thermal conductivity and differences between tensile and compressive strengths. Unlike metals, ceramics have relatively few free electrons and therefore are essentially nonconductive and considered to be dielec- tric. In general, dielectrical strengths, which range between 200 and 350 V/mil (7.8 ϫ 10 6 and 13.8 ϫ 10 6 V/m), are lower than those of plastics. Electrical resistivity of many ceramics decreases rather than increases with an increase in impurities, and is markedly affected by temperature. Practically all ceramic materials have excellent chemical resis- tance, being relatively inert to all chemicals except hydrofluoric acid and, to some extent, hot caustic solutions. Organic solvents do not affect them. Their high surface hardness tends to prevent breakdown by abrasion, thereby retarding chemical attack. All technical ceramics will withstand prolonged heating at a minimum of 1830°F (999°C). Therefore atmospheres, gases, and chemicals cannot penetrate the material surface and produce internal reactions which normally are accelerated by heat. Aluminum-ceramic coatings are used to protect aircraft-turbine and other turbomachinery parts from corrosion and heat at tempera- tures to 2000°F (1093°C) and greater. For compressor applications in ground-based turbines, aluminum-filled, chromate-phosphate coat- ings sealed with a ceramic topcoat have more than doubled service life. Aluminum-ceramic coatings are also alternatives to cadmium plating of fasteners and other products and used for galvanic protec- tion of dissimilar materials. Nickel-ceramic coatings, with silicon carbide or silicon carbide and phosphorus added to the nickel matrix for hardness and hexagonal boron nitride or silicon nitride for lubric- ity are used in Japan on cylinder bores and pistons of outboard- marine, motorcycle, and snowmobile engines to increase wear resistance. Paintable ceramic coatings, a specialty of Zyp Coatings, Inc., combine corrosion resistance with heat resistance to 2000°F (1093°C). Piezoelectric ceramics produce voltage proportional to applied mechanical force and, conversely, mechanical force when electric volt- age is applied. Morgan Matroc classifies these materials into hard, soft, and custom groups. Lead zirconate titanate ceramics encom- pass both “hard” and “soft” groups. The hard, such as the company’s PZT-4, 4D, and 8, can withstand high levels of electrical excitation and stress. They are suited for high-voltage or high-power generators and transducers. The soft, such as PZT-5A, 5B, 5H, 5J, and 5R as well as 7A and 7D, feature greater sensitivity and permittivity. Under high drive conditions, however, they are susceptible to self-heating beyond their operating temperature range. They are used in sensors, low-power motor-type transducers, receivers, low-power generators, 210 CERAMICS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses hydrophones, accelerometers, vibration pickups, inkjet printers, and towed array lines. Modified lead metaniobate, PN-1 and 2, features higher operating temperatures and is used in accelerometers, flow detectors, and thickness gages. All are available as rods, tubes, disks, plates, rings, and blocks as well as in custom shapes. Because of their extreme hardness, hot hardness, wear resistance, and chemical inertness, ceramics are used for cutting tools, mainly in the form of inserts fixed to a toolholder, to increase machining speeds or metal-removal rates, and to enhance machining of certain metals and alloys relative to traditional cutting-tool materials. On the other hand, the materials are more costly and brittle. The most commonly used ceramics for cutting tools are based on alumina or silicon nitride. Various other ceramics are added to the powder mix to enhance sintering or mechanical properties, toughness primarily. Principal alumina-based materials, for example, contain titanium carbide, zirconia, or silicon carbide. Other additives include titanium nitride, titanium boride, titanium carbonitride, and zirconium car- bonitride. Silicon nitride is generally stronger and tougher than the alumina but alumina, aluminum nitride, or silica is required as a sin- tering additive to achieve dense