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Magnesium nitrate
Identifiers
CAS number 10377-60-3 Yes check.svgY
15750-45-5 (dihydrate)
13446-18-9 (hexahydrate)
PubChem 25212
UN number 1474
RTECS number OM3750000 (anhydrous)
OM3756000 (hexahydrate)
Properties
Molecular formula Mg(NO3)2
Molar mass 148.30 g/mol
256.30 g/mol (hexahydrate)
Appearance White crystalline solid
Density 2.3 g/cm3 (anhydrous)
1.46 g/cm3, solid (dihydrate)
Melting point

88.9 °C (362 K), hexahydrate

Boiling point

330 °C (603 K) decomp.

Solubility in water 125 g/100 mL
Solubility moderately soluble in ethanol
Refractive index (nD) 1.34 (hexahydrate)
Hazards
MSDS External MSDS
EU Index Not listed
Main hazards Irritant
NFPA 704
NFPA 704.svg
0
2
3
OX
Flash point Non-flammable
Related compounds
Other anions Magnesium sulfate
Magnesium chloride
Other cations Beryllium nitrate
Calcium nitrate
Strontium nitrate
Barium nitrate
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Magnesium nitrate is a hygroscopic salt with the formula Mg(NO3)2. In air, it quickly forms the hexahydrate with the formula Mg(NO3)2·6H2O (and molar weight of 256.41 g/mol). It is very soluble in both water and ethanol.

Contents

Uses

Magnesium nitrate occurs in mines and caverns as nitromagnesite. This form is not common, although it may be present where guano contacts magnesium-rich rock. It is used in the ceramics, printing, chemical and agriculture industries. Its fertilizer grade has 10.5% nitrogen and 9.4% magnesium, so it is listed as 10.5-0-0 + 9.4% Mg. Fertilizer blends containing magnesium nitrate usually have ammonium nitrate, calcium nitrate, potassium nitrate and micronutrients; these blends are used in the greenhouse and hydroponics trade.

Reactions

The magnesium nitrate used in commerce is a man-made product. It can be synthesized in a variety of ways. The reaction between nitric acid and magnesium metal

2 HNO3 + Mg → Mg(NO3)2 + H2

or magnesium oxide

2 HNO3 + MgO → Mg(NO3)2 + H2O

results in magnesium nitrate.

Magnesium hydroxide and ammonium nitrate also react to form magnesium nitrate as ammonia is released as a by-product.

Mg(OH)2 + 2 NH4NO3 → Mg(NO3)2 + 2 NH3 + 2 H2O

Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt. Instead, magnesium nitrate hexahydrate decomposes into magnesium oxide, oxygen, and nitrogen oxides.

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2

The absorption of these nitrogen oxides in water is one possible route way to synthesize nitric acid. Although it is inefficient, it does not require the use of another strong acid.

Anhydrous magnesium nitrate is also used to increase the concentration of nitric acid past its azeotrope of approximately 68% nitric acid and 32% water. It is also occasionally used as a desiccant.

References

External links








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