Creosote
Encyclopedia
Creosote is the portion of chemical products obtained by the distillation
of a tar
that remains heavier than water, notably useful for its anti-septic and preservative
properties. It is produced in some quantities from the burning of wood and coal in blast furnace
s and fireplace
s; commonly found inside chimney flues when the wood or coal burns incompletely, producing soot and tarry smoke, and is the compound responsible for the preservation and the flavor of meat in the process of smoking. The name is derived from the Greek kréas (κρέας), meaning "flesh", and sōtēr (σωτήρ), meaning "preserver".
The two main types in industrial production are wood-tar creosote and coal-tar creosote — the coal-tar variety, having stronger and more toxic properties, has chiefly been used as a preservative for wood; while the wood-tar variety has been used for meat preservation, wood treatment, and for medicinal purposes as an expectorant, anti-septic, astringent
, anaesthetic and laxative
, though these have mostly been replaced by newer medicines. Coal-tar creosote had also in the past been used as an escharotic to burn malignant skin tissue and in dentistry to prevent necrosis, but no longer is used that way because of its toxic, carcinogenic properties and because better and safer treatments are now available. Varieties of creosote have also been made from both petroleum
and oil shale
called oil-tar creosote, when derived from the oil tar, and water-gas-tar creosote when derived from the water gas tar. Creosote also has been made from pre-coal formations such as lignite
, giving to lignite-tar creosote and peat
, giving to peat-tar creosote.
Creosotes are commercially valuable, and therefore are produced industrially on a large scale, either for direct use, or as raw material for the production or extraction of various chemicals. There are several other names for such fluids, but most aren't trustworthy, being regional, or applying only some variants of them, or to other fluids as well. For example, pitch oil is used both for some kinds of creosote-like fluids and for kerosene.
derivatives and share some amount of simple phenols, but they aren't the only active element of any of them. For its useful effect, wood-tar creosote relies on the presence of methyl ethers of phenol, and coal-tar creosote on the presence of naphthalene
s and anthracene
s; otherwise each of them would dissolve in water.
Creosote was first discovered in its wood-tar form in 1832 by Carl Reichenbach
, when he found it both in the tar and pyrolingeous acids obtained by a dry distillation of beechwood. Because pyroligneous acid
was known as an anti-septic and meat preservative
, Reichenbach did experiments with dipping meat in diluted solution of distilled creosote. He found that the meat was dried without undergoing putrefaction
and had a delicious, smoky flavor. This led him to reason that creosote was the anti-septic principle contained in smoke, and further argued the creosote he found in wood-tar was also in coal-tar, animal-tar, and amber-tar in the same abundancy as in wood-tar.
Soon after, in 1834, Friedrich F. Runge
discovered carbolic acid in coal-tar, and Auguste Laurence obtained it from phenylhydrate, which was soon determined to be the same compound. There was no clear view on the relationship between carbolic acid and creosote; Runge described it as having similar caustic and anti-septic properties, but noted that it was different, in that it was an acid and formed salts. Nonetheless, Reichenbach argued that creosote was also the active element, as it was in pyroligneous acid. Despite evidence to the contrary, his view held sway with most chemists, and it became commonly accepted wisdom that creosote, carbolic acid, and phenylhydrate were identical substances, with different degrees of purity.
Carbolic acid was soon commonly sold under the name "creosote", and the rarity of wood-tar creosote in some places led chemists to believe that it was the same substance as described by Reichenbach. In the 1840s, Eugen F. von Gorup-Besanez
, after realizing that two samples of substances labeled as creosote were different, started a series of investigations to determine the chemical nature of carbolic acid, leading to a conclusion that it more resembled chlorinated quinones and must have been a different, entirely unrelated substance. Independently, there were investigations into the chemical nature of creosote. A study by F.K. Völkel revealed that purified creosote resembled the smell of guaiacol, and later studies by Heinrich Hlasiwetz
determined an element common in guaiacum and cresote which he called creosol, and that creosote contained a mixture of creosol and guaiacol. Later investigations by Gorup-Besanez, A.E. Hoffmann and Siegfried Marasse had shown that wood-tar creosote also contained phenols, giving it a feature in common with coal-tar creosote.
Historically, coal-tar creosote has been distinguished from what was thought of creosote proper — what would refer to the original substance of Reichenbach's discovery — and referred to specifically as "creosote oil". But because creosote from coal-tar and wood-tar are obtained from a similar process and have some common uses, they've also been seen in the same class of substances, with the terms "creosote" or "creosote oil" referring to either product.
Wood-tar creosote is a colourless to yellowish greasy liquid with a smoky odor, produces a sooty flame when burned, and has a burned taste. It is buoyant, with a specific gravity
of 1.037 to 1.087, retains fluidity at a very low temperature, and boils at 205-225°C. When transparent, it is in its purest form. Dissolution in water requires up to 200 times the amount of water as the base creosote. The creosote is a combination of plant phenolics: primarily guaiacol
and creosol
(4-methylguaiacol), which will typically constitute 50% of the oil; second in prevalence, cresol
and xylenol
; the rest being a combination of monophenols and polyphenol
s.
The simple phenols are not the only valued element in wood-tar creosote; on their own they coagulate
albumin
, the water-soluble proteins contained in meat, so serve as a preserving agent, but also cause disintegration. Most of the phenols in the creosote are methoxy
derivatives — they contain the methoxy group linked to the benzene
nucleus (O–CH3). The level of high methyl derivates created from the action of heat on wood (also apparent in the methyl alcohol produced through distillation) make wood-tar creosote substantially different from coal-tar creosote. Guaiacol is a methyl ether of pyrocatechin, while creosol is a methyl ether of methyl-pyrocatechin, the next homolog
of pyrocatechin. Methyl ethers differ from simple phenols in that they're less soluble in water, and less caustic and poisonous. This allows meat to successfully be preserved without disintegration, and allows creosote to as a medical treatment.
Because wood-tar creosote is used for its guaiacol and creosol content, its generally derived from beechwood rather than other woods, since it distills with a higher proportion of those chemicals to other phenolics. The creosote can be obtained by distilling the wood tar, and treating the fraction heavier than water with a sodium hydroxide solution. The alkaline solution would then separated from the insoluble oily layer, boiled upon contact with air to reduce impurities, and decomposed by diluted sulphuric acid. This produces a crude creosote, which would be purified by re-solution in alkali and re-precipitation with acid, and then redistilled with the fraction passing over between 200° and 225° constituting the purified creosote.
When ferric chloride is added to a dilute solution, it will turn green; a characteristic of ortho-oxy derivatives of benzene. It dissolves in sulphuric acid to a red liquid, which slowly changes to purple-violet. Shaken with hydrochloric acid in the absence of air, it becomes red, the color changing in the presence of air to dark brown or black.
In preparation of food by smoking, guaiacol contributes mainly to the smoky taste
, while the dimethyl ether of pyrogallol, syringol
, is the main chemical responsible for the smoky aroma.
Soon after it was discovered and recognized as the principle of meat smoking, wood-tar creosote became used as a replacement for the process. Several methods were used to apply the creosote. One was to dip the meat in pyroligneous acid or a water of diluted creosote, as Reichenbach did, or brush it over with them, and within one hour the meat would have the same quality of that of traditionally smoked preparations. Sometimes the creosote was diluted in vinegar rather than water, as vinegar was also used as a preservative. Another was to place the meat in a closed box, and place with it a few drops of creosote in a small bottle. Because of the volatility of the creosote, the atmosphere was filled with a vapor containing it, and it would cover the flesh.