material. SiALONs consist of vari- ous amounts of alumina and silicon nitride, sometimes with zirconia or yttria additives. Larsenite, of Blasch Precision Ceramics, Inc., is a ceramic compos- ite of alumina and silicon carbide. It is more resistant to thermal shock than alumina and resists oxidation at higher temperatures [over 3000°F (1649°C)] than the carbide. It is made by firing alumina and a particular grain size of silicon carbide, which then forms a lat- tice and improves the thermal shock resistance of the alumina. The composite has been used instead of fused silica for nozzles used in atomizing metals into powder. Sulfide ceramics, developed at Argonne National Laboratory, hold promise for effective bonding of difficult-to-join materials, such as ceramics to metals. Because they form at lower temperatures than traditional welds, joints are stronger and less brittle. Materials having coefficients of thermal expansion differing by as much as 200% have been joined. The ceram- ics are candidates for use in lithium-iron sulfide batteries being developed for battery-powered cars. Ecoceramics is the term given to silicon carbide ceramics devel- oped from renewable resources and environmental waste (natural wood and sawdust) at the National Aeronautics and Space Administration Glenn Research Center. Parts are to net shape, pyrolyzed at 1800°F (982°C), and infiltrated with molten silicon or silicon alloys. CERMETS. A composite material made up of ceramic particles (or grains) dispersed in a metal matrix. Particle size is greater than CERMETS 211 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses 39 in (1 m), and the volume fraction is over 25% and can go as high as 90%. Bonding between the constituents results from a small amount of mutual or partial solubility. Some systems, however, such as the metal oxides, exhibit poor bonding between phases and require additions to serve as bonding agents. Cermet parts are produced by powder-metallurgy (PM) techniques. They have a wide range of prop- erties, depending on the composition and relative volumes of the metal and ceramic constituents. Some cermets are also produced by impreg- nating a porous ceramic structure with a metallic matrix binder. Cermets can be used in powder form as coatings. The powder mixture is sprayed through an acetylene flame and is fused to the base mater- ial. Although a great variety of cermets have been produced on a small scale, only a few types have significant commercial use. These fall into two main groups: oxide-based and carbide-based cermets. The most common type of oxide-based cermets contains aluminum-oxide ceramic particles (ranging from 30 to 70% volume fraction) and a chromium or chromium-alloy matrix. In general, oxide-based cermets have a specific gravity of 4.5 to 9.0 and a tensile strength of 21,000 to 39,000 lb/in 2 (145 to 269 MPa). Modulus of elasticity ranges from 37 ϫ 10 6 to 50 ϫ 10 6 lb/in 2 (255,000 to 345,000 MPa) and the hardness is Rockwell A 70 to 90. The outstanding characteristic of oxide-based cer- mets is that the metal or ceramic can be either the particle or the matrix constituent. The 6 MgO– 94 Cr cermets reverse the roles of the oxide and chromium; that is, MgO is added to improve the fabrication and performance of the chromium. Chromium is not ductile at room temperature. Adding MgO not only permits press forging at room tem- perature but also increases oxidation resistance to 5 times that of pure chromium. Of the cermets, the oxide-based alloys are probably the simplest to fabricate. Normal PM or ceramic techniques can be used to form shapes, but these materials can also be machined or forged. The oxide-based cermets are used for high-speed cutting tools for difficult- to-machine materials. Other uses include thermocouple-protection tubes, molten-metal-processing equipment parts, mechanical seals, gas-turbine flameholders (resistance to flame erosion), and flow con- trol pins (because of chromium-alumina’s resistance to wetting and erosion by many molten metals and to thermal shock). There are three major groups of carbide-based cermets: tung- sten, chromium, and titanium. Each of these groups is made up of a variety of