Magnesium nitrate refers to inorganic compounds with the formula Mg(NO3)2(H2O)x, where x = 6, 2, and 0. All are white solids. The anhydrous material is hygroscopic, quickly forming the hexahydrate upon standing in air. All of the salts are very soluble in both water and ethanol.
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||148.32 g/mol (anhydrous)|
184.35 g/mol (dihydrate)
256.41 g/mol (hexahydr.)
|Appearance||White crystalline solid|
|Density||2.3 g/cm3 (anhydrous) |
2.0256 g/cm3 (dihydrate)
1.464 g/cm3 (hexahydrate)
|Melting point||129 °C (264 °F; 402 K) (dihydrate) |
88.9 °C (hexahydrate)
|Boiling point||330 °C (626 °F; 603 K) decomposes|
|71 g/100 mL (25 °C)|
|Solubility||moderately soluble in ethanol, ammonia|
Refractive index (nD)
Heat capacity (C)
|141.9 J/mol K|
|164 J/mol K|
Std enthalpy of
Gibbs free energy (ΔfG⦵)
|Occupational safety and health (OHS/OSH):|
|H272, H315, H319, H335|
|P210, P220, P221, P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P403+P233, P405, P501|
|NFPA 704 (fire diamond)|
|Safety data sheet (SDS)||External MSDS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is ?)
The magnesium nitrate used in commerce is made by the reaction of nitric acid and various magnesium salts.
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 also have ammonium nitrate, calcium nitrate, potassium nitrate and micronutrients in most cases; these blends are used in the greenhouse and hydroponics trade.
Magnesium nitrate reacts with alkali metal hydroxide to form the corresponding nitrate:
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:
It is also occasionally used as a desiccant.