Materials Handbook 15th 2010 Part 12 doc

Barium titanate crystals are used to replace quartz for electronicuse.. Ethylenediamine tartrate crystals may be used to replace quartz for telephone and sonar work.. Finely groundquartz

Barium titanate crystals are used to replace quartz for electronic

use Ethylenediamine tartrate crystals may be used to replace

quartz for telephone and sonar work

Quartz is harder than most minerals, being Mohs 7, and thecrushed material is much used for abrasive purposes Finely groundquartz is also used as a filler, and powdered quartz is employed as aflux in melting metals When quartz is fused, it loses its crystalline

structure and becomes a silica glass with a specific gravity of 2.2,

compressive strength 210,000 lb/in2 (1,448 MPa), tensile strength4,000 lb/in2 (28 MPa), Mohs hardness 5, and dielectric strength 410V/mil (16  106V/m) The chemical formula of this material is some-times given as SiO3, but is really SiO2repeated in a lattice structure

but different from that of quartz crystal Fused quartz, or quartz

glass, is used for bulbs, optical glass, crucibles, and tubes and rods

in furnaces Its softening and working temperature is about 3040°F(1671°C), and it fuses at 3193°F (1755°C) The translucent material,made from sand, has a specific gravity of 2.7, with much lowerstrength It withstands rapid changes of temperature withoutbreaking Fused quartz made from rock crystal is transparent to vis-ible light, while fused silica is normally translucent or opaque

Vitreosil is fused quartz, containing 99.8% silica It comes opaque,

translucent, and transparent It transmits ultraviolet and shortwavelengths, has high electrical resistance, and has a coefficient of

expansion about one-seventeenth that of ordinary glass Quartz

tubing for electronic use comes in round, square, hexagonal, and

other shapes The softening point is 3033°F (1667°C) Tubing assmall as 0.003 in (0.008 cm), produced by Monsanto Co., is flexibleand as strong as steel

Quartz fiber originally was made by extruding the molten quartz

through a stream of high-pressure hot air which produced a fluffymass of fine fibers of random lengths Quartz fibers are now madewith many differing compositions and methods of manufacture.Fibers used for wool or mat have a diameter of 39 to 591
in (1 to 15

m) Those used for continuous filament may be as small as 0.0035 in

(0.009 cm) Astroquartz and Astroquartz II fiber, of JPS Glass and

Industrial Fabrics, are 99.95% fused silica The specific gravity is 2.2,tensile strength 870,000 lb/in2 (6000 MPa), elastic modulus 10  106

lb/in2 (69,000 MPa), the dielectric strength 3.78, and the thermalexpansion almost zero It is an excellent electrical insulator It isinsoluble in water, nonhygroscopic, and resistant to halogens andmost common acids but not hydrofluoric or hot phosphoric It shouldnot be used in strong alkali concentrations It is used in high-temperature composites, radome and antenna applications,high-speed printed-circuit boards, and insulation blankets

Quartz yarn made from these filaments is used for weaving into

tape and fabric Quartz paper, or ceramic paper, developed by the

Naval Surface Weapons Center and used to replace mica for electricalinsulation, is made from quartz fiber by mixing with bentonite andsheeting on a papermaking machine It has high dielectric strength

and withstands temperatures to 3000°F (1649°C) Micro quartz is

felted, fine quartz fibers for insulation The felted material has a sity of 3 lb/ft3 (48 kg/m3) and is capable of service temperatures to2000°F (1093°C)

den-Since quartz crystallizes more slowly than many other minerals,the natural crystals may include other minerals which were crys-

tallized previously Sagenite is a form of crystalline quartz

con-taining hairlike crystals crossing in a netlike manner A variety offibered quartz with a pale-amethyst color which shows deep red by

transmitted light, found in Russia and Colorado, is called onegite.

Rutilated quartz is clear quartz penetrated by rutile crystals A

smoky, dark quartz of this type is the Venushair stone.