The application of wood tar to sea-going vessels was practiced through the 18th century and early 19th century, before the creosote was isolated as a compound. Wood-tar creosote wasn't found to be as effective in wood treatments, because it was harder to impregnate the creosote into the wood cells, but still experiments were done, including by many governments, because it proved to be less expensive on the market.
Even before creosote as a chemical compound was discovered, it was the chief active component of medicinal remedies in different cultures around the world.
Larrea tridentata, or the so-called creosote bush, as named after its distinct creosote smell, was used by Native Americans
in the Southwest as a treatment for many maladies. The Cohahuillia Indians used the plant for intestinal complaints and tuberculosis
, the Pima would drink a decoction of the leaves as an emetic, and applied the boiled leaves as poultices to wounds or sores. Popago Indians prepared it medicinally for stiff limbs, snake bites, and menstrual cramps. Guaiacum
, after which the guaiacol in creosote was named, was used by native Caribbean islanders to treat tropical diseases and later for syphilis
.
During antiquity, pitches and resins were used commonly as medicines. Pliny
mentions a variety of tar-like substances being used as medicine, including cedria and pissinum. Cedria was the pitch and resin of the cedar tree, being equivalent to the oil of tar and pyrolingeous acid which are used in the first stage of distilling creosote. He recommends cedria to ease the pain in a toothache, as an injection in the ear in case of hardness of hearing, to kill parasitic worms, as a preventative for impregnation, as a treatment for phthiriasis
and porrigo, as an antidote for the poison of the sea hare
, as a liniment for elephantiasis
, and as an ointment to treat ulcers both on the skin and in the lungs. He further speaks of cedria being used as the embalming agent for preparing mummies. Pissinum was a tar water that was made by boiling cedria, spreading wool fleeces over the vessels to catch the steam and then wringing it out.
The Pharmacopeé of Lyons, published in 1786, says that cedar tree oil can induce vomiting, and suggests it helps medicate tumors and ulcers. Physicians contemporary to the discovery of creosote recommended ointments and pills made from tar or pitch to treat skin diseases. Tar water
had been used as a folk remedy since the Middle Ages to treat affections like dyspepsia. Bishop Berkeley
wrote several works on the medical virtues of tar water, including a philosophical work in 1744 titled Siris: a chain of philosophical reflexions and inquiries concerning the virtues of tar water, and divers other subjects connected together and arising one from another, and a poem where he praised its virtues. Pyroligneous acid was also used at the time in a medicinal water called Aqua Binelli.
Given this history, and the anti-septic properties known to creosote, it became popular among physicians in the 19th century. A dilution of creosote in water was sold in pharmacies as Aqua creosoti, as suggested by the previous use of pyroligneous acid. It was prescribed to quell the irritability of the stomach and bowels and detoxify, treat ulcers and abscesses, neutralize bad odors, and stimulate the mucous tissues of the mouth and throat. Creosote in general was listed as an irritant
, styptic, anti-septic, narcotic
, and diuretic
, and in small doses when taken internally as a sedative
and anaesthetic. It was used to treat ulcers, and as a way to sterilize the tooth and deaden the pain in case of a tooth-ache.
Creosote was suggested as a treatment for tuberculosis
by Reichenbach as soon as 1833. Following Reichenbach, it was argued for by John Elliotson
and Sir John Rose Cormack. Elliotson, inspired by the use of creosote to induce vomiting during an outbreak of cholera
, suggested its use for tuberculosis through inhalation. He also suggested it for epilepsy, neuralgia, diabetes and chronic glanders. The idea of using it for tuberculosis failed to take hold, and use of this purpose was dropped, until the idea was revived later in 1876 by the British doctor G. Anderson Imlay, who suggested it be applied locally in spray to the bronchial mucous membrane. This was followed up in 1877 when it was argued for in a clinical paper by Charles Bouchard
and Henri Gimbert. Germ theory had been established by Pasteur
in 1860, and Bouchard, arguing that a bacillus
was responsible for the disease, sought to rehabilitate creosote for its use as an anti-septic to treat it. He began a series of trials with Gimbert to convince the scientific community, and claimed a promising cure rate. A number of publications in Germany confirmed his results in the following years.
Following that, that was a period of experimentation of different techniques and chemicals using creosote in tuberculosis, which lasted until about 1910, when radiation therapy looked to be a more promising treatment. Guaiacol, instead of a full creosote solution, was suggested by Hermann Sahli
in 1887; he argued it had the active chemical of creosote and had the advantage of being of definite composition, and with less of a less unpleasant taste and odor. A number of solutions of both creosote and guaiacol appeared on the market, such as phosphotal and guaicophosphal, phosphites of creosote and guaiacol; eosot and geosot, valerinates of creosote and guaicol; phosot and taphosot, phosphate and tannophospate of creosote; and creosotal and tanosal, tannates of creosote. Creosote and eucalptus oil were also a remedy used together, administered through a vaporizor and inhaler. Since then, more effective and safer treatments for tuberculosis have been developed.
In the 1940s, Canadian-based Eldon Boyd experimented with guaiacol and a recent synthetic modification — glycerol guaiacolate (guaifenesin
) — on animals. His data showed that both drugs were effective in increasing secretions into the airways in laboratory animals, when high enough doses were given.
Wood-tar creosote is to some extent used for wood preservation, but generally mixed with coal-tar creosote, since it isn't as effective. Commercially available preparations of "liquid smoke
", marketed to add a smoked flavor to meat and aid as a preservative, consist primarily of creosote and other constituents of smoke. Creosote is the element which gives liquid smoke its function; guaicol lends to the taste and the creosote oils help act as the preservative.
The guaifenesin
developed by Eldon Boyd is still commonly used today as an expectorant, sold over the counter, and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections. Guaifenesin is a component of Mucinex, Robitussin DAC
, Cheratussin DAC, Robitussin AC, Cheratussin AC, Benylin
, DayQuil
Mucous Control, Meltus, and Bidex 400.
Seirogan is a popular Kampo
medicine in Japan, used as an anti-diarrheal, and has 133 mg wood creosote from beech, pine, maple or oak wood per adult dose as its primary ingredient. Seirogan was first used as a gastrointestinal medication by the Royal Japanese Army in Russia during the Russo-Japanese War of 1904-5. Creomulsion is a cough medicine in the United States, introduced in 1925, that is still sold and contains beechwood creosote.
Creosote, in the form of samples from the creosote bush
, is often found as a herbal remedy and supplement under the name chaparral, and in the form of beechwood creosote under the name kreosotum or kreosote.
Coal-tar creosote is greenish-brown liquid, with different degrees of darkness, viscosity, and fluorescence depending on how its made. When freshly made, the creosote is a yellow oil with a greenish cast and highly fluorescent; the fluorescence increased by exposure to air and light. After settling, the oil is dark green by reflected light and dark red by transmitted light. To the naked eye, it will generally appear brown. The creosote (often called "creosote oil") consists almost wholly of aromatic hydrocarbon
s, with some amount of bases and acids and other neutral oils. The flash point is 70–75°C and burning point is 90–100°C, and when burned it releases a greenish smoke. The smell largely depends on the naptha content in the creosote; if there is a high amount, it will have a naptha-like smell; otherwise it will smell more like tarry.
In the process of coal-tar distillation, the distillate is collected into four fractions; the "light oil", which remains lighter than water, the "middle oil" which passes over when the light oil is removed; the "heavy oil", which sinks; and the "anthracene oil", which when cold is mostly solid and greasy, of a buttery consistence. Creosote refers to the portion of coal tar which distills as "heavy oil", typically between 230–270°C, also called "dead oil"; it sinks into water but still is fairly liquid. Carbolic acid is produced in the second fraction of distillation and is often distilled into what is referred to as "carbolic oil".
