NH4HCO3
Ammoniumhydrogencarbonat

Chemical properties

Ammonium hydrogen carbonate forms colourless crystals according to the orthorhombic crystal system. Compared to the similar ammonium carbonate, the white crystalline powder appears more coarse-grained. The salt dissolves well in water, the solubility increases with increasing temperature. The aqueous solution reacts slightly basic. Ammonium hydrogen carbonate which is not too old is odourless and relatively stable, decomposition takes place only very slowly at room temperature. When heated, it decomposes to ammonia, carbon dioxide and water.

Ammonium bicarbonate can be used as a baking agent for rising dough due to the carbon dioxide produced when heated. To prevent ammonia from remaining in the dough, a mixture of ammonium carbonate, ammonium bicarbonate and a small amount of ammonium carbamate NH4OCO(NH2) is used in the ammonium bicarbonate salt.

Production

Ammonium hydrogen carbonate is formed when ammonium carbonate is dissolved in water and the salt is allowed to crystallize. Ammonium carbonate decomposes slowly in air to ammonium bicarbonate. When carbon dioxide is introduced into ammonia solution at 35 to 40 °C, ammonium bicarbonate is also obtained, which can be separated by filtering or centrifuging and subsequent drying at a temperature of 40 °C.

Use

As it has a defined composition, it is more suitable as a baking agent (“ABC drive” / baking powder) for the production of Christmas pastries such as gingerbread and speculoos in large-scale automated baking plants than deer horn salt. It is approved in the EU as food additive number E 503ii and is marketed with the additive in its purest form.

In the People’s Republic of China, ammonium bicarbonate was formerly used in large quantities as the main nitrogen fertiliser. Production began in 1958 and took place in over 1000 small plants. In the meantime, it has mainly been replaced by urea, but by 2012, its market share will still be 17 %.