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Dimethyl Sulfate

Dimethyl sulfate

Dimethyl sulfate is a flammable, extremely toxic, and likely carcinogenic chemical compound with formula (₃)₂₄. It occurs as a clear oily liquid with a slight onion-like odor. Dimethyl sulfate is used in the production of dyes and perfumes, and as a methylating agent in the manufacture of organic compounds. It has also been used in chemical warfare.

External links

- [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0148.htm International Chemical Safety Card 0148]
- [http://www-cie.iarc.fr/htdocs/monographs/vol71/018-dimethsulf.html IARC Monograph: "Dimethyl sulfate"]
-

Flammable

Flammability is the ease with which a substance will ignite, causing fire or combustion. Materials that will ignite at temperatures commonly encountered are considered flammable, with various specific definitions giving a temperature requirement. The flash point is the important characteristic. Flash points below 200 °F (93 °C) are regulated in the United States by OSHA as potential workplace hazards. Examples of flammable liquids are gasoline, ethanol, and acetone. Diesel fuel is in one of the less heavily regulated flammability categories, and biodiesel is considered nonflammable with a flash point usually over 300 °F (150 °C), even though biodiesel will combust inside of a diesel engine. The word flammable is of relatively recent origin but has in many contexts, especially safety, taken the place of the word inflammable, an older term with the same meaning. Some find inflammable misleading, falsely concluding that the Latin prefix in- (here an intensifier) always means "not." [http://www.bartleby.com/61/47/F0164700.html Discussion] Hence gasoline trucks will doubtlessly continue to be labelled flammable, while for those in internet circles inflaming someone will continue to have a very different meaning from flaming them.

External link

- [http://www.osha.gov/SLTC/smallbusiness/sec8.html United States Occupational Safety & Health Administration (OSHA) regulations regarding flammability] Category:Thermodynamics

Carcinogen

In pathology, a carcinogen is any substance or agent that promotes cancer. Carcinogens are also often, but not necessarily, mutagens or teratogens. Carcinogens may cause cancer by altering cellular metabolism or damaging DNA directly in cells, which interferes with normal biological processes. Usually cells are able to detect this and attempt to repair the DNA; if they cannot, they may undergo programmed cell death to protect the organism. However, when the damage interferes with genes responsible for programmed cell death or perhaps encourages cell division, cancer may occur. Rapidly dividing cells, such as in skin, the stomach and intestinal lining, breast tissue, and reproductive organs, are particularly sensitive to carcinogens due to any damaged DNA being quickly replicated. Unrepaired DNA replication can then lead to further accumulation of mutations between cell divisions. Most carcinogens consumed by humans are produced by plants to prevent animals from eating them (as are alkaloids). Plants containing large amounts of carcinogens include aristolochia and bracken. Aflatoxin B₁, which is produced by the fungus Aspergillus flavus growing on stored grains, nuts and peanut butter, is an example of a potent, naturally-occurring microbial carcinogen. Cooking protein-rich food at high temperatures, such as broiling or barbecuing meats, can lead to the formation of many potent carcinogens that are comparable to those found in cigarrette smoke (i.e., benzo[a]pyrene). Pre-cooking meats in a microwave oven for 2-3 minutes before broiling can help minimize the formation of these carcinogens. DDT, benzene, kepone, EDB, asbestos, and the waste rock of oil-shale mining have all been classified as carcinogenic. As far back as the 1930s, industrial and tobacco smoke were identified as sources of dozens of carcinogens, including benzopyrene, tobacco-specific nitrosamines such as nitrosonornicotine (NNN), and reactive aldehydes such as formaldehyde — which is also a hazard in embalming and making plastics. Vinyl chloride from PVC is a carcinogen. Certain viruses such as Hepatitis B and human papilloma viruses have been found to cause cancer in humans. The first one shown to cause cancer in animals was chicken sarcoma virus, discovered in 1910 by Peyton Roux. CERCLA identifies all radionuclides as carcinogens, although the nature of the emitted radiation (alpha, beta, or gamma, and the energy), its consequent capacity to cause ionization in tissues, and the magnitude of radiation exposure, determine the potential hazard. For example, Thorotrast, an (incidentally-radioactive) suspension previously used as a contrast medium in x-ray diagnostics, is thought by some to be the most potent human carcinogen known because of its retention within various organs and persistent emission of alpha particles. Both Wilhelm Röntgen and Marie Curie died of cancer caused by radiation exposure during their experiments. The non-reproducing cells of the (non-gametogenic) tissues of adult insects are particularly resistant. Recent reports have implicated acrylamide in fried or overheated carbohydrate foods (such as french fries and potato chips) as a possible carcinogen. Studies are underway at the FDA and European regulatory agencies to assess its potential risk. The charred residue on barbecued meats has been identified as a carcinogen, along with many other tars. Co-carcinogens are chemicals which do not separately cause cancer, but do so in specific combinations.

IARC classification of carcinogens

- Group 1: the agent (mixture) is carcinogenic to humans. The exposure circumstance entails exposures that are carcinogenic to humans.
- Group 2A: the agent (mixture) is probably carcinogenic to humans. The exposure circumstance entails exposures that are probably carcinogenic to humans.
- Group 2B: the agent (mixture) is possibly carcinogenic to humans. The exposure circumstance entails exposures that are possibly carcinogenic to humans.
- Group 3: the agent (mixture or exposure circumstance) is not classifiable as to its carcinogenicity to humans.
- Group 4: the agent (mixture) is probably not carcinogenic to humans. Further details can be found in the [http://www-cie.iarc.fr/ IARC Monographs].

External links

- [http://ntp.niehs.nih.gov/index.cfm?objectid=03C9B512-ACF8-C1F3-ADBA53CAE848F635 U.S. National Toxicology Program's Report on Carcinogens] Category:Biochemicals Category:Cancer
- Category:Toxicology ms:Karsinogen

Chemical compound

A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. For example, dihydrogen monoxide (water, ₂) is a compound composed of two hydrogen atoms for every oxygen atom. In general, this fixed ratio must be fixed due to some sort of physical property, rather than an arbitrary man-made selection. This is why materials such as brass, the superconductor YBCO, the semiconductor aluminium gallium arsenide, or chocolate are considered mixtures or alloys rather than compounds. A defining characteristic of a compound is that it has a chemical formula. Formulas describe the ratio of atoms in a substance, and the number of atoms in a single molecule of the substance (thus the formula for ethene is ₂₄ rather than ₂). The formula does not indicate that a compound is composed of molecules; for example, sodium chloride (table salt, ) is an ionic compound. Compounds may have a number of possible phases. Most compounds can exist as solids. Molecular compounds may also exist as liquids or gases. All compounds will decompose to smaller compounds or individual atoms if heated to a certain temperature (called the decomposition temperature). Every chemical compound that has been described in the literature carries a unique numerical identifier, its CAS number.

Types of compounds

- Acids
- Bases
- Ionic compounds
- Salts
- Oxides
- Organic compounds

Liquid

A liquid (a phase of matter) is a fluid whose volume is fixed under conditions of constant temperature and pressure; and, whose shape is usually determined by the container it fills. Furthermore, liquids exert pressure on the sides of a container as well as on anything within the liquid itself; this pressure is transmitted undiminished in all directions. If a liquid is at rest in a uniform gravitational field, the pressure

p

at any point is given by :

p=\rho gz

where

\rho

is the density of the liquid (assumed constant) and

z

is the depth of the point below the surface. Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected. Liquids have traits of surface tension and capillarity; they generally expand when heated, and contract when cooled. Objects immersed in liquids are subject to the phenomenon of buoyancy. Liquids at their respective boiling point change to gases, and at their freezing points, change to a solids. Via fractional distillation, liquids can be separated from one another as they vaporise at their own individual boiling points. Cohesion between molecules of liquid is insufficient to prevent those at free surface from evaporating. It should be noted that glass at normal temperatures is not a "supercooled liquid", but a solid. See the article on glass for more details.

