Ammonium bicarbonate

Ammonium bicarbonate

Overview
Ammonium bicarbonate, a compound with formula
NH4(C(=O)OHO), also called bicarbonate of ammonia, ammonium hydrogen carbonate, hartshorn, AmBic or powdered baking ammonia, is the bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

.

Ammonium bicarbonate is produced in the process that also leads to ammonium carbonate
Ammonium carbonate
Ammonium carbonate is a commercial salt with the chemical formula 2CO3. It is used when crushed as a smelling salt. It can be crushed when needed in order to revive someone who has fainted...

. Commercial ammonium carbonate was formerly known as sal volatile or salt of hartshorn
Hartshorn
Harts' horns, are the horns of the male red deer. Various substances were made from the shavings of the animals' horns.The oil of hartshorn is a crude animal oil obtained from the destructive distillation of the deers' bones or horns....

 and was formerly obtained by the dry distillation of nitrogenous organic matter such as hair, horn, decomposed urine, etc., but is now obtained by heating a mixture of sal ammoniac
Sal ammoniac
Sal ammoniac is a rare mineral composed of ammonium chloride, NH4Cl. It forms colorless to white to yellow-brown crystals in the isometric-hexoctahedral class. It has very poor cleavage and a brittle to conchoidal fracture. It is quite soft, with a Mohs hardness of 1.5 to 2, and has a low specific...

, or ammonium sulfate and chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

, to redness in iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 retorts, the vapours being condensed in lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

en receivers.
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Encyclopedia
Ammonium bicarbonate, a compound with formula
NH4(C(=O)OHO), also called bicarbonate of ammonia, ammonium hydrogen carbonate, hartshorn, AmBic or powdered baking ammonia, is the bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

.

Ammonium bicarbonate is produced in the process that also leads to ammonium carbonate
Ammonium carbonate
Ammonium carbonate is a commercial salt with the chemical formula 2CO3. It is used when crushed as a smelling salt. It can be crushed when needed in order to revive someone who has fainted...

. Commercial ammonium carbonate was formerly known as sal volatile or salt of hartshorn
Hartshorn
Harts' horns, are the horns of the male red deer. Various substances were made from the shavings of the animals' horns.The oil of hartshorn is a crude animal oil obtained from the destructive distillation of the deers' bones or horns....

 and was formerly obtained by the dry distillation of nitrogenous organic matter such as hair, horn, decomposed urine, etc., but is now obtained by heating a mixture of sal ammoniac
Sal ammoniac
Sal ammoniac is a rare mineral composed of ammonium chloride, NH4Cl. It forms colorless to white to yellow-brown crystals in the isometric-hexoctahedral class. It has very poor cleavage and a brittle to conchoidal fracture. It is quite soft, with a Mohs hardness of 1.5 to 2, and has a low specific...

, or ammonium sulfate and chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

, to redness in iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 retorts, the vapours being condensed in lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

en receivers. The crude product is refined by sublimation, when it is obtained as a white fibrous mass, which consists of a mixture of hydrogen ammonium carbonate, NH4•HCO3, and ammonium carbamate, NH2COONH4, in molecular proportions; on account of its possessing this constitution it is sometimes called ammonium sesquicarbonate. It possesses a strong ammoniacal smell, and on digestion with alcohol the carbamate is dissolved and a residue of ammonium bicarbonate is left; a similar decomposition taking place when the sesquicarbonate is exposed to air. Ammonia gas passed into a strong aqueous solution of the sesquicarbonate converts it into normal ammonium carbonate, (NH4)2CO3, which can be obtained in the crystalline condition from a solution prepared at about 30 °C. This compound on exposure to air gives off ammonia and passes back to ammonium bicarbonate.

Ammonium bicarbonate can also be formed by passing carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 through a solution of the normal compound, when it is deposited as a white powder, which has no smell and is only slightly soluble in water. The aqueous solution of this salt liberates carbon dioxide on exposure to air or on heating, and becomes alkaline in reaction. The aqueous solutions of all the carbonates when boiled undergo decomposition with liberation of carbon dioxide and the substance with which the carbonate ion reacted to form the bicarbonate, in this case, ammonia:
NH4HCO3 → NH3 + H2O + CO2.

Properties


At room temperature, ammonium bicarbonate is a white, crystalline powder with a slight odor of ammonia that can dissolve in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 to give a mildly alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

ne solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

. It is insoluble in acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

 and alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

s. Ammonium bicarbonate decomposes at 36 to 60 °C into ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, and water vapor in an endothermic
Endothermic
In thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...

 process (as it is with many ammonium salts) and so causes a drop in the temperature of the water. When reacted with acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, carbon dioxide is produced, while reactions with alkalis produce ammonia.