compositional types or grades. Tungsten-carbide cermets contain up to about 30% cobalt as the matrix binder. They are the heaviest type of cermet (specific gravity is 11 to 15). Their outstand- ing properties include high rigidity, compressive strength, hardness, and abrasion resistance. Modulus of elasticity ranges between 65ϫ10 6 212 CERMETS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses to 95ϫ10 6 lb/in 2 (448,000 to 655,000 MPa), and hardness is about Rockwell A 90. Structural uses of tungsten carbide–cobalt (WC-Co) cermets include wire-drawing dies, precision rolls, gages, and valve parts. Higher-impact grades can be applied where die steels were for- merly needed to withstand impact loading. Combined with superior abrasion resistance, the higher impact strength results in substantial die-life improvement. Double-cemented tungsten carbide-cobalt (DC WC-Co), developed by Smith Tool, is made from material already containing WC-Co in the cobalt matrix binder. DC-14Co has a hardness of 64 Rockwell C, the same wear resistance as WC-14Co but 50% greater toughness. DC-12Co has a hardness of 62 Rockwell C. Most titanium-carbide cermets have nickel or nickel alloys as the metallic matrix, which results in high-temperature resistance. They have relatively low density combined with high stiffness and strength at temperatures above 2200°F (1204°C). Typical properties are specific gravity, 5.5 to 7.3; tensile strength, 75,000 to 155,000 lb/in 2 (517 to 1,069 MPa); modulus of elasticity, 36ϫ10 6 to 55ϫ10 6 lb/in 2 (248,000 to 379,000 MPa); and Rockwell hardness A 70 to A 90. Typical uses are integral turbine wheels, hot-upsetting anvils, hot- spinning tools, thermocouple protection tubes, gas-turbine nozzle vanes and buckets, torch tips, hot-mill-roll guides, valves, and valve seats. Chromium-carbide cermets contain from 80 to 90% chromium carbide, with the balance being either nickel or nickel alloys. Tensile strength is about 35,000 lb/in 2 (241 MPa), the tensile modulus about 50ϫ10 6 to 56ϫ10 6 lb/in 2 (345,000 to 386,000 MPa), and hardness about Rockwell A 88. They have superior resistance to oxidation, excellent corrosion resistance, and relatively low density (specific gravity is 7.0). Their high rigidity and abrasion resistance make them suitable for gages, oil-well check valves, valve liners, spray nozzles, bearing seal rings, bearings, and pump rotors. Other cermets are barium-carbonate-nickel and tungsten-thoria, which are used in higher-power pulse magnetrons. Some proprietary compositions are used as friction materials. In brake applications, they combine the thermal conductivity and toughness of metals with the hardness and refractory properties of ceramics. Uranium-dioxide cer- mets have been developed for use in nuclear reactors. Cermets play an important role in sandwich-plate fuel elements, and the finished ele- ment is a siliconized silicon carbide with a core containing uranium oxide. Control rods have been fabricated from boron carbide–stainless steel and rare-earth oxides–stainless steel. Other cermets developed for use in nuclear equipment include chromium-alumina cermets, nickel-magnesia cermets, and iron-zirconium-carbide cer- mets. Nonmagnetic compositions can be formulated for use where magnetic materials cannot be tolerated. CERMETS 213 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses CESIUM. Also spelled caesium. A rare metal, symbol Cs, obtained from the mineral pollucite, 2Cs 2 O и 2Al 2 O 3 и 9SiO 2 и H 2 O, of southwest Africa and Canada. The metal resembles rubidium and potassium, is silvery white and very soft. It oxidizes easily in the air, ignites at ordi- nary temperatures, and decomposes water with explosive violence. It can be contained in vacuum, inert gas, or anhydrous liquid hydrocar- bons protected from oxygen and air. The specific gravity is 1.903, melt- ing point 83.3°F (28.5°C), and boiling point 1238°F (670°C). It is used in low-voltage tubes to scavenge the last traces of air. It is usually marketed in the form of its compounds such as cesium nitrate, CsNO 3 , cesium fluoride, CsF, or cesium carbonate, Cs 2 CO 3 . In the form of cesium chloride, CsCl, it is used on the filaments of radio