edited by: MICHAELR. SLABAUGH HELENJ. JAMES Weber State College Ogden. Utah 84408
chern I mpplernent Chemicals in Everyday Life Raymond 6. Seymour Department of Polymer Science. University of Southern Mississippi, Hattiesburg, MS 39406
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In mite of the fact that we and all other livine" animals and -~~ plants are composed of chemicals, few nonscientists recognize the imoortance of chemistrv in our dailv lives. In addition to heing made up of proteins, nncleic acids, and calcium nhosohate . . bones. we are the world's nremier consumer of chemicals. We need chemicals, such as carbohydrates, fats, and prohod, natural and synthe;ic fihers for our clothreins tor ing, wood, brick, nnd cement for our shelter. and n variety of chemical products for our exploration, recreation, ventilation, communication, decoration, sanitation, and education. ~
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Food
People have always been dependent on organic chemicals for their food. Primitive people picked wild berries and fruit and obtained protein by hunting and fishing. Today we are inst as denendent on oreanic chemicals for food, but our iegetahledand meat areksually supplied by farmers, who are becoming less numerous because of advances in agriculture. Of course, in spite of many dramatic improvements in aericulture. we are still denendent on ohotosvnthesis for the " conversion of carbon dioxide and water from the atmosphere to carhohvdrates in our nlants. The enerev for this catalvtic conversion of gases and vapor to solids comes from the sun. Plants also require nitrogen, potassium, phosphorus, and traces of many mineral elements. Legumes are able to convert atmospheric gaseous nitrogen to solid nitrates in a process called "fixation", but most of the nitrogen needed by plants must be obtained from natural and synthetic fertilizers. European farmers used animal manure, and American Indians used fish as fertilizers. Suhscquently. sodium initrate tiY;#.UO,)irom guano deposits in Chile was used, but mmt uf tndq's nitrogenuus t'ertilizrr is derived f r ( m ammonia. which is ohtainrd hs the cntalstic combination of hydrogen and nitrogen at relatively high nressure. Fritz Haher, who developed a commercially viable version of this nitrocen fixation process, received the Nobel Prize in 1918. The ammonia from the Haber process is catalytically oxidized to produce nitric acid (HNOa). The ammonium nitrate (NH4N03)obtained from the neutralization of nitric acid by ammonia is used both as an explosive in warfare and as a fertilizer in agriculture. Potassium salts, called potash, because of their presence in wood ash, are mined at Trona, California, and in Saskatchewan, Canada. Insoluble calcium p h o s p h a t e (Ca.JPOd)?). . ... .. -. . which is mined in Florida. Tennessee. and Wvoming, is converted to soluble superphosphate by reaction with sulfuric acid (H2S04).The monohasic calcium phos-
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phate (Ca(H2P04)2.H20)is soluble in water. The label on fertilizer bags lists the percentage of nitrogen, phosphorus, and potassium, respectively. he iarmer uses chenilc~lherhirides to rid his farmland of w e d s and chemic,al insecticides to kill insects. The Chinese used arsenic compounds, such as arsenic sulfide (As&), 1000 years ago, hut the modern farmer utilizes modern orennie oesticides. Paul Muller received the Nobel Prize in " 19.18 fur dixwering that dichlurodiphenyltrichioroerhane (Dll'1'1 a.ss an effective rontnrt insecticide. Unfortunnt~lv, DDT and other chlorinated insecticides are not specific and these "hard insecticides" mav kill desirable insects, such as bees. These "broad spectrum" insecticides are also persistent and are accumulated in the fat tissue of birds. DDT has been displaced by more toxic hut less persistent insecticides, such as Malathion, which is an organic derivative of phosphoric acid (H3PO4). Carbarnates such as carbarvl (Sevin) are less toxic and less persistent but these compounds are synthesized from organic isocyanates, such as methyl isocyanate (CH3NCO),which, as shown by the Bhonal disaster: should be handled with extreme care The most widely used herbicides are 2,4-D and 2,4,5-T which are di- and trichloronhenoxvacetic acid,. respectively. . These compounds are heing replaced by more selective herbicides. such as amides, dinitroanilines, triazines, and nreas. Fumigants, such as dichloropropane (C12C3Hs)are used to destrov nematoids. Hemorrhaae-causing compounds, such as u,arlaran, are used ro kill rldenrs. \Vhile about 5 million tons (~ipestiridesare uied annually in the