Onion

:For the parody newspaper, see The Onion. Onion in the general sense can be used for any plant in the Genus Allium but used without qualifiers usually means Allium cepa L., also called the garden onion. Onions (usually but not exclusively the bulbs) are edible with a distinctive strong flavour and pungent odour which is mellowed and sweetened by cooking. They generally have a papery outer skin over a fleshy, layered inner core. Used worldwide for culinary purposes, they come in a wide variety of forms and colors. Onions may be grown from seed or very commonly from "sets". Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants which produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned. Either planting method may be used to produce spring onions or green onions, which are just onions harvested while immature, although "green onion" is also a common name for the Welsh onion, Allium fistulosum which never produces dry bulbs. Onions are frequently used in school science laboratories because they have particularly large cells which are easily visible even through rather low-end optical microscopes. See how to prepare an onion cell slide for details.

History

how to prepare an onion cell slide] Onions are one of the earliest crops mentioned in written text, in the Bible's Book of Numbers (11:5) as part of the Egyptian diet of that time. Six types of onions were known at the time of Pliny the Elder's Natural History. It is thought that bulbs from the onion family have been utilised as a food source for millennia. In Palestinian Bronze Age settlements, traces of onion remains were found alongside fig and date stones dating back to 5000 BC. It would be pure conjecture to suggest these were cultivated onions. The archaeological and literary evidence suggests cultivation probably took place around two thousand years later in ancient Egypt. This happened alongside the cultivation of leeks and garlic and it is thought that workers who built the pyramids were fed radishes and onions.[http://www.selfsufficientish.com/onion.htm]

Culinary and medicinal uses

radish radish Onions are available in fresh, frozen, canned, and dehydrated forms. Onions can be used, usually chopped or sliced, in almost every type of food, including cooked foods and fresh salads, and as a spicy garnish; they are rarely eaten on their own (except in poor or traditional cultures), but usually act as accompaniment to the main course.
- Depending on the variety, an onion can be sharp and pungent or mild and even sweet.
- Chopped, it is one of the three vegetables considered the holy trinity of Louisiana Creole and Cajun cuisine.
- Cocktail onions, or pickled pearl onions, are used to garnish drinks such as Gibsons. They appear to be at least somewhat effective against colds, heart disease, diabetes, and other diseases and contain antiinflammatory, anticholesterol, and anticancer components. In many parts of the underdeveloped world, onions are used to heal blisters and boils. In the United States, products that contain onion extract (such as "Mederma") are used in the treatment of topical scars.

Nutrition

[http://www.selfsufficientish.com/onion.htm Source]

Why do onions make you cry?

As onions are sliced, cells are broken open. Onion cells have two sections, one with enzymes called allinases, the other with sulfides (amino acid sulfoxides). The enzymes break down the sulfides and generate sulfenic acids. Sulfenic acid is unstable and decomposes into a volatile gas called syn-ropanethial-S-oxide. The gas then dissipates through the air and eventually reaches one's eye, where it will react with the water to form a mild solution of sulfuric acid. The sulfuric acid irritates the nerve endings in the eyes, making them sting. The tear glands then produce tears in response to this irritation, to dilute and flush out the irritant. The release of gas can thus best be prevented by cutting the onions under running tap water or completely under water, though this may not be very practical. Wetting the onions and your hands before slicing will lessen the effect, as some of the gas will react with the moisture on the onions and on your skin (instead of the moisture on your eyes). This reaction may result as an odour which may be removed with lemon. It also helps to breathe exclusively through the mouth during the preparation. Using a sharp knife will rupture fewer cells and cause less eye irritation. For more tips and information, please check links in External links section. Chilled onions (onions kept in the fridge for a while) will make you 'cry' less than onions kept at room temprature because lower temperature inhibits the enzymes and gas diffusion. Also, some people 'freeze' the knife (leave it in the freezer for around 2 minutes) before cutting the onions to prevent the tears. Different species of onions will release different amounts of sulfenic acids, thus some will cause more tear formation and irritation than others.

Types of onion (Allium cepa)

- Bulb onions
- Multiplier onions
- Shallot (most of the types in the markets are Allium cepa)
- Potato onion
- Tree onions or Egyptian onions
- Vidalia onion (sweet onion grown near Vidalia, Georgia, a region with low amounts of sulfur in the soil)

Related species

The genus Allium is a large one, and most of the species are considered to be "onions" in the looser sense. Commonly raised vegetable alliums include the leeks, garlic, elephant garlic, chives, shallots, Welsh onions and garlic chives. There are also species, such as Allium moly, grown for ornament. Several species of Allium, including A. canadense and A. diabolense, can be collected in the wild and their leaves and bulbs used as food.

References

- Imani, S. et al. Plant biochemistry: an onion enzyme that makes the eyes water. Nature, v. 419, Oct. 17, 2002: 685.
- Hamilton, Dave (2004). [http://www.selfsufficientish.com/onion.htm "Selfsufficientish - Onion - Alluim, Cepa"]. Retrieved May 1, 2005.

External links

- [http://www.onions-usa.org/ National Onion Association]

Eye Irritation Information

- [http://science.howstuffworks.com/question539.htm How stuff works article on eye irritation by onions]
- [http://www.loc.gov/rr/scitech/mysteries/onion.html Library of Congress article] (more details on eye irritation)
- [http://www.americanchemistry.com/chemmag.nsf/WebMagazineArticle?ReadForm&mfpk-543ms4 Article at americanchemistry.com]
- [http://members.aol.com/stevef88/discuss/onions.htm The Secret to Cutting Onions Without Crying] and why the common myths don't work

Eclectic Herbal Information

- [http://www.henriettesherbal.com/eclectic/kings/allium-cepa.html King's American Dispensatory] @ Henriette's Herbal
- [http://www.botanical.com/botanical/mgmh/o/onion-07.html Mrs. Grieve's] "A Modern Herbal" @ Botanical.com
- [http://www.botanical.com/botanical/mgmh/o/onipot08.html Potato Onion (Allium cepa, var. aggregatum) ] Mrs. Grieve's "A Modern Herbal" @ Botanical.com
- [http://www.botanical.com/botanical/mgmh/o/onitre09.html Tree Onion (Allium cepa, var. proliferum) ] Mrs. Grieve's "A Modern Herbal" @ Botanical.com

Homeopathic Information

- [http://www.homeoint.org/books3/kentmm/all-cep.htm Allium cepa (all-cep.)] "Kent's Lectures on Homeopathic Materia Medica" by Dr Robert Séror
- [http://www.homeoint.org/books5/allenprimer/all-c.htm Allium cepa] "A Primer of Materia Medica for practitioners of Homœopathy" by Timothy Allen Category:Liliopsida Category:Onions ms:Bawang ja:タマネギ zh-min-nan:Chhang-thâu

Dye

A dye can generally be described as a colored substance that has an affinity to the substrate to which it is being applied. The dye is usually used as an aqueous solution, and may require a mordant to improve the fastness of the dye on the fiber. In contrast, a pigment generally has no affinity for the substrate, and is insoluble. Archaeological evidence shows that, particularly in India and the Middle East, dyeing has been carried out for over 5000 years. The dyes were obtained from either animal, vegetable or mineral origin, with no or very little processing. By far the greatest source of dyes has been from the plant kingdom, notably roots, berries, bark, leaves and wood, but only a few have ever been used on a commercial scale.

