Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the formula Ca(NO₃)₂(H₂O)_x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the

tetrahydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was underst ...

. Both anhydrous and hydrated forms are colourless

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

s. Calcium nitrate is mainly used as a component in

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

s, but it has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an

efflorescence In chemistry, efflorescence (which means "to flower out" in French) is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or ...

where

manure Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nutri ...

contacts

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

in a dry environment as in stables or

caverns A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium

potassium nitrate Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitrat ...

decahydrate.

Production and reactivity

Norgessalpeter was synthesized at

Notodden Notodden () is a List of towns and cities in Norway, city and List of municipalities of Norway, municipality in Vestfold og Telemark Counties of Norway, county, Norway. It is part of the Districts of Norway, traditional region of Øst-Telemark. ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

in 1905 by the

Birkeland–Eyde process The Birkeland–Eyde process was one of the competing industrial processes in the beginning of nitrogen-based fertilizer production. It is a multi-step nitrogen fixation reaction that uses electrical arcs to react atmospheric nitrogen (N2) with ox ...

. Most of the world's calcium nitrate is now made in

Porsgrunn is a city and municipality in Telemark in the county of Vestfold og Telemark in Norway. It is part of the traditional region of Grenland. The administrative centre of the municipality is the city of Porsgrunn. The municipality of Porsgrunn w ...

. It is produced by treating limestone with

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

, followed by neutralization with ammonia: :CaCO₃ + 2 HNO₃ → Ca(NO₃)₂ + CO₂ + H₂O It is also an intermediate product of the Odda Process: :Ca₅(PO₄)₃OH + 10 HNO₃ → 3 H₃PO₄ + 5 Ca(NO₃)₂ + H₂O It can also be prepared from an aqueous solution of

ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...

, and

calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has m ...

: :2 NH₄NO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2 NH₄OH Like related

alkaline earth metal The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...

nitrates, calcium nitrate decomposes upon heating (starting at 500 °C) to release

nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...

: :2 Ca(NO₃)₂ → 2 CaO + 4 NO₂ + O₂ ΔH = 369 kJ/mol

Applications

Use in agriculture

The fertilizer grade (15.5-0-0 + 19% Ca) is popular in the

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...

and

hydroponics Hydroponics is a type of horticulture and a subset of hydroculture which involves growing plants, usually crops or medicinal plants, without soil, by using water-based mineral nutrient solutions in aqueous solvents. Terrestrial or aquatic plan ...

trades; it contains

and

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, as the "double salt" 5Ca(NO3)2.NH4NO3.10H2O. This is called

calcium ammonium nitrate Calcium ammonium nitrate or CAN, also known as nitro-limestone or nitrochalk, is a widely used inorganic fertilizer, accounting for 4% of all nitrogen fertilizer used worldwide in 2007. Production The term "calcium ammonium nitrate" is applied ...

and often the name calcium nitrate prill is used as it always comes in a prilled (granular) form. 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 A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

, air-stable derivative is the urea

complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...

Ca(NO₃)₂·4 C(NH₂)₂ which has been sold as Cal-Urea. Calcium nitrate is also used to control certain plant diseases. For example, dilute calcium nitrate (and

calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Ca ...

) sprays are used to control bitter pit and cork spot in apple trees.

Waste water treatment

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 sulfide. 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.

Concrete

Calcium nitrate is used in set accelerating concrete admixtures. This use with

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

plasticizer A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticiz ...

s.Justines, H. (2010) "Calcium Nitrate as a Multifunctional Concrete Admixture" Concrete Magazine, Vol 44, No. 1, p.34. The nitrate ion leads to formation of iron hydroxide, whose protective layer reduces corrosion of the concrete reinforcement.

Latex coagulant

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.N. C. Dafader, Y. N. Jolly, M. E. Haque, F. Akhtar & M. U. Ahmad: The Role of Coagulants on the Preparation of Dipped film from Radiation Vulcanized Natural Rubber Latex. Polymer-Plastics Technology and Engineering. Volume 38, Issue 2, 1999, pages 267-274. Online: http://www.tandfonline.com/doi/abs/10.1080/03602559909351576

Cold packs

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 storage

Calcium nitrate can be used as a part of molten salt mixtures. Typical are binary mixtures of calcium nitrate and

or ternary mixtures including also

sodium nitrate Sodium nitrate is the chemical compound with the formula . This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. T ...

.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.htmlWIPO 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 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.

References

{{nitrates Calcium compounds Nitrates Nitrate minerals Pyrotechnic oxidizers Pyrotechnic colorants Inorganic fertilizers Concrete admixtures