Modern inorganic chemistry

GROUP VI 299

Concentrated sulphuric acid

sc

Burners

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h Glover SO2,nitrc

* tower air,mois

T

80% sulphuric

acid

KJS fumes Lead nitre

lure ^ chambers fum

l

N,Chamber acid

jus^Gay-Lussac

es tower

I

Nitrated acid

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Figure 10,5. The Lead Chamber process for the manufacture of sulphuric acid

SO 2 + H 2 O -> H 2 SO 3

H 2 SO 3 + NO 2 ~> SO 5 NH 2

'sulphonitronic acid'

This substance can then react in two possible ways :

2SO 5 NH NO 2 -> 2(NO)(HSO 4 ) H 2 O + NO

or

SO 5 NH 2 ^ H 2 SO 4 + NO

The nitrosyl hydrogensulphate formed can also react in two ways,
viz.:

or

2(NO)(HSO 4 ) + SO 2 + 2H 2 O =± 2SO 5 NH 2 + H 2 SO 4

4(NO)(HSO 4 ) -f 2H 2 O ^ 4H 2 SO 4 + 4NO 4- O

The final products are then sulphuric acid, nitrogen oxide and
oxygen: the two latter react and the cycle goes on. Theoretically
therefore, the nitrous fumes are never used up. In practice, however,
some slight replacement is needed and this is achieved by adding
a little concentrated nitric acid to the mixture in the Glover tower:

(NO)(HSO 4 ) + HNO 3 ^ H 2 SO 4 + 2NO 2

3. The conversion of sulphur trioxide to sulphuric acid arises as
   a separate reaction only in the Contact process.
   Sulphur trioxide is not very soluble in water but dissolves readily
   in concentrated sulphuric acid.
   The sulphur trioxide from the Contact chamber is passed into