Oxalic Acid (also called Ethanedioic Acid) is a colourless, crystalline, toxic
organic compound belonging to the family of dicarboxylic acids; melting at 187
C;
soluble in water, alcohol, and ether. It occurs in the form of its metal salts
(usually calcium or potassium) in many plants. It is commercially manufactured
by heating sodium formate in the presence of an alkali catalyst to form sodium
oxalate, which should be converted to free oxalic acid when treated with
sulfuric acid. It is also prepared by oxidizing carbohydrates with nitric acid,
by heating saw dust with caustic alkalies or by fermentation of sugar solutions
in the presence of certain molds. Oxalic acid is the only possible compound in
which two carboxyl groups are joined directly; for this reason oxalic acid is
one of the strongest acids in organic compounds. Unlike other carboxylic acids,
oxalic acid (and formic acid) is readily oxidized and combine with calcium,
iron, sodium, magnesium, or potassium to form less soluble salts called
oxalates. Oxalic acid and oxalates are useful as reducing agents for
photography, bleaching, and rust removal. They are widely used as an purifying
agent in pharmaceutical industry, precipitating agent in rare-earth metal
processing, bleaching agent in textile and wood industry, rust-remover for metal
treatment, grinding agent, waste water treatment. acid rinse in laundries and
removing scale from automobile radiators.
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