- Structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting point
- Boiling point
- Density
- Solubility
- Heating effect
- Obtaining
- Location in nature
- Applications
- In recent studies
- In disease studies
- References
The magnesium nitrate is an inorganic solid with the chemical formula Mg (NO 3) 2. It is an ionic compound formed by the union of a magnesium cation Mg 2+ and two nitrate anions NO 3 -.
Mg (NO 3) 2 is a white crystalline solid. It is very hygroscopic, that is, it absorbs water from the environment easily. When remaining in contact with the surrounding air, it tends to form its hexahydrate Mg (NO 3) 2 • 6H 2 O.
Magnesium nitrate Mg (NO 3) 2 powder. Ondřej Mangl. Source: Wikimedia Commons.
Magnesium nitrate hexahydrate Mg (NO 3) 2 • 6H 2 O has in its crystalline structure 6 molecules of water H 2 O for each molecule of Mg (NO 3) 2. Magnesium nitrate is found in caves and mines in the form of the mineral nitromagnesite.
Mg (NO 3) 2 is obtained commercially by reacting magnesium metal Mg with nitric acid HNO 3.
It has a wide variety of uses, such as in agriculture as a fertilizer because it provides nutrients for plants such as nitrogen (N) and magnesium (Mg).
It is used in the fireworks or pyrotechnics industry and also in obtaining concentrated nitric acid. It is used in chemical analysis, in physics experiments, and in medical and scientific studies.
Structure
Anhydrous magnesium nitrate is made up of one Mg 2+ magnesium cation and two NO 3 - nitrate anions.
Structure of Mg (NO 3) 2. Edgar181. Source: Wikimedia Commons.
The magnesium ion Mg 2+ has the electronic configuration: 1s 2, 2s 2 2p 6, 3s 0, since it has given up the two electrons of the outermost shell (3s). This conformation is very stable.
The NO 3 - ion has a flat and symmetrical structure.
Planar structure of the nitrate ion NO 3 -. The dotted lines indicate the equitable distribution of electrons between the three NO bonds. Benjah-bmm27. Source: Wikimedia Commons.
In the structure of NO 3 - the negative charge is continuously distributed between the three oxygen atoms.
Resonance structures of the nitrate ion NO 3 -, to explain the equitable distribution of the negative charge between the three oxygen atoms. Benjah-bmm27. Source: Wikimedia Commons.
Nomenclature
-Anhydrous magnesium nitrate: Mg (NO 3) 2
-Magnesium nitrate dihydrate: Mg (NO 3) 2 • 2H 2 O
-Magnesium nitrate hexahydrate: Mg (NO 3) 2 • 6H 2 O
-Magnesium dinitrate
Properties
Physical state
-Mg (NO 3) 2 anhydrous: white solid, cubic crystals.
-Mg (NO 3) 2 dihydrate: white crystalline solid.
-Mg (NO 3) 2 hexahydrate: colorless solid, monoclinic crystals
Molecular weight
-Mg (NO 3) 2 anhydrous: 148.31 g / mol
-Mg (NO 3) 2 hexahydrate: 256.41 g / mol
Melting point
-Mg (NO 3) 2 hexahydrate: 88.9 ºC
Boiling point
-Mg (NO 3) 2 hexahydrate: does not boil, decomposes at 330 ºC
Density
-Mg (NO 3) 2 anhydrous: 2.32 g / cm 3
-Mg (NO 3) 2 dihydrate: 1.456 g / cm 3
-Mg (NO 3) 2 hexahydrate: 1,464 g / cm 3
Solubility
Anhydrous magnesium nitrate is very soluble in water: 62.1 g / 100 mL at 0 ºC; 69.5 g / 100 mL at 20 ° C. It is also very hygroscopic, being in contact with air quickly forms the hexahydrate.
Mg (NO 3) 2 dihydrate is also very soluble in water and in ethanol. It is hygroscopic.
Mg (NO 3) 2 hexahydrate is also very soluble in water. It is moderately soluble in ethanol. It is the most stable of the three in contact with air, that is, of the three it is the one that absorbs the least water from the environment.
Heating effect
When an aqueous solution of Mg (NO 3) 2 is subjected to evaporation of the water, the salt that crystallizes is the hexahydrate: Mg (NO 3) 2 • 6H 2 O. Hexahydrate means that in the solid each molecule of Mg (NO 3) 2 is attached to 6 water molecules.
There is also the dihydrate Mg (NO 3) 2 • 2H 2 O, in which the solid Mg (NO 3) 2 is bound to 2 water molecules.
Heating the Mg (NO 3) 2 • 6H 2 O hexahydrate does not obtain the anhydrous salt, since magnesium nitrate has a high affinity for water.
For this reason, when heated above its melting point, it initially forms a mixed salt of magnesium nitrate and hydroxide Mg (NO 3) 2 • 4Mg (OH) 2.
This mixed salt, upon reaching 400 ºC, decomposes to magnesium oxide MgO and nitrogen oxide gases are released.
