Ammonium carbonate is a common inorganic compound, typically appearing as a white crystalline solid or powder. It is sometimes referred to by its historical names, such as “sal volatile” or “salt of hartshorn,” which allude to its characteristic and pungent odor. This chemical is highly water-soluble and possesses a unique property of readily breaking down, which accounts for many of its practical uses.
The Chemical Formula for Ammonium Carbonate
The chemical formula for ammonium carbonate is (NH4)2CO3. It is a highly soluble material, capable of dissolving 25 grams in 100 milliliters of water at 20°C. This compound is not particularly stable, as it begins to decompose at a relatively low temperature, with its melting point listed at 58°C. The decomposition involves the release of gasses, a property central to its use as a leavening agent. The Chemical Abstracts Service (CAS) number assigned to this compound is 506-87-6.
Ionic Structure and Composition
Ammonium carbonate is classified as an ionic compound. The structure is built from two distinct components: the ammonium cation and the carbonate anion. The ammonium cation is a polyatomic ion represented as NH4+, carrying a single positive charge. This cation itself is held together by covalent bonds between the nitrogen and hydrogen atoms.
The second component is the carbonate anion, which has the formula CO3(2-) and carries a double negative charge. The overall structure of the compound must be electrically neutral, meaning the total positive charge must exactly cancel the total negative charge. To achieve this balance, two ammonium cations, each with a 1+ charge, are required to neutralize the 2- charge of a single carbonate anion. This requirement is why the subscript “2” is placed outside the parentheses enclosing the NH4 group in the final chemical formula.
Common Industrial and Household Applications
The instability of ammonium carbonate is what drives its most recognizable applications. When heated, it breaks down completely into ammonia gas, carbon dioxide gas, and water vapor. This property makes it an effective leavening agent in baking, where it is known as “baker’s ammonia” or “hartshorn.” Because the decomposition leaves no solid residue, it is particularly favored for producing thin, dry baked goods like crackers and cookies.
In a medicinal context, the compound has long been used in the production of smelling salts. The resulting sharp, pungent odor serves as a stimulant. Beyond these household uses, the compound is utilized in the textile industry, where its alkaline nature helps with wool refining and color fixation during dyeing processes. It also serves as a nitrogen source in some agricultural fertilizers and is an ingredient in specific cleaning and pharmaceutical formulations, such as cough expectorants.