Calcium nitrite 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
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
. In this compound, as in all
nitrites
The nitrite ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also r ...
,
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
is in a +3 oxidation state. It has many applications such as
antifreeze
An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, all ...
, rust inhibitor of steel and wash
heavy oil.
Properties
At room temperature and pressure, the compound is an odorless white or light yellowish powder. It is freely
soluble
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solubil ...
in water with a
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
of 2.26 g/cm
3. Its
melting point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
is of 390 °C and it is stable under ordinary conditions of use and storage. It is also characterized for its strong
oxidizing
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
character.
Nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
(III) is a stronger
oxidizer
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
than
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
(V) because at valence III it has less electrons to recover than nitrate at valence V and so the number of electrons to capture is lower. This facilitates the electronic transfer and increases the
kinetic
Kinetic (Ancient Greek: κίνησις “kinesis”, movement or to move) may refer to:
* Kinetic theory of gases, Kinetic theory, describing a gas as particles in random motion
* Kinetic energy, the energy of an object that it possesses due to i ...
of the oxidation reaction.
Synthesis
Calcium nitrite can be produced by different synthesis processes. One is by reacting
hydrated lime
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 ma ...
with
NOX
In atmospheric chemistry, is shorthand for nitric oxide () and nitrogen dioxide (), the nitrogen oxides that are most relevant for air pollution.
These gases contribute to the formation of smog and acid rain, as well as affecting tropos ...
gas, which typically comes from a
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 ...
plant. At the acid plant,
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
is burned to produce the NO
X gas for acid as well as calcium nitrite.
Also, it can be prepared as detailed below, forming a solution of
sodium nitrite
Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...
and
calcium nitrate
Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an inorganic compound 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 anhyd ...
; cooling the solution to precipitate
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 ...
; forming a
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 ...
of calcium nitrite/calcium hydroxide; and in the presence of water, decomposing double salt to form a solution of calcium nitrite and insolubilize
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 ...
. Essentially the function of calcium hydroxide is to carry calcium nitrite; calcium hydroxide forms the insolubilized double salt which can be used to separate from calcium nitrite portions from the solution. After, the double salt is dissolved liberating calcium nitrite and regenerating the calcium hydroxide.
1. Precipitation of double salt
: + + →
2. Liberation of calcium nitrite
: → (aq) + +
Uses
Calcium nitrite has a great variety of uses. It can be use as
antifreeze
An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, all ...
due to its high solubility, either in solution or powder. It can promote the hydration of minerals in cement using this antifreeze at sub freezing temperature, the operative temperature can be reduced to −20 °C. It also work as metal
corrosion inhibitor
In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness ...
, so it can protect steel in concrete buildings and structures from rust, to extend life of specific buildings.
Nitrite's success as a
corrosion inhibitor
In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness ...
for the protection of embedded steel in reinforced concrete comes from the "smart" behavior of the AFm phase (AFm is shorthand for a family of hydrated calcium aluminate hydrate phases: aluminate-ferrite-monosubstituent phases); normally it stores nitrite in preference to
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...
,
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
, and
hydroxyl ion
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...
s so that the nitrite concentrations of pore fluid are low. However, if chloride ingress occurs in service (from sea water or de-icing salt), the AFm undergoes ion exchange, gaining
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
and forming
Friedel's salt
Friedel's salt is an anion exchanger mineral belonging to the family of the layered double hydroxides (LDHs). It has affinity for anions as chloride and iodide and is capable of retaining them to a certain extent in its crystallographical stru ...
(Cl-AFm), while releasing soluble
nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
ions to the pore fluid. As a result, the aqueous ratio of
2−">O2− −">l−increases which assures corrosion inhibition of embedded steel.
The corrosion inhibition mechanism of nitrite in concrete is twofold: on one hand, the concentration of the very corrosive
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
anions (responsible for the
pitting corrosion
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation re ...
of steel rebars) in the concrete pore water decreases after their uptake into the AFm phases and on the other hand, nitrites also oxidize the Fe
2+ ions present around the corroding rebars leading to the precipitation of poorly soluble
iron oxy-hydroxides onto the steel surface contributing to its
passivation.
Calcium nitrite is widely used in concrete for high-rise construction, highways, bridges, railroads, airports, and large-scale
hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
s. It also might enable coastal areas to use chloride-containing sea sand in concrete.
Calcium nitrite is also used as a heavy oil
detergent
A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...
and in
pharmaceutical
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...
s,
dyes
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...
and
metallurgy industries. It can substitute for
sodium nitrite
Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...
, a product often used as a
heat transfer
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
fluid in thermal energy storage units for large air-conditioning or process cooling applications.
Safety
It is a poisonous inorganic oxidiser, which can not be mixed with organic
ammonium salt
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
,
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
or
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
. It has to be kept in heat-proof place, because when the temperature is higher than 220 °C it will reduce and
decompose
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
into
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...
. During transportation it is important to protect it from rain and
insolation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre (W/m ...
, and protect its package from breakage. Also, the warehouse should be ventilated and dry.
See also
*
Calcium nitrate
Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an inorganic compound 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 anhyd ...
References
{{calcium compounds
Nitrites
Calcium compounds
Concrete admixtures
Corrosion inhibitors
Oxidizing agents