123.8 g/100 ml (100 °C)
Solubility Soluble in ethanol, methanol
Slightly soluble in pyridine
Insoluble in ethers, halocarbons, hydrocarbons
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Sigma-Aldrich (anhydrous)
Sigma-Aldrich (tetrahydrate)
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
250-275 mg/kg (rat, oral)
1,715 mg/kg (mouse, oral)
Related compounds
Related compounds
Chromium(III) chloride
Iron(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Manganese(II) chloride is the chemical compound with the formula MnCl2, a salt of manganese metal. It is available as anhydrous, monohydrate, dihydrate and tetrahydrate.

Manganese(II) chloride occurs in nature as the rare mineral scacchite, first identified in the volcanic fumaroles of Vesuvius.

Properties

Chemical

Manganese(II) chloride is a weak Lewis acid.

Addition of organic ligands to solutions of manganese(II) and oxidation in air will give Mn(III) complexes.

Physical

Manganous chloride is an odorless pink solid, soluble in water, but insoluble in most organic solvents.

Availability

Manganese(II) chloride is sold by chemical suppliers.

Preparation

Manganese chloride is produced by treating manganese dioxide with concentrated hydrochloric acid.

MnO2 + 4 HCl → MnCl2 + 2 H2O + Cl2

Since the reaction releases chlorine gas, this must be done outside or in a fumehood.

Chlorine-free routes involve adding the hydrochloric acid to manganese metal or manganese carbonate/hydroxide.

Mn + 2 HCl → MnCl2 + H2
Mn(OH)2 + 2 HCl → MnCl2 + 2 H2O
MnCO3 + 2 HCl → MnCl2 + H2O + CO2

Manganese carbonate can be obtained by reacting manganese dioxide with oxalic acid.

The double replacement reaction between manganese(II) sulfate and calcium chloride will give manganese dichloride, while calcium sulfate precipitates out of the reaction. Manganese sulfate can be easily obtained by bubbling sulfur dioxide in an aqueous suspension of manganese dioxide.

MnSO4 + CaCl2 → MnCl2 + CaSO4

The resulting suspension is filtered to remove the insoluble calcium sulfate. The filtered MnCl2 solution is placed on a heating bath, where water is evaporated to concentrate it. The concentrated solution is cooled to crystallize the compound. If the source of manganese dioxide used is batteries, multiple recrystallizations are required to remove iron impurities.

All the above procedures will give the hydrated form of this salt. To obtain the anhydrous form, the compound is heated in an oxygen-less or free atmosphere, like under inert gas or an organic solvent like methanol, or in a stream of hydrogen chloride.

A route to obtain the anhydrous form involves reacting manganese metal with dry hydrogen chloride or chlorine gas at high temperatures.

Mn + 2 HCl → MnCl2 + H2
Mn + Cl2 → MnCl2

Projects

  • Make dry cell batteries
  • Make Mn coordination complexes
  • Make sodium permanganate
  • Make manganese dioxide

Handling

Safety

Manganese dichloride is harmful in ingested. Long-term exposure to manganese dust or compounds will lead to manganese poisoning or manganism.

Storage

Manganese(II) chloride doesn't have special storage conditions, any clean plastic container is sufficient.

Disposal

Manganese(II) chloride should be precipitated to the less soluble manganese dioxide and then sent to waste disposal centers. Waste batteries centers might also pick up manganese waste.

Diluted manganese chloride can be used as source of manganese for plants.

References

Relevant Sciencemadness threads