Commercial creosote will contain substances from six groups. The two groups occur in the greatest amounts and are the products of the distillation process — the "tar acids", which distill below 205°C and consist mainly of phenols, cresols, and xylenols, including carbolic acid — and aromatic hydrocarbons, which divide into naphthalene
s, which distill approximately between 205° and 255°C, and constituents of an anthracene
nature, which distill above 255°C. The quantity of each varies based on the quality of tar and temperatures used, but generally, the tar acids won't exceed 5%, the naphthalenes will make up 15 to 50%, and the anthracenes will make up 45% to 70%. The hydrocarbons are mainly aromatic; derivatives of benzene and related cyclic compounds such as naphthalene
, anthracene
, phenanthrene
, acenapthene, and fluorine
. Creosotes from vertical-retort and low temperature tars contain, in addition, some paraffinic and olefinic hydrocarbons. The tar-acid content also depends on the source of the tar — it may be less than 3% in creosote from coke-oven tar and as high as 32% in creosote from vertical retort tar. All of these have anti-septic properties. The tar acids are the strongest anti-septics but have the highest degree of solubility in water and are the most volatile; so, like with wood-tar creosote, phenols are not the most valued component, as by themselves they would lend to being poor preservatives. In addition, creosote will contain several products naturally occurring in coal — nitrogen-containing heterocycles, such as acridines, carbazoles, and quinolines, referred to as the "tar bases" and generally make up about 3% of the creosote — sulfur-containing heterocycles, generally benzothiophenes — and oxygen-containing heterocycles, dibenzofurans. Lastly, creosote will contain a small number of aromatic amines produced by the other substances during the distillation process and likely resulting from a combination of thermolysis and hydrogenation. The tar bases are often extracted by washing the creosote with aqueous mineral acid, although they're also suggested to have anti-septic ability similar to the tar acids.
Commercially used creosote is often treated to extract the carbolic acid, naphthalene, or anthracene content. The carbolic acid or naphthalene is generally extracted to be used in other commercial products. American produced creosote oils typically will have low amounts of anthracene and high amounts of naphthalene, because when forcing the distillate at a temperature that produces anthracene the soft pitch will be ruined and only the hard pitch will remain; this ruins it for use in roofing purposes, and only leaves a product which isn't commercially useful.
The use of coal-tar creosote on a commercial scale began in 1838, when a patent covering the use of creosote oil to treat timber was taken out by John Bethell in 1838. The process he used became referred to as the "Bethell process" and later became more widely known as the fuel-cell process. It involves sealing wood in a pressure chamber and applying a vacuum to remove air and moisture from the wood cells. The wood is then pressure treated in order to impregnate it with the preservative chemicals. Afterwards the a vacuum is applied again to separate the excess solution from the timber. The same year a method to treat wood using zinc choloride was patented by Sir William Burnett and referred to as the "Burnett process". One of the chief uses of creosoted wood was in preserving railway ties (sleepers) so they didn't need to be replaced due to wood rot.
Besides treating wood, it was also used for lighting and fuel. In the beginning, it was only used for lighting needed in harbor and outdoor work, where the smoke that was produced from burning it was of little inconvenience. By 1879, lamps had been created that ensured a more complete combustion by using compressed air, removing the drawback of the smoke. Creosote was also processed into gas and used for lighting that way. As a fuel, it was used to power ships at sea and blast furnaces for different industrial needs, once it was discovered to be more efficient than unrefined coal or wood. It was also used industrially for the softening of hard pitch, and burned produce lamp black. By 1890, the production of creosote in the United Kingdom
totaled approximately 29,900,000 gallons per year.
In 1854, Alexander McDougall
and Angus Smith developed and patented a product called McDougall's Powder as a sewer deodorant; it was mainly composed from carbolic acid derived from creosote. McDougall in 1864, experimented with his solution to remove entozoa parasites from cattle pasturing on a sewage farm. This later led to widespread use of creosote as a cattle wash and sheep dip. External parasites would be killed in a creosote diluted dip, and drenching tubes would be used to administer doses to the animals stomach to kill internal parasites.
Two later methods for creosoting wood were introduced after the turn of the century, referred to as empty-cell processes, because they involve compressing the air inside the wood so that the preservative can only coat the inner cell walls rather than saturating the interior cell voids. This is a less effective, though usually satisfactory, method of treating the wood, but is used because it requires less of the creosoting material. The first method, the "Rüping process" was patented in 1902, and the second, the "Lowry process" was patented in 1906. Later in 1906, the "Allardyce process" and "Card process" were patented to treat wood with a combination of both creosote and zinc chloride. In 1912, it was estimated that a total of 150,000,000 gallons were produced in the United States per year.
Coal-tar creosote, despite its toxicity, was used as a stimulant and escharotic, as a caustic agent used to treat ulcers and malignancies and cauterize wounds and prevent infection and decay. It was particularly used in dentistry, used to destroy tissues and arrest necrosis
Coal-tar creosote is the most widely used wood treatment today; both industrially, processed into wood using pressure methods such as "fuel-cell process" or "empty-cell process", and more commonly applied to wood through brushing. In addition to toxicity to fungi, insects, and marine borers, it serves as a natural water repellant. Its commonly used to preserve and waterproof cross ties, pilings, telephone poles, power line poles, marine pilings, and fence posts. Although suitable for use in preserving the structural timbers of buildings, its not generally used that way because it is difficult to apply.
Due to its carcinogen
ic character, the European Union has regulated the quality of creosote for the EU market and requires that the sale of creosote be limited to professional users. The United States Environmental Protection Agency
regulates the use of coal tar creosote as a wood preservative under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act
. Creosote is considered a restricted-use pesticide and is only available to licensed pesticide applicators
, and even death
. Longer direct skin contact with low levels of creosote mixtures or their vapors can result in increased light sensitivity, damage to the cornea
, and skin damage. Longer exposure to creosote vapors can cause irritation
of the respiratory tract
.
The International Agency for Research on Cancer
(IARC) has determined that coal tar creosote is probably carcinogenic to humans, based on adequate animal evidence and limited human evidence. It is instructive to note that the animal testing relied upon by IARC involved the continuous application of creosote to the shaved skin of rodents. After weeks of creosote application, the animal
s developed cancerous skin lesions and in one test, lesions of the lung. The United States Environmental Protection Agency
has stated that coal tar creosote is a probable human carcinogen
based on both human and animal studies. As such, the Federal Occupational Safety and Health Administration
(OSHA) has set a permissible exposure limit of 0.2 milligrams of coal tar creosote per cubic meter of air (0.2 mg/m3) in the workplace during an 8-hour day, and the Environmental Protection Agency (EPA) requires that spills or accidental releases into the environment of one pound (0.454 kg) or more of creosote be reported to them.
There is no unique exposure pathway of children to creosote. Children exposed to creosote will probably experience the same health effects seen in adults exposed to creosote. It is unknown whether children differ from adults in their susceptibility to health effects from creosote.
A 2005 mortality study of creosote workers found no evidence supporting an increased risk of cancer death, as a result of exposure to creosote. Based on the findings of the largest mortality study to date of workers employed in creosote wood treating plants, there is no evidence that employment at creosote wood-treating plants or exposure to creosote-based preservatives was associated with any significant mortality increase from either site-specific cancers or non-malignant diseases. The study consisted of 2,179 employees at eleven plants in the United States where wood was treated with creosote preservatives. Some workers began work in the 1940s to 1950s. The observation period of the study covered 1979- 2001. The average length of employment was 12.5 years. One third of the study subjects were employed for over 15 years.
The largest health effect of creosote is deaths caused by residential fires.
