Castor oil
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Castor oil is a vegetable oil pressed from castor beans, the seeds of the plant Ricinus communis.<ref name="ullmanns">Template:Cite book</ref> The seeds are 40 to 60 percent oil.<ref>Template:Cite book</ref> It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is Template:Convert and its density is 0.961 g/cm3.<ref>Template:Cite bookTemplate:Full citation needed</ref> It includes a mixture of triglycerides in which about 90 percent of fatty acids are ricinoleates. Oleic acid and linoleic acid are the other significant components.
Some 270,000–360,000 tonnes (600–800 million pounds) of castor oil are produced annually for a variety of uses.<ref name="onlinelibrary.wiley.com"/> Castor oil and its derivatives are used in the manufacturing of soaps, lubricants, hydraulic and brake fluids, paints, dyes, coatings, inks, cold-resistant plastics, waxes and polishes, nylon, and perfumes.<ref name="onlinelibrary.wiley.com">Template:Cite journal</ref>
EtymologyEdit
The name probably comes from a confusion between the Ricinus plant that produces it and another plant, the Vitex agnus-castus.<ref>Template:Cite news</ref><ref>Template:Cite book</ref> An alternative etymology, though, suggests that it was used as a replacement for castoreum.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
HistoryEdit
Use of castor oil as a laxative is attested to in the Template:Circa Ebers Papyrus,<ref>Template:Cite book</ref> and it was in use several centuries earlier.<ref>Bryan, p. xvii</ref> Midwifery manuals from the 19th century recommended castor oil and 10 drops of laudanum for relieving "false pains."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
CompositionEdit
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Castor oil is well known as a source of ricinoleic acid, a monounsaturated, 18-carbon fatty acid. Among fatty acids, ricinoleic acid is unusual in that it has a hydroxyl functional group on the 12th carbon atom. This functional group causes ricinoleic acid (and castor oil) to be more polar than most fats. The chemical reactivity of the alcohol group also allows chemical derivatization that is not possible with most other seed oils.
Because of its ricinoleic acid content, castor oil is a valuable chemical in feedstocks, commanding a higher price than other seed oils. As an example, in July 2007, Indian castor oil sold for about US$0.90/kg ($0.41/lb),Template:Citation needed whereas U.S. soybean, sunflower, and canola oils sold for about $0.30/kg ($0.14/lb).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
| Acid name | Range | Type |
|---|---|---|
| Ricinoleic acid | 85–95 | ω−9 |
| Oleic acid | 2–6 | ω−9 |
| Linoleic acid | 1–5 | ω−6 |
| α-Linolenic acid | 0.5–1 | ω−3 |
| Stearic acid | 0.5–1 | saturated |
| Palmitic acid | 0.5–1 | saturated |
| Dihydroxystearic acid | 0.3–0.5 | saturated |
| Others | 0.2–0.5 |
Human usesEdit
Castor oil has been used orally to relieve constipation or to evacuate the bowel before intestinal surgery.<ref name="drugs">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The laxative effect of castor oil is attributed to ricinoleic acid, which is produced by hydrolysis in the small intestine.<ref name=drugs/> Use of castor oil for simple constipation is medically discouraged because it may cause violent diarrhea.<ref name=drugs/>
Food and preservativeEdit
In the food industry, food-grade castor oil is used in food additives, flavorings, candy (e.g., polyglycerol polyricinoleate in chocolate),<ref>Template:Cite journal</ref> as a mold inhibitor, and in packaging. Polyoxyethylated castor oil (e.g., Kolliphor EL)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is also used in the food industries.<ref>Template:Cite journal</ref> In India, Pakistan, and Nepal, food grains are preserved by the application of castor oil. It stops rice, wheat, and pulses from rotting. For example, the legume pigeon pea is commonly available coated in oil for extended storage.
