The spent sulfite liquor from the acid sulfite process produces a sulfonated lignin that can be used for several industrial applications. Tall oils are a mixture of rosin acids, fatty acids, and a small amount of unsaponifiable substances. Crude tall oil is produced by splitting with sulfuric acid, the sodium salts of the rosin and fatty acid produced when pine wood is pulped by the kraft process. A wide ratio of fatty acids to resin acids can be obtained, ranging from pure fatty acids to pure rosin acids. The only restriction on the amount produced is that one ton of pulp yields only about 70 pounds of crude oil.
Tall oils are in high demand in the industrial arena due to their low cost and accessibility.
Whole tall oil is the lowest priced organic acid in the world. They react to form water-soluble soaps when reacted with alkali, ammonia, amines, and form oil soluble soaps when reacted with the salts of heavy metals. Although many of the reactions of Rosin acids are the same as those of fatts acids, a few others should be mentioned. The reaction with lime or zinc oxide produce a high melting oil that is used in varnishes and printing inks. There is interest in a small fraction of the beta-sitosterol.