Oil-tar creosote is derived from the tar that forms when using petroleum or shale oil in the manufacturing of gas. The distillation of the tar from the oil occurs at very high temperatures; around 980°C. The tar forms at the same time as the gas, and once processed for creosotes contains a high percentage of cyclic hydrocarbons, a very low amount of tar acids and tar bases, and no true anthracenes have been identified. Historically, this has mainly been produced in the United States in the Pacific coast, where petroleum has been more abundant than coal. Limited quantities have been used industrially, either alone, mixed with coal-tar creosote, or fortified with pentachlorophenol.
rather than bituminous coal, and varies considerably from coal-tar creosote. Also called "lignite oil", it has a very high content of tar acids, and has been used to increase the tar acids in normal creosote when necessary. When it has been produced, its generally been applied in mixtures with coal-tar creosote or petroleum. Its effectiveness when used alone has not been established. In an experiment with southern yellow pine fence posts in Mississippi, straight lignite-tar creosote was giving good results after about 27 years exposure, although not as good as the standard coal-tar creosote used in the same situation.
-tar, but they've been mostly unsuccessful, due to the problems with winning and drying peat on an industrial scale. Peat tar by itself has in the past been used as a wood preservative.
.
Over the course of a season creosote deposits can become several inches thick. This creates a compounding problem, because the creosote deposits reduce the draft (airflow through the chimney) which increases the probability that the wood fire is not getting enough air to burn at high temperature. Since creosote is highly combustible, a thick accumulation creates a fire hazard. If a hot fire is built in the stove or fireplace, and the air control left wide open, this may allow hot oxygen into the chimney where it comes in contact with the creosote which then ignites—causing a chimney fire
. Chimney fires often spread to the main building because the chimney gets so hot that it ignites any combustible material in direct contact with it, such as wood. The fire can also spread to the main building from sparks emitting from the chimney and landing on combustible roof surfaces. In order to properly maintain chimneys and heaters that burn wood or carbon-based fuels, the creosote buildup must be removed. Chimney sweep
s perform this service for a fee.
73% of heating fires and 25% of all residential fires in the United States are caused by failure to clean out creosote buildup. Since 1990 the number of creosote caused fires has decreased in the United States by 75%. This is partly due to the use of efficient wood-burning stove
s that fully burn the volatiles in the smoke, and partly due to the decrease in the use of wood heating during two decades of milder Winter weather, and low fuel prices.
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
of a tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
that remains heavier than water, notably useful for its anti-septic and preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....
properties. It is produced in some quantities from the burning of wood and coal in blast furnace
Blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
s and fireplace
Fireplace
A fireplace is an architectural structure to contain a fire for heating and, especially historically, for cooking. A fire is contained in a firebox or firepit; a chimney or other flue allows gas and particulate exhaust to escape...
s; commonly found inside chimney flues when the wood or coal burns incompletely, producing soot and tarry smoke, and is the compound responsible for the preservation and the flavor of meat in the process of smoking. The name is derived from the Greek kréas (κρέας), meaning "flesh", and sōtēr (σωτήρ), meaning "preserver".
The two main types in industrial production are wood-tar creosote and coal-tar creosote — the coal-tar variety, having stronger and more toxic properties, has chiefly been used as a preservative for wood; while the wood-tar variety has been used for meat preservation, wood treatment, and for medicinal purposes as an expectorant, anti-septic, astringent
Astringent
An astringent substance is a chemical compound that tends to shrink or constrict body tissues, usually locally after topical medicinal application. The word "astringent" derives from Latin adstringere, meaning "to bind fast"...
, anaesthetic and laxative
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...
, though these have mostly been replaced by newer medicines. Coal-tar creosote had also in the past been used as an escharotic to burn malignant skin tissue and in dentistry to prevent necrosis, but no longer is used that way because of its toxic, carcinogenic properties and because better and safer treatments are now available. Varieties of creosote have also been made from both petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
and oil shale
Oil shale
Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen from which liquid hydrocarbons called shale oil can be produced...
called oil-tar creosote, when derived from the oil tar, and water-gas-tar creosote when derived from the water gas tar. Creosote also has been made from pre-coal formations such as lignite
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
, giving to lignite-tar creosote and peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
, giving to peat-tar creosote.
Creosotes are commercially valuable, and therefore are produced industrially on a large scale, either for direct use, or as raw material for the production or extraction of various chemicals. There are several other names for such fluids, but most aren't trustworthy, being regional, or applying only some variants of them, or to other fluids as well. For example, pitch oil is used both for some kinds of creosote-like fluids and for kerosene.
Creosote oils
For some part of their history, wood-tar creosote and coal-tar creosote were suggested to be the same substance — only in different purities — which gives to their common name; the two were only determined to be chemically different substances later on. All types of creosote are composed of phenolPhenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
derivatives and share some amount of simple phenols, but they aren't the only active element of any of them. For its useful effect, wood-tar creosote relies on the presence of methyl ethers of phenol, and coal-tar creosote on the presence of naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
s and anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
s; otherwise each of them would dissolve in water.
Creosote was first discovered in its wood-tar form in 1832 by Carl Reichenbach
Carl Reichenbach
Baron Dr. Carl Ludwig von Reichenbach was a notable chemist, geologist, metallurgist, naturalist, industrialist and philosopher, and a member of the prestigious Prussian Academy of Sciences...
, when he found it both in the tar and pyrolingeous acids obtained by a dry distillation of beechwood. Because pyroligneous acid
Pyroligneous acid
Pyroligneous acid, also called wood vinegar, is a dark liquid produced through the natural act of carbonization, which occurs when wood is heated in an airless container during charcoal production.-Chemical components:...
was known as an anti-septic and meat preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....
, Reichenbach did experiments with dipping meat in diluted solution of distilled creosote. He found that the meat was dried without undergoing putrefaction
Putrefaction
Putrefaction is one of seven stages in the decomposition of the body of a dead animal. It can be viewed, in broad terms, as the decomposition of proteins, in a process that results in the eventual breakdown of cohesion between tissues and the liquefaction of most organs.-Description:In terms of...
and had a delicious, smoky flavor. This led him to reason that creosote was the anti-septic principle contained in smoke, and further argued the creosote he found in wood-tar was also in coal-tar, animal-tar, and amber-tar in the same abundancy as in wood-tar.
Soon after, in 1834, Friedrich F. Runge
Friedrich Ferdinand Runge
Friedlieb Ferdinand Runge was a German analytical chemist....
discovered carbolic acid in coal-tar, and Auguste Laurence obtained it from phenylhydrate, which was soon determined to be the same compound. There was no clear view on the relationship between carbolic acid and creosote; Runge described it as having similar caustic and anti-septic properties, but noted that it was different, in that it was an acid and formed salts. Nonetheless, Reichenbach argued that creosote was also the active element, as it was in pyroligneous acid. Despite evidence to the contrary, his view held sway with most chemists, and it became commonly accepted wisdom that creosote, carbolic acid, and phenylhydrate were identical substances, with different degrees of purity.
Carbolic acid was soon commonly sold under the name "creosote", and the rarity of wood-tar creosote in some places led chemists to believe that it was the same substance as described by Reichenbach. In the 1840s, Eugen F. von Gorup-Besanez
Eugen Freiherr von Gorup-Besanez
Eugen Freiherr von Gorup-Besanez was an Austrian-German chemist.-Biography:He was educated in Graz and at Vienna, Padua, Munich, and Göttingen. He was appointed professor of chemistry at Erlangen in 1849...