Obtaining
It can be prepared by reacting magnesium carbonate MgCO 3 with nitric acid HNO 3, giving off carbon dioxide CO 2:
MgCO 3 + 2 HNO 3 → Mg (NO 3) 2 + CO 2 ↑ + H 2 O
It can also be obtained with Mg (OH) 2 magnesium hydroxide and nitric acid:
Mg (OH) 2 + 2 HNO 3 → Mg (NO 3) 2 + 2 H 2 O
Commercially it is obtained in several ways:
1- Reacting the magnesium metal Mg with nitric acid HNO 3.
2- By reacting magnesium oxide MgO with nitric acid HNO 3.
3- Uniting magnesium hydroxide Mg (OH) 2 and ammonium nitrate NH 4 NO 3, forming the magnesium nitrate with the release of ammonia NH 3.
Location in nature
Mg (NO 3) 2 hexahydrate occurs naturally in mines and caves or caves in the form of the mineral nitromagnesite.
This mineral is present when guano comes into contact with magnesium-rich rocks. Guano is the material resulting from the excrement of seabirds and seals in very dry environments.
Applications
Mg (NO 3) 2 hexahydrate is used in the ceramic, chemical and agricultural industries.
This compound is a fertilizer because it provides nitrogen (N), which is one of the three basic elements required by plants, and magnesium (Mg), which is also an important secondary component for them.
In this way it is used with other ingredients in greenhouses and in hydroponic cultivation. The latter consists of growing the plants in an aqueous solution with fertilizer salts instead of soil.
Hydroponic cultivation. The channels through which the aqueous solution with fertilizer salts such as magnesium nitrate Mg (NO 3) 2 can be observed. Author: Marsraw. Source: Pixabay.
It is also used as a catalyst in obtaining petrochemical compounds. It allows adjusting the viscosity in certain processes. Anhydrous magnesium nitrate is used in pyrotechnics, that is, for the manufacture of fireworks.
Fireworks contain magnesium nitrate Mg (NO 3) 2. Author: Free-Photos. Source: Pixabay.
Anhydrous magnesium nitrate is a dehydrating agent. It is used, for example, to obtain concentrated nitric acid, as it removes water and concentrates acid vapors up to 90-95% HNO 3.
Concentrated nitric acid. The original uploader was Fabexplosive at Italian Wikipedia.. Source: Wikimedia Commons.
It is also used to coat ammonium nitrate and allow pearling of such compressed material.
It is useful in the formulation of inks, toner (black powder used in photocopying systems) and coloring products. It serves as a magnesium standard in analytical chemistry.
The cerium magnesium nitrate salt Mg (NO 3) 2 • Ce (NO 3) 3 is of interest in low-temperature physics experiments, as it is used as a coolant in adiabatic demagnetization experiments (without heat transfer).
This magnesium and cerium salt has been used to establish extremely low temperature levels on the Kelvin scale (close to absolute zero).
In recent studies
Several researchers have used Mg (NO 3) 2 in compositions with synthetic and natural polymers to increase the conductivity in magnesium ion batteries.
It has also been investigated in the construction of supercapacitors for the storage of high power energy.
In disease studies
Magnesium nitrate has been administered to laboratory rats with arterial hypertension (high pressure) and found to effectively lower blood pressure and attenuate or soften the effects of complications of this disease.
It has also shown protective effects against neurological disorders (neuronal disorders) and against death in rats during carotid artery plugging processes.
References
- Qian, M. et al. (2018). Extraordinary Porous Few-Layer Carbons of High Capacitance from Pechini Combustion of Magnesium Nitrate Gel. ACS Appl Mater Interfaces 2018, 10 (1): 381-388. Recovered from ncbi.nlm.nih.gov.
- Manjuladevi, R. et al. (2018). A study on blend polymer electrolyte based on poly (vynil alcohol) -poly (acrylonitrile) with magnesium nitrate for magnesium battery. Ionics (2018) 24: 3493. Recovered from link.springer.com.
- Kiruthika, S. et al. (2019). Eco-friendly biopolymer electrolyte, pectin with magnesium nitrate salt, for application in electrochemical devices. J Solid State Electrochem (2019) 23: 2181. Recovered from link.springer.com.
- Vilskerts R. et al. (2014). Magnesium nitrate attenuates blood pressure rise in SHR rats. Magnes Res 2014, 27 (1): 16-24. Recovered from ncbi.nlm.nih.gov.
- Kuzenkov VS and Krushinskii AL (2014). Protective effect of magnesium nitrate against neurological disorders provoked by cerebral ischemia in rats. Bull Exp Biol Med 2014, 157 (6): 721-3. Recovered from ncbi.nlm.nih.gov.
- Ropp, RC (2013). Group 15 (N, P, As, Sb and Bi) Alkaline Earth Compounds. Magnesium Nitrate. In Encyclopedia of the Alkaline Earth Compounds. Recovered from sciencedirect.com.
- Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Volume 1. Fourth Edition. John Wiley & Sons.
- US National Library of Medicine. (2019). Magnesium Nitrate. Recovered from: pubchem.ncbi.nlm.nih.gov.