tubes to increase sensitivity. It interacts with the thorium of the fila- ment to produce positive ions. In photoelectric cells, cesium chloride is used for a photosensitive deposit on the cathode, since cesium releases its outer electron under the action of ordinary light, and its color sensi- tivity is higher than that of other alkali metals. The high-voltage recti- fying tube for changing alternating current to direct current has cesium metal coated on the nickel cathode and has cesium vapor for current carrying. The cesium metal gives off a copious flow of electrons and is continuously renewed from the vapor. Cesium vapor is also used in the infrared signaling lamp, or photophone, as it gives infrared waves without visible light. Cesium 137, recovered from the waste of atomic plants, is a gamma-ray emitter with a half-life of 33 years. It is used in teletherapy, but the rays are not as penetrating as cobalt 60, and twice as much is required to produce equal effect. CHALK. A fine-grained limestone, or a soft, earthy form of calcium carbonate, CaCO 3 , composed of finely pulverized marine shells. The natural chalk comes largely from the southern coast of England and the north of France, but high-calcium marbles and limestones are the sources of most U.S. chalk and precipitated calcium carbonate. Chalk is employed in putty, crayons, paints, rubber goods, linoleum, cal- cimine, and as a mild abrasive in polishes. Whiting and Paris white are names given to grades of chalk that have been ground and washed for use in paints, inks, and putty. French chalk is a high grade of massive talc cut to shape and used for marking. Chalk should be white, but it may be colored gray or yellowish by impuri- ties. The commercial grades depend on the purity, color, and fineness of the grains. The specific gravity may be as low as 1.8. Precipitated calcium carbonate is the whitest of the pigment exten- ders. Kalite, of Diamond Alkali Co., is a precipitated calcium carbonate of 39-in (1-m) particle size, and Suspenso, Surfex, and Nonferal are grades with particle sizes from 197 to 394 in (5 to 10 m). 214 CESIUM Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses Whitecarb RC, of Witco Corp., for rubber compounding, is a fine- grained grade, 2.56 in (0.065 m), coated to prevent dusting and for easy dispersion in the rubber. Purecal SC is a similar material. Limeolith, Calcene, of PPG Industries, and Kalvan, of R. T. Vanderbilt Co., Inc., are precipitated calcium carbonates. A highly puri- fied calcium carbonate for use in medicine as an antacid is Amitone. CHAMOIS. A soft, pliable leather originally made from the skins of the chamois, Antilopa rupicapra, a small deer inhabiting the moun- tains of Europe but now nearly extinct. The leather was a light-tan color, with a soft nap. All commercial chamois is now made from the skins of lamb, sheep, and goat or from the thin portion of split hides. The Federal Trade Commission limited the use of the term chamois to oil-dressed sheepskins mechanically sueded, but there are no techni- cal precedents for such limitation. The original artificial chamois was made by tanning sheepskins with formaldehyde or alum, impreg- nating with oils, and subjecting to mechanical sueding; but chamois is also made by various special tannages with or without sueding. Those treated with fish oils have a distinctive feel. Chamois leather will withstand soaking in hot water and will not harden on drying. It is used for polishing glass and plated metals. Buckskin, a similar pli- able leather, but heavier and harder, was originally soft-tanned, oil- treated deerskin, but is now made from goatskins. CHARCOAL. An amorphous form of carbon, made by enclosing billets in a retort and exposing them to a red heat for 4 or 5 h. It is also made by covering large heaps of wood with earth and permitting them to burn slowly for about a month. Much charcoal is now pro- duced as a by-product in the distillation of wood, a retort charge of 10 cords of wood yielding an average of 2,650 gal (10,030 L) of pyrolig- neous liquor, 11,000 lb (4,950 kg) of gas, and 6 tons (5.4 metric tons) of charcoal. Wood charcoal is used as a fuel, for making black gun- powder, for