, after realizing that two samples of substances labeled as creosote were different, started a series of investigations to determine the chemical nature of carbolic acid, leading to a conclusion that it more resembled chlorinated quinones and must have been a different, entirely unrelated substance. Independently, there were investigations into the chemical nature of creosote. A study by F.K. Völkel revealed that purified creosote resembled the smell of guaiacol, and later studies by Heinrich Hlasiwetz
Heinrich Hlasiwetz
Heinrich Hlasiwetz was an Austrian chemist.- Bibliography :* Johannes Uray, Organische Chemie in chemischer Forschung und Lehre an österreichischen Universitäten zwischen 1840 und 1870. In: Bericht über den 25. Österreichischen Historikertag in St. Pölten 2008. St. Pölten 2010, S...
determined an element common in guaiacum and cresote which he called creosol, and that creosote contained a mixture of creosol and guaiacol. Later investigations by Gorup-Besanez, A.E. Hoffmann and Siegfried Marasse had shown that wood-tar creosote also contained phenols, giving it a feature in common with coal-tar creosote.
Historically, coal-tar creosote has been distinguished from what was thought of creosote proper — what would refer to the original substance of Reichenbach's discovery — and referred to specifically as "creosote oil". But because creosote from coal-tar and wood-tar are obtained from a similar process and have some common uses, they've also been seen in the same class of substances, with the terms "creosote" or "creosote oil" referring to either product.
Wood-tar creosote
EWLINE
|
Wood-tar creosote is a colourless to yellowish greasy liquid with a smoky odor, produces a sooty flame when burned, and has a burned taste. It is buoyant, with a specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 1.037 to 1.087, retains fluidity at a very low temperature, and boils at 205-225°C. When transparent, it is in its purest form. Dissolution in water requires up to 200 times the amount of water as the base creosote. The creosote is a combination of plant phenolics: primarily guaiacol
Guaiacol
Guaiacol is a naturally occurring organic compound with the formula C6H4. Although it is biosynthesized by a variety of organisms, this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke,...
and creosol
Creosol
Creosol is an ingredient of creosote. Compared with phenol, creosol is a less toxic disinfectant.-Sources :* Coal tar creosote* Wood creosote* Reduction product of vanillin using zinc powder in strong hydrochloric acid...
(4-methylguaiacol), which will typically constitute 50% of the oil; second in prevalence, cresol
Cresol
Cresols are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds which are categorized as phenols . Depending on the temperature, cresols can be solid or liquid because they have melting points not far from room...
and xylenol
Xylenol
Xylenol or dimethylphenol is an arene compound with two methyl groups and a hydroxyl group. 6 isomers exist of xylenol of which 2,6-xylenol with both methyl group in an ortho position with respect to the hydroxyl group is the most important...
; the rest being a combination of monophenols and polyphenol
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
s.
EWLINE
|
The simple phenols are not the only valued element in wood-tar creosote; on their own they coagulate
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
albumin
Albumin
Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...
, the water-soluble proteins contained in meat, so serve as a preserving agent, but also cause disintegration. Most of the phenols in the creosote are methoxy
Methoxy
In chemistry , methoxy refers to the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula O–CH3.The word is used in organic nomenclature usually to describe an ether...
derivatives — they contain the methoxy group linked to the benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
nucleus (O–CH3). The level of high methyl derivates created from the action of heat on wood (also apparent in the methyl alcohol produced through distillation) make wood-tar creosote substantially different from coal-tar creosote. Guaiacol is a methyl ether of pyrocatechin, while creosol is a methyl ether of methyl-pyrocatechin, the next homolog
Homology (chemistry)
In chemistry, homology refers to the appearance of homologues. A homologue is a compound belonging to a series of compounds differing from each other by a repeating unit, such as a methylene group, a peptide residue, etcetera....
of pyrocatechin. Methyl ethers differ from simple phenols in that they're less soluble in water, and less caustic and poisonous. This allows meat to successfully be preserved without disintegration, and allows creosote to as a medical treatment.
| EWLINE |
Because wood-tar creosote is used for its guaiacol and creosol content, its generally derived from beechwood rather than other woods, since it distills with a higher proportion of those chemicals to other phenolics. The creosote can be obtained by distilling the wood tar, and treating the fraction heavier than water with a sodium hydroxide solution. The alkaline solution would then separated from the insoluble oily layer, boiled upon contact with air to reduce impurities, and decomposed by diluted sulphuric acid. This produces a crude creosote, which would be purified by re-solution in alkali and re-precipitation with acid, and then redistilled with the fraction passing over between 200° and 225° constituting the purified creosote.
When ferric chloride is added to a dilute solution, it will turn green; a characteristic of ortho-oxy derivatives of benzene. It dissolves in sulphuric acid to a red liquid, which slowly changes to purple-violet. Shaken with hydrochloric acid in the absence of air, it becomes red, the color changing in the presence of air to dark brown or black.
In preparation of food by smoking, guaiacol contributes mainly to the smoky taste
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
, while the dimethyl ether of pyrogallol, syringol
Syringol
Syringol is a dimethyl ether of pyrogallol. It is slightly soluble in water. It is combustible, with flash point of 140 °C.Together with guaiacol, syringol and its derivates are characteristic products of pyrolysis of lignin. As such, syringol is an important component of wood smoke...
, is the main chemical responsible for the smoky aroma.
Industrial
Soon after it was discovered and recognized as the principle of meat smoking, wood-tar creosote became used as a replacement for the process. Several methods were used to apply the creosote. One was to dip the meat in pyroligneous acid or a water of diluted creosote, as Reichenbach did, or brush it over with them, and within one hour the meat would have the same quality of that of traditionally smoked preparations. Sometimes the creosote was diluted in vinegar rather than water, as vinegar was also used as a preservative. Another was to place the meat in a closed box, and place with it a few drops of creosote in a small bottle. Because of the volatility of the creosote, the atmosphere was filled with a vapor containing it, and it would cover the flesh.
The application of wood tar to sea-going vessels was practiced through the 18th century and early 19th century, before the creosote was isolated as a compound. Wood-tar creosote wasn't found to be as effective in wood treatments, because it was harder to impregnate the creosote into the wood cells, but still experiments were done, including by many governments, because it proved to be less expensive on the market.
Medical
Even before creosote as a chemical compound was discovered, it was the chief active component of medicinal remedies in different cultures around the world.
Larrea tridentata, or the so-called creosote bush, as named after its distinct creosote smell, was used by Native Americans
Native Americans in the United States
Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...
in the Southwest as a treatment for many maladies. The Cohahuillia Indians used the plant for intestinal complaints and tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
, the Pima would drink a decoction of the leaves as an emetic, and applied the boiled leaves as poultices to wounds or sores. Popago Indians prepared it medicinally for stiff limbs, snake bites, and menstrual cramps. Guaiacum
Guaiacum
Guaiacum, sometimes spelled Guajacum, is a genus of flowering plants in the caltrop family Zygophyllaceae. It contains five species of slow-growing shrubs and trees, reaching a height of approximately but are usually less than half of that...
, after which the guaiacol in creosote was named, was used by native Caribbean islanders to treat tropical diseases and later for syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
.
During antiquity, pitches and resins were used commonly as medicines. Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
mentions a variety of tar-like substances being used as medicine, including cedria and pissinum. Cedria was the pitch and resin of the cedar tree, being equivalent to the oil of tar and pyrolingeous acid which are used in the first stage of distilling creosote. He recommends cedria to ease the pain in a toothache, as an injection in the ear in case of hardness of hearing, to kill parasitic worms, as a preventative for impregnation, as a treatment for phthiriasis
Phthiriasis
Phthiriasis is a common eyelid infestation, caused by Phthirus pubis .Pediculosis is an eyelid infestation by either Pediculus humanus corporis or Pediculus humanus capitus lice...
and porrigo, as an antidote for the poison of the sea hare
Sea hare
The clade Aplysiomorpha, commonly known as Sea hares or Sea Bags , are medium-sized to very large Opisthobranchia with a soft internal shell made of protein...