Aventurine is a form of quartz crystal containing the inclusion in

the form of flakes or spangles It comes from the Ural Mountainsand from India and is prized for gems For costume jewelry it is

made synthetically in great quantities under the name of

gold-stone by melting the inclusions into quartz glass Amethyst, topaz, and many other gemstones are quartz The golden-yellow

topaz of Mexico and Brazil is a type of quartz called citrine The yellow variety called imperial topaz in Brazil is rare, but yellow-brown stones are common Pink topaz is also rare, but can

be made by heating yellow-brown stones with a risk of breaking.Inferior-colored amethysts may also be made into yellow or orange

citrine by heating The rose quartz of South Dakota is prized in

the beautiful rose color, but in the large deposits the shades mayrun from milky white through pale pink to deep rose-red The beststones are used for gems, as are also the translucent pink crystalsfrom Maine Other grades are cut into vases, ornaments, and archi-

tectural facings Chalcedony is a cryptocrystalline quartz with a

waxy luster deposited in rock veins from colloidal solution, or inconcentric rings on rocks Its fibers are biaxial instead of the uniax-

ial of quartz The chalcedony of South Dakota known as beckite

fluoresces under ultraviolet light Chalcedony was an ancient stone and was used for intaglios and seals and for figurines andvases Some chalcedony from New Mexico and Arizona is stained

gem-and cut for costume jewelry Chrysoprase is a translucent,

apple-green variety of cryptocrystalline quartz colored with hydratednickel silicate found in Silesia It is highly valued for mural decora-tions and as a gemstone

The so-called massive topaz used as a refractory material

instead of kyanite is not true topaz or quartz The massive topazmined in North Carolina contains about 50% Al2O3 and 40 SiO2,with iron oxide When calcined for refractory use, it has the samecomposition as kyanite The topaz from the wolframite mines of SãoPaulo, Brazil, used for refractories, has a high alumina content and

a high fluorine content The purer crystals have a melting point of

3416°F (1880°C) The quartz known as cristobalite, used as a

refractory, differs from ordinary quartz only in crystal structure It

has a melting point of 3140°F (1725°C) Jasper is a variety of

quartz colored red with iron oxide It is cut and polished as an

orna-mental building stone Egyptian jasper is brown with dark zones.

In ancient times many of the gemstones were silica stones, and the

Athiaenon stone from Cyprus was jasper of bright colors The jasper iron ore of Michigan has an iron content of about 33% with

less silica than taconite, making it easier to crush, but tion must be done by flotation, which is more expensive than themagnetic separation of taconite

concentra-Quartzite is a rock composed of quartz grains cemented together

by silica It is firm and compact and breaks with uneven, splinteryfractures Most of the quartzites used are made up of angulargrains of quartz and are white or light in color with a glisteningappearance It often resembles marble, but is harder and does noteffervesce in acid Quartzite is employed for making silica brick,abrasives, and siliceous linings for tube mills It is also ratherwidely used as a structural stone and as a broken stone for roads It

is found as a widely distributed common rock Medina quartzite,

from Pennsylvania, contains 97.8% silica The melting point isabout 3092°F (1700°C)

quassia tree, Picroena excelsa, and of the Surinam quassia, Quassia

amara, of the West Indies and northern South America The

Jamaica quassia is a large tree, sometimes called bitter ash

because the leaves resemble those of the common ash The wood isyellow, light, dense, and tough It is odorless, but has an intensivelybitter taste The wood is imported mostly as chips for the production

of the extract which is used in medicine as a bitter tonic, and in ticides It is also used as an ingredient in stock-feed tonics for cattle

insec-In tropical countries the wood is valued for furniture, as it is resistant

to insects The wood of the Surinam quassia is darker in color,

heav-ier, and harder, but has similar properties Quassin, extracted from

quassia, is used to denature alcohol

QUEBRACHO The wood of the quebracho colorado, or red

que-bracho, tree, Aspidospera queque-bracho, found only along the west

bank of the Parana and Paraguay rivers in Argentina andParaguay It contains about 24% tannin The wood is exceedinglyhard and has a brownish-red color, often spotted and stained almostblack Quebracho is valued as a firewood in Argentina, and is usedfor crossties and posts, but is too brittle for structural work Ittakes a fine polish and is very durable, carvings of this wood being

in perfect condition after 300 years The density is 78 lb/ft3 (1,250kg/m3) Quebracho extract, from the wood, is a hard, resinous,

brownish-black, and extremely bitter solid containing 62% solubletannins One and one-tenth ton (1 metric ton) of wood yields about