Organic dyes

The first man-made organic dye, mauveine, was discovered by William Henry Perkin in 1856. Many thousands of dyes have since been prepared and, because of vastly improved properties imparted upon the dyed materials, quickly replaced the traditional natural dyes. Dyes are now classified according to how they are used in the dyeing process. Acid dyes are water-soluble anionic dyes that are applied to fibers such as silk, wool, nylon and modified acrylic fibers using neutral to acid dyebaths. Attachment to the fiber is attributed, at least partly, to salt formation between anionic groups in the dyes and cationic groups in the fiber. Acid dyes are not substantive to cellulosic fibers. Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find some use for wool and silk. Usually acetic acid is added to the dyebath to help the uptake of the dye onto the fiber. Basic dyes are also used in the coloration of paper. Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dyebath, at or near boiling point, with the addition of either sodium chloride (NaCl) or sodium sulfate (Na₂SO₄). Direct dyes are used on cotton, paper, leather, wool, silk and nylon. They are also used as pH indicators and as biological stains. Mordant dyes require a mordant, which improves the fastness of the dye against water, light and perspiration. The choice of mordant is very important as different mordants can change the final colour significantly. Most natural dyes are mordant dyes and there is therefore a large literature base describing dyeing techniques. The most important mordant dyes are the synthetic mordant dyes, or chrome dyes, used for wool; these comprise some 30% of dyes used for wool, and are especially useful for black and navy shades. The mordant, potassium dichromate, is applied as an after-treatment. Vat dyes are essentially insoluble in water and incapable of dyeing fibres directly. However, reduction in alkaline liquor produces the water soluble alkali metal salt of the dye, which, in this leuco form, has an affinity for the textile fibre. Subsequent oxidation reforms the original insoluble dye. Reactive dyes utilize a chromophore containing a substituent that is capable of directly reacting with the fibre substrate. The covalent bonds that attach reactive dye to natural fibers make it among the most permanent of dyes. "Cold" reactive dyes, such as Procion MX, Cibacron F, and Drimarene K, are very easy to use because the dye can be applied at room temperature. Reactive dye is by far the best choice for dyeing cotton and other cellulose fibers at home or in the art studio. Disperse dyes were originally developed for the dyeing of cellulose acetate, and are substantially water insoluble. The dyes are finely ground in the presence of a dispersing agent and then sold as a paste, or spray-dried and sold as a powder. They can also be used to dye nylon, triacetate, polyester and acrylic fibres. In some cases, a dyeing temperature of 130 °C is required, and a pressurised dyebath is used. The very fine particle size gives a large surface area that aids dissolution to allow uptake by the fibre. The dyeing rate can be significantly influenced by the choice of dispersing agent used during the grinding. Azo dyeing is a technique in which an insoluble azoic dye is produced directly onto or within the fibre. This is achieved by treating a fibre with both diazoic and coupling components. With suitable adjustment of dyebath conditions the two components react to produce the required insoluble azo dye. This technique of dyeing is unique, in that the final colour is controlled by the choice of the diazoic and coupling components.

Natural dyes

Animal origin

These include tyrian purple (vat dye), kermes and cochineal (mordant dyes) and techelet.

Vegetable origin

Substantive dyes include safflower and turmeric, while indigo and woad are vat dyes. Mordant dyes include alizarin (madder), dyer's broom, brazilwood, quercitron bark, weld and old fustic. Cudbear is unclassified.

Inorganic dyes

These include eosin and iron buff.

Food dyes

One other class which describes the role of dyes, rather than their mode of use, is the food dye. Because food dyes are classed as food additives, they are manufactured to a higher standard than some industrial dyes. Food dyes can be direct, mordant and vat dyes, and their use is strictly controlled by legislation. Many are azoic dyes, although anthraquinone and triphenylmethane compounds are used for colours such as green and blue. Some naturally-occurring dyes are also used.

Other

A number of other classes have also been established, including:
- Oxidation bases, for mainly hair and fur
- Sulfur dyes, for textile fibres
- Leather dyes, for leather
- Fluorescent brighteners, for textile fibres and paper
- Solvent dyes, for wood staining and producing coloured lacquers, solvent inks, colouring oils, waxes.
- Carbene dyes, a recently developed method for colouring multiple substrates

Chemical classification

External links

- [http://www.pburch.net/dyeing/aboutdyes.shtml About Dyes] Category:Dyes ja:染料 simple:Dye

Perfume

:For the book "Perfume" by Patrick Süskind, see Perfume (book). Perfume is a mixture of fragrant essential oils and aroma compounds, fixatives, and solvents used to give the human body, objects, and living spaces a lasting and pleasant smell. The amount and type of solvent mix with the fragrance oil dictates whether a perfume is considered a perfume extract, Eau de parfum, Eau de toilette, or Eau de Cologne. Eau de Cologne

Obtaining odorants

Before perfumes can be composed, the odorants used in various perfume compositions must first be obtained. Synthetic odorants are produced through organic synthesis and purified. Odorants from natural sources require the use of various methods to extract the aromatics from the raw materials. The results of the extraction are either essential oils, absolutes, concretes, or butters, depending on the amount of waxes in the extracted product.
- Distillation: A common technique for obtaining aromatic compounds from flowers, plants, and grasses, such as orange blossoms and roses. The raw material is placed in a distillation still with water and heated until the fragrant compounds are driven from the material and re-collected through condensation of the distilled vapour. The water used in distillation, which retains some of the fragrant compounds and oils from the raw material is called hydrosol.
- Maceration/Solvent extraction: The most commonly used and economically important technique for extracting aromatics in the modern perfume industry. Raw materials are submerged in a solvent that can dissolve the desired aromatic compounds. Maceration lasts anywhere from hours to months. Fragrant compounds for woody and fibrous plant materials are often obtained in this matter as are all aromatics from animal sources. The technique can also be used to extract odorants that are too volatile for distillation or easily denatured by heat. Commonly used solvents for maceration/solvent extraction include ethanol, hexane, and dimethyl ether.
- Expression: Raw material is squeezed or compressed and the oils are collected. Of all raw materials, only the fragrant oils from the peels of fruits in the citrus family are extracted in this manner since the oil is present in large enough quantities as to make this extraction method economically feasible.
- Enfleurage: Absorption of aroma materials into wax and then extracting the odorous oil with alcohol. Extraction by enfleurage was commonly used when distillation was not possible due to the fact that some fragrant compounds denature through high heat. This technique is not commonly used in the present day industry due to its prohibitive cost and the existence of more efficient and effective extraction methods.

Composing perfumes

Perfume oils usually contain tens to hundreds of ingredients. Included in the perfume are fixatives, which bind the various fragrances together, include balsams, ambergris, and secretions from the scent glands of civets and musk deer (undiluted, these have unpleasant smells but in alcoholic solution they act as preserving agents). The mixture is normally aged for one year.

Description of a perfume

musk deer It is impossible to describe a perfume according to its components because the exact formulas are kept secret. Even if the formulas are known, the ingredients are often too numerous to provide a useful classification. On the other hand, it is possible to group perfumes into olfactive families and describe them through the notes that appear as they slowly evaporate. Perfumes can also be classified according to their concentration.

