Castor oil is a vegetable oil pressed from , the seeds of the plant Ricinus communis.
Some 270,000–360,000 tonnes (600–800 million pounds) of castor oil are produced annually for a variety of uses.
Etymology
The name probably comes from a confusion between the
Ricinus plant that produces it and another plant, the
Vitex agnus-castus.
An alternative etymology, though, suggests that it was used as a replacement for
castoreum.
History
Use of castor oil as a laxative is attested to in the
Ebers Papyrus,
and it was in use several centuries earlier.
[Bryan, p. xvii] Midwifery manuals from the 19th century recommended castor oil and 10 drops of
laudanum for relieving "false pains."
Composition
Castor oil is well known as a source of
ricinoleic acid, a
unsaturated fat, 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), whereas U.S. soybean, sunflower oil, and canola oils sold for about $0.30/kg ($0.14/lb).
Human uses
Castor oil has been used orally to relieve
constipation or to evacuate the
bowel before
intestine surgery.
The
laxative effect of castor oil is attributed to
ricinoleic acid, which is produced by
hydrolysis in the
small intestine.
[ Use of castor oil for simple constipation is medically discouraged because it may cause violent diarrhea.][
]
Food and preservative
In the food industry, food-grade castor oil is used in food additives, flavorings, candy (e.g., polyglycerol polyricinoleate in chocolate),
Emollient
Castor oil has been used in Cosmetics 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.
Medicine
Castor oil is used as a vehicle for serums administering steroid hormones such as estradiol valerate via intramuscular or subcutaneous injection.
Alternative medicine
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."
Childbirth
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 Labor induction; there is, however, evidence that taking it causes nausea and diarrhea.
Punishment
Since children commonly strongly dislike the taste of castor oil, some parents child discipline with a dose of it.[For an American example see ][For a Canadian examples see ] Physicians recommended against the practice because it may associate medicines with punishment and make children afraid of the doctor.
Use in torture
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.["Bearded like a medieval condottiere, bluff yet suave, fearless and supple, Italo 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 , The New York Times, July 1, 1940, p. 18. This form of torture was potentially deadly, as the administration of the castor oil was often combined with nightstick beatings, especially to the Buttocks, so that the resulting diarrhea would not only lead to dangerous dehydration but also Infection 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.
Industrial uses
Coatings
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.[
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.][
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.]
Chemical precursor
Castor oil can react with other materials to produce other chemical compounds that have numerous applications.[Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, page 6162]
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.[
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.]
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.
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 .
Lubrication
Vegetable oils such as castor oil are typically unattractive alternatives to petroleum-derived lubricants because of their poor oxidation stability.
Castor oil has been suggested as a lubricant for because it does not degrade natural rubber seals.
Turkey red oil
Turkey red oil, also called sulphonated (or sulfated) castor oil, is made by adding sulfuric acid to vegetable oils, most notably castor oil.[ It was the first synthetic detergent after ordinary soap. It is used in formulating , softeners, and dye.]
Biodiesel
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.[ Biodiesel from Castor Oil: A Promising Fuel for Cold Weather (PDF) by Carmen Leonor Barajas Forero, 2004-10-12. Retrieved 2012-01-24.]
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.[ The Promise of the Castor Bean by Elizabeth Johnson, Biodiesel Magazine, 2004-12-01. Retrieved 2012-01-24.]
Early aviation and aeromodelling
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.
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 when the residue accumulates within the engine's bearing races. One British manufacturer of four-cycle model engines has stated the "varnish" created by using castor oil in small percentages can improve the pneumatic seal of the sleeve valve, improving such an engine's performance over time.
Safety
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.
See also
-
Botanol, a flooring material derived from castor oil
-
Castor wax
-
List of unproven and disproven cancer treatments
Further reading
-
– overview of chemical properties and manufacturing of castor oil
External links