551 lb (250 kg) of solid extract The liquid extract contains 25 to35% tannin It is employed in tanning leather and is rapid-acting,but is seldom used alone, as it makes a dark leather It is mixedwith alum and salt, or with chestnut extract Some extract is used

in boiler compounds, but one of the larger uses has been for the

treatment of oil-well-drilling muds Aerosol Q, of American

Cyanamid Co., is powdered quebracho and an organic colloid for

oil-well muds White quebracho, Schinopois lorentsii, is a smaller

tree than the red quebracho, growing over a wider area ofArgentina, Brazil, and Paraguay It produces a similar tannin

Some urunday extract is produced in Argentina for export instead

of quebracho The urunday wood is red and very hard, but not as

brittle as quebracho, and is valued for cabinetwork The tanninfrom the wood is similar to quebracho extract

RADIOACTIVE METALS. Metallic elements which emit radiations thatare capable of penetrating matter opaque to ordinary light They giveout light and appear luminous, also having an effect on photographicplates The metal radium is the most radioactive of all the naturalelements, and was much used for luminous paints for the hands ofwatches and instrument pointers Because of the emission of danger-ous gamma rays, however, it has been replaced for this purpose by

radioactive isotopes of other metals These isotopes, such as cobalt

60, used as a source of gamma rays, and krypton 85, for beta rays,

are marketed selectively Radioactive metals are used in medicine, forluminous paints, for ionization, for breaking particle bonds in pow-dering minerals, for polymerization and other chemical reactions, andfor various electronic applications

The metals which are naturally radioactive, such as uranium andthorium, all have high atomic weights The radiating power is atomic

and is unaffected in combinations Radium and other radioactive

metals are changing substances Radium gives out three types of

rays; some of the other elements give out only one or two The sure of the rate of radioactivity is the curie, which is the equivalent ofthe radioactivity of 0.0022 lb (1 g).

Each radioactive metal has a definite breakdown period,

mea-sured in half-life Actinium, which is element 89, has a half-life of 21.7 years It emits alpha particles to decay to actinium K, which is the radioactive isotope of francium, and then emits beta particles.

Radioactive metals break down successively into other elements Bycomparison of changing atomic weights, it has been deduced thatthe metal lead is the ultimate product, and uranium the parentmetal under existing stability conditions But heavier metals, now

no longer stable under present conditions, have been produced

syn-thetically, notably plutonium The heavy element 103 was first duced in 1961 and named lawrencium in honor of the inventor of

pro-the cyclotron Not all radiation produces radioactive materials, and

by controlled radiation useful elements may be introduced intoalloys in a manner not possible by metallurgy The crystal lattice of

an alloy can be expanded, or atoms displaced in the lattice, thusaltering the properties of the alloy In like manner, the molecules ofplastics may be cross-linked or otherwise modified by the applica-tion of radiation For example, ethylene bottles may be irradiatedafter blowing to give higher strength and stiffness Radioactive iso-topes are also used widely in chemistry and in medicine and assources of electric power

RADIUM. The best-known radioactive metal, symbol Ra, scattered

in minute quantities throughout almost all classes of rocks, but mercially obtainable only from the uranium ores monazite,carnotite, and uraninite It is a breakdown product, and it disinte-grates with a half-life of 1,590 years The metal is white, but it tar-nishes rapidly in air The melting point is about 1292°F (700°C) Itwas discovered in 1898 by Curie, and the original source was fromthe pitchblende of the Sudetenland area of Austria after extraction

com-of thorium oxide, but most com-of the present supply comes from thecarnotite of Zaire and from the pitchblende of western Canada Onegram of radium and 7,800 lb (3,538 kg) of uranium are obtainedfrom 370 tons (336 metric tons) of pitchblende The ratio of radium

to uranium in any uranium ore is about 1:3,000,000 Radium is keted in the form of bromides or sulfate in tubes and is extremelyradioactive in these forms

mar-In a given interval of time, a definite proportion of the atoms break

up with the expulsion of , ß, and rays When an alpha particle isemitted from radium, the atom from which it is emitted becomes a

new substance, the inert gas radon, or element 86, with a half-life of

3.82 days During its short life, it is a definite elemental gas, but itdeposits as three isotopes in solid particles, decaying through polo-nium to lead Radium is most widely known for its use in therapeuticmedicine It is also used for inspecting metal castings for flaws.

