Magnesium Nitrate Hexahydrate [Mg(NO3)2.6H2O]

2015-7-8 6:14:12 Nitrates

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.


Chemical FormulaMg(NO3)2.6H2O

Molecular Weight256

CAS No.13446-18-9


Physical and Chemical Characteristics (Typical)


Standards (Agricultural Grade)

Physical Property

White crystal granule, soluble in water easily



Water Insolubles  ≤


Iron (Fe) ≤


Heavy Metals(Pb) ≤


PH Value


MgO (Mg) ≥


Nitrogen (N)≥




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Magnesium nitrate occurs in mines and caverns as nitromagnesite. This form is not common, although it may be present where guanocontacts 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 andhydroponics trade.


The magnesium nitrate used in commerce is a man-made product. It can be synthesized in a variety of ways. The reaction betweennitric 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


Magnesium Nitrate reacts with alkali metal hydroxide to form the corresponding nitrate: Mg(NO3)2 + 2 NaOH → Mg(OH)2 + 2 NaNO3.

Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition 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 to synthesize nitric acid. Although inefficient, this method does not require the use of any 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.































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