Making ammonium sulfate

Ammonium sulfate, (NH₄)₂SO₄, is a used as a . It can be manufactured by reacting ammonia solution with sulfuric acid:

ammonia + sulfuric acid → ammonium sulfate

2NH₃(aq) + H₂SO₄(aq) → (NH₄)₂SO₄(aq)

Ammonia is made in the , which involves a between nitrogen and hydrogen:

nitrogen + hydrogen ⇌ ammonia

The reaction conditions in the Haber process are:

Sulfuric acid is made from the raw materials of sulfur, air and water. Several stages are involved but they can be simplified like this:

The second reaction takes place at a temperature of 450°C.

The reaction between ammonia gas and sulfuric acid takes place in a continuous process at 60°C, to form ammonium sulfate on a very large scale.

In the laboratory, ammonium sulfate is made by reacting measured volumes of ammonia solution and sulfuric acid solution.

25 cm³ of ammonia solution is measured using a measuring cylinder or volumetric pipette and poured into a conical flask.
Two drops of methyl orange indicator are added. This will turn yellow in the alkaline ammonia solution.
Dilute sulfuric acid is added from a burette slowly until the methyl orange indicator turns orange. If too much acid is added it will turn red.
The volume of sulfuric acid which has been added is recorded, and then the neutral solution of ammonium sulfate which contains the indicator is thrown away.
The experiment is repeated without the indicator but with the same volumes of ammonia and sulfuric acid.
The ammonium sulfate is crystallised by evaporating the water and drying the crystals in an oven or desiccator.

Factor	Industrial method	Laboratory method
Temperature	Different stages require temperatures between 60°C and 450°C	Room temperature for the neutralisation, then heating with a Bunsen burner to evaporate the water
Equipment and process	Very expensive chemical plant machinery, used in a continuous process	Cheap and versatile laboratory equipment, used in a batch process
Starting materials	Reactants are made from raw materials, eg sulfur, air, water	Reactants are purchased from a chemical supplier
Scale/yield	Huge quantities can be made quickly.	Small quantities are made slowly
Running costs	Automatic control mechanisms and machinery reduces the labour costs and running costs	The method is very labour-intensive, so running costs are high

Factor	Temperature
Industrial method	Different stages require temperatures between 60°C and 450°C
Laboratory method	Room temperature for the neutralisation, then heating with a Bunsen burner to evaporate the water

Factor	Equipment and process
Industrial method	Very expensive chemical plant machinery, used in a continuous process
Laboratory method	Cheap and versatile laboratory equipment, used in a batch process

Factor	Starting materials
Industrial method	Reactants are made from raw materials, eg sulfur, air, water
Laboratory method	Reactants are purchased from a chemical supplier

Factor	Scale/yield
Industrial method	Huge quantities can be made quickly.
Laboratory method	Small quantities are made slowly

Factor	Running costs
Industrial method	Automatic control mechanisms and machinery reduces the labour costs and running costs
Laboratory method	The method is very labour-intensive, so running costs are high

Fertilisers - AQAMaking ammonium sulfate