草酸

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.

PHYSICAL AND CHEMICAL PROPERTIES (DIHYDRATE)

PHYSICAL STATE

white crystals

MELTING POINT

101 - 102 C

BOILING POINT

149 - 160 C (sublimes)

SPECIFIC GRAVITY

1.6 - 1.7

SOLUBILITY IN WATER

1 g/7ml

pH

VAPOR DENSITY

4.4

AUTOIGNITION

REFRACTIVE INDEX

NFPA RATINGS

Health: 3; Flammability: 1; Reactivity: 0

FLASH POINT

163 C

STABILITY

Stable under ordinary conditions

APPLICATIONS

Purifying agent, Precipitating agent, Bleaching agent, Metal treatment, Grinding agent, Waste water treatment, Reducing agent

SALES SPECIFICATION (DIHYDRATE)

APPEARANCE

white crystals

TOTAL ACIDITY

99.6% min

IRON

0.001% max

LOSS ON IGNITION

0.08% max

SULFATE

0.08% max

CHLORIDE

0.002% max

HEAVY METAL

0.001% max