United States, their use ,will decrease as chemists develop specific pheromones or sex attractants. These volatile compounds, which are emitted by female insects, are effective attractants in extremely small concentrations. Most important, they are usually simple hydrocarbons or derivatives that are readily and economically synthesized in the laboratory. Food produced by a relatively few farmers, on a large scale, must be preserved so that it is unspoiled when acquired hy the consumer. The ancients preserved food by drying, salting, sugaring, and pickling. These arts are still practiced and reinforced by canning, refrigerating, freezing, packaging, and by the use of preservatives. Drying deprives the microorganisms of water, which is essential for their growth, and salting and sugaring reduce the available water. Pickling provides a hostile environment for most microorganisms. However, some molds and yeasts mav grow at these low oH values. When meat is salted with so&uk nitrite ( N ~ N Oa ~ pink ~ , color develops because of the reaction of nitric oxide (NO) with blood pigments. Corned beef is still preserved with sodium n i t r a t e ( ~ a ~ 0 3 ) . The canning process or apperitization, which was invent~~~~
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Volume 64
Number 1 January 1987
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ed by Nicholas Appert during the Napoleonic Wars, destroys microorganisms and prevents further penetration by microorganisms. The crude bottle used by Appert has been displaced by tin-coated iron cans, plastic-lined cans, and olastic nouches. Manv" nlastic oackaees are essentiallv im. " pervious to the atmosphere. The contents of these packages may he sterilized by heat or radiation and cooked in microwave ovens. Refrigeration and freezing, which use dichlorodifluoromethane (Freon) as a refrieerant, provide an environment that is too cold for the gro&h of most microorganisms. Swiss cheese contains about 1% of a natural moldicide, calcium propionate (Ca(0OCC2H&) which serves as an antimycotic agent. Other additives that are "generally regarded as safe" (GRAS) by the Food and Drug Administration (FDA). mav. also he added in small amounts to imnrove flavor, improve texture, and prevent spoilage. Marearine is ~ r o d u c e dhv the oartial hvdroeenation of deodohzed vegetable oils and the flavor df this spread is enriched by the addition of biacetyl (H3CCOCOCH3) and acetoin (CH:$HOHCOCH3), which are natural constituents of butter. Potato chips keep well when properly packaged, hut corn chips become rancid unless a small amount of an antioxidant, such as butylated hydroxytoluene (BHT), is added as a preservative. Benzoic acid (&HsC02H) and its sodium salt are also used widely as preservatives. Clothlng Primitive people clothed themselves with animal skins, and according to Genesis Adam and Eve used fig leaves to clothe themselves. However, as people became more civilized, their needs for clothing increased not only for protection from the environment hut also for adornment. Flax, which is used to make linen, is one of the oldest cultivated plants and was the principal vegetable fiher prior to medieval times. Linen, which is a cellulosic textile, was displaced to a large extent by cotton during the last few centuries. Cotton, which is now the world's most important vegetable fiber, was cultivated by ancient civilizations in China, Egypt, India, Mexico, and Peru. More than 30 species of Gossypium are known, but the most useful is G. hirsutium, which has a relatively short fiber. The separation of cotton seeds from the cellulosic fiher was labor-intensive prior to the invention of the cotton gin by Eli Whitney in 1793. Subsequently, the southern United States became the leading producer of this fiher. The United States, Russia, and China each account for about 20% of the world's cotton production. More than 19 million tons of cotton are produced annually in this country. However, cotton is no longer Kine of Fibers. Cotton's share of the United States' fiber ma&et has declined from more than 50% in 1966 to less than 25% in 1985, and this trend is continuing. Cotton seeds contain about 20% of an unsaturated glyceride. This oil, which is obtained hv crushing the seeds, has been used in paint manufacture and may aGo he converted to a solid by the catalytic addition of hydrogen (H2). These solid products, which contain less unsaturated oils, are used for margarine and shortening (Crisco, Spry, etc.). The carbon atoms in an unsaturated hydrocarbon are bonded by two single bonds and one double bond. Silk, which is a proteinaceous (polyamide) fiber, was produced in China as early as the 3rd millennium BC, hut prior to 550 AD sericulture was a closelv . -guarded secret and silk garments were worn almost exclusively by nobility. All natural fihers except silk are discontinuous, short staple fibers. However, since silk is a continuous filament, Rohert Hooke predicted in 1664 that the production of manmade filaients was possible. Over two centuries later, in 1884, Count Hilarie de Chardonnet forced a cellulose trinitrate solution in ethanol ( C ~ H S O Hand ) ethyl ether 64
