Chisholm Trail Ychiz-omX 19th-century route for cattle drives from Texas to Kansas, probably named for the trader Jesse Chisholm (1806?- 1868?). The trail ran from south of San Antonio, across Oklahoma to Abilene, Kan., where a railhead was established in 1867. Between 1867 and 1871 1.5 million head of cattle were driven north over the trail to be shipped to markets in the East. After the 1880s the trail’s importance declined as other railheads were established.
Chisinau \,ke-she-'nau\ formerly (1812-1918, 1940-91) Kishinev Vki-shi-.nefN City (pop., 1999: 655,000), capital of Moldova. It lies on a tributary of the Dniester River. Ruled by Moldavia in the 15th century and taken by the Ottoman Turks in the 16th century, it was ceded to Russia in 1812. From 1918 the city was controlled by Romania; it was ceded back to the Soviet Union in 1940 and became the capital of the newly formed Moldavian S.S.R. The city is a commercial centre and the site of a university.
chitin Vkl-CnX White, homy substance found in the external skeleton of crabs, lobsters, and many insects; in internal structures of some other invertebrates; and in some fungi, algae, and yeasts. It is a polysaccharide, the monomer unit being glucosamine. It is used industrially in purifying wastewater, thickening and stabilizing foods and pharmaceuticals, and sizing and strengthening paper, and as a wound-healing agent, an ion- exchange resin, a membrane for industrial separations, and a binder for dyes, fabrics, and adhesives.
Chittagong \'chi-t9-,gaq\ City (pop., 2001 prelim.: city, 2,199,590; metro, area, 3,361,244), chief Indian Ocean port, Bangladesh. It is the country’s second most important industrial city, with jute mills, engineer¬ ing works, and a large oil refinery. Known to Arab sailors by the 10th century ad, it was conquered by Muslims in the 14th century and occu¬ pied by the governor of Bengal in the 17th century. Ceded to Britain’s East India Company in 1760, it was constituted a municipality in 1864. Damaged in the conflict between India and Pakistan in 1971, its port facilities were rebuilt. It is the site of the University of Chittagong (founded 1966).
Ch'iu Ch'u-chi See Qiu Chuji
chivalry Vshi-v3l-re\ Knightly class of feudal Europe, and especially the gallantry and honor expected of medieval knights. The ideal of cour¬ teous knightly conduct developed in the 12th-13th century. It arose out of feudal obligation (see feudalism) and stressed loyalty and obeisance by a knight to his God, his lord, and his lady, thus melding Christian and military virtues. Chivalry was greatly strengthened by the Crusades, a military endeavor on behalf of Christianity, which led to the founding of
the earliest orders of chivalry, the Knights of Malta and the Templars. In addition to loyalty and honor, the chivalric virtues included valor, piety, courtesy, and chastity. Questions of love and honor were combined in the ethos of courtly love. The knight’s lady was meant to be unobtainable, ensuring chastity; the feminine ideal thus became melded with the Virgin Mary. In the 14th—15th century, chivalry came to be associated increas¬ ingly with aristocratic display and public ceremony, particularly in joust¬ ing tournaments, rather than with service in the field.
chive Small, hardy perennial plant ( Allium schoenoprcisum ) of the lily family, related to the onion. Its small, white, elongated bulbs and thin, tubu¬ lar leaves grow in clumps. Dense, attractive, spherical umbels of bluish or lilac flowers rise above the foli¬ age. The leaves may be cut off at ground level and used for seasoning foods.
Chivington Massacre See Sand Creek Massacre
chlamydia \kl3-'mi-de-9\ Any of the bacterial parasites that make up the genus Chlamydia, which cause several diseases in humans, including conjunctivitis and chlamydial pneu¬ monia. One form causes a variety of sexually transmitted diseases. In men, symptoms are similar to those of gonorrhea. In women, chlamydial infec¬ tion ordinarily produces few, if any, symptoms, and most infected women thus are unaware of their condition. However, untreated infections in women can lead to sterility, a higher risk of premature births, and ectopic pregnancies. Chlamydia frequently causes conjunctivitis or pneumonia in the newborn infant. Treatment is with antibiotics.
Chlamydomonas Ykla-mo-'da-mo-nosN Genus of single-celled green algae considered to be primitive life-forms of evolutionary significance. The cell has a spherical cellulose membrane, an eyespot, and a cup-shaped, pigment-containing chloroplast. Though capable of photosynthesis, Chlamydomonas may also absorb nutrients through the cell surface. It is found in soil, ponds, and ditches polluted by manure. It may colour water green. A red-pigmented species turns melting snow red.
chlorella \klo-'re-l3\ Any green algae of the genus Chlorella, found in fresh or salt water and in soil. They have a cup-shaped chloroplast. Chlo- rellas are used often in studies of photosynthesis, in mass cultivation experiments, and for purifying sewage wastes. Because they multiply rapidly and are rich in proteins and in B-complex vitamins, they have been studied as a potential food product for humans both on Earth and in outer space. Chlorella farms, closed systems that provide humans with food, water, and oxygen, have been established in the U.S., Japan, The Neth¬ erlands, Germany, and Israel.
chlorine Nonmetallic chemical element, chemical symbol Cl, atomic number 17. It is a toxic, corrosive, greenish yellow GAS (as the diatomic molecule Cl 2 ) that severely irritates the eyes and respiratory system (and was used for that purpose as a chemical-warfare agent in World War I). As the chloride ion and in the hypochlorite ion, it has valence 1 ; in the chlo¬ rite, chlorate, and perchlorate ions, it has higher valences. Chlorine and its compounds are important industrial materials with myriad uses in the manufacture of other chlorinated compounds (e.g., PVC, hydrochloric acid, ethylene dichloride, trichloroethylene, PCBs), in water purification (municipal systems, swimming pools), in textile industries, in flame retar¬ dants, in special batteries, and in food processing. Sodium chloride (table salt) is by far the most familiar of its compounds. See also bleach.
chlorite Widespread group of layer silicate minerals composed of hydrous aluminum silicates, usually of magnesium and iron. The name, from the Greek for “green,” refers to chlorite’s typical colour. Chlorites have a silicate layer structure similar to that in micas. They characteris¬ tically occur as alteration products of other higher temperature minerals and are most common in sedimentary and igneous rocks and in some metamorphic rocks.
chloroethylene See vinyl chloride
chlorofluorocarbon (CFC) Any of several organic compounds con¬ taining carbon, fluorine, chlorine, and hydrogen. A number of different CFCs have been made and sold under the trade name Freon. Developed
Wild chives (Allium schoenoprasum)
INGMAR HOLMASEN
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chloroform ► cholera I 397
in the 1930s, these halogenated hydrocarbons were widely used as refrig¬ erants and aerosol propellants and in other applications because they are nontoxic and nonflammable and readily evaporate and condense. How¬ ever, CFCs released into the atmosphere rise into the stratosphere, where solar radiation breaks them down; the chlorine released reacts with ozone, depleting the ozone layer. In 1992 most developed countries agreed to end CFC production by 1996; 1997 production, weighted according to the ozone depletion potential of each CFC, was 10% of peak (1988) produc¬ tion.