Page 105 - Encyclopedia of Chemical Compounds 3 Vols

ALUMINUM POTASSIUM SULFATE

The alums were known as far back as ancient Egypt
Aluminum potassium sulfate.
and China, where they were used as deodorants. Alums are
Red atoms are oxygen; yellow
atoms are sulfur; turquoise effective for this purpose because they are astringents, sub-
atom is potassium; and orange stances that cause tissues to shrink or contract, thus redu-
atom is aluminum. Gray sticks cing the tendency of sweat glands to produce perspiration.
indicate double bonds.
As astringents, alums were also used in the field of medicine
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to treat wounds and prevent bleeding. Until the nineteenth
century, however, chemists did not recognize that the sub-
stance they knew as alum was actually a variety of different
compounds.

HOW IT IS MADE
Aluminum potassium sulfate occurs naturally in the form
of the minerals alunite and kalinite. Where these minerals
are available, the compound can be mined and purified to
obtain potash alum. Where the minerals are not available,
the compound can be produced synthetically by combining
aqueous aluminum sulfate with aqueous potassium sulfate.
The two compounds react with each other in solution to form
the double salt, aluminum potassium sulfate, which can then
be extracted by allowing the solutions to evaporate, during
which the desired compound crystallizes out.

54 CHEMICAL COMPOUNDS