Journal of Chemical Education
((CzH&O) (collodion) through small holes (spinnerets) and produced a continuous filament by the evapcration of the solvents. This flammable "artificial silk" was revlaced in . 1892 by viscose r&on which was produced by Cross, Bevan, and Beadle. The cellulose in the viscose process is immersed in aqueous sodium hydroxide [NaOHJ ~ n dthis alkali rellulose is reacted with rarl~ondisulfide tCS?r ta, produce suluhle celluluse xnnthate (ROCS.:. NR',where R reoresents cellulose). This cellulose deriva& (viscose) is force2 through spinnirets into an acid hath in which the regenerated cellulose rrnwnl precipitates as a nlntinuous filament. Cellophane is produced by forcing the viscose through a slit dye into an tons of ravon is nroduced annualarid hath. A l ~ ~3umillion t ly worldwide but the production oi both'rayon and celloohane is decreasing because of comnetition from svnthetic khers and films. Acetate rayon is produced by forcingasolution of cellulose acetate (R(OH)(02CCH3)d in acetone (H3CCOCH3) through a spinneret and evaooratine the acetone, ~ y i o nwhich , was the first truly synthetic fiber, was produced by W. Carothers and J. Hill in the 1930's. Nylon is produced by heating the salt formed by the condensation of hexamethylenediamine (H2N(CH&NH2) and adipic acid (H02C(CH2)&02H). This fiher is labelled nylon-66 to indicate the number of carhon atoms present in each of the reactants. The polymer consists of over 100 of these repeatThis ing units or mers (-NH(CH2),jNHCO(CH2)&(-). polyamide is melted and forced through spinnerets to produce nylon filaments. About 55% of todav's ~roductionof nylon-66 is used for b accounts ior carpets, and 201 is used fur apparel. ~ i r cord nhtnlt 25"o of the total nylon output. O\,t:r 1 million tons of nylon are prudwed annually in the Knited States. The most widely used synthetic fiher is polyethylene terephth:ilute which was synthesized by J. R. WhinfieldandJ. T. Dickwn of Calico Printers Assoriarim in England in the late 1910's. Carothers s\,nthesized fihers from alinhatic valvesters in the 1930's, but these softened when i r k e d a i d were not produced commercially. The aromatic polyester fibers are made by the reaction of ethylene glycol (HO(CH&OH) and terephthalic acid (H02CC6H4C02H). These fibers, which are melt spun, do not soften when ironed and are water repellent. About 50% of the production of polyester fiber is used for apparel, 30% for industrial uses and 20% for home furnishings. Over 1.5 million tons of polyester fiher are produced annually in the United States. Acrylic fibers are produced by forcing a solution of polyacrylonitrile (CCHz-CHCN+,) in dimethylformamide (HCON(CHd2) through spinnerets and precipitating the filaments in a nonsolvent. Polyacrylonitrile was known for a few decades before Du Pont and Monsanto discovered solvents for this polymer. The polymer has little affinity for dves. . . hut Orlon can he dved in the oresence of con~er(I1) .. salts. Acrylan is a copolymer made up of repeating units of acrylonitrile (H2C=CHCN) a n d vinylpyridine (H2C=CH(NCsH4)). About 65%of acrylic fibers are used for apparel and 3090 for home furnishings. Over 350,000 tons of acrylic fihers are produced annually in the United States. F i b e r s a r e also p r o d u c e d f r o m p o l y p r o p y l e n e (+CHCH3CH2+,) by a fibrillation process in which tape is stretched and passed over closely spaced pins. Because of the oresence of a hvdroeen atom on a secondarv carhon atom, this fiher is digrazed in sunlight but can be used in "indoor-outdoor caroet" when antioxidants are added to the fiber. A soecialtv elastic fiber called Soandex is a copolvmer consiiting of multiple stiff urechane repeating i n i t s (-(CH2)s-NHC09-) and multiple flexible polyester units (blocks). ~~~
Shelter Primitive people who lived in caves decorated the walls of these caves. As people become more civilized, thev built huts from sun-driedmi&res of vegetable fibers and adobe clay, kiln-dried clay bricks, concrete, and wood. Wood was also used for building after the invention of the framesaw in 1500 RC:
