Man's physical universe



to sulfur trioxide, which then reacts with water to produce sulfuric


2SO2 + O2 —>- 2SO3

sulfur dioxide oxygen sulfur trioxide

SO3 + H2O >- H2SO4

sulfur trioxide water sulfuric acid

When sulfur is burned in air, only sulfur dioxide is produced. A

catalyst (see Section 5 of this Unit), i.e., an added material which, by its

mere presence, changes the rate of a chemical reaction, must be employed

to add an extra oxygen to sulfur dioxide to form sulfur trioxide.

the "lead chamber" process the catalyst consists of oxides of nitrogen;

in the contact process the catalyst consists of finely divided platinum

or other materials. Because sulfuric acid is a heavy, oily liquid and

was formerly prepared from vitriol, it is called "oil of vitriol," and its

salts are called "vitriols"; for example, copper sulfate is called "blue


Sulfuric acid is so important in modern industry that its production

is one of the best indexes of industrial prosperity in general. The

annual production of sulfuric acid is about 7,000,000 tons. Sulfuric

acid is the cheapest and most satisfactory acid for many purposes.

Large quantities of sulfuric acid are used in the treatment of phosphate

rock, which is insoluble in water, to produce calcium superphosphate,

which is soluble in w^ater, for use in fertilizers. Its reactivity with

unsaturated compounds is applied in the refining of petroleum; and its

great affinity for water makes it useful in reactions in which nitric acid


used to nitrate such material as cellulose or toluene, because these

reactions will not go to completion unless the water is removed as

rapidly as it is produced.

CeHsCHs + 3HNO3 —> C6H2(N02)3CH3 + 3 H2O

toluene nitric acid T.N.T. water


Sulfuric acid has such a great affinity for water that it will extract

water from carbohydrates, leaving carbon as a residue.

Because of this

property, clothing and the skin of laboratory workers must be protected

against sulfuric acid. The low volatility of sulfuric acid makes possible

its use in the preparation of the other, more volatile acids. For example:

2NaN03 + H2SO4 —>- 2HNO3 + Na2S04

sodium nitrate sulfuric acid nitric acid sodium sulfate

2NaCl + H2SO4 —>- 2HC1 + Na2S04

sodium chloride sulfuric acid hydrochloric acid sodium sulfate

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