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| Names | |||
|---|---|---|---|
| IUPAC name Ammonium hydrogen carbonate | |||
| Other names Bicarbonate of ammonia, ammonium bicarbonate, hartshorn, AmBic, powdered baking ammonia | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChemSpider |
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| ECHA InfoCard | 100.012.647 | ||
| EC Number |
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| E number | E503(ii)(acidity regulators, ...) | ||
| RTECS number |
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| UNII | |||
| UN number | 3077 | ||
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| Properties | |||
| NH4HCO3 | |||
| Molar mass | 79.056 g/mol | ||
| Density | 1.586 g/cm3 | ||
| Melting point | 41.9 °C (107.4 °F; 315.0 K) decomposes | ||
| 11.9 g/100 mL (0 °C) 21.6 g/100 mL (20 °C) 24.8 g/100 mL (25 °C) 36.6 g/100 mL (40 °C) | |||
| Solubility | insoluble inmethanol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Decomposes to releaseammonia | ||
| GHS labelling: | |||
 [1] | |||
| Warning | |||
| H302[1] | |||
| P264,P270,P301+P312,P330,P501[2] | |||
| NFPA 704 (fire diamond) | |||
| Flash point | Nonflammable | ||
| Safety data sheet (SDS) | ICSC 1333 | ||
| Related compounds | |||
Otheranions | Ammonium carbonate | ||
Othercations | Sodium bicarbonate Potassium bicarbonate | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Ammonium bicarbonate is aninorganic compound with formula (NH4)HCO3. The compound has many names, reflecting its long history. Chemically speaking, it is thebicarbonatesalt of theammonium ion. It is a colourless solid that degrades readily to carbon dioxide, water and ammonia.
Ammonium bicarbonate is produced by combining carbon dioxide and ammonia:
Since ammonium bicarbonate is thermally unstable, the reactionsolution is kept cold, which allows the precipitation of the product as white solid. About 100,000 tons were produced in this way in 1997.[3]
Ammonia gas passed into a strongaqueous solution of the sesquicarbonate (a 2:1:1 mixture of (NH4)HCO3, (NH4)2CO3, and H2O) converts it into normalammonium 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 reverts to ammonium bicarbonate.
Compositions containing ammonium carbonate have long been known. They were once produced commercially, formerly known assal volatile or salt ofhartshorn. It was obtained by thedry distillation of nitrogenous organic matter such as hair, horn, leather. In addition to ammonium bicarbonate, this material containsammonium carbamate (NH4CO2NH2), andammonium carbonate ((NH4)2CO3). It is sometimes called ammonium sesquicarbonate. It possesses a strong ammoniacal smell, and on digestion with alcohol, the carbamate is dissolved leaving a residue of ammonium bicarbonate.[3]
A similar decomposition takes place when the sesquicarbonate is exposed to air.
Ammonium bicarbonate is used in the food industry as aleavening agent for flat baked goods, such as cookies and crackers. It was commonly used in the home before modern-daybaking powder was made available. Many baking cookbooks, especially from Scandinavian countries, may still refer to it ashartshorn or hornsalt,[4][5] while it is known as "hirvensarvisuola" in Finnish, "hjortetakksalt" or "hornsalt" in Norwegian, "hjortetakssalt" in Danish, "hjorthornssalt" in Swedish, and "Hirschhornsalz" in German (lit., "salt of hart's horn"). Although there is a slight smell of ammonia during baking, this quickly dissipates, leaving no taste. It is used in, for example, Swedish "drömmar" biscuits and Danish "klejner" Christmas biscuits, and German Lebkuchen. In many cases it may be replaced withbaking soda or baking powder, or a combination of both, depending on the recipe composition and leavening requirements.[6] Compared to baking soda orpotash, 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 that 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 has been assignedE number E503 for use as a food additive in theEuropean Union.
It is commonly used as an inexpensive nitrogenfertilizer in China, but is now being phased out in favor ofurea for quality and stability. This compound is used as a component in the production of fire-extinguishing compounds, pharmaceuticals,dyes, pigments, and it is also a basic fertilizer, being a source of ammonia. Ammonium bicarbonate is still widely used in the plastics and rubber industry, in the manufacture ofceramics, in chrome leathertanning, and for the synthesis ofcatalysts.[citation needed]
It is also used for buffering solutions to make them slightly alkaline during chemical purification, such ashigh-performance liquid chromatography. Because it entirely decomposes to volatile compounds, this allows rapid recovery of the compound of interest byfreeze-drying. Relatedly it is also useful as an alkaline buffering agent for analyticalLC–MS as its volatility allows it to be rapidly removed automatically from the sample stream in the low pressure spray chambers used by many standard mass spectrometry detectors found at the end of typical LC-MS systems, such aselectrospray ionization detectors. This is critical as most mass spectrometry detectors become signal saturated or even damaged with more than a trace amount of ions entering the detector proper at any one time. This issue limits buffering agents and other additives in LC-MS buffers to either extremely trace concentrations or to fairly volatile compounds. In pH ranges from about 7 to 9, ammonium bicarbonate is one of the only options available as the primary buffering agent for most LC-MS buffers.
Ammonium bicarbonate is also a key component of theexpectorant cough syrup "Senega and Ammonia".
It's also used as an attractant for catching insects such as the walnut husk fly (Rhagoletis completa).
It dissolves inwater to give a mildlyalkaline solution. It is insoluble inacetone andalcohols.
Ammonium bicarbonate decomposes above about 36 °C intoammonia,carbon dioxide, and water in anendothermic process and so causes a drop in the temperature of the water:
When treated withacids, ammonium salts are also produced:
Reaction with base produces ammonia.
It reacts with sulfates of alkaline-earth metals precipitating their carbonates:
It also reacts with alkali metal halides, giving alkali metal bicarbonate and ammonium halide:
The compound occurs in nature as an exceedingly rare mineralteschemacherite.[7][8] It can also be obtained from deer antlers.[9]
Ammonium bicarbonate is anirritant to theskin,eyes andrespiratory system. Short-term health effects may occur immediately or shortly after exposure to ammonium bicarbonate. Breathing ammonium bicarbonate can irritate the nose, throat and lungs causing coughing, wheezing and/or shortness of breath. Repeated exposure may cause bronchitis to develop with cough, and/or shortness of breath. Health effects can occur some time after exposure to ammonium bicarbonate and can last for months or years.
Where possible, operations should be enclosed and the use of local exhaust ventilation at the site of chemical release is recommended. If local exhaust ventilation or enclosure is not used, respirators are necessary. Wear protective work clothing and change clothes and wash thoroughly immediately after exposure to ammonium bicarbonate.[10]
Ammonium bicarbonate from China used to make cookies was found to be contaminated withmelamine, and imports were banned in Malaysia following the2008 Chinese milk scandal.[11]