The crude log cabin, built in America's wilderness three centuries ago, did not require paint, but those built from sod and lumber needed paint for protection from weathering and for decoration. The first paint was distemper, a water dispersion of pigment and a natural binder, such as egg white. These waterborne paints were displaced, to some extent, by oilpaints, in whichthe unsaturated oil, suchas linseed oil, dried (polymerized) in the presence of air and a drier (catalyst). The latter was a salt of a heavy metal such as lead, cobalt, or manganese. However, as a result of the need to protect the environment against pollution by the solvents in paints, oil-based paints and solvent-based paints are being replaced by waterborne and high-solids coatings. Solutions of cellulose nitrate, which dry faster than oilbased paints, were introduced in the earlv part of the 20th century and became the preferred finish for automobiles. These have been displaced, to some extent, bx. alkvds . and acrylics. Alkyds are condensation products of phthalic acid (H02CCsH&OzH), glycerol ((HOCH2)zCHOH), and an unsaturated oil, such as that used in oil paints. Alkyds, which are the most widely used coatings, are supplemented by w a t e r b o r n e p a i n t s , b a s e d o n polyvinyl a c e t a t e (CH2CH(02CCH3),) and polymethyl methacrylate (CH2C(CHd(COzCHdn). In addition to using paint for protection and decoration, civilized man also used glass for windows in his home. Glass, which is produced by heating a mixture of sand (silicon dioxide, Si02), sodium carbonate (Na2COa) and limestone (calcium carbonate, CaC03) at 1300 "C was produced in Egypt in 3000 BC. Window glass was made by the Crown process in which a glob of molten glass was blown and one side of the blown globe was flattened. Panes of glass were cut from the flat disc formed after the globe was reheated and rotated. Subsequently, sheets of molten glass were cast continuously on molten tin. Because of the hazards associated with the breakage of brittle glass, it is being replaced, to some extent, by clear sheets of polymethyl methacrylate and polycarbonate. Polyvinyl chloride (fCHzCHC1 j),) is also extruded for window frames, siding, pipes, and conduits used in modern homes. Likewise, polystyrene (f CH2-CH(C6H5)j,) is being used for making furniture. Copolymers of ethylene (H2C=CH2) and propylene (HC(CH3)=CHz) are used for single-ply roofing. Polystyrene foam and glass fibers are used for insulation, and plastics, such as melamine-formaldehyde resins and polystyrene, are used for dishware.
Travel and Exploration After primitive people had satisfied their needs for food. c1othing;and sbelkr, ;hey started to travel, both for impror: ing their lifestyle and for trading. Foot travel was supplemented by tra;el on domesticated beasts of burden, suih as oxen and asses. Wagons were used for transportation after the invention of the wheel. Sailing and travel by horse-drawn wagons were supplemented bv the invention of the steam and internal combustion engines in the 19th century. Modern transportation, which has been called "the most imoortant industrv in the world", now uses land, sea, and air f i r exploration. All these means of travel require chemical products.
The availability of vulcanized rubher, which was invented 11s Charles Goodvear in 1838. has u ~ m a d e dmodern land travel. ~ a t u r a ir u b b e r (from ~ e u e abrasiliensis) (fCHzC(CHa)=CHCH&-.) was available to the Aztecs for centuries, but this thermoplastic gum had limited utility until i t was cross-linked (cured) by the addition of a small amount of sulfur. Sulfur forms cross links between thelinear chains of polyisoprene a t intervals of about every 100 carbon atoms. Hard rubber has a high cross-link density and is inflexible, but the flexibility is retained in vulcanized soft rubber. The sulfur cross links prevent cold flow of rubber and permit it to be used in pneumatic tires. The resistance to wear has been increased-by the addition of about an equal amount of carbon black to the rubber. The resistance to aging of rubber is enhanced by the addition of antioxidants, such as octyldiphenylamine ( ( C S H ~ ~ ) ( C ~ H ~ ) ~ N ) . Accelerators, which are catalysts for the cross-linking of rubber with sulfur, must also be added to the ruhber mix before thermal curine.. (vulcanization). The nrincioal~~~-~~ rubber . accelerator is 2-mercaptobenzothiae;)e (Captax). When natural ruhber was not avuilable durine World War 11, it was replaced hy a copolymer of s t y r e n e (CFHICH=CH,J and butadiene (H?C=CH-CH=CH7). ~&u;al rubber was made available aft& the end of the war, but instead of