All carboxylic acids give the following general tests.
It becomes red when a blue litmus sheet is added to an aqueous solution of carboxylic acid.
A saturated solution of NaHCO3 in carboxylic acid yields effervescences due to the formation of carbon dioxide.
In addition to the above, the following are typical tests of formic acid.
Silver mirror is obtained by heating ammoniuam silver nitrate in formic acid.
Red precipitate is formed due to cuprus oxide being formed when heated with a fehling solution in formic acid.
White precipitate is formed due to the formation of mercurus chloride when formic acid is heated with mercuric chloride solution.
It is neutralized by ammonium hydroxide and a red color is obtained by adding a few drops of feric chloride solution.
On heating this acid with concentrated sulfuric acid, carbon monoxide gas is released which burns with flame.