Calcium nitrate, also called Norgessalpeter (Norwegian saltpeter), is an inorganic compound with the formula Ca(NO3)2. This colourless salt absorbs moisture from the air and is commonly found as a tetrahydrate. It is mainly used as a component in fertilizers but has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an efflorescence where manure contacts concrete or limestone in a dry environment as in stables or caverns. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium potassium nitrate decahydrate.
Kalksalpeter, nitrocalcite, Norwegian saltpeter, lime nitrate
3D model (JSmol)
|Molar mass||164.088 g/mol (anhydrous) |
236.15 g/mol (tetrahydrate)
|Appearance||colorless solid |
|Density||2.504 g/cm3 (anhydrous)|
1.896 g/cm3 (tetrahydrate)
|Melting point|| 561 °C (1,042 °F; 834 K) (anhydrous)|
42.7 °C (109 °F; 316 K) (tetrahydrate)
|Boiling point||decomposes (anhydrous) |
132 °C (270 °F; 405 K) (tetrahydrate)
1212 g/L (20 °C)
2710 g/L (40 °C)
1050 g/L (0 °C)
1290 g/L (20 °C)
3630 g/L (100 °C)
|Solubility||soluble in ammonia |
almost insoluble in nitric acid
|Solubility in ethanol||51.4 g/100 g (20 °C)|
62.9 g/100 g (40 °C)
|Solubility in methanol||134 g/100 g (10 °C)|
144 g/100 g (40 °C)
158 g/100 g (60 °C)
|Solubility in acetone||16.8 g/kg (20 °C)|
|Safety data sheet||ICSC 1037|
|R-phrases (outdated)||R22, R41|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|302 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Production and reactivityEdit
It is produced by treating limestone with nitric acid, followed by neutralization with ammonia:
- CaCO3 + 2 HNO3 → Ca(NO3)2 + CO2 + H2O
It is also an intermediate product of the Odda Process:
- Ca3(PO4)2 + 6 HNO3 + 12 H2O → 2 H3PO4 + 3 Ca(NO3)2 + 12 H2O
- 2 NH4NO3 + Ca(OH)2 → Ca(NO3)2 + 2 NH4OH
- 2 Ca(NO3)2 → 2 CaO + 4 NO2 + O2 ΔH = 369 kJ/mol
Use in agricultureEdit
The fertilizer grade (15.5-0-0 + 19% Ca) is popular in the greenhouse and hydroponics trades; it contains ammonium nitrate and water, as the "double salt" 5Ca(NO3)2.NH4NO3·10H2O. This is called calcium ammonium nitrate. Formulations lacking ammonia are also known: Ca(NO3)2·4H2O (11.9-0-0 + 16.9 Ca) and the water-free 17-0-0 + 23.6 Ca. A liquid formulation (9-0-0 + 11 Ca) is also offered. An anhydrous, air-stable derivative is the urea complex Ca(NO3)2·4[OC(NH2)2], which has been sold as Cal-Urea.
Waste water treatmentEdit
Calcium nitrate is used in waste water pre-conditioning for odour emission prevention. The waste water pre-conditioning is based on establishing an anoxic biology in the waste water system. In the presence of nitrate, the metabolism for sulfates stops, thus preventing formation of hydrogen sulphide. Additionally easy degradable organic matter is consumed, which otherwise can cause anaerobic conditions downstream as well as odour emissions itself. The concept is also applicable for surplus sludge treatment.
Calcium nitrate is used in set accelerating concrete admixtures. This use with concrete and mortar is based on two effects. The calcium ion accelerates formation of calcium hydroxide and thus precipitation and setting. This effect is used also in cold weather concreting agents as well as some combined plasticizers. The nitrate ion leads to formation of iron hydroxide, whose protective layer reduces corrosion of the concrete reinforcement.
Calcium nitrate is a very common coagulant in latex production, especially in dipping processes. Dissolved calcium nitrate is a part of the dipping bath solution. The warm former is dipped into the coagulation liquid and a thin film of the dipping liquid remains on the former. When now dipping the former into the latex the calcium nitrate will break up the stabilization of the latex solution and the latex will coagulate on the former.
The dissolution of calcium nitrate tetrahydrate is highly endothermic (cooling). For this reason, calcium nitrate tetrahydrate is sometimes used for regenerable cold packs.
Molten salts for heat transfer and storageEdit
Calcium nitrate can be used as a part of molten salt mixtures. Typical are binary mixtures of calcium nitrate and potassium nitrate or ternary mixtures including also sodium nitrate. Those molten salts can be used to replace thermo oil in concentrated solar power plants for the heat transfer, but mostly those are used in heat storage.
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- European Patent Application EP0049761: Use of a ternary mixture of salts as a heat transmitting medium and/or as a heat storage medium. http://www.freepatentsonline.com/EP0049761A1.html
- WIPO Patent Application WO/2014/044652: USE OF A CALCIUM POTASSIUM NITRATE SALT FOR THE MANUFACTURE OF A HEAT TRANSFER FLUID. http://www.freepatentsonline.com/WO2014044652A1.html