accounting for 100%. i t now accounts for less than 30% of all rubber (eiastomers) used. The improvements in rubber quality, downsizing of tires, and the trend toward radial tires had reduced the demand for rubber. Tires account for over 80% of all rubher used in the United States. About 3 million tons of rubber is used annually in the United States and over 2 million tons of this is synthetic rubber, Butadiene can be polymerized to a cispolyhutadiene which is more like natural ruhher than SBR. The first boat ride was probably in a tree trunk. Later, trunks were tied together to form rafts, and trunks were dug out to make canoes. The original cotton sails of s h i ~ have s been replaced by nylon, a n d t h e wind power has been augmented by steam- or gasoline-engine Dower. The wooden structures have also been rep1aced;toa large extent, by fiber glass-reinforced polyester plastics. The prepol~merused to impregnate the fiber glass mat consists o f a n unsaturated polyester, dissolved in styrene. The latter is polymerized by the addition of an initiator (erroneouslv called a catalvst) - . such as henzoyl peroxide ( C ~ H ~ C H Z O Z C H ~ C ~ H S ) . The first aircraft was a lighter-than-air, hot air balloon flown by the Montgolfier brothers in Paris in 1783. The modern dirigible cabins are made from fiber glass-reinforced epoxy resin,and the aircraft is lifted by helium-filled, neoprene-coated polyester envelopes. The crude heavier-than-air wooden planes flown by the Wright brothers a t Kitty Hawk, North Carolina, in 1903, have been replaced by metal fuselages and wings. However, the heavy metal is now being replaced by graphite-reinforced epoxy resin composites to produce lighter weight aircraft that consume less fuel. Unlike the aluminum Sputnik launched in 1957, Soyuz (USSR) and Cosnor (USA) spacecraft, satellites, and space stations are constructed, to a large extent, from reinforced plastics and are propelled by liquid propellants, such as hydrazine (HzNNHz), liquid hydrogen, and dinitrogen tetroxide (N204), or by solid propellants such as ammonium perchlorate (NH4C104)and aluminum powder embedded in polvurethane. - ~ i q u i dpolymers that are convertible to solids, in situ, without the application of heat. are essential for the nrodnction of s ~ l i d ~ ~ r o ~ e l l a~ikewise, nts. polymers that'can be produced in outerspace are essential for the construction of space stations. ~ o s oft the developments that have taken place in the space age would have been impossible without the availability of modern synthetic polymers.
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Volume 64 Number 1 January 1987
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sports and ~ e c r e a t i o n Fishing and hunting, which are characterized as sports, were essential for survival for earlv civilizations. Likewise, wrestling was practiced for defenseagainst enemies, hut this activity was proclaimed as a sport by the Sumerians over 5000 years ago. The Olympic games, which began in 776 BC, may he considered as the original organized sports. Mary, Queen of Scots, popularized golf during her reign (1542-1567), and her son James lifted the han on soccer in 1603. The first American football game was nlaved between Rutgers and Princeton ~niversitFesin 18&. ~ a s e h a l has l been nlaved in the United States since 1815. The aame of hask2ba"ll was invented by J. Naismith in springfieid, Massachusetts, in 1891. All of these sports required equipment, which is still being improved. Lacrosse and tennis are no longer played with wooden racquets with gut strings but with graphite-reinforced, epoxy resin composite racquets with aromatic nylon (aramid) strings. Hand-molded sand eolf tees have been ;eplaced by tough injection-molded poiycarhonate, and golf halls now consist of a core of synthetic cis-polybutadiene covered by an ionomer copolymer of ethylene (HzC=CHz) and methacrvlic acid (H?C=C(CHXO?H). . . Golf club shafts, like tennis racquets, fishing poles, and vaulting poles, are now made from graphite-reinforced epoxy resins by means of a pultrusion "process" in which a bundle of filaments, impregnated with uncured resin, are drawn through a circular dye and cured by heat. Other contributions of the chemist to sports and recreafoottion are molded ABS (acrvlonitrile-butadiene-stvrene) hall helmets, po~yprbpyieneskating surfaces; reinforced plastic boats, and racing cars. The latter may have aramidreinforced epoxy resin bodies and polyamide-imide motors. The buoyancy of boats is improved by the use of polyurethane unicellular foam, and injuries in jumping events are reduced by the use of flexible