, as a liniment for elephantiasis
Elephantiasis
Elephantiasis is a disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs and male genitals. In some cases the disease can cause certain body parts, such as the scrotum, to swell to the size of a softball or basketball. It is caused by...
, and as an ointment to treat ulcers both on the skin and in the lungs. He further speaks of cedria being used as the embalming agent for preparing mummies. Pissinum was a tar water that was made by boiling cedria, spreading wool fleeces over the vessels to catch the steam and then wringing it out.
The Pharmacopeé of Lyons, published in 1786, says that cedar tree oil can induce vomiting, and suggests it helps medicate tumors and ulcers. Physicians contemporary to the discovery of creosote recommended ointments and pills made from tar or pitch to treat skin diseases. Tar water
Tar water
Tar-water is a Medieval medicine consisting of pine tar and water. It was foul tasting and so slowly dropped in popularity, but was revived in the Victorian era....
had been used as a folk remedy since the Middle Ages to treat affections like dyspepsia. Bishop Berkeley
George Berkeley
George Berkeley , also known as Bishop Berkeley , was an Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism"...
wrote several works on the medical virtues of tar water, including a philosophical work in 1744 titled Siris: a chain of philosophical reflexions and inquiries concerning the virtues of tar water, and divers other subjects connected together and arising one from another, and a poem where he praised its virtues. Pyroligneous acid was also used at the time in a medicinal water called Aqua Binelli.
Given this history, and the anti-septic properties known to creosote, it became popular among physicians in the 19th century. A dilution of creosote in water was sold in pharmacies as Aqua creosoti, as suggested by the previous use of pyroligneous acid. It was prescribed to quell the irritability of the stomach and bowels and detoxify, treat ulcers and abscesses, neutralize bad odors, and stimulate the mucous tissues of the mouth and throat. Creosote in general was listed as an irritant
Irritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
, styptic, anti-septic, narcotic
Narcotic
The term narcotic originally referred medically to any psychoactive compound with any sleep-inducing properties. In the United States of America it has since become associated with opioids, commonly morphine and heroin and their derivatives, such as hydrocodone. The term is, today, imprecisely...
, and diuretic
Diuretic
A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
, and in small doses when taken internally as a sedative
Sedative
A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....
and anaesthetic. It was used to treat ulcers, and as a way to sterilize the tooth and deaden the pain in case of a tooth-ache.
Creosote was suggested as a treatment for tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
by Reichenbach as soon as 1833. Following Reichenbach, it was argued for by John Elliotson
John Elliotson
John Elliotson was an English physician, born in Southwark, London.He studied medicine first at the University of Edinburgh , where he was influenced by Thomas Brown, M.D...
and Sir John Rose Cormack. Elliotson, inspired by the use of creosote to induce vomiting during an outbreak of cholera
Cholera
Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...
, suggested its use for tuberculosis through inhalation. He also suggested it for epilepsy, neuralgia, diabetes and chronic glanders. The idea of using it for tuberculosis failed to take hold, and use of this purpose was dropped, until the idea was revived later in 1876 by the British doctor G. Anderson Imlay, who suggested it be applied locally in spray to the bronchial mucous membrane. This was followed up in 1877 when it was argued for in a clinical paper by Charles Bouchard
Charles-Joseph Bouchard
Charles-Joseph Bouchard was a French pathologist born in Montier-en-Der, a commune the department of Haute-Marne. He studied medicine in Lyon and Paris, where he obtained his doctorate in 1866. In 1874 he became a physician at Bicêtre Hospital, and in 1879 was appointed chair of general pathology...
and Henri Gimbert. Germ theory had been established by Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...
in 1860, and Bouchard, arguing that a bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...
was responsible for the disease, sought to rehabilitate creosote for its use as an anti-septic to treat it. He began a series of trials with Gimbert to convince the scientific community, and claimed a promising cure rate. A number of publications in Germany confirmed his results in the following years.
Following that, that was a period of experimentation of different techniques and chemicals using creosote in tuberculosis, which lasted until about 1910, when radiation therapy looked to be a more promising treatment. Guaiacol, instead of a full creosote solution, was suggested by Hermann Sahli
Hermann Sahli
Hermann Sahli was a Swiss internist who was a native of Bern. In 1878 he earned his doctorate from the University of Bern, and subsequently became an assistant to Ludwig Lichtheim in Bern. Afterwards he traveled to Leipzig, where he worked under Julius Friedrich Cohnheim and Carl Weigert...
in 1887; he argued it had the active chemical of creosote and had the advantage of being of definite composition, and with less of a less unpleasant taste and odor. A number of solutions of both creosote and guaiacol appeared on the market, such as phosphotal and guaicophosphal, phosphites of creosote and guaiacol; eosot and geosot, valerinates of creosote and guaicol; phosot and taphosot, phosphate and tannophospate of creosote; and creosotal and tanosal, tannates of creosote. Creosote and eucalptus oil were also a remedy used together, administered through a vaporizor and inhaler. Since then, more effective and safer treatments for tuberculosis have been developed.
In the 1940s, Canadian-based Eldon Boyd experimented with guaiacol and a recent synthetic modification — glycerol guaiacolate (guaifenesin
Guaifenesin
Guaifenesin INN or guaiphenesin , also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections.-History:Similar medicines derived from the guaiac tree were in use as a...
) — on animals. His data showed that both drugs were effective in increasing secretions into the airways in laboratory animals, when high enough doses were given.
Industrial
Wood-tar creosote is to some extent used for wood preservation, but generally mixed with coal-tar creosote, since it isn't as effective. Commercially available preparations of "liquid smoke
Liquid Smoke
Liquid smoke is a substance produced from smoke passed through water. Liquid smoke is used for both food preservation and flavoring. While some worry that liquid smoke contains carcinogenic compounds, research suggests that the concentration levels are well under the acceptable limit formed by the...
", marketed to add a smoked flavor to meat and aid as a preservative, consist primarily of creosote and other constituents of smoke. Creosote is the element which gives liquid smoke its function; guaicol lends to the taste and the creosote oils help act as the preservative.
Medical
The guaifenesin
Guaifenesin
Guaifenesin INN or guaiphenesin , also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections.-History:Similar medicines derived from the guaiac tree were in use as a...
developed by Eldon Boyd is still commonly used today as an expectorant, sold over the counter, and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections. Guaifenesin is a component of Mucinex, Robitussin DAC
Robitussin DAC
Robitussin DAC is an exempt narcotic cold medicine, which is available in the United States in a solution. A version without pseudoephedrine is called Robitussin AC. Cherastussin DAC and AC are manufactured by Qualitest. Under U.S...
, Cheratussin DAC, Robitussin AC, Cheratussin AC, Benylin
Benylin
Benylin is a brand name owned by Johnson & Johnson for a range of cough, cold and flu medications. The flagship cough syrup and cold care brand is marketed in several countries as Benylin DM, for its active ingredient, dextromethorphan...
, DayQuil
DayQuil
DayQuil is a medicine intended to relieve symptoms of the common cold and flu. Made by Vicks, it is available in syrup and capsule form. DayQuil's night time counterpart is NyQuil, which contains sedative antihistamines. Because DayQuil lacks antihistamines, it does not cause drowsiness, and thus...
Mucous Control, Meltus, and Bidex 400.