Olfactive families

Traditionally, fragrances that are clasified in seven olfactive families, whose names may vary:
- Floral: Fragrances that are dominated by the scent of one or more types of flowers. When only one flower is used, it is called a soliflore (as in Dior's Diorissimo, with jasmine).
- Chypre: Fragrances build on a similar base consisting of bergamot, jasmine and oakmoss. This family of fragrances is named after a perfume by François Coty by the same name. Meaning Cyprus in French, the term alludes to where this base was inspired. This fragrance family is characterized by a scent reminiscent of apricot and custard.
- Fougère: Fragrances built on a base of lavender, coumarin and oakmoss. Many men's fragrances belong to this family of fragrances, which is characterized by its sharp herbaceous and woody scent.
- Leather: A family of fragrances which features the scents honey, tobacco, wood, and wood tars in its middle or base notes and a scent that alludes to leather.
- Woody: Fragrances that are dominated by the woody scents, typically of sandalwood and cedar. Patchouli, with in camphorous smell is also used in this fragrance family.
- Orientals or ambers: A large fragrance class featuring the scents of vanilla and animal scents together with flowers and woods. Typically enhanced by camphorous oils and incense resins, which bring to mind Victorian era imagery of the East and Far East.
- Citrus: An old fragrance family that until recently consisted mainly of "freshening" Eau de colognes due to the low tenacity of citrus scents. Development of newer fragrance compounds has allowed for the creation of primarily citrus fragrances.

Fragrance Notes

A mixture of alcohol and water is used as the solvent for the aromatics. On application, body heat causes the solvent to quickly disperse, leaving the fragrance to evaporate gradually over several hours. The rate of evaporation (vapor pressure) and the odor strength of the compound partly determine the tenaciousness of the compound and determine its perfume note classification.
- Top notes: Scents that are perceived a few minutes after the application of a perfume. Top notes create the scents that form a person's initial impression of a perfume. Because of this, they are very important in the selling of a perfume. The scents of this note class are usually described as "fresh," "assertive" or "sharp." The compounds that contribute to top notes are strong in scent, very volatile, and evaporate quickly. Citrus and ginger scents are common top notes.
- Heart notes or Middle notes: The scent of a perfume that emerges after the top notes dissipate. The heart note compounds form the "heart" or main body of a perfume and act to smooth the sharpness from the initial impression of a perfume caused by the top notes. Not surprisingly, the scent of heart note compounds is usually more mellow and "rounded." Scents from this note class appear anywhere from 10 minutes to 1 hour after the application of a perfume. Lavender and rose scents are typical heart notes.
- Base notes: The scent of a perfume that appears after the departure of the heart notes. Base notes bring depth and solidness to a perfume. Compounds of this class are usually the fixatives used to hold and boost the strength of the lighter top and heart notes. The compounds of this class of scents are typically rich and "deep" and are usually not perceived until 30 minutes after the application of the perfume or during the period of perfume dry-down. Musk, vetiver and scents of plant resins are commonly used as base notes.

Concentration

Perfumes oils, or the "juice" of a perfume composition, are diluted with a suitable solvent to make the perfume more usable. This is done because undiluted oils contain volatile components that would be too concentrated for people with sensitive skin or allergies. Although dilutions of the perfume oil can be done using solvents such as jojoba, fractionated coconut oil, and wax, the most common solvents for perfume oil dilution is ethanol or a mixture of ethanol and water. The percent of perfume oil by volume in a perfume is listed as follows:
- Perfume extract: 20%-40% aromatic compounds
- Eau de parfum: 10-30% aromatic compounds
- Eau de toilette: 5-20% aromatic compounds
- Eau de cologne: 2-3% aromatic compounds As the percentage of aromatic compounds decreases, the intensity and longevity of the scent decrease. It should be noted that different perfumeries or perfume houses assign different amounts of oils to each of their perfumes. As such, although the oil concentration of a perfume in eau de parfum dilution will necessarily be higher than the same perfume in eau de toilette form, the same trends may not necessarily apply to different perfume compositions much less across different perfume houses.

History of perfume and perfumery

ethanol Perfumery, or the art of making perfumes, began in ancient Egypt but was developed and further refined by the Romans and the Arabs. Knowledge of perfumery came to Europe as early as the 14th century. During the Renaissance period, perfumes were used primarily by royalty and the wealthy to mask bodily odors resulting from the sanitary practices of the day. In the Islamic culture, perfume usage has been documented as far back as the 6th century and its usage is considered a religious duty. The Prophet Muhammad said, "The taking of a bath on Friday is compulsory for every male Muslim who has attained the age of puberty and (also) the cleaning of his teeth with Siwak (type of twig used as a toothbrush), and the using of perfume if it is available." (Recorded in Sahih Bukhari) Partly due to this patronage, the western perfumery industry was created. By the 18th century, aromatic plants were being grown in the Grasse region of France to provide the growing perfume industry with raw materials. Even today, France remains the centre of the European perfume design and trade. Perfumers were also known to create poisons; for instance, a French duchess was murdered when a perfume/poison was rubbed into her gloves and was, thus, slowly absorbed into her skin.

Famous perfumes classified by year of creation

- 1714 : Eau de Cologne by Farina (Johann Maria Farina 1685-1766)
- 1889 : Jicky by Guerlain (Aimé Guerlain)
- 1917 : Chypre by François Coty (François Coty)
- 1919 : Mitsouko by Guerlain (Jacques Guerlain)
- 1919 : Tabac Blond by Caron (Ernest Daltroff)
- 1921 : N°5 by Chanel (Ernest Beaux)
- 1925 : Shalimar by Guerlain (Jacques Guerlain)
- 1927 : Arpège by Lanvin (André Fraysse)
- 1929 : Soir by Paris by Bourjois (Ernest Beaux)
- 1930 : Joy by Jean Patou (Henri Alméras)
- 1934 : Pour Un Homme by Caron (Ernest Daltroff)
- 1944 : Bandit by Robery Piguet (Germaine Cellier)
- 1945 : Femme by Rochas (Edmond Roudnitska)
- 1948 : L'Air du temps by Nina Ricci (Francis Fabron)
- 1956 : Diorissimo by Christian Dior (Edmond Roudnitska)
- 1959 : Monsieur by Givenchy
- 1959 : Cabochard by Parfums Grès (Bernard Chant)
- 1966 : Eau sauvage by Christian Dior (Edmond Roudnitska)
- 1969 : Ô by Lancôme (Robert Gonnon)
- 1977 : Opium by Yves Saint-Laurent (Jean-Louis Sieuzac)
- 1978 : Azzaro Pour Homme by Azzaro (Gérard Anthony, Martin Heiddenreich, Richard Wirtz)
- 1978 : Magie Noire by Lancôme (PFW)
- 1979 : Anaïs Anaïs by Cacharel (Roger Pellegrino)
- 1981 : Nombre Noir by Shiseido (Serge Lutens, Jean-Yves Leroy)
- 1983 : Paris by Yves Saint-Laurent (Sophia Grosjman)
- 1984 : Coco by Chanel (Jacques Polge)
- 1985 : Poison by Christian Dior (Jean Guichard)
- 1987 : Loulou by Cacharel (Jean Guichard)
- 1990 : Trésor by Lancôme (Sophia Grosjman)
- 1992 : Angel by Thierry Mugler (Olvier Cresp and Yves de Chiris)
- 1993 : Jean-Paul Gaultier by Jean-Paul Gaultier (Jacques Cavallier)
- 1995 : CK One by Calvin Klein (Firmenich)
- 1995 : Dolce Vita by Christian Dior (Pierre Bourdon and Maurice Roger)
- 1995 : Le Mâle by Jean-Paul Gaultier (Francis Kurkdjian)
- 2001 : Coco Mademoiselle by Chanel (Jacques Polge)
- 2001 : Nu by Yves Saint-Laurent (Jacques Cavallier)