polyurethane foam mats. Ventilation, Heating, and Cooling 'I'hr cave people built their fires uutside their caws, hut more civilized people built rhimneys to remove smoke from their a h ~ l e iFires . were first contained in cnvities built from rock and mud, but these were replaced by open braziers. Cast iron stoves were made in China in the first centurv AD, and this modern convenience was adopted by Europeans in the 15th centurv. A blast furnace. in which iron oxide (FezOs)was reduced by carbon in the presence of limestone (CaCOa), was built in Saugus, Massachusetts, in 1647. In 1742, Benjamin Franklin invented the Franklin stove, which, when placed in a fireplace, radiated heat to warm the inside atmosphere. Wood, charcoal, and coal, which were used as fuel, were supplemented by natural gas in the 1840's and later by oil and kerosene and then by electricity in 1914. Natural gas (CH,), oil, which is a mixture of aliphatic hvdrocarhons with the general formula (H(CHAH). .. and coal, which has a high carion content, contin"e to he used as fuel. However, these fuels are being supplemented by synthetic fuels, produced by the catalytic hydrogenation of lowgrade coal. The use of the uranium fission process for the production of energy is also increasing. This energy source will be supplemented, in the future, by energy from hydrogen fusion. Unfortunately, these sources of energy, like many other sources of energy, may also he used for destructive devices, such as explosives. The art of air conditioning was developed in the 19th centurv hut was not used until 1911 when W. Carrier designedUthefirst practical system. The pioneer refrigerant used both for refriaeration and air conditionina was ammonia, which was compressed and cooled outsid; the system and then allowed to expand in the system to be cooled.
66
Journal ol Chemical Education
Ammonia refrigerants have been replaced by fluorocarbons, such as dichlorodifluoromethane (ClzCFz) (Freon). The metal ducts used to transport hot or cold air are now beine made from elastics. such as oolwinvl chloride (PVC) and Ligh-density polyeth$ene r linear;^^^^). It is custom: arv to add flame retardants. such as organic chlorides and antimony oxide (SbzO3), to these plastics to prevent combustion of these materials. Communications The paintings on the ceilings of the Altimira cave in Spain (ca. 9500 BC) oredated those on the walls of the Barrier canyon in u g h (ca. 4000 BC). The oldest written system was the Sumerian cuneiform (wedge shaoed) svmbols. which evolved from pictographs about 3500 j 3 ~ ?he . Egyptians used hieroglyphics on the pith of sedge Cyperuspapyrus as early as 2400 BC. Scrolls were made by joining many sheets together on a wooden rod. The oldest known book was printed from cast bronze type in Korea in 1397. Tsari Lon made paper from cellulosic fibers in the first centurv AD. A oaner-makine machine with an endless belt was devised by the ~ o u d r i n i kbrothers in the 19th century, and this tvDe machine is used todav- to convert cellulose . uulo . to a c o n t i u k s sheet of paper. Johann Gutenberg built a printing press and produced the first Bible, the first printed hook in Europe. Zinc plates were introduced in the late 19th centurv. Many other advances in printing have taken place, but printing ink continues to be used. This pigmented material is essentially a dispersion of carbon black and synthetic resins in a k l a t i l i solvent. Carbon black is produced by the incomplete combustion of gaseous or liauid . .oetroleum feedstocks. The printed word, as a means of communication, has been auamented hv the use of the t,elenhoue, radio. television. and a variety of cipying and recordhg machines; None of these modern instruments would he possible without synthetic polymers as electric insulators and solid state components. The importance of plastics in communication is illustrated by the development of low-density polyethylene (LDPE, [-CH2CH2-In). This plastic, which is now produced in the United States at an annual rate of more than 4 million tons. was discovered accidentally by Fawcett and Gibson in thd early 1930's. These chemists noted a solid residue when they tried to condense ethylene and heuzaldehyde a t extremely hiah Dressures (2500 atm). Subsequent investiaations showed that a trace of oxygen had served as an initiator for this previously unknown polymerization of ethylene. ICI, which is the largest chemical company in England, built a plant, and the LDPE was used as an insulator for coaxial cable in the RADAR early warning system during World War 11. LDPE, which is a branched polymer, has been supplemented by