Benzoic acid is a scaly or needle like crystal with the smell of benzene or formaldehyde. Melting point 122.13 ℃, boiling point 249 ℃, relative density 1.2659 (15 / 4 ℃). When it sublimates rapidly at 100 ℃, its steam has a strong irritant, which is easy to cause cough after inhalation. Slightly soluble in water, easily soluble in ethanol, ether and other organic solvents. Benzoic acid is a weak acid, stronger than fatty acid. Their chemical properties are similar, and they can form salts, esters, acyl halides, amides, anhydrides, etc., which are not easy to be oxidized. The electrophilic substitution reaction can take place on the benzene ring of benzoic acid, and the main products are intermediate substitution products.