carbonizing steel, and for making activated charcoal for filtering and absorbent purposes. Gunpowder charcoal is made from alder, willow, or hazelwood. Commercial wood charcoal is usu- ally about 25% of the original weight of the wood and is not pure car- bon. The average composition is 95% carbon and 3 ash. It is an excellent fuel, burning with a glow at low temperatures and with a pale-blue flame at high temperatures. Until about 1850, it was used in blast furnaces for melting iron, and it produces a superior iron with less sulfur and phosphorus than when coke is used. Red char- coal is an impure charcoal made at a low temperature that retains much oxygen and hydrogen. CHARCOAL 215 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses CHAULMOOGRA OIL. A brownish, semisolid oil from the seeds of the fruit of the tree Taraktogenos kurzii and other species of Thailand, Assam, and Indonesia. It is used chiefly for skin diseases and for lep- rosy. A similar oil is also obtained from other genera of bushes and trees of the family Flacourtiaceae; and that obtained from some species of Hydnocarpus, called lukrabo oil or krabao oil, is superior to the true chaulmoogra oil. The tree H. anthelminthica, native to Thailand, is cultivated in Hawaii. This oil consists mainly of chaul- moogric and hydnocarpic acids, which are notable for their optical activity. Sapucainha oil, from the seeds of the tree Carpotroche brasiliensis, of the Amazon Valley, contains chaulmoogric, hydno- carpic, and gorlic acids and is a superior oil. Gorliseed oil, from the seeds of the tree Onchoba echinata of tropical Africa, and culti- vated in Costa Rica and Puerto Rico, contains about 80% chaul- moogric acid and 10 gorlic acid. Dilo oil is from the kernels of the nuts of the tree Calophyllum inophyllum of the South Sea Islands. In Tahiti it is called tamanu. The chaulmoogric acids are cyclopen- tenyl compounds, (CH) 2 (CH) 2 CH(CH 2 ) x COOH, made easily from cyclopentyl alcohol. CHEESECLOTH. A thin, coarse-woven cotton fabric of plain weave, 40 to 32 count, and of coarse yarns. It was originally used for wrapping cheese, but is now employed for wrapping, lining, interlining, filter- ing, as a polishing cloth, and as a backing for lining and wrapping papers. The cloth is not sized and may be either bleached or unbleached. It comes usually 36 in (0.91 m) wide. The grade known as beef cloth, originally used for wrapping meats, is also the preferred grade for polishing enameled parts. It is made of No. 22 yarn or finer. For covering meats the packing plants now use a heavily napped knitted fabric known as stockinett. It is made either as a flat fabric or in seamless tube form, and it is also used for covering inking and oiling rolls in machinery. Lighter grades of cheesecloth, with very open weave, known as gauze, are used for surgical dressings and for backings for paper and maps. Baling paper is made by coating cheesecloth with asphalt and pasting to one side of heavy kraft or Manila paper. Cable paper, for wrapping cables, is sometimes made in the same way but with insulating varnish instead of asphalt. Buckram is a coarse, plain-woven open fabric similar to cheesecloth but heavier and highly sized with water-resistant resins. It is usually made of cotton, but may be of linen, and is white or in plain colors. It is used as a stiffening material, for bookbindings, inner soles, and interlinings. Cotton bunting is a thin, soft, flimsy fabric of finer 216 CHAULMOOGRA OIL Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses yarn and tighter weave than cheesecloth, used for flags, industrial linings, and decorations. It is dyed in solid colors or printed. But usu- ally the word bunting alone refers to a more durable, nonfading, lightweight, worsted fabric in plain weave. CHELATING AGENTS. Also called chelants and used to capture undesirable metal ions in water solutions, affect their chemical reac- tivity, dissolve metal compounds, increase color intensity in organic dyes, treat waters and organic acids, and preserve quality of food prod- ucts and pharmaceuticals. Three major classes of organic chelants are aminopolycarboxylic acids (APCAs), phosphonic acids, and