high-density polyethylene (HDPE). This linear (unbranched) nolvmer was svnthesized first bv Nohel Lanreate Karl ~iegle; He produced HDPE by the polymerization of ethvlene in the Dresence of a coordination catalvst. dimethylaiuminum chloride ((CH&AlCI) and titaniumtri: chloride (TiCls), at moderate pressures (3 atm). Hogan and Banks also produced HDPE, at about the same time as Ziegler. Their catalyst was chromium oxide (Cr03),supported on silica ( S i 0 ~ ) . Another polyolefin, polypropylene, was produced by several investigators in the earlv 1950's. Giulio Natta received the Nohel prize for this disc&ery, but in 1984, the US Patent Office ruled that Hoaan - and Banks were the true inventors of polypropylene. Copolymers of ethylene a n d other alpha olefins (H(CHz),CH=CHd called linear low-density polyethylene (LLDPE), which were developed in the early 1980's, are
replacing LDPE in many applications. LLDPE is tougher than LDPE and can he used as thin film for the production of trash hags, etc. Decoration Textiles and ceramics are inherently decorative hut are n gthe use of dves and pigments. Natumade more a .~.~ e a l i hv ral dyes, such as inbigo and a h a & , which-were used in ancient times, were made obsolete after William Perkin commercialized the production of mauve, made by the oxidation of aniline sulfate (CsHSNH3+.HSO4-),in 1856. Alizarin was synthesized by Graebe and Liehermann in 1868, and indigo was synthesized by Baeyer in 1880. Toxic white lead (2PhC03.Pb(OH)2), which has been used as a paint pigment, has been replaced by white titanium dinxide (Tion). Carbon hlack is used as a pigment, hut a synthetic dye called nigrnsine is preferred for hlack colors. Iron oxide is available in many colors under specific names, such as siennas, umbers, and ochres. A large variety of synthetic organic dves and pigments is also available. As eluiidatedby wit; 1876, a useful dye must contain colored " erouns. called chromoohores. and auxnchromes, which are attracted to the surface to bedyed. Chromophore, which is derived from the Greek words khroma, meaning "color", and phoros, meaning "hearing", are groups with double bonds, such as NO%,C=O, N=N, C=C, C=N, C=S, N=O, and quininoids. The auxochrome, which is derived from the Greek words auxein, meaning "to increase", is a reactive group such as OH, NH2, or RNH. The first dyes, commercialized by Perkin, were derivatives of triphenylmethane ((CsHs)3CH),which was obtained from coal tar. Other synthetic dyes are the azo dyes, anthraquinone vat dyes, and phthalocyanines. In spite of the fact that the synthetic dye industry was first developed in England, most of the improvements and industrial expansion took place in Germany. The American synthetic dye industrv was established after World War I. The Egyptians painted their eyelashes, eyelids, and eyebrows with Kohl, a mixture of soot and galena (lead sulfide, PbS) and edged the underside of the& eyes with ground malachite green. They also used henna to dye their hair and fingernails, as well as rouge and lipstick. Many of the cosmetic preparations used in the 17th century, such as red mercuric sulfide (HgS) and mercury chloride (HgCld for lipstick and skin lotions, were toxic. Modern face oowder contains talc (McmSLOdOH)z), chalk (CaCOa),kaolin (China clay), zinc o x i d e ( ~ n 0 )titani, um dioxide (Ti02),and other selected pigments. Fingernail polish is a pigmented cellulose nitrate lacquer. The solvent, ethyl acetate (H3CCOOC2HS),is also used as apolish remover. ~~
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been replaced to a large extent by synthetic detergents, which can be used in hard water. The pioneer synthetic detergents, introduced in the 1930's, were anionic surfactants that gave a rich lather even in hard water. The lack of biodegradability in the original branched alkylhenzene sulfonate (RC6H4SOd-,Na+) was overcome to a large extent by the introduction of biodegradable linear alkyl sulfonates. The natural and synthetic anionic detergents, whose cleaning power was enhanced by the addition of sodium tripolyphosphate (STPP, NasP3Ol0),were excellent detergents for cotton but were not as good as nonionic detergents for washing synthetic fabrics. The increase in use of synthetic fibers and bans on the use of . phosphates have caused an increase in the demand for nonionic surfactants. The ~rincipalnonfnaming, noninnic detergents are ethylated al;wh(,lr such as the nnnylphenyl ethers nf polyethyl~O1l). rne el\wl ( H ( C l l l ) n C ~ H , O ~ C H I C H ~ O ~ C H : ~ C H Cationic-surfactants, such as quaternary ammonium compounds (R4N+,CI-) are used as disinfectant cleaners, hair conditioners. fabric . . - ~and ~ ~ softeners. ~ ~ ~ ~ In addition t o STPP, whose use in detergents has declined from 1million tons to 650 thousand tons annuallv, the detergent industry also used bleaches such as sndium perhorate (NaBOzH202-3H20) and sodium hypochlorite (NaOCI), chelating agents such as tetracetylethylenediamine (TAED). and antideoosition agents such as sodium carboxvR is cell;methyl&ulose (CMC, R C H ~ O O - , ~ awhere +, lose). ~~
