Ammonium bicarbonate

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Food grade (NH4)HCO3

Ammonium bicarbonate or ammonium hydrogen carbonate is an inorganic compound with the chemical formula (NH4)HCO3. In older literature it may be referred to as hartshorn, as is ammonium carbonate.

Properties

Chemical

Ammonium carbonate will slowly decompose to give off ammonia, carbon dioxide and water vapors. The reaction occurs faster at higher temperatures:

(NH4)HCO3 → NH3 + H2O + CO2

Ammonium carbamate is another potential by-product of decomposition.

When treated with acids, it releases carbon dioxide:

(NH4)HCO3 + HCl → NH4Cl + H2O + CO2

It also reacts with alkali metal halides, giving ammonium halide and alkali metal bicarbonate:

NH4HCO3 + LiCl → NH4Cl + LiHCO3
NH4HCO3 + NaBr → NH4Br + NaHCO3
NH4HCO3 + KI → NH4I + KHCO3

Physical

Ammonium bicarbonate is a white salt, soluble in water, but insoluble in organic solvents like methanol, diethyl ether. It will slowly decompose over time, even at low temperatures, releasing ammonia gas, which gives the salt a strong smell. The decomposition occurs faster at high temperatures.

Availability

Ammonium bicarbonate can be bought from food stores as "smelly" baking powder, either very pure or mixed with other carbonates, such as sodium bicarbonate or magnesium carbonate. Sometimes it's referred to as simply "ammonium", usually the label name.

Preparation

Ammonium bicarbonate can be made by bubbling an excess of carbon dioxide gas through a cold solution of ammonia.

CO2 + NH3 + H2O → (NH4)HCO3

Alternatively, it can be made by heating a mixture of ammonium nitrate, sodium bicarbonate or carbonate, and water in one container, and channeling the generated gases into a chilled empty container, where it will crystallize on the walls.

Projects

  • Ammonium carbonate synthesis
  • Generate ammonia gas
  • Synthesize any other ammonium salt. Both forms of Hartshorn are very convenient precursors to all salts of ammonium.

Handling

Safety

Ammonium bicarbonate gives off ammonia fumes, which are irritating and toxic if they build up in a closed environment.

Storage

Ammonium bicarbonate is best stored in closed containers and kept in cold places. To limit the ammonia gas released, you can store the ammonium bicarbonate in a resealable bag, which in turn can be placed in a container.

Disposal

Ammonium bicarbonate can be neutralized with any acid and safely dumped in both soil and down the drain, as it poses no danger to the environment.

References

Relevant Sciencemadness threads