poly- carboxylic acids. The APCAs include ethylenediaminetetraacetic acid (EDTA), N-hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), and nitrilotriacetic acid (NTA). The phosphonic acids include ethylene- diaminetetramethylene phosphonic (EDTMP), diethylenetri- aminepentamethylene phosphonic (DTPMP), and nitrilotrimethylene phosphonic (ATMP). The polycarboxylic acids include citrates, gluconates, polycrylates, and polyaspar- tates. APCAs are stable at high temperatures and pH values, have a strong attraction for metals, and are not too costly. Their chelate sta- bility surpasses that of the other two classes; they are useful in most industrial applications, including metal cleaning, gas treatment by sulfur removal, and pulp and wood processing. The phosphonic acids are more costly but are stable over wide ranges of temperature and pH values. They are used to treat waters to inhibit corrosion of stor- age vessels and for metals and plastics processing. The polycarboxylic acids are weak and less stable, but inexpensive and useful for alka- line-earth and hardness-ion control. In the United States, the major chelant producers are Dow Chemical, Akzo-Nobel, and BASF, the last having purchased Ciba Specialty’s Trilon, Chel, and Sequestrine products. Phosphates, have been severely restricted for environmental reasons, especially in household detergents. EDTA has been impli- cated for raising metal concentrations in rivers by remobilizing metals in sludge. Citrates, which are biodegradable, are being used increas- ingly as substitutes for phosphates in liquid laundry detergents. NTA, a biodegradable member of EDTA, has largely replaced phosphates in detergents in Canada but is listed as a suspected carcinogen in the United States. Zeolites, though not chelants, serve as phosphate sub- stitutes in detergents but are not as effective in removing magnesium. Polyelectrolytes, lightweight polymers of acrylic acid and maleic anhydride, reduce scale formation by dispersing calcium as fine par- ticles. CHELATING AGENTS 217 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses Two rather new chelants are Bayer Corp.’s iminodisuccinate (IDS) and polyaspartic acid (PAA). Both are maleic anydride derivatives, combine chelating and dispersing, are biodegradable, and are suitable for detergents and water treatment. Hampshire Chemical, part of Dow Chemicals, developed N-lauroyl chelating surfactants, such as LED3A, which is also biodegradable, is compati- ble with enzymes and cationic surfactants, and tolerates hard water. Regarding hard waters, its calcium-binding capacity is greater than that of EDTA’s at higher concentrations. A chelating polymer from Nalco Chemical contains sodium styrene sulfonate, a fluorescent compound that allows spectrophoto monitoring of captured calcium and magnesium ions in boilers. CHEMICAL INDICATORS. Dyestuffs that have one color in acid solu- tions and a different color in basic or alkaline solutions. They are used to indicate the relative acidity of chemical solutions, as the dif- ferent materials have different ranges of action on the acidity scale. The materials are mostly weak acids, but some are weak bases. The best known is litmus, which is red below a pH of 4.5 and blue above a pH of 8.3 and is used to test strong acids or alkalies. It is a natural dye prepared from several varieties of lichen, Variolaria, chiefly Rocella tinctoria, by alllowing them to ferment in the presence of ammonia and potassium carbonate. When fermented, the mass has a blue color and is mixed with chalk and made into tablets of papers. It is used also as a textile dye, wood stain, and food colorant. Azolitmin, C 7 H 7 O 4 N, is the coloring matter of litmus and is a red- dish-brown powder. Orchil, or cudbear, is a red dye from another species. Alkanet, also called orcanette, anchusa, or alkanna, is made from the root of the plant Alkanna tinctoria growing in the Mediterranean countries, Hungary, and western Asia. The coloring ingredient, alkannin, is soluble in alcohol, benzene, ether, and oils, and is produced in dry extract as a dark red, amorphous, slightly acid powder. It is also used for coloring fats and oils in pharmaceuticals