Tests for Carboxylic Acids

pH of an Aqueous Solution

Solubility in Sodium Bicarbonate

pH of an Aqueous Solution for Carboxylic Acids

Standard
5% Acetic acid solution

Procedure
See procedure for solubility tests with water.

Sodium Bicarbonate Test for Carboxylic Acids

Carboxylic Acid

Standard
5% Acetic acid solution

Procedure
A few drops or a few crystals of the unknown sample are dissolved in 1mL of methanol and slowly added to 1 mL of a saturated solution of sodium bicarbonate.

Positive Test
Evolution of a carbon dioxide gas is a positive test for the presence of the carboxylic acid and certain phenols listed in the Complications section.

Complications
Negatively substituted phenols such as nitrophenols, aldehydrophenols, and polyhalophenols are sufficiently acidic to dissolve in 5% sodium bicarbonate.