EmollientEdit
Castor oil has been used in cosmetic products included in creams and as a moisturizer. It is often combined with zinc oxide to form an emollient and astringent, zinc and castor oil cream, which is commonly used to treat infants for nappy rash.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>
MedicineEdit
Castor oil is used as a vehicle for serums administering steroid hormones such as estradiol valerate via intramuscular or subcutaneous injection.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Alternative medicineEdit
Despite the lack of evidence, castor oil is sometimes claimed to be able to cure diseases. According to the American Cancer Society, "available scientific evidence does not support claims that castor oil on the skin cures cancer or any other disease."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ChildbirthEdit
Despite some undesirable side effects, castor oil is used for labor induction. There is no high-quality research proving that ingestion of castor oil results in cervical ripening or induction of labor; there is, however, evidence that taking it causes nausea and diarrhea.<ref name=":1" /><ref name=":2" /> A systematic review of "three trials, involving 233 women, found there has not been enough research done to show the effects of castor oil on ripening the cervix or inducing labour or compare it to other methods of induction. The review found that all women who took castor oil by mouth felt nauseous. More research is needed into the effects of castor oil to induce labour."<ref name=":1">Template:Cite journal</ref><ref name=":2">Template:Cite journal</ref> Castor oil is still used for labor induction in environments where modern drugs are not available; a review of pharmacologic, mechanical, and "complementary" methods of labor induction published in 2024 by the American Journal of Obstetrics and Gynecology stated that castor oil's physiological effect is poorly understood but "given gastrointestinal symptomatology, a prostaglandin mediation has been suggested but not confirmed."<ref>Template:Cite journal</ref> According to Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk (2008), castor oil should not be ingested or used topically by pre-term pregnant women.<ref name=":3">Template:Cite book</ref> There is no data on the potential toxicity of castor oil for nursing mothers.<ref name=":3" />
PunishmentEdit
Since children commonly strongly dislike the taste of castor oil, some parents punished children with a dose of it.<ref>For an American example see Template:Cite book</ref><ref>For a Canadian examples see Template:Cite book</ref> Physicians recommended against the practice because it may associate medicines with punishment and make children afraid of the doctor.<ref>Template:Cite book</ref>
Use in tortureEdit
A heavy dose of castor oil could be used as a humiliating punishment for adults. Colonial officials used it in the British Raj (India) to deal with recalcitrant servants.<ref>Template:Cite book</ref>
Belgian military officials prescribed heavy doses of castor oil in Belgian Congo as a punishment for being too sick to work.<ref>Template:Cite book</ref> Castor oil was also a tool of punishment favored by the Falangist and later Francoist Spain during and following the Spanish Civil War.<ref name=":0">Template:Cite book</ref> Its use as a form of gendered violence to repress women was especially prominent.<ref name=":0" /><ref name="Juan">{{#invoke:citation/CS1|citation
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This began during the war where Nationalist forces would specifically target Republican-aligned women, both troops and civilians, who lived in Republican-controlled areas.<ref name=":0" />
The forced drinking of castor oil occurred alongside sexual assault, rape, torture and murder of these women.<ref name=":0" /><ref name="Juan"/> Its most notorious use as punishment came in Fascist Italy under Benito Mussolini. It was a favorite tool used by the Blackshirts to intimidate and humiliate their opponents.<ref>Template:Cite encyclopedia</ref><ref>Template:Cite news</ref><ref>Template:Cite book</ref>
Political dissidents were force-fed large quantities of castor oil by fascist squads so as to induce bouts of extreme diarrhea in the victims. This technique was said to have been originated by Gabriele D'Annunzio or Italo Balbo.<ref>"Bearded like a medieval condottiere, bluff yet suave, fearless and supple, [Italo Balbo] was not the type to pass unnoticed anywhere. His admirers here chose to forget the Blackshirt club-wielder and reputed inventor of the castor-oil treatment for Fascist foes"
Marshal Balbo Template:Webarchive, The New York Times, July 1, 1940, p. 18.</ref> This form of torture was potentially deadly, as the administration of the castor oil was often combined with nightstick beatings, especially to the rear, so that the resulting diarrhea would not only lead to dangerous dehydration but also infect the open wounds from the beatings. However, even those victims who survived had to bear the humiliation of the laxative effects resulting from excessive consumption of the oil.<ref name="Did Mussolini">{{#invoke:citation/CS1|citation
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Industrial usesEdit
CoatingsEdit
Castor oil is used as a biobased polyol in the polyurethane industry. The average functionality (number of hydroxyl groups per triglyceride molecule) of castor oil is 2.7, so it is widely used as a rigid polyol and in coatings.<ref name=ullmanns/> One particular use is in a polyurethane concrete where a castor-oil emulsion is reacted with an isocyanate (usually polymeric methylene diphenyl diisocyanate) and a cement and construction aggregate. This is applied fairly thickly as a slurry, which is self-levelling. This base is usually further coated with other systems to build a resilient floor.<ref>Template:Cite journal</ref> Castor oil is not a drying oil, meaning that it has a low reactivity with air compared with oils such as linseed oil and tung oil. However, dehydration of castor oil yields linoleic acids, which do have drying properties.<ref name=ullmanns/> In this process, the OH group on the ricinoleic acid along with a hydrogen from the next carbon atom are removed, forming a double bond which then has oxidative cross-linking properties and yields the drying oil. It is considered a vital raw material.<ref>Template:Cite journal</ref>
Chemical precursorEdit
Castor oil can react with other materials to produce other chemical compounds that have numerous applications.<ref>Template:Cite journal</ref><ref name="uses">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Transesterification followed by steam cracking gives undecylenic acid, a precursor to specialized polymer nylon 11, and heptanal, a component in fragrances.<ref>Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, page 6162</ref> Breakdown of castor oil in strong base gives 2-octanol, both a fragrance component and a specialized solvent, and the dicarboxylic acid sebacic acid. Hydrogenation of castor oil saturates the alkenes, giving a waxy lubricant.<ref name=ullmanns/> Castor oil may be epoxidized by reacting the OH groups with epichlorohydrin to make the triglycidyl ether of castor oil which is useful in epoxy technology.<ref>Template:Cite book</ref> This is available commercially as Heloxy 505.<ref>Template:Cite book</ref>
The production of lithium grease consumes a significant amount of castor oil. Hydrogenation and saponification of castor oil yields 12-hydroxystearic acid, which is then reacted with lithium hydroxide or lithium carbonate to give high-performance lubricant grease.<ref>Template:Cite book</ref>
Since it has a relatively high dielectric constant (4.7), highly refined and dried castor oil is sometimes used as a dielectric fluid within high-performance, high-voltage capacitors.