and in cosmetics, for giving an even red color to wines, and for color- ing wax. Some coal-tar indicators are malachite green, which is yellow below a pH of 0.5 and green above 1.5; phenolphthalein, which is colorless below 8.3 and magenta above 10.0; and methyl red, which is red below 4.4 and yellow above 6.0. A universal indicator is a mixture of a number of indicators that gives the whole range of color changes, thereby indicating the entire pH range. But such indicators must be compared with a standard to determine the pH value. The change in color is caused by a slight rearrangement of the atoms of the molecule. Some of the indicators, such as thymol blue, exhibit two color changes at different acidity ranges because of the 218 CHEMICAL INDICATORS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses presence of more than one chromophore arrangement of atoms. These can thus be used to indicate two separate ranges on the pH scale. Curcumin, a crystalline powder obtained by percolating hot acetone through turmeric, changes from yellow to red over the pH range of 7.5 to 8.5, and from red to orange over the range of 10.2 to 11.8. Test papers are strips of absorbent paper that have been saturated with an indicator and dried. They are used for testing for acidic or basic solutions, and not for accurate determination of acidity range or hydrogen-ion concentration, such as is possible with direct use of the indicators. Alkannin paper, also called Boettger’s paper, is a white paper impregnated with an alcohol solution of alkanet. The paper is red, but it is turned to shades from green to blue by alkalies. Litmus paper is used for acidity testing. Starch-iodide paper is paper dipped in starch paste containing potassium iodide. It is used to test for halogens and oxidizing agents such as hydrogen peroxide. CHERRY. The wood of several species of cherry trees native to Europe and the United States. It is brownish to light red, darkening on expo- sure, and has a close, even grain. The density is about 40 lb/ft 3 (641 kg/m 3 ). It retains its shape well and takes a fine polish. The annual cut of commercial cherry wood is small, but it is valued for instru- ment cases, patterns, paneling, and cabinetwork. American cherry is mostly from the tree Prunus serotina, known as the black cherry, although some is from the tree P. emarginata. The black cherry wood formerly used for airplane propellers has a specific gravity of 0.53 when oven-dried, compressive strength perpendicular to the grain of 1,170 lb/in 2 (8.1 MPa), and shear strength parallel to the grain of 1,180 lb/in 2 (8.1 MPa). This tree is thinly scattered throughout the eastern part of the United States. The wood is light to dark reddish with a beautiful luster and silky sheen, but has less figure than mahogany. English cherry is from the trees P. cerasus and P. avium. CHESTNUT. The wood of the tree Castanea dentata, which once grew plentifully along the Appalachian range from New Hampshire to Georgia, but is now very scarce. The trees grow to a large size, but the wood is inferior to oak in strength, though similar in appearance. It is more brittle than oak; has a coarse, open grain often of spiral growth; and splits easily in nailing. The color is light brown or yellowish. It was used for posts, crossties, veneers, and some mill products. The wood contains from 6 to 20% tannin, which is obtained by soaking the chipped wood in water and evaporating. Chestnut extract was val- ued for tanning leather, giving a light-colored strong leather. The seed nuts of all varieties of chestnut are used for food and are eaten fresh, boiled, or roasted. The European chestnut, C. sativa and C. vesca, also called the Spanish chestnut and the Italian chestnut, has CHESTNUT 219 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses [...]... metallic luster The melting point is about 3900°F (2 149 °C), but when it is mixed with binders as a refractory, the fusion point is lowered New Caledonia ore has 50% chromic oxide, Turkish ore averages 48 to 53%, Brazilion ore runs 46 to 48 %, and Cuban ore averages only 35% The high-grade Guleman ore of Turkey contains 52% Cr2O3, 14 Al2O3, 10 .4 FeO, 4. 