Ammonium sulphate is an inorganic salt with the chemical formula (NH4)2SO4. Ammonium sulphate has various industrial applications, but should also be handled very carefully as it can be highly hazardous to humans. Its primary use is as a fertilizer for agriculture as it contains 21% nitrogen and 24% sulphur. Ammonium sulphate occurs in nature in the form of a mineral called mascagnite. Mascagnite is a rare mineral and is present in volcanic fumaroles and coal fire dumps.
Ammonium sulphate is prepared by treating ammonia with sulphuric acid. The chemical reaction is written as:
2 NH3 + H2SO4 → (NH4)2SO4
Another method of preparing ammonium sulphate is adding gypsum salt to an ammonium carbonate solution. Calcium carbonate and ammonium sulphate are the products of the reaction. The calcium carbonate is precipitated from the mixture, leaving behind a solution of ammonium sulphate.
Ammonium sulphate is used as a fertilizer for crops grown on alkaline soil. When ammonium sulphate is added to an alkaline soil, ammonium ions are released along with small amount of acid which lower the pH of the soil. Apart from this, it also acts as a nitrogen source for plant growth.
Ammonium sulphate is used in horticulture as a spray adjuvant for water soluble insecticides, herbicides and fungicides. Its function is to bind the iron and calcium cations that are present in the water.
Ammonium sulphate is used for purifying proteins by selective precipitation or salting out the protein from the solution, thus providing a simple way of fractionating complex protein mixtures.
Ammonium sulphate is used as an acidity regulator in flours and breads, and the food grade ammonium sulphate is recognised as safe by the US FDA and the European Union.
Ammonium sulphate is listed as an ingredient for many US vaccines by the Centre for Disease Control.