Natural and synthetic aromatics

Plant sources

Plants have long been used in perfumery as a source of essential oils and aroma compounds. These aromatics are usually secondary metabolites produced by plants as protection against herbivores as well as to attract pollinators. Plants are by far the largest source of fragrant compounds used in perfumery. The sources of these compounds may be derived from various parts of a plant. A plant can offer more than one source of aromatics, for instance the aerial portions and seeds of coriander have remarkably different odors from each other. Orange leaves, blossoms, and fruit zest are the respective sources of petit grain, neroli, and orange oils.
- Flowers and Blossoms: Undoubtably the largest source of aromatics. Includes the flowers of several species of rose and lavender, as well as jasmine, osmanthus, mimosa, tuberose, as well as the blossoms of citrus and ylang-ylang trees. Although not traditionally thought of as a flower, the unopened flower buds of the clove are also commonly used. Orchid flowers are not commercially used to produce essential oils or absolutes.
- Leaves and Twigs: Commonly used for perfumery are patchouli, sage, violets, rosemary, and citrus leaves. Sometimes leaves are valued for the "green" smell they bring to perfumes, examples of this include hay and tomato leaf.
- Roots, rhizomes and bulbs: Commonly used terrestrial portions in perfumery include iris rhizomes, vetiver roots, various rhizomes of the ginger family.
- Seeds: Commonly used seeds include tonka bean, coriander, caraway, cocoa, nutmeg, mace, cardamom, and anise.
- Fruits: Fresh fruits such as apples, strawberries, cherries unfortunately do not yield the expected odors; if you find such fragrance notes in a perfume, they're synthetic. Notable exceptions include litsea cubeba, vanilla, and juniper berry. The most commonly used fruits yield their aromatics from the rind; they include citrus such as oranges, lemons, limes, and grapefruit.
- Woods: Highly important in providing the base notes to a perfume, wood oils and distillates are indispensible in perfumery. Commonly used woods include sandalwood, rosewood, agarwood, birch, cedar, juniper, and pine.
- Bark: Commonly used barks includes cinnamon and cascarilla. The fragrant oil in sassafras root bark is also used either directly or purified for its main constituent, safrole, which is used in the synthesis of other fragrant compounds such as helional.
- Resins: Valued since antiquity, resins have been widely used in incense and perfumery. Highly fragrant and antiseptic resins and resin-containing perfumes have been used by many cultures as medicines for a large variety of ailments. Commonly used resins in perfumery include labdanum, frankincense/olibanum, myrrh, Peru balsam, gum benzoin. Pine and fir resins are a particularly valued source of terpenes used in the organic synthesis of many other synthetic or naturally occurring aromatic compounds. Some of what is called amber and copal in perfumery today is the resinous secretion of fossil conifers.
- Lichens: Commonly used lichen includes oakmoss and treemoss thalli.

Animal sources

- Musk: Originally derived from the musk sacs from the Asian musk deer, it has now been replaced by the use of synthetic musks due to its price and various ethical issues.
- Civet: Also call Civet Musk, this is obtained from the odorous sacs of the civets, animals in the family Viverridae, related to the Mongoose.
- Castoreum: Obtained from the odorous sacs of the North American beaver.
- Ambergris: Lumps of oxidized fatty compounds, whose precursors were secreted and expelled by the Sperm Whale. Ambergris is commonly referred as "amber" in perfumery and should not be confused with yellow amber, which is used in jewelry.
- Honeycomb: Distilled from the honeycomb of the Honeybee.

Synthetic sources

Synthetic aromatics are created through organic synthesis from various chemical compounds that are obtained from petroleum distillates, pine resins, or other relatively cheap organic feedstock. Synthetics can provide fragrances which are not found in nature. For instance, Calone, a compound of synthetic origin, imparts a fresh ozonous metallic marine scent that is widely used in contemporary perfumes. Synthetic aromatics are often used as an alternate source of compounds that are not easily obtained from natural sources. For example, linalool and coumarin are both naturally occurring compounds that can be cheaply synthesized from terpenes. Orchid scents are usually not obtained directly from the plant itself but are instead synthetically created to match the fragrant compounds found in various orchids. The majority of the world's synthetic aromatics are created by relatively few companies. They include:
- International Flavors and Fragrances (IFF)
- Givaudan-Roure
- Firmenich
- Quest International
- Takasago
- Symrise Each of these companies patent several processes for the production of aromatic synthetics annually. See Aroma compound

Health and ethical issues

Use of Aromatics

In some cases, an excessive use of perfumes may cause allergic reactions of the skin. For instance, acetophenone, ethyl acetate and acetone while present in many perfumes, are also known or potential respiratory allergens. It is important to note that there is no benefit from creating a perfume exclusively from natural materials. There are several reasons for this:
- Many natural aroma materials are in fact inherently toxic and are either banned or restricted by IFRA. These naturals have been replaced by safer artificial or synthetic materials.
- Many natural materials and essential oil contain the same chemicals used in perfumes that are classified as allergens, many of them at higher concentrations.
- Perfume composed only of expensive natural materials could be very expensive. Synthetic aromatics make possible perfumes at reasonable prices.
- In the distillation of natural essential oils any biocides (including pesticides, herbicides, or fungicides) that have been applied while the plant is growing may be concentrated into the essential oil making the oil toxic. Unless the essential oil is distilled from a certified organic origin, it may be dangerous.
- There are many new synthetic aromas that bear no olfactory relationship to any natural material and yet modern perfumery depends on these new odours for the infinite variety of perfumes available today. Many synthetics have very beautiful aromas not available in nature.

Natural Musk

Musk was traditionally taken from the male musk deer Moschus moschiferus. This requires the killing of the animal in the process. Although the musk pod is produced only by a young male deer in oestrus musk hunters usually did not discriminate between the age and sex of the deers. Due to the high demand of musk and indiscriminate hunting, populations were severely depleted. As a result, the deer is now protected by law and international trade of musk from Moschus moschiferus is prohibited:

"Musk deer are protected under national legislation in many countries where they are found. The musk deer populations of Afghanistan, Bhutan, India, Nepal and Pakistan are included in Appendix I of CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This means that these musk deer and their derivatives are banned from international commercial trade." [http://www.traffic.org/factfile/factfile_muskdeer.html]

Due to its legality, rarity, high price, and ethical reasons, it is the policy of many perfume companies to use synthetic musk in place of natural musk for ethical reasons. Numerous synthetic musks of high quality are readily available. [http://www.ifraorg.org/GuideLines.asp approved safe by IFRA].

External links

- [http://www.biblioparfum.net Biblioparfum] An impressive personal collection of more than 600 books about perfume (mostly French)
- [http://www.fabulousfragrances.com Fabulous Fragrances] An educational perfume portal with information on perfume usage, fragrance classifications, and history. Includes books by Jan Moran (Fabulous Fragrances II) and Michael Edwards (Fragrances of the World), as well as online programs, a forum, and a Q & A column, Scents of Style, where readers can ask questions.
- [http://hjem.get2net.dk/bojensen/EssentialOilsEng/EssentialOils.htm A guide to natural fragrances] A site with information regarding various fragrant plants used in perfumery and their active chemical odorants. Images of both plant and odorant structure.
- [http://www.schoolscience.co.uk/content/5/chemistry/smells/index.html The sense of smell.] Educational site with information regarding the sense of smell, the process of fragrance evaluation, and a bit on organic synthesis of fragrance chemicals.
- [http://www.osmoz.com/index_menu.asp osMoz] Overview of the perfume and cologne making process, fragrance classifications, and a directory of leading perfumers.
- [http://www.leffingwell.com/perfume.htm Leffingwell & Associates] An independent consulting agency on fragrance and flavour chemicals Category:Perfumery Category:Olfaction ja:香水

Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon.The study of organic compounds is termed organic chemistry. Many of these compounds, such as proteins, fats, and carbohydrates (sugars), are also of prime importance in biochemistry. The dividing line between organic and inorganic is contended and historically arbitrary; generally speaking, however, organic compounds are defined as those compounds which have carbon-hydrogen bonds, and inorganic compounds, those without. Thus carbonic acid is inorganic, whereas formic acid, the first fatty acid, is organic, although it could as well be called "carbonous acid" and its anhydride, carbon monoxide, is inorganic. The name "organic" is a historical name, dating back to 19th century, when it was believed that organic compounds could only be synthesised in living organisms through vis vitalis - the "life-force". The theory that organic compounds were fundamentally different than those that were "inorganic", that is, not synthesized through a life-force, was disproven with the synthesis of urea, an organic compound, from potassium cyanate and ammonium sulfate by Friedrich Wöhler. Most pure organic compounds are artificially produced; however, the term "organic" is also used to describe products produced without artificial chemicals (see organic production).