4 Fe2O3, 16 magnesia, and 2.5 silica Most of the domestic... may be made by the electrolysis of common salt The specific gravity of the gas is 3.2 14, or 2 .48 6 times heavier than air The boiling point is 28.5°F (Ϫ33.6°C), and the gas becomes liquid at atmospheric pressure at a temperature of Ϫ 24. 48°F (Ϫ31°C) The vapor pressure ranges from 39 .4 lb (17.9 kg) at 32°F (0°C) to 602 .4 lb (273.2 kg) at 212°F (100°C) The gas is an irritant and not a cumulative poison,... refrigerators It is marketed compressed into cylinders as a colorless liquid The specific gravity is 0.897, freezing point Ϫ221 .4 F (Ϫ 140 °C), and boiling point 54. 5°F (12.5°C) The condensing pressure in refrigerators is 12 .4 lb (5.6 kg) at 6°F (Ϫ 14 C), and the pressure of vaporization is 10.1 lb (4. 6 kg) at 5°F (Ϫ15°C) Its disadvantage as a refrigerant is that it is highly inflammable, and there is no simple test... treatments, tensile properties range from 35,000 to 70,000 lb/in2 ( 241 to 48 3 MPa) ultimate strength, 15,000 to 62,000 lb/in2 (103 to 42 7 MPa) yield strength, and 15 to 42 % elongation Electrical conductivity ranges from 40 to 85% that of copper Chromium coppers are used for resistance-welding electrodes, cable connectors, and electrical parts Any alloy steel containing chromium and molybdenum as key alloying... specifically to steels in the AISI 41 XX series, which contain only 0.030 to 1.20% chromium and 0.08 to 0.35 molybdenum Chromium imparts oxidation and corrosion resistance, hardenability, and high-temperature strength Molybdenum also increases strength, controls hardenability, and reduces the tendency to temper embrittlement AISI 41 30 steel, which contains 0.30% carbon, and 41 40 (0 .40 ) are probably the most... (www.digitalengineeringlibrary.com) Copyright © 20 04 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Materials, Their Properties and Uses CHROMIUM-MOLYBDENUM STEEL 229 Wrought chromium coppers are designated C18200, C1 840 0, and C18500 and contain 0 .4 to 1.0% chromium C18200 also contains as much as 0.10% iron, 0.10 silicon, and 0.05 lead C1 840 0 contains as much as... cladding metal on one side will be 10 to 20% of the weight of the sheet A composite plate having an 18–8 stainless-steel cladding to a thickness of 20% on one side saves 144 lb (65 kg) of chromium and 64 lb (29 kg) of nickel per 1,000 lb (45 4 kg) of total plate The clads may also be extremely thin Many trade names have evolved over the years Pluramelt, of Allegheny Ludlum Steel Corp., is composite steel... makes them unsuitable for good tile, pipe, or pottery Kingsley clay of Georgia, used for artware, wall tile, dishes, and refractories, has only 0 .4% iron oxide, 0.15 Na2O, 0.1 K2O, and 0.05 CaO It contains about 45 % silica, 40 alumina, and 1.15 titanium oxide The seito ware of Japan is made with the Gaerome clay found near Nagoya It is a granite with quartz particles, and when used with a high percentage... (www.digitalengineeringlibrary.com) Copyright © 20 04 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Materials, Their Properties and Uses 240 COAL lard and pork products The clove tree attains a height up to 40 ft (12.2 m), bearing in 7 or 8 years, and continuing to bear for a century, yielding 8 to 10 lb (3.6 to 4. 5 kg) of dried cloves annually Clove... Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 20 04 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Materials, Their Properties and Uses 244 COBALT AND COBALT ALLOYS crystal form, which is stable below 782°F (41 7°C), and a cubic form stable at higher temperatures to the melting point Cobalt has valences . Turkish ore averages 48 to 53%, Brazilion ore runs 46 to 48 %, and Cuban ore averages only 35%. The high-grade Guleman ore of Turkey contains 52% Cr 2 O 3 , 14 Al 2 O 3 , 10 .4 FeO, 4. 4 Fe 2 O 3 , 16. point Ϫ221 .4 F (Ϫ 140 °C), and boiling point 54. 5°F (12.5°C). The condensing pressure in refrigerators is 12 .4 lb (5.6 kg) at 6°F (Ϫ 14 C), and the pressure of vaporization is 10.1 lb (4. 6 kg) at 5°F. 70,000 lb/in 2 ( 241 to 48 3 MPa) ultimate strength, 15,000 to 62,000 lb/in 2 (103 to 42 7 MPa) yield strength, and 15 to 42 % elongation. Electrical con- ductivity ranges from 40 to 85% that of