Turpentine oil
Turpentine (which is also called spirit of turpentine, oil of turpentine, terebenthine, terebenthene, terebinthine and, colloquially, turps)[2] is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Principally used as a specialized solvent, it is also a source of material for organic syntheses.
Turpentine is composed of terpenes, primarily the monoterpenes alpha- and beta-pinene, with lesser amounts of carene, camphene, limonene, and terpinolene.[3]
Substitutes include white spirit or other petroleum distillates – although the constituent chemicals are very different.[4]
The word turpentine derives (via French and Latin) from the Greek word τερεβινθίνη terebinthine, in turn the feminine form (to conform to the feminine gender of the Greek word, which means "resin") of an adjective (τερεβίνθινος) derived from the Greek noun (τερέβινθος) for the terebinth tree.[5]
Although the word originally referred to the resinous exudate of terebinth trees (e.g. Chios turpentine, Cyprus turpentine, and Persian turpentine),[6][7] it now refers to that of coniferous trees, namely crude turpentine (e.g. Venice turpentine is the oleoresin of larch),[8] or the volatile oil part thereof, namely oil (spirit) of turpentine; the later usage is much more common today.[9]
Important pines for turpentine production include: maritime pine (Pinus pinaster), Aleppo pine (Pinus halepensis), Masson's pine (Pinus massoniana), Sumatran pine (Pinus merkusii), longleaf pine (Pinus palustris), loblolly pine (Pinus taeda), slash pine (Pinus elliottii), and ponderosa pine (Pinus ponderosa).
To tap into the sap producing layers of the tree, harvesters used a series of hacks to remove the pine bark. Once debarked, pine trees secrete crude turpentine (oleoresin) onto the surface of the wound as a protective measure to seal the opening, resist exposure to micro-organisms and insects, and prevent vital sap loss. Harvesters wounded trees in V-shaped streaks down the length of the trunks to channel the crude turpentine into containers. It was then collected and processed into spirits of turpentine. Crude turpentine yield may be increased by as much as 40% by applying paraquat herbicides to the exposed wood.[10]
The V-shaped cuts are called "catfaces" for their resemblance to a cat's whiskers. These marks on a pine tree indicate it was used to collect resin for turpentine production.[11]
Turpentine (and rosin) are produced as naval stores.[12] Pine trees especially in North Carolina were tapped for sap which was doubly distilled to make turpentine and rosin (aka resin)–hence the name tar heel. The trees were scored with a ledge called a "box" to collect the sap. Large numbers of enslaved people were used to score the trees, and collect and process the sap. Historian Jeremy B. Zallen describes this as industrial slavery, which was different from the more common instance of slaves in agriculture. By the 1840s camphine (also spelled camphene) became one of the dominant lamp fuels in the US.[12]
The pine trees of North Carolina were well suited to camphine production. The business also provided additional need for slaves as production expanded. Backwoods became more productive. Slaves were often leased in winter when agriculture was slower. The value of many was protected by life insurance. Wilmington became a center of the camphine industry. In cities, gas lighting was also available, but used by the upper classes. Camphine was the fuel of the average family.
Zallen reports that after Ft. Sumter, turpentine producers were cut off from major markets. Emancipation left them without manpower to collect and process turpentine. The camps were flammable. Many were burned in William Tecumseh Sherman's march from Savannah to Goldsboro.
Crude turpentine collected from the trees may be evaporated by steam distillation in a copper still. Molten rosin remains in the still bottoms after turpentine has been distilled out.[10] Such turpentine is called gum turpentine.[13] The term gum turpentine may also refer to crude turpentine, which may cause some confusion.
Turpentine may alternatively be extracted from destructive distillation of pine wood,[3] such as shredded pine stumps, roots, and slash, using the light end of the heavy naphtha fraction (boiling between 90 and 115 °C or 195 and 240 °F) from a crude oil refinery. Such turpentine is called wood turpentine. Multi-stage counter-current extraction is commonly used so fresh naphtha first contacts wood leached in previous stages and naphtha laden with turpentine from previous stages contacts fresh wood before vacuum distillation to recover naphtha from the turpentine. Leached wood is steamed for additional naphtha recovery prior to burning for energy recovery.[14]
When producing chemical wood pulp from pines or other coniferous trees, sulfate turpentine may be condensed from the gas generated in Kraft process pulp digesters. The average yield of crude sulfate turpentine is 5–10 kg/t pulp.[15] Unless burned at the mill for energy production, sulfate turpentine may require additional treatment measures to remove traces of sulfur compounds.[16]
As a solvent, turpentine is used for thinning oil-based paints, for producing varnishes, and as a raw material for the chemical industry. Its use as a solvent in industrialized nations has largely been replaced by the much cheaper turpentine substitutes obtained from petroleum such as white spirit. A solution of turpentine and beeswax or carnauba wax has long been used as a furniture wax.
Spirits of turpentine, called camphine, was burned in lamps with glass chimneys in the 1830s through the 1860s. Turpentine blended with grain alcohol was known as burning fluid. Both were used as domestic lamp fuels, gradually replacing whale oil, until kerosene, gas lighting and electric lights began to predominate.
Turpentine is also used as a source of raw materials in the synthesis of fragrant chemical compounds. Commercially used camphor, linalool, alpha-terpineol, and geraniol are all usually produced from alpha-pinene and beta-pinene, which are two of the chief chemical components of turpentine. These pinenes are separated and purified by distillation. The mixture of diterpenes and triterpenes that is left as residue after turpentine distillation is sold as rosin.
Turpentine and petroleum distillates such as coal oil and kerosene, were used in folk medicine for abrasions and wounds, as a treatment for lice, and when mixed with animal fat, as a chest rub or inhaler for nasal and throat ailments.[17][18] Vicks chest rubs still contain turpentine in their formulations, although not as an active ingredient.[19]
Turpentine, now understood to be dangerous for consumption, was a common medicine among seamen during the Age of Discovery. It was one of several products carried aboard Ferdinand Magellan's fleet during the first circumnavigation of the globe.[20] Taken internally it was used as a treatment for intestinal parasites. This is dangerous, due to the chemical's toxicity.[21][22]
Turpentine enemas, a very harsh purgative, had formerly been used for stubborn constipation or impaction.[23] They were also given punitively to political dissenters in post-independence Argentina.[24]
As an organic solvent, turpentine's vapour can irritate the skin and eyes, damage the lungs and respiratory system, as well as the central nervous system when inhaled, and cause damage to the renal system when ingested, among other things.[30] Ingestion can cause burning sensations, abdominal pain, nausea, vomiting, confusion, convulsions, diarrhea, tachycardia, unconsciousness, respiratory failure,[31] and chemical pneumonia.
The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for turpentine exposure in the workplace as 100 ppm (560 mg/m3) over an 8-hour workday. The same threshold was adopted by the National Institute for Occupational Safety and Health (NIOSH) as the recommended exposure limit (REL). At levels of 800 ppm (4480 mg/m3), turpentine is immediately dangerous to life and health.[32]