Oxalic acid provides general tests of carboxylic acid.
Effervescences are obtained due to the formation of CO2 gas when
oxalic acid is added to the NaHCO3 solution. Specific tests are as
follows.
The addition of calcium chloride to a neutral solution
of oxalic acid gives a white precipitate of calcium oxalate, which is insoluble
in acetic acid but soluble in mineral acids.
The oxalic acid becomes colourless when the oxalic acid
solution is added to the hot and acidic potassium par magnate solution.
On heating it with concentrated sulphuric acid, carbon
monoxide gas is formed which burns with a blue flame.
The addition of silver nitrate to neutral solution of
oxalic acid gives a white precipitate, which is soluble in ammonium hydroxide
and does not give silver mirror when heated.