LubricationEdit
Vegetable oils such as castor oil are typically unattractive alternatives to petroleum-derived lubricants because of their poor oxidative stability.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Castor oil has better low-temperature viscosity properties and high-temperature lubrication than most vegetable oils, making it useful as a lubricant in jet, diesel, and racing engines.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The viscosity of castor oil at 10 °C is 2,420 centipoise,<ref name=Mat_hand>Template:Cite book</ref> but it tends to form gums in a short time, so its usefulness is limited to engines that are regularly rebuilt, such as racing engines. Lubricant company Castrol took its name from castor oil.
Castor oil has been suggested as a lubricant for bicycle pumps because it does not degrade natural rubber seals.<ref>Template:Cite book</ref>
Turkey red oilEdit
Turkey red oil, also called sulphonated (or sulfated) castor oil, is made by adding sulfuric acid to vegetable oils, most notably castor oil.<ref name=HP/> It was the first synthetic detergent after ordinary soap. It is used in formulating lubricants, softeners, and dyeing assistants.<ref name=HP>Template:Cite book</ref>
BiodieselEdit
Castor oil, like currently less expensive vegetable oils, can be used as feedstock in the production of biodiesel. The resulting fuel is superior for cold winters, because of its exceptionally low cloud point and pour point.<ref>Biodiesel from Castor Oil: A Promising Fuel for Cold Weather (PDF) Template:Webarchive by Carmen Leonor Barajas Forero, 2004-10-12. Retrieved 2012-01-24.</ref>
Initiatives to grow more castor for energy production, in preference to other oil crops, are motivated by social considerations. Tropical subsistence farmers would gain a cash crop.<ref>The Promise of the Castor Bean Template:Webarchive by Elizabeth Johnson, Biodiesel Magazine, 2004-12-01. Retrieved 2012-01-24.</ref>
Early aviation and aeromodellingEdit
Castor oil was the preferred lubricant for rotary engines, such as the Gnome engine after that engine's widespread adoption for aviation in Europe in 1909. It was used almost universally in rotary-engined Allied aircraft in World War I. Germany had to make do with inferior ersatz oil for its rotary engines, which resulted in poor reliability.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>
The methanol-fueled, two-cycle, glow-plug engines used for aeromodelling, since their adoption by model airplane hobbyists in the 1940s, have used varying percentages of castor oil as lubricants. It is highly resistant to degradation when the engine has its fuel-air mixture leaned for maximum engine speed. Gummy residues can still be a problem for aeromodelling powerplants lubricated with castor oil, however, usually requiring eventual replacement of ball bearings when the residue accumulates within the engine's bearing races. One British manufacturer of sleeve valved four-cycle model engines has stated the "varnish" createdTemplate:Fact by using castor oil in small percentages can improve the pneumatic seal of the sleeve valve, improving such an engine's performance over time.
SafetyEdit
The castor seed contains ricin, a toxic lectin. Heating during the oil extraction process denatures and deactivates the lectin. Harvesting castor beans, though, may not be without risk.<ref>Template:Cite journal</ref> The International Castor Oil Association FAQ document states that castor beans contain an allergenic compound called CB1A. This chemical is described as being virtually nontoxic, but has the capacity to affect people with hypersensitivity. The allergen may be neutralized by treatment with a variety of alkaline agents. The allergen is not present in the castor oil itself.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
- Botanol, a flooring material derived from castor oil
- Castor wax
- List of unproven and disproven cancer treatments
ReferencesEdit
Further readingEdit
- Template:Kirk-Othmer – overview of chemical properties and manufacturing of castor oil
External linksEdit
Template:Laxatives Template:Fatsandoils Template:Authority control