Uses


Ammonium bicarbonate is used in the food industry as a raising agent
Leavening agent
A leavening agent is any one of a number of substances used in doughs and batters that cause a foaming action which lightens and softens the finished product...

 for flat baked goods, such as cookies and crackers, and in China in steamed buns and Chinese almond cookies. It was commonly used in the home before modern day baking powder was made available to home bakers. In China it is called edible or food-grade "smelly powder". Many baking cookbooks (especially from Scandinavian countries) may still refer to it as hartshorn
Hartshorn
Harts' horns, are the horns of the male red deer. Various substances were made from the shavings of the animals' horns.The oil of hartshorn is a crude animal oil obtained from the destructive distillation of the deers' bones or horns....

 or hornsalt (e.g., NO: “hjortetakksalt”, “salt of hart’s horn”) In many cases it may be substituted with baking soda or baking powder or a combination of both, depending on the recipe composition and leavening requirements. Compared to baking soda or potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

, hartshorn has the advantage of producing more gas for the same amount of agent, and of not leaving any salty or soapy taste in the finished product, as it completely decomposes into water and gaseous products which evaporate during baking. It cannot be used for moist, bulky baked goods however, such as normal bread or cakes, since some ammonia will be trapped inside and will cause an unpleasant taste.

It is commonly used as an inexpensive nitrogen fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 in China, but is now being phased out in favor of urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

 because of its relatively low quality and instability. This compound is used as a component in the production of fire-extinguishing compounds, pharmaceuticals, dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

s, pigments, and it is also a basic fertilizer being a source of ammonia. Ammonium bicarbonate is still widely used in the plastic and rubber industry, in the manufacture of ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

s, in chrome leather tanning
Tanning
Tanning is the making of leather from the skins of animals which does not easily decompose. Traditionally, tanning used tannin, an acidic chemical compound from which the tanning process draws its name . Coloring may occur during tanning...

, and for the synthesis of catalysts.

It is also used for buffering solutions to slightly alkaline pH during chemical purification, such as HPLC. Because it entirely decomposes to volatile compounds this allows rapid recovery of the compound of interest by freeze-drying.

Reactions


Ammonium bicarbonate decomposes to carbon dioxide, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, and water vapor on heating; it liberates CO2 when treated with dilute mineral acids:
NH4HCO3 + HCl
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 → NH4Cl + CO2 + H2O.


It reacts with sulfates of alkaline-earth metals precipitating out their carbonates:
CaSO4
Calcium sulfate
Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...

 + 2 NH4HCO3CaCO3
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 + (NH4)2SO4
Ammonium sulfate
Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...

 + CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 + H2O.


It also reacts with alkali metal halides, giving alkali metal bicarbonate and ammonium halide:
NH4HCO3 + NaCl
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 → NH4Cl
Ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...

 + NaHCO3
Sodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

;
NH4HCO3 + KI
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...

 → NH4I
Ammonium iodide
Ammonium iodide is the chemical compound NH4I. It is used in photographic chemicals and some medications. It can be prepared by the action of hydroiodic acid on ammonia. It is easily soluble in water, from which it crystallizes in cubes. It is also soluble in ethanol...

 + KHCO3
Potassium bicarbonate
Potassium bicarbonate , is a colorless, odorless, slightly basic, salty substance...

;
NH4HCO3 + NaBr
Sodium bromide
Sodium bromide is an inorganic compound with the formula NaBr. It is a high-melting white, crystalline solid that resembles sodium chloride. It is a widely used source of the bromide ion and has many applications.-Synthesis, structure, reactions:...

 → NH4Br
Ammonium bromide
Ammonium bromide, NH4Br, is the ammonium salt of hydrobromic acid. The chemical crystallizes in colorless prisms, possessing a saline taste; it sublimes on heating and is easily soluble in water...

 + NaHCO3.

Safety


Ammonium bicarbonate is an irritant
Irritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...

 to the skin
Human skin
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...

, eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s and respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

. Ammonium bicarbonate from China used to make cookies was found to be contaminated with melamine
Melamine
Melamine is an organic base and a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 66% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses....

, and imports banned in Malaysia in the 2008 Chinese milk scandal
2008 Chinese milk scandal
The 2008 Chinese milk scandal was a food safety incident in the People's Republic of China, involving milk and infant formula, and other food materials and components, adulterated with melamine....

.