Chemical warfare

Chemical warfare is warfare (and associated military operations) using the toxic properties of chemical substances to kill, injure or incapacitate the enemy. Chemical warfare is different from the use of conventional weapons or nuclear weapons because the destructive effects of chemical weapons are not primarily due to any explosive force. The offensive use of living organisms (such as anthrax) is considered to be biological warfare rather than chemical warfare; the use of nonliving toxic products produced by living organisms (e.g., toxins such as botulinum toxin, ricin, or saxitoxin) is considered chemical warfare under the provisions of the Chemical Weapons Convention, however. Under this Convention, any toxic chemical, regardless of its origin, is considered as a chemical weapon unless it is used for purposes that are not prohibited (an important legal definition, known as the General Purpose Criterion). About 70 different chemicals have been used or stockpiled as Chemical Weapons (CW) agents during the 20th century. Chemical weapons are classified as weapons of mass destruction by the United Nations, and their production and stockpiling was outlawed by the Chemical Weapons Convention of 1993. Under the Convention, chemicals that are toxic enough to be used as chemical weapons, or may be used to manufacture such chemicals, are divided into three groups according to their purpose and treatment:
- Schedule 1 – Have few, if any, legitimate uses. These may only be produced or used for research, medical, pharmaceutical or protective purposes (mustard gas, lewisite).
- Schedule 2 – Have no large-scale industrial uses, but may have legitimate small-scale uses (dimethyl methylphosphonate, a precursor to sarin).
- Schedule 3 – Have legitimate industrial uses (phosgene, chloropicrin).

Chemical warfare technology

Although crude chemical warfare has been employed in many parts of the world for thousands of years, "modern" chemical warfare began during World War I. Initially, only well-known commercially available chemicals and their variants were used. These included chlorine and phosgene gas. The methods of dispersing these agents during battle were relatively unrefined and inefficient. Germany, the first side to employ chemical warfare on the battlefield, simply opened canisters of chlorine upwind of the opposing side and let the prevailing winds do the dissemination. Soon after, the French modified artillery munitions to contain phosgene – a much more effective method that became the principal means of delivery. Since the development of modern chemical warfare in World War I, nations have pursued research and development on chemical weapons that falls into four major categories: new and more deadly agents; more efficient methods of delivering agents to the target (dissemination); more reliable means of defense against chemical weapons; and more sensitive and accurate means of detecting chemical agents.

Chemical weapon agents

A chemical used in warfare is called a chemical weapon agent (CWA). About 70 different chemicals have been used or stockpiled as chemical weapon agents during the 20th century. These agents may be in liquid, gas or solid form. Liquid agents are generally designed to evaporate quickly; such liquids are said to be volatile or have a high vapor pressure. Many chemical agents are made volatile so they can be dispersed over a large region quickly. The earliest target of chemical weapon agent research was not toxicity, but development of agents that can affect a target through the skin and clothing, rendering protective gas masks useless. In July 1917, the Germans first employed mustard gas, the first agent that circumvented gas masks. Mustard easily penetrates leather and fabric to inflict painful burns on the skin. Chemical weapon agents are divided into lethal and incapacitating categories. A substance is classified as incapacitating if less than 1/100 of the lethal dose causes incapacitation, e.g., through nausea or visual problems. The distinction between lethal and incapacitating substances is not fixed, but relies on a statistical average called the LD₅₀.

Persistency

All chemical weapon agents are classified according to their persistency, a measure of the length of time that a chemical agent remains effective after dissemination. Chemical agents are classified as persistent or nonpersistent. Agents classified as nonpersistent lose effectiveness after only a few minutes or hours. Purely gaseous agents such as chlorine are nonpersistent, as are highly volatile agents such as sarin and most other nerve agents. Tactically, nonpersistent agents are very useful against targets that are to be taken over and controlled very quickly. Generally speaking, nonpersistent agents present only an inhalation hazard. By contrast, persistent agents tend to remain in the environment for as long as a week, complicating decontamination. Defense against persistent agents requires shielding for extended periods of time. Non-volatile liquid agents, such as blister agents and the oily VX nerve agent, do not easily evaporate into a gas, and therefore present primarily a contact hazard.

Classes of chemical weapon agents

Chemical weapon agents are organized into several categories according to the manner in which they affect the human body. The names and number of categories varies slightly from source to source, but in general, types of chemical weapon agents are as follows: There are other chemicals used militarily that are not technically considered to be "chemical weapon agents," such as:
- Defoliants that destroy vegetation, but are not immediately toxic to human beings. (Agent Orange, for instance, used by the United States in Vietnam, contained dioxins and is known for its long-term cancer effects and for causing genetic damage leading to serious birth deformities.)
- Incendiary or explosive chemicals (such as napalm, extensively used by the United States in Vietnam, or dynamite) because their destructive effects are primarily due to fire or explosive force, and not direct chemical action.
- Viruses, bacteria, or other organisms. Their use is classified as biological warfare.

Chemical weapon designations

Most chemical weapons are assigned a one- to three-letter "NATO weapon designation" in addition to, or in place of, a common name. Binary munitions, in which precursors for chemical weapon agents are automatically mixed in shell to produce the agent just prior to its use, are indicated by a "-2" following the agent's designation (for example, GB-2 and VX-2). Some examples are given below:

Chemical agent delivery

The most important factor in the effectiveness of chemical weapons is the efficiency of its delivery, or dissemination, to a target. The most common techniques include munitions (such as bombs, projectiles, warheads) that allow dissemination at a distance and spray tanks which disseminate from low-flying aircraft. Developments in the techniques of filling and storage of munitions have also been important. Although there have been many advances in chemical weapon delivery since World War I, it is still difficult to achieve effective dispersion. The dissemination is highly dependent on atmospheric conditions because many chemical agents act in gaseous form. Thus, weather observations and forecasting are essential to optimize weapon delivery and reduce the risk of injuring friendly forces.

Dispersion

Binary munition Dispersion is the simplest technique of delivering an agent to its target. It consists of placing the chemical agent upon or adjacent to a target immediately before dissemination, so that the material is most efficiently used. World War I saw the earliest implementation of this technique, when German forces simply opened canisters of chlorine and allowed the wind to carry the gas across enemy lines. While simple and easy, this technique had numerous disadvantages. Delivery depended greatly on wind speed and direction. If the wind was fickle, as at Loos, the gas could blow back, causing friendly casualties. Gas clouds gave plenty of warning, allowing the enemy time to protect themselves, though many soldiers found the sight of a creeping gas cloud unnerving. Also gas clouds had limited penetration, capable only of affecting the front-line trenches before dissipating. Although it produced limited results in World War I, this technique shows how simple chemical weapon dissemination can be. Shortly after this "open canister" dissemination, French forces developed a technique for delivery of phosgene in a non-explosive artillery shell. This technique overcame many of the risks of dealing with gas in cylinders. First, gas shells were independent of the wind and increased the effective range of gas, making any target within reach of guns vulnerable. Second, gas shells could be delivered without warning, especially the clear, nearly odorless phosgene — there are numerous accounts of gas shells, landing with a "plop" rather than exploding, being initially dismissed as dud high explosive or shrapnel shells, giving the gas time to work before the soldiers were alerted and took precautions. The major drawback of artillery delivery was the difficulty of achieving a killing concentration. Each shell had a small gas payload and an area would have to be subjected to saturation bombardment to produce a cloud to match cylinder delivery. Over the years, there were some refinements in this technique. In the 1950s and early 1960s, chemical artillery rockets contained a multitude of submunitions, so that a large number of small clouds of the chemical agent would form directly on the target.

