dark, odorous liquid by-product of the sulfate (kraft) process of paper manufacture, used after refining to make coatings, sizing for paper, paint, varnish, linoleum, drying oils, emulsions, lubricants, and soaps. Tall oil is principally a mixture of resin acids, such as abietic acid, and fatty acids, such as oleic and linoleic acids, with some sterols and other compounds. It is obtained by chemically treating the cooking liquor used in the operation of pulping wood for paper.