Seirogan is a popular Kampo
Kampo
, alternatively shortened as just , is the Japanese study and adaptation of Traditional Chinese medicine. The basic works of Chinese medicine came to Japan between the 7th and 9th centuries. Since then, the Japanese have created their own unique herbal medical system and diagnosis...
medicine in Japan, used as an anti-diarrheal, and has 133 mg wood creosote from beech, pine, maple or oak wood per adult dose as its primary ingredient. Seirogan was first used as a gastrointestinal medication by the Royal Japanese Army in Russia during the Russo-Japanese War of 1904-5. Creomulsion is a cough medicine in the United States, introduced in 1925, that is still sold and contains beechwood creosote.
Creosote, in the form of samples from the creosote bush
Creosote bush
Larrea tridentata is known as Creosote bush as a plant, chaparral as a medicinal herb, and as "gobernadora" in Mexico, Spanish for "governess," due to its ability for inhibiting the growth of nearby plants to have more water. In Sonora, it is more commonly called "hediondilla." It is a flowering...
, is often found as a herbal remedy and supplement under the name chaparral, and in the form of beechwood creosote under the name kreosotum or kreosote.
Coal-tar creosote
|
Coal-tar creosote is greenish-brown liquid, with different degrees of darkness, viscosity, and fluorescence depending on how its made. When freshly made, the creosote is a yellow oil with a greenish cast and highly fluorescent; the fluorescence increased by exposure to air and light. After settling, the oil is dark green by reflected light and dark red by transmitted light. To the naked eye, it will generally appear brown. The creosote (often called "creosote oil") consists almost wholly of aromatic hydrocarbon
Aromatic hydrocarbon
An aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent...
s, with some amount of bases and acids and other neutral oils. The flash point is 70–75°C and burning point is 90–100°C, and when burned it releases a greenish smoke. The smell largely depends on the naptha content in the creosote; if there is a high amount, it will have a naptha-like smell; otherwise it will smell more like tarry.
In the process of coal-tar distillation, the distillate is collected into four fractions; the "light oil", which remains lighter than water, the "middle oil" which passes over when the light oil is removed; the "heavy oil", which sinks; and the "anthracene oil", which when cold is mostly solid and greasy, of a buttery consistence. Creosote refers to the portion of coal tar which distills as "heavy oil", typically between 230–270°C, also called "dead oil"; it sinks into water but still is fairly liquid. Carbolic acid is produced in the second fraction of distillation and is often distilled into what is referred to as "carbolic oil".
| EWLINE |
Commercial creosote will contain substances from six groups. The two groups occur in the greatest amounts and are the products of the distillation process — the "tar acids", which distill below 205°C and consist mainly of phenols, cresols, and xylenols, including carbolic acid — and aromatic hydrocarbons, which divide into naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
s, which distill approximately between 205° and 255°C, and constituents of an anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
nature, which distill above 255°C. The quantity of each varies based on the quality of tar and temperatures used, but generally, the tar acids won't exceed 5%, the naphthalenes will make up 15 to 50%, and the anthracenes will make up 45% to 70%. The hydrocarbons are mainly aromatic; derivatives of benzene and related cyclic compounds such as naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
, anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
, phenanthrene
Phenanthrene
Phenanthrene is a polycyclic aromatic hydrocarbon composed of three fused benzene rings. The name phenanthrene is a composite of phenyl and anthracene. In its pure form, it is found in cigarette smoke and is a known irritant, photosensitizing skin to light...
, acenapthene, and fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
. Creosotes from vertical-retort and low temperature tars contain, in addition, some paraffinic and olefinic hydrocarbons. The tar-acid content also depends on the source of the tar — it may be less than 3% in creosote from coke-oven tar and as high as 32% in creosote from vertical retort tar. All of these have anti-septic properties. The tar acids are the strongest anti-septics but have the highest degree of solubility in water and are the most volatile; so, like with wood-tar creosote, phenols are not the most valued component, as by themselves they would lend to being poor preservatives. In addition, creosote will contain several products naturally occurring in coal — nitrogen-containing heterocycles, such as acridines, carbazoles, and quinolines, referred to as the "tar bases" and generally make up about 3% of the creosote — sulfur-containing heterocycles, generally benzothiophenes — and oxygen-containing heterocycles, dibenzofurans. Lastly, creosote will contain a small number of aromatic amines produced by the other substances during the distillation process and likely resulting from a combination of thermolysis and hydrogenation. The tar bases are often extracted by washing the creosote with aqueous mineral acid, although they're also suggested to have anti-septic ability similar to the tar acids.
Commercially used creosote is often treated to extract the carbolic acid, naphthalene, or anthracene content. The carbolic acid or naphthalene is generally extracted to be used in other commercial products. American produced creosote oils typically will have low amounts of anthracene and high amounts of naphthalene, because when forcing the distillate at a temperature that produces anthracene the soft pitch will be ruined and only the hard pitch will remain; this ruins it for use in roofing purposes, and only leaves a product which isn't commercially useful.
Industrial
The use of coal-tar creosote on a commercial scale began in 1838, when a patent covering the use of creosote oil to treat timber was taken out by John Bethell in 1838. The process he used became referred to as the "Bethell process" and later became more widely known as the fuel-cell process. It involves sealing wood in a pressure chamber and applying a vacuum to remove air and moisture from the wood cells. The wood is then pressure treated in order to impregnate it with the preservative chemicals. Afterwards the a vacuum is applied again to separate the excess solution from the timber. The same year a method to treat wood using zinc choloride was patented by Sir William Burnett and referred to as the "Burnett process". One of the chief uses of creosoted wood was in preserving railway ties (sleepers) so they didn't need to be replaced due to wood rot.
Besides treating wood, it was also used for lighting and fuel. In the beginning, it was only used for lighting needed in harbor and outdoor work, where the smoke that was produced from burning it was of little inconvenience. By 1879, lamps had been created that ensured a more complete combustion by using compressed air, removing the drawback of the smoke. Creosote was also processed into gas and used for lighting that way. As a fuel, it was used to power ships at sea and blast furnaces for different industrial needs, once it was discovered to be more efficient than unrefined coal or wood. It was also used industrially for the softening of hard pitch, and burned produce lamp black. By 1890, the production of creosote in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
totaled approximately 29,900,000 gallons per year.
In 1854, Alexander McDougall
Alexander McDougall
Alexander McDougall was an American seaman, merchant, a Sons of Liberty leader from New York City before and during the American Revolution, and a military leader during the Revolutionary War. He served as a major general in the Continental Army, and as a delegate to the Continental Congress...
and Angus Smith developed and patented a product called McDougall's Powder as a sewer deodorant; it was mainly composed from carbolic acid derived from creosote. McDougall in 1864, experimented with his solution to remove entozoa parasites from cattle pasturing on a sewage farm. This later led to widespread use of creosote as a cattle wash and sheep dip. External parasites would be killed in a creosote diluted dip, and drenching tubes would be used to administer doses to the animals stomach to kill internal parasites.
Two later methods for creosoting wood were introduced after the turn of the century, referred to as empty-cell processes, because they involve compressing the air inside the wood so that the preservative can only coat the inner cell walls rather than saturating the interior cell voids. This is a less effective, though usually satisfactory, method of treating the wood, but is used because it requires less of the creosoting material. The first method, the "Rüping process" was patented in 1902, and the second, the "Lowry process" was patented in 1906. Later in 1906, the "Allardyce process" and "Card process" were patented to treat wood with a combination of both creosote and zinc chloride. In 1912, it was estimated that a total of 150,000,000 gallons were produced in the United States per year.
