Calcium ammonium nitrate or CAN, also known as nitro-limestone or nitrochalk, is a widely used inorganic

fertilizer A fertilizer or fertiliser 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 liming materials or other non-nutrient soil amendments. Man ...

, accounting for 4% of all nitrogen fertilizer used worldwide in 2007.

Production

The term "calcium ammonium nitrate" is applied to multiple different, but closely related formulations. One variety of calcium ammonium nitrate is made by adding powdered

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

ammonium nitrate Ammonium nitrate is a chemical compound with the 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, but does not form hydrates. It is predominantly us ...

; another, fully water-soluble version, is a mixture of

calcium nitrate Calcium nitrate are inorganic compounds with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhydrous and hydrated forms are colourless salts. Hydrated ...

and ammonium nitrate, which crystallizes as a

hydrate 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 understo ...

double salt A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula ) and Tutton's salts (with the general formula ). Other examples include potassium sodium tartrate, a ...

:Yara Calcinit Technical Data
/ref> 5Ca(NO₃)₂•NH₄NO₃•10H₂O. Unlike ammonium nitrate, these calcium containing formulations are not classified as oxidizers by the United States Department of Transportation. Consumption of CAN was 3.54 million tonnes in 1973/74, 4.45 million tonnes in 1983/84, 3.58 million tonnes in 1993/94. Production of calcium ammonium nitrate consumed 3% of world ammonia production in 2003.

Physical and chemical properties

Calcium ammonium nitrate is

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

. Its dissolution in water is

endothermic An endothermic process is a chemical or physical process that absorbs heat from its surroundings. In terms of thermodynamics, it is a thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, ...

, leading to its use in some instant cold packs.

Use

Most calcium ammonium nitrate is used as a fertilizer. Fertilizer grade CAN contains roughly 8% calcium and 21-27% nitrogen. CAN is preferred for use on

acid soil Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the nega ...

s, as it acidifies soil less than many common nitrogen fertilizers. It is also used in place of ammonium nitrate where ammonium nitrate is banned. Calcium ammonium nitrate is used in some instant cold packs as an alternative to

. Calcium ammonium nitrate has seen use in

improvised explosives An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechan ...

. The CAN is not used directly, but is instead first converted to ammonium nitrate; "More than 85% of the IEDs used against U.S. forces in Afghanistan contain homemade explosives, and of those, about 70% are made with ammonium nitrate derived from calcium ammonium nitrate". CAN and other fertilizers were banned in the

Malakand Division Malakand Division is an administrative division of Khyber Pakhtunkhwa province of Pakistan. Malakand is the second-largest division by population while Mingora, its capital, is the third largest city in the province. CNIC code of Malakand Divis ...

and in

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...

following reports of its use by militants to make explosives. Due to these bans, "

Potassium chlorate Potassium chlorate is the inorganic compound with the molecular formula KClO3. In its pure form, it is a white solid. After sodium chlorate, it is the second most common chlorate in industrial use. It is a strong oxidizing agent and its most impor ...

— the stuff that makes matches catch fire — has surpassed fertilizer as the explosive of choice for insurgents."Potassium chlorate — the stuff that makes matches catch fire — has surpassed fertilizer as the explosive of choice for insurgents.
/ref>

References

{{reflist Calcium compounds Ammonium compounds Nitrates Inorganic fertilizers Double salts