Education There is archeological evidence that writing, mathematics, astronomy, architecture, and government were taught in temple schools by priests in the early third millenium BC in Egypt and Sumer. In the fifth century, the Greek Sophists added metaphysics, ethics, and philosophy, and Plato, a disciple of Socrates, established one of the first universities in 387 BC. The develooment of movable t w e . in 1436, catalyzed the publication or books. Both ~ a r t G ~ u t h and e r ~ o h Calvin n advocated readine of the Bible. and Ignatium Lovola estahlished colleges throughout ~ u r b p in e the 16th century. Slate hoards and chalk, used in the 18th century, have been replmed t ~ ypaper and plastic ball-point pens or pultrurlrd plast~cpencils. Cellulose acetate film is used in prw jectors, and polyrthylene terephthalate (I'FT) tape is used in recorders and duplicators. The learning of Latin and Greek and even German is no longer essential for understanding ancient philosophy or modern chemistry. The 18th century scholar was conversant in Latin and Greek, hut the 20th centnry scholar must he knowledeeable about science and chemistrv. in particular. . Progressive schools are adding an S for science to the three R's. and thus students are acquiring- better understanding of the world around them. Today's students use computers to solve problems and even make use of computer simulation of chemical reactions and computer-assisted design of various structures. From their plastic housings to the silicon in the chips, the computers are dependent on chemistry. Of course, most other aids to modern education are also dependent on chemistry. v
Sanitation: Soaps and Detergents Recipes for soap making based on potash and vegetable oils have been found on clay tablets dating from the third millenium BC in Mesopotamia. The Greek physician, Galen, advocated the use of soap to prevent skin disease. Soapberry (Sapindus sapudacae) contains saponin, which has been used as a cleaning agent by primitive civilizations in the tropics. Soap is made by the alkaline hydrolysis (saponification) of tridvcerides of fattv acids, such as those found in tallow. In t h e i8th century ~ i c h o l a sLehlanc developed a process for making sodium carbonate that made large-scale soap making possible. In the Leblanc process, salt cake (Na2SOa)is mixed with limestone (CaCOs) and coal (C) and heated. The product (black ash) is leached with water, carbon dinxide is added, and sodium carbonate (NanCOs) is produced. S o a p , which is e s s e n t i a l l y s n d i u m s t e a r a t e ( N ~ O O C C I ~ Hcontinues ~ ~ ) , to be used in bar soap. Soap has
Summary As consumers, we are dependent on chemists and farmers for our food, shelter, and clothing and for other needs. Fortunately, the chemist has provided drugs to cure illness, and equipment for our exploration, recreation, ventilation, cnmmunication, decoration, sanitation, and education. Those critics who are not appreciative of the accomplishments of chemists should he reminded that today's problems such as Volume 64 Number 1 January 1987
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enjoy his or her present lifestyle. The slogan, formerly used by Du Pont, "Better things for better living through chemistry", is still appropriate. We are dependent on chemistry for living and will be more dependent on this our branch of science in the future. General References Carson,R. "Silent Spring"; Houghfon-Mifnin: Boston, 1962
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Journal of Chemical Education
~auffman.G.B.; s&, H. H. he central science h a y s on chemistry..: ~ e x a a Christian University Press: Ft. Worth,TX. 19U. ieff,R, W,..Msn MadeFibe rs..: Wiley:New York, 1975, seymou~,R. ~ : ~ ~ o d ~lastics~echnoiogy..; om ~ e s t o n ~: e s t o nVA, , 1975. Seymour. R. B.: Carraher, C. E. "Polymer Chemistry: An Introduction"; Dekker: New York, 1982. stin., R. w "chemistw for the consumer": AIIWand ~ a m n &ton, : MA, 1978. Witfcoff, H. A,; Reuben, 8. C. "ladustrial Organic Chemicals in Porspedive, Part 2. Technolom, Formulation end Use";Wiley: New York, 1980.
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