Medical
Coal-tar creosote, despite its toxicity, was used as a stimulant and escharotic, as a caustic agent used to treat ulcers and malignancies and cauterize wounds and prevent infection and decay. It was particularly used in dentistry, used to destroy tissues and arrest necrosis
Industrial
Coal-tar creosote is the most widely used wood treatment today; both industrially, processed into wood using pressure methods such as "fuel-cell process" or "empty-cell process", and more commonly applied to wood through brushing. In addition to toxicity to fungi, insects, and marine borers, it serves as a natural water repellant. Its commonly used to preserve and waterproof cross ties, pilings, telephone poles, power line poles, marine pilings, and fence posts. Although suitable for use in preserving the structural timbers of buildings, its not generally used that way because it is difficult to apply.
Due to its carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic character, the European Union has regulated the quality of creosote for the EU market and requires that the sale of creosote be limited to professional users. The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
regulates the use of coal tar creosote as a wood preservative under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act
Federal Insecticide, Fungicide, and Rodenticide Act
The Federal Insecticide, Fungicide, and Rodenticide Act , et seq. is a United States federal law that set up the basic U.S. system of pesticide regulation to protect applicators, consumers, and the environment. It is administered by the Environmental Protection Agency and the appropriate...
. Creosote is considered a restricted-use pesticide and is only available to licensed pesticide applicators
Health effects
According to the Agency for Toxic Substances and Disease Registry (ATSDR), eating food or drinking water contaminated with high levels of coal tar creosote may cause a burning in the mouth and throat, and stomach pains. ATSDR also states that brief direct contact with large amounts of coal tar creosote may result in a rash or severe irritation of the skin, chemical burns of the surfaces of the eyes, convulsions and mental confusion, kidney or liver problems, unconsciousnessUnconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...
, and even death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
. Longer direct skin contact with low levels of creosote mixtures or their vapors can result in increased light sensitivity, damage to the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
, and skin damage. Longer exposure to creosote vapors can cause irritation
Irritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
of the respiratory tract
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
.
The International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....
(IARC) has determined that coal tar creosote is probably carcinogenic to humans, based on adequate animal evidence and limited human evidence. It is instructive to note that the animal testing relied upon by IARC involved the continuous application of creosote to the shaved skin of rodents. After weeks of creosote application, the animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s developed cancerous skin lesions and in one test, lesions of the lung. The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
has stated that coal tar creosote is a probable human carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
based on both human and animal studies. As such, the Federal Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
(OSHA) has set a permissible exposure limit of 0.2 milligrams of coal tar creosote per cubic meter of air (0.2 mg/m3) in the workplace during an 8-hour day, and the Environmental Protection Agency (EPA) requires that spills or accidental releases into the environment of one pound (0.454 kg) or more of creosote be reported to them.
There is no unique exposure pathway of children to creosote. Children exposed to creosote will probably experience the same health effects seen in adults exposed to creosote. It is unknown whether children differ from adults in their susceptibility to health effects from creosote.
A 2005 mortality study of creosote workers found no evidence supporting an increased risk of cancer death, as a result of exposure to creosote. Based on the findings of the largest mortality study to date of workers employed in creosote wood treating plants, there is no evidence that employment at creosote wood-treating plants or exposure to creosote-based preservatives was associated with any significant mortality increase from either site-specific cancers or non-malignant diseases. The study consisted of 2,179 employees at eleven plants in the United States where wood was treated with creosote preservatives. Some workers began work in the 1940s to 1950s. The observation period of the study covered 1979- 2001. The average length of employment was 12.5 years. One third of the study subjects were employed for over 15 years.
The largest health effect of creosote is deaths caused by residential fires.
Oil-tar creosote
| EWLINE |
Oil-tar creosote is derived from the tar that forms when using petroleum or shale oil in the manufacturing of gas. The distillation of the tar from the oil occurs at very high temperatures; around 980°C. The tar forms at the same time as the gas, and once processed for creosotes contains a high percentage of cyclic hydrocarbons, a very low amount of tar acids and tar bases, and no true anthracenes have been identified. Historically, this has mainly been produced in the United States in the Pacific coast, where petroleum has been more abundant than coal. Limited quantities have been used industrially, either alone, mixed with coal-tar creosote, or fortified with pentachlorophenol.
Water-gas-tar creosote
Water-gas-tar creosote is also derived from petroleum oil or shale oil, but by a different process; its distilled during the production of water-gas. The tar is a by-product resulting from enrichment of water gas with gases produced by thermal decomposition of petroleum. Of the creosotes derived from oil, its practically the only one used for wood preservation. It has the same degree of solubility as coal-tar creosote and is easy to impregnate into wood. Like standard oil-tar creosote, it has a low amount of tar acids and tar bases, and has less anti-septic qualities. Petri dish tests have shown that water-gas-tar creosote is one-sixth as anti-septically effective as that of that of coal-tar.Lignite-tar creosote
Lignite-tar creosote is produced from ligniteLignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
rather than bituminous coal, and varies considerably from coal-tar creosote. Also called "lignite oil", it has a very high content of tar acids, and has been used to increase the tar acids in normal creosote when necessary. When it has been produced, its generally been applied in mixtures with coal-tar creosote or petroleum. Its effectiveness when used alone has not been established. In an experiment with southern yellow pine fence posts in Mississippi, straight lignite-tar creosote was giving good results after about 27 years exposure, although not as good as the standard coal-tar creosote used in the same situation.
Peat-tar creosote
There have also been attempts to distill creosote from peatPeat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
-tar, but they've been mostly unsuccessful, due to the problems with winning and drying peat on an industrial scale. Peat tar by itself has in the past been used as a wood preservative.
Build-up in chimneys
Burning wood and fossil fuels at low temperature causes incomplete combustion of the oils in the wood, which are off-gassed as volatiles in the smoke. As the smoke rises through the chimney it cools, causing water, carbon, and volatiles to condense on the interior surfaces of the chimney flue. The black oily residue that builds up is referred to as creosote, which is similar in composition to the commercial products by the same name, but with a higher content of carbon blackCarbon black
Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its...
.
Over the course of a season creosote deposits can become several inches thick. This creates a compounding problem, because the creosote deposits reduce the draft (airflow through the chimney) which increases the probability that the wood fire is not getting enough air to burn at high temperature. Since creosote is highly combustible, a thick accumulation creates a fire hazard. If a hot fire is built in the stove or fireplace, and the air control left wide open, this may allow hot oxygen into the chimney where it comes in contact with the creosote which then ignites—causing a chimney fire
Chimney fire
A chimney fire is the combustion of residue deposits referred to as creosote, on the inner surfaces of chimney tiles, flue liners, stove pipes, etc. The process begins with the incomplete combustion of fuel in the attached appliance, usually a wood or coal stove...
. Chimney fires often spread to the main building because the chimney gets so hot that it ignites any combustible material in direct contact with it, such as wood. The fire can also spread to the main building from sparks emitting from the chimney and landing on combustible roof surfaces. In order to properly maintain chimneys and heaters that burn wood or carbon-based fuels, the creosote buildup must be removed. Chimney sweep
Modern chimney cleaning
Today, chimney sweeps still maintain a thriving new industry in many parts of the world. The industry has expanded from the maintenance of wood-burning fireplace and appliance venting systems to include venting for many types of heating appliances...
s perform this service for a fee.
73% of heating fires and 25% of all residential fires in the United States are caused by failure to clean out creosote buildup. Since 1990 the number of creosote caused fires has decreased in the United States by 75%. This is partly due to the use of efficient wood-burning stove
Wood-burning stove
For a list of stove types see Stove .A wood-burning stove is a heating appliance capable of burning wood fuel and wood-derived biomass fuel. Generally the appliance consists of a solid metal closed fire chamber, a grate and an adjustable air control...
s that fully burn the volatiles in the smoke, and partly due to the decrease in the use of wood heating during two decades of milder Winter weather, and low fuel prices.