Thermal dissemination

1960s Thermal dissemination is the use of explosives or pyrotechnics to deliver chemical agents. This technique, developed in the 1920s, was a major improvement over earlier dispersal techniques, in that it allowed significant quantities of an agent to be disseminated over a considerable distance. Thermal dissemination remains the principal method of disseminating chemical agents today. Most thermal dissemination devices consist of a bomb or projectile shell that contains a chemical agent and a central "burster" charge; when the burster detonates, the agent is expelled laterally. Thermal dissemination devices, though common, are not particularly efficient. First, a percentage of the agent is lost by incineration in the initial blast and by being forced onto the ground. Second, the sizes of the particles vary greatly because explosive dissemination produces a mixture of liquid droplets of variable and difficult to control sizes. The efficacy of thermal detonation is greatly limited by the flammability of some agents. For flammable aerosols, the cloud is sometimes totally or partially ignited by the disseminating explosion in a phenomenon called flashing. Explosively disseminated VX will ignite roughly one third of the time. Despite a great deal of study, flashing is still not fully understood, and a solution to the problem would be a major technological advance. Despite the limitations of central bursters, most nations use this method in the early stages of chemical weapon development, in part because standard munitions can be adapted to carry the agents.

Aerodynamic dissemination

Aerodynamic dissemination is the non-explosive delivery of a chemical agent from an aircraft, allowing aerodynamic stress to disseminate the agent. This technique is the most recent major development in chemical agent dissemination, originating in the mid-1960s. This technique eliminates many of the limitations of thermal dissemination by eliminating the flashing effect and theoretically allowing precise control of particle size. In actuality, the altitude of dissemination, wind direction and velocity, and the direction and velocity of the aircraft greatly influence particle size. There are other drawbacks as well; ideal deployment requires precise knowledge of aerodynamics and fluid dynamics, and because the agent must usually be dispersed within the boundary layer (less than 200–300 ft above the ground), it puts pilots at risk. Significant research is still being applied toward this technique. For example, by modifying the properties of the liquid, its breakup when subjected to aerodynamic stress can be controlled and an idealized particle distribution achieved, even at supersonic speed. Additionally, advances in fluid dynamics, computer modeling, and weather forecasting allow an ideal direction, speed, and altitude to be calculated, such that weapon agent of a predetermined particle size can predictably and reliably hit a target.

Sociopolitical climate of chemical warfare

While the study of chemicals and their military uses was widespread in China, the use of toxic materials has historically been viewed with mixed emotions and some disdain in the West. One of the earliest reactions to the use of chemical agents was from Rome. Struggling to defend themselves from the Roman legions, Germanic tribes poisoned the wells of their enemies, with Roman jurists having been recorded as declaring "armis bella non venenis geri", meaning "war is fought with weapons, not with poisons." It is perhaps because of this view that in Europe before World War I, the use of poisonous chemicals in battle was typically the result of local initiative, and not the result of an active chemical weapons program. There are many reports of the isolated use of chemical agents in individual battles or sieges, but there was no true tradition of their use outside of incendiaries and smoke. Despite this tendency, there have been several attempts to initiate large-scale implementation of poison gas in several wars, but with the notable exception of World War I, the responsible authorities generally rejected the proposals for ethical reasons. For example, in 1854 Lyon Playfair, a British chemist, proposed using a cyanide-filled artillery shell against enemy ships during the Crimean War. The British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy." This general concern over the use of poison gas manifested itself in 1899 at the Hague Conference with a proposal prohibiting shells filled with asphyxiating gas. The proposal was passed, despite a single dissenting vote from the United States. The American representative, Naval Capt. Alfred Thayer Mahan, justified voting against the measure on the grounds that "the inventiveness of Americans should not be restricted in the development of new weapons." After extensive use of chemical weapons in World War I, the popular view of chemical weapons grew from distaste to disgust, such that their use had become the ultimate atrocity in the minds of most people at the time. So much so, in fact, that in 1925, sixteen of the world's major nations signed the Geneva Protocol, thereby pledging never to use gas biological methods of warfare again. Notably, in the United States, the Protocol languished in the Senate until 1975, when it was finally ratified.

Efforts to eradicate chemical weapons

- August 27 1874: The Brussels Declaration Concerning the Laws and Customs of War is signed, specifically forbidding the "employment of poison or poisoned weapons."
- September 4 1900: The Hague Conference, which includes a declaration banning the "use of projectiles the object of which is the diffusion of asphyxiating or deleterious gases," enters into force.
- February 6 1922: After World War I, the Washington Arms Conference Treaty prohibited the use of asphyxiating, poisonous or other gases. It was signed by the United States, Britain, Japan, France, and Italy, but France objected to other provisions in the treaty and it never went into effect.
- September 7 1929: The Geneva Protocol enters into force, prohibiting the use of poison gas and bacteriological methods of warfare. As of 2004, there are 132 signatory nations.
- May 1991: President George H.W. Bush unilaterally commits the United States to destroying all chemical weapons and to renounce the right to chemical weapon retaliation.
- The U.S. Congress has since passed legislation requiring the destruction of the entire stockpile by December 31 2004. Official U.S. policy is to support the Chemical Weapons Convention as a means to achieve a global ban on this class of weapons and to halt their proliferation.
- April 29 1997: The Chemical Weapons Convention enters into force, augmenting the Geneva Protocol of 1925 by outlawing the production, stockpiling and use of chemical weapons.

Chemical weapon proliferation

Main article: Chemical weapon proliferation Despite numerous efforts to reduce or eliminate them, some nations continue to research and/or stockpile chemical weapon agents. To the right is a summary of the nations that have either declared weapon stockpiles or are suspected of secretly stockpiling or possessing CW research programs. Notable examples include China and Israel. According to the testimony of Assistant Secretary of State for Intelligence and Research Carl W. Ford before the Senate Committee on Foreign Relations, it is very probable that China has an advanced chemical warfare program, including research and development, production, and weaponization capabilities. Furthermore, there is considerable concern from the US regarding China's contact and sharing of chemical weapons expertise with other states of proliferation concern, including Syria and Iran. As of December 2004, Israel has signed but not ratified the Chemical Weapons Convention, and according to the Russian Federation Foreign Intelligence Service, Israel has significant stores of chemical weapons of its own manufacture. It possesses a highly developed chemical and petrochemical industry, skilled specialists, and stocks of source material, and is capable of producing several nerve, blister and incapacitating agents. In 1974, in a hearing before the U.S. Senate Armed Services Committee, General Almquist stated that Israel had an offensive chemical weapons capability.

