Benzoic acid.
C₇H₆O₂, PhCOOH. Colourless fustrous leaflets, m.p. 122°C, b.p. 249°C.
It was first described in 1608 when it was sublimed out of gum benzoin. It also occurs in many other resins. Benzoic acid is manufactured by the air oxidation of toluene in the liquid phase at 150°C and 4-6 atm. in the presence of a cobalt catalyst; by the partial decarboxylation of phthalic anhydride in either the liquid or vapour phase in the presence of water; by the hydrolysis of benzotrichloride (from the chlorination of toluene) in the presence of zinc chloride at 100°C.

It gives benzene when heated with soda lime. It is very stable towards oxidizing agents.
Much of the benzoic acid produced is converted to sodium benzoate, which is used as a food preservative (as is the acid) and a corrosion inhibitor. Other important uses of the acid are in the manufacture of alkyd resins, plasticzers, caprolactam, dyestuffs and pharmaceuticals.

Benzoin (C₆H₅CHOH.CO.C₆H₅).
(1) A crystalline optical active substance, m.p. 133.7°C. It is used in organic synthesis. (2) Gum Benzamin. A natural brown aromatic resin formed from certain tree. It is used in the manufacture of perfumes and cosmetics.

Benzole.
A mixture of predominantly aromatic hydrocarbons produced by the carbonization of coal, obtained from coal gas by adsorption or from coal by distillation.

Benzotrichloride, a,a,a - trichlorulune.
C₇H₅C_l3.PhCC_l3. Colourless liquid, b.p. 213-214°C. Insoluble in water, miscible with organic solvents.
It is prepared by fully chlorinating toluene. When heated with water at 100°C, or with lime, benzonic acid is obtained.