Ammonia (DIN 8960)

Ammonia is a colourless toxic gas with a pungent smell. lt is lighter than air and readily soluble in water, alcohols, acetone and chloroform. Thus 1 litre of water at 273 K (0 °C) and 1 bar can absorb 880 g of Ammonia, but only 340 g at 313 K (40 °C). Ammonia bums with difficulty and generally cannot continue burning after the source of ignition is removed. Ammonia is characterised by its basic (alkaline) action resulting from the uptake of protons by a proportion of the ammonia.

When an aqueous solution (ammonia water) is heated, ammonia escapes completely, and for this reason it is called “volatile alkali”. Ammonia severely attacks copper in all forms, i.e. even in its alloys (brass, bronze). They must therefore be avoided completely as construction materials, e.g. for valves and pipes. Ammonia is formed in nature by putrefaction processes of nitrogenous organic compounds, especially of proteins. This process is also responsible for the emissions of ammonia from liquid manure.

Manufacture: Ammonia is obtained in the laboratory from an ammonium salt and calcium hydroxide or milk of lime.

Ammonia is obtained industrially by the Haber-Bosch process. This involves reacting hydrogen and nitrogen at elevated temperature and high pressure by use of an iron catalyst.

In 1923 Mittasch carried out about 20,000 individual experiments to develop this catalyst. The origin of the required synthesis gas depends on the available raw materials. Before World War II, coal gasification was the main source, today it is natural gas.

Use: Ammonia is a basic raw material for the chemical industry and constitutes the starting point for a large number of chemical syntheses. Examples of important downstream products include artificial fibres, nitric acid and nitrates, sulphonamides, urea, hydrocyanic acid and cyanides, sodium carbonate, fertilisers and nitriles. An approx. 10% aqueous solution is commonly called spirit of hartshorn and can be used as a cleanser and to neutralise chlorine or formaldehyde after disinfection processes. A new application is the combined removal of compounds of sulphur and nitrogen from flue gases to form ammonium sulphate and nitrate in coal-fired power stations and refuse incinerators.

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