In the 15th century it was made either
by burning sulphur with saltpetre (potassium nitrate) or by distilling
the acid from a mixture of silica and Iron III sulphate (ferric
sulphate, known as vitriol, hence the old name of sulphuric acid
used by alchemists - 'oil of vitriol').
In 1746, John Roebuck established the lead chamber process, in
which sulphur was mixed with saltpetre (potassium nitrate) and
a catalyst, and then burnt inside a lead chamber. The sulphur
dioxide produced was dissolved in water on the floor of the chamber,
lead metal being used because it does not react with the resulting
The process was improved in the 19th century by blowing air into
the chamber and by recycling most of the nitrogen oxides produced.
The Contact Process
In 1831 Peregrine
Phillips, a British vinegar merchant, patented the Contact Process for making sulphuric acid. Serious production
did not begin, however, until the 1880s onwards.
The Contact Process has been the dominant process used to manufacture
sulphuric acid for most of the past 100 years.
In this process, sulphur dioxide is oxidised
to sulphur trioxide, and the sulphur
trioxide is then reacted with water. A platinum catalyst was used originally, but this was later replaced by vanadium (V) oxide, which is cheaper and less easily poisoned.
more details of the Contact Process, click here.
The conversion of sulphur dioxide to sulphuric
acid is a very efficient process, achieving 98.5% efficiency using
conventional methods. Even this can be improved, however, by using
two stages of sulphur trioxide absorption, resulting in efficiency
up to 99.6%. Click here for
more details on this.
The need to reduce sulphur dioxide emissions
has led to the contact process and several other methods being
used where the primary aim is to remove sulphur dioxide. It would
not be acceptable to do this in a way that simply generated a
lot of other waste, and so these methods generally produce sulphuric
|"Wet" Contact Process
||Cleaning emissions from molybdenum
smelting, flue gas de-sulphurisation, hydrogen sulphide treatment
|Modified Lead Chamber Process
|| Treating effluent gases with
low sulphur dioxide content, and with a SO2/NOx
|Hydrogen Peroxide Process
||When local conditions require
almost zero sulphur dioxide emissions, this will achieve 99%
removal of the gas. It is, however, very expensive!