History

Chemical warfare in ancient and classical times

Chemical weapons have been used for millennia in the form of poisoned arrows, but evidence can be found for the existence of more advanced forms of chemical weapons in ancient and classical times. A good example of early chemical warfare was the late Stone Age (10 000 BC) hunter-gatherer societies in Southern Africa, known as the San. They used poisoned arrows, tipping the wood, bone and stone tips of their arrows with poisons obtained from their natural environment. These poisons were mainly derived from scorpion or snake venom, but it is believed that some poisonous plants were also utilised. The arrow was fired into the target of choice, usually an antelope (the favourite being an Eland), with the hunter then tracking the doomed animal until the poison caused its collapse. Dating from the 4th century BC, writings of the Mohist sect in China describe the use of bellows to pump smoke from burning balls of mustard and other toxic vegetables into tunnels being dug by a besieging army. Even older Chinese writings dating back to about 1000 BC contain hundreds of recipes for the production of poisonous or irritating smokes for use in war along with numerous accounts of their use. From these accounts we know of the arsenic-containing "soul-hunting fog", and the use of finely divided lime dispersed into the air to suppress a peasant revolt in AD 178. The earliest recorded use of gas warfare in the West dates back to the 5th century BC, during the Peloponnesian War between Athens and Sparta. Spartan forces besieging an Athenian city placed a lighted mixture of wood, pitch, and sulfur under the walls hoping that the noxious smoke would incapacitate the Athenians, so that they would not be able to resist the assault that followed. Sparta wasn't alone in its use of unconventional tactics during these wars: Solon of Athens is said to have used hellebore roots to poison the water in an aqueduct leading from the Pleistrus River around 590 BC during the siege of Cirrha.

The rediscovery of chemical warfare

During the Renaissance, people again considered using chemical warfare. One of the earliest such references is from Leonardo da Vinci, who proposed a powder of sulfide of arsenic and verdigris in the 15th century: :throw poison in the form of powder upon galleys. Chalk, fine sulfide of arsenic, and powdered verdegris may be thrown among enemy ships by means of small mangonels, and all those who, as they breathe, inhale the powder into their lungs will become asphyxiated. It is unknown whether this powder was ever actually used. In the 17th century during sieges, armies attempted to start fires by launching incendiary shells filled with sulphur, tallow, rosin, turpentine, saltpeter, and/or antimony. Even when fires were not started, the resulting smoke and fumes provided a considerable distraction. Although their primary function was never abandoned, a variety of fills for shells were developed to maximize the effects of the smoke. In 1672, during his siege of the city of Groningen, Christoph Bernhard van Galen (the Bishop of Münster) employed several different explosive and incendiary devices, some of which had a fill that included belladonna, intended to produce toxic fumes. Just three years later, August 27 1675, the French and the Germans concluded the Strasbourg Agreement, which included an article banning the use of "perfidious and odious" toxic devices. In 1854, Lyon Playfair, a British chemist, proposed a cacodyl cyanide artillery shell for use against enemy ships as way to solve the stalemate during the siege of Sevastopol. The proposal was backed by Admiral Thomas Cochrane of the Royal Navy. It was considered by the Prime Minister, Lord Palmerston, but the British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy." Playfair’s response was used to justify chemical warfare into the next century: :There was no sense in this objection. It is considered a legitimate mode of warfare to fill shells with molten metal which scatters among the enemy, and produced the most frightful modes of death. Why a poisonous vapor which would kill men without suffering is to be considered illegitimate warfare is incomprehensible. War is destruction, and the more destructive it can be made with the least suffering the sooner will be ended that barbarous method of protecting national rights. No doubt in time chemistry will be used to lessen the suffering of combatants, and even of criminals condemned to death. Later, during the American Civil War, New York school teacher John Doughty proposed the offensive use of chlorine gas, delivered by filling a 10 inch (254 millimeter) artillery shell with 2 to 3 quarts (2 to 3 liters) of liquid chlorine, which could produce many cubic feet (a few cubic meters) of chlorine gas. Doughty’s plan was apparently never acted on, as it was probably presented to Brigadier General James W. Ripley, Chief of Ordnance, who was described as being congenitally immune to new ideas. meter

Chemical warfare in World War I

Main article: Use of poison gas in World War I The French were the first to use chemical weapons during the First World War, using tear gas. The first full-scale deployment of chemical weapon agents was during World War I, originating in the Second Battle of Ypres, April 22 1915, when the Germans attacked France, Canadian and Algerian troops with chlorine gas. Deaths were light, though casualities relatively heavy. A total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine, phosgene and mustard gas. Official figures declare about 1,176,500 non-fatal casualties and 85,000 fatalities directly caused by chemical weapon agents during the course of the war. To this day unexploded WWI-era chemical ammunition is still frequently uncovered when the ground is dug in former battle or depot areas and continues to pose a threat to the civilian population in Belgium and France. The French and Belgian governments have had to launch special programs for treating discovered ammunition. After the war, most of the unused German chemical weapon agents were dropped into the Baltic Sea. Over time, the salt water causes the shell casings to corrode, and mustard gas occasionally leaks from these containers and washes onto shore as a wax-like solid resembling amber. Even in this solidified form, the agent is active enough to cause severe contact burns to anybody handling it.

Chemical warfare in the interwar years

After World War I, the United States and many of the European powers attempted to take advantage of the opportunities that the war created by attempting to establish and hold colonies. During this interwar period, chemical agents were occasionally used to subdue populations and suppress rebellion. Following the defeat of the Ottoman Empire in 1917, the Ottoman government collapsed completely, and the former empire was divided amongst the victorious powers in the Treaty of Sèvres. The British occupied Mesopotamia (present-day Iraq) and established a colonial government. In 1920, the Arab and Kurdish people of Mesopotamia revolted against the British occupation, which cost the British dearly. As the Mesopotamian resistance gained strength, the British resorted to increasingly repressive measures, and Winston Churchill himself, in his role as Colonial Secretary, authorized the use of chemical agents, mostly mustard gas, on the Mesopotamian resistors. Mindful of the financial cost of suppressing the dissidents, Churchill was confident that chemical weapons could be inexpensively employed against the Mesopotamian tribes, saying "I do not understand this squeamishness about the use of gas. I am strongly in favour of using poison gas against uncivilised tribes." [http://www.informationwar.org/state%20terrorism/Britain_using_chemical_weapons.htm] Opposition to the use of gas and technical difficulties may have prevented the gas from being used in Mesopotamia (historians are currently divided on the issue)[http://www.bbc.co.uk/history/war/iraq/britain_iraq_07.shtml]. Chemical weapons had caused so much misery and revulsion in World War I that their use had become the ultimate atrocity in the minds of most people at the time. So much so, in fact, that in 1925, sixteen of the world's major nations signed the Geneva Protocol, thereby pledging never to use gas or bacteriological methods of warfare. While the United States signed the protocol, the Senate did not ratify it until 1975. During the Rif War in Spanish-occupied Morocco in 1921-1927, combined Spanish and French forces dropped mustard gas bombs in an attempt to put down the Berber rebellion. (See also: Rif, Abd el-Krim) In 1935 Fascist Italy used mustard gas during the invasion of Ethiopia in the Second Italo-Abyssinian War. Ignoring the Geneva Protocol, which it signed seven years earlier, the Italian military dropped mustard gas in bombs, sprayed it from airplanes, and spread it in powdered form on the ground. 15,000 chemical casualties were reported, mostly from mustard gas.

Chemical warfare in World War II

Geneva Protocol, discovered by Germany in 1938.]] During World War II, chemical warfare was revolutionized by Nazi Germany's accidental discovery of the nerve agents tabun, sarin and soman. The Nazis developed and manufactured large quantities of several agents, but chemical warfare was not extensively used by either side. Recovered Nazi documents suggest that German intelligence incorrectly thought that the Allies also knew of these compounds, interpreting their lack of mention in the Allies' scientific journals as evidence that information about them was being suppressed. Germany ultimately decided not to use the new nerve agents, fearing a potentially devastating Allied retaliatory nerve agent deployment. William L. Shirer, in The Rise and Fall of the Third Reich, writes that the British high command considered the use of chemical weapons as a last-ditch defensive measure in the event of a Nazi invasion of Britain. Although chemical weapons were not deployed on a large scale during World War II, there were some recorded uses of them by the Axis Powers, when retaliation wasn't feared:
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