Sulphur and the manufacture of Sulphuric acid

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Sulphur-Industrial and inorganic chemistry

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The characteristics of sulphur

Colour Sulphur is a yellow coloured element.
Metallic or non-metallic? It is a non-metallic element.
Group It is found in group VI of the periodic table.
Electrical conductivity It doesn’t conduct electricity.
Melting point 1150C
Dissolves in
  • Carbon disulfide
  • Methylbenzene (toluene)
Allotropes of sulphur Rhombic and Monoclinic sulphur
Strenght It is a brittle element
Where is sulphur found? It is found in metallic ores such as:

  • Copper pyrites (fool’s gold)(CuFeS2)
  • Zinc blende (ZnS)

It is also found in crude oil and natural gas. This needs to be removed or else it may cause environmental problems. Sulphur obtained from these products is called as recovered sulphur.

It is found native in underground beds in the USA, Mexico, Russia and Poland.

Method of extracting sulphur It is extracted using the Frasch process.


Sulphur image II

Uses of Sulphur

  • Sulphur is used to produce sulphuric acid
  • It is used to vulcanise rubber
  • It is used in the manufacture of matchsticks, fireworks and fungicides
  • Moreover, It is also used as a sterilising agent and in medicines

 Sulphur dioxide

Colour Sulphur dioxide is a colourless and poisonous gas
Sulphur dioxide is produced when Substances containing sulphur are burned in oxygen gas
When Sulphur dioxide is dissolved in water, It forms an acidic solution of sulphurous acid (H2SO3), which turns moist pH paper change colour to red.
Odour (smell)  It has a choking, pungent smell.
Test for sulphur dioxide When dissolved, Sulphur dioxide changes the colour of acidified potassium (VII) manganate from purple to colourless.
Uses of Sulphur dioxide
Sulphur dioxide is used as a bleaching agent for paper manufacturing. It is used as a preservative.
Moreover, It is used as a fumigant. Furthermore, It is also used to kill bacteria in order to preserve food.


Sulphuric acid

Most of the sulphur extracted is used in the manufacturing of sulphuric acid. Let us see how this is done!

Sulphuric acid is manufactured using the contact process.

Important conditions of the contact process
Catalyst Vanadium (V) oxide (V2O5)
Optimum temperature 4500C
Atmospheric pressure 1-2 atm
Sulphur is burnt in oxygen to form sulphur dioxide S(s) + O2(g) + SO2(g)
Sulphur dioxide is mixed with more oxygen to form Sulphur trioxide 2SO2(g)+ O2(g) + 2SO3(g)
Sulphur trioxide needs to be mixed with water to form sulphuric acid; but this is not done as it can cause an acidic mist to form and damage the environment.


Instead, Sulphur trioxide undergoes the following process:

Sulphur trioxide is dissolved in concentrated sulphuric acid. This results in the formation of a substance called oleum. SO3(g) + H2SO4(l) à H2S2O7(l)


Finally, add water to Oleum. This results in sulphuric acid being produced H2S2O7(l) + H2O(l) à H2SO4(l)

Uses of concentrated sulphuric acid

Concentrated sulphuric acid is used:

  • for making detergents
  • as a catalyst
  • as a dehydrating agent

Uses of dilute sulphuric acid

Dilute sulphuric acid is used:

  • For making fertilizers.
  • To treat metals to remove oxidisation before painting.
  • For anodising aluminium.
  • As an acid in car batteries.
  • For manufacturing paints, dyes and fibres.
  • As a common laboratory reagent



The salts of sulphuric acid are called sulphates.

Sulphates can be identified by a simple test-tube reaction. To test for the presence of a sulphate, add a few drops of dilute hydrochloric acid to your unknown followed by a few drops of barium chloride.

If a sulphate is present, a white precipitate of barium sulphate forms.

Properties of sulphuric acid

Concentrated sulphuric acid is a very corrosive substance.

Dilute sulphuric acid Concentrated sulphuric acid
Dilute sulfuric acid is a typical strong dibasic acid. Concentrated sulphuric acid is a powerful dehydrating agent.
A dibasic acid is one with two replaceable hydrogen

atoms which may produce two series of salts –

normal and acid salts

  Concentrated sulphuric acid is used to dry gases (except ammonia).   Concentrated sulphuric acid is a powerful oxidising agent.   Concentrated sulphuric acid can be used to produce nitric and hydrochloric acid.


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