Turpentine Oil
Collier's New Encyclopedia (1921)
the volatile oil distilled from crude turpentine, and existing in the wood, bark, leaves, and other parts of coniferous trees. These oils, according to the source from which they are obtained, exhibit considerable and marked diversities in their physi cal as well as in their optical properties. The several varieties when rectified are colorless, mobile liquids, having a peculiar aromatic but disagreeable odor. They are insoluble in water, slightly soluble in aqueous alcohol, miscible in all proportions with absolute alcohol, ether, and carbon disulphide. They dissolve iodine, sulphur, phosphorus, also fixed oils and resins. Two principal varieties are from Pinus maritima, and from the turpentine collected in the Southern States of America. The former has a sp. gr. of 0.864, at , and plane boils 161° turns the of polarization to the left; the latter has the same specific gravity and boiling point, but turns the plane of polarization to the right. Both oils absorb oxygen from the air, and acquire powerful oxidizin oxidizing properties from the probable formation of an organic peroxide, C10H14O4. Turpentine absorbs chlorine with such energy as sometimes to set it on fire. It belongs to a group of volatile oils to which the name of terpenes has been given. They are derived from the plants of the coniferous and aurantiaceous orders, yielding, for example, turpentine and lemon oils respectively. Tu Turpentine oil is of great importance in the arts, and is specially employed for giving consistency to oil paints and varnishes, rnishes, conferring on them drying properties.
What Has Changed in the Last Century
When Collier's wrote this in 1921, turpentine was still the standard thinner for oil paints and varnishes, and the great American supply came from gum tapped out of living Southern pines. Both facts have since been overturned: cheap petroleum distillates (white spirit or mineral spirits) took over as paint thinner after the Second World War, water-based latex and alkyd paints displaced much oil painting altogether, and most turpentine sold today is sulfate turpentine, a by-product recovered from kraft wood-pulp mills rather than collected by tapping. The chemistry Collier's sketched has been pinned down: the terpene in question is chiefly alpha-pinene, C10H16, and the left- and right-handed rotations it noted in the French and American oils are now understood as mirror-image forms of the same molecule. The old internal medicinal uses have been abandoned as well, turpentine now being treated as a poison and a common cause of skin sensitization.
Written for this edition, 2026.