Radium-beryllium powder is marketed for use as a neutron

source

RAMIE. A fiber used for cordage and for various kinds of coarse

fab-rics, obtained from the plant Urtica nivea, of temperate climates, and U tenacissima, of tropical climates The former plant has leaves

white on the underside, and the latter has leaves all green The

name rhea is used in India to designate the latter species It is also

grown in China, Egypt, Brazil, and Florida The plants grow in tall,slender stalks like hemp and belong to the nettle family The bastfibers underneath the bark are used, but are more difficult to sepa-rate than hemp fiber owing to the insolubility of the adhesive gums.The fibers are 8 times stronger than cotton, 4 times stronger thanflax, and nearly 3 times stronger than hemp They are fine andwhite and are as silky as jute They are not very flexible and are not

in general suitable for weaving, but their high wet strength,absorbent qualities, and resistance to mildew make the fibers suit-able for warp yarns in wool and rayon fabrics The yarn is used alsofor strong, wear-resistant canvas for such products as fire hose Thefiber is valued for marine gland packings and for twine The compo-sition is almost pure cellulose, and the tow and waste are used for

making cigarette paper China grass is the hand-cleaned but not degummed fiber It is stiff and greenish yellow Grass cloth is woven fabric made in China from ramie Swatow grass cloth,

imported into the United States, is made of ramie fibers in parallelstrands, not twisted into yarns

canbra oil An oil obtained from seeds of the mustard family,

Cruciferae The genus Brassica, a form of turnip, species of which are referred to as B campestris, B rapa, B napus, and B hirta, is

grown in India, Pakistan, Europe, and Canada Rapeseed is one of

the principal oil seeds of the world It is widely used as an edible oil,for making factice, and for mixing with lubricating and cutting oilsand for quenching oils The seeds are very small, with 1 oz (28 g)having as many as 40,000 seeds The seeds contain 40% oil The edi-ble oil is cold-pressed and refined with caustic soda The burningand lubricating oils are refined with sulfuric acid The refined oilhas a pungent, mustardlike odor that can be removed by deodoriza-tion The iodine value is about 100, the specific gravity 0.915, and

the flash point 455°F (235°C) The oil contains palmitic, oleic,

linoleic, and stearic acids and 43 to 50% of the typical acid, erucic

acid, also called brassidic acid, C21H41COOH It has a meltingpoint of 93°F (34°C) It occurs also in grape seed oil For edible oils,the erucic acid is reduced, generally to less than 5%; the high-erucic-acid oils are used industrially as lubricant additives.Genetic variants with no erucic acid have also been made Edible

low-erucic-acid canola oils for food applications are made by Agro

Ingredients, Inc Colza oil is a rape oil extracted from French seed,

used to mix with mineral oils to make cutting oils The name colza

now refers to any refined rape oil Chinese colza oil, from B.

campestris chinoleifera, contains the mustard volatile oil The

spe-cific gravity is 0.91, saponification value 174, and iodine number100.3 From 15 to 20% of blown rapeseed oil is mixed with mineral

oil for lubricating marine engines Crambe seed oil, from Crambe

abyssinica, an Asiatic mustard, contains 55 to 60% erucic acid The

erucic can be broken down to perlargonic acid used as a substitute

for dibasic acids such as azelaic and brassylic acids Cameline oil, called also dodder oil and German sesame oil, has the same uses

as rape oil It is from the plant Camelina sativa grown in central

Europe The seeds contain 35% oil which contains oleic and palmiticacids and erucic acid The seed itself is high in mineral and proteincontent and is used in birdseed mixtures

rapidly create precise models of prototype parts using computer-basedsystems and computer-aided-design data They are also used to maketools and limited quantities of parts

Several systems are laser-based Stereolithography, of 3D Systems,

Inc., involves sequential curing of a liquid photopolymer on a

descending platform by an ultraviolet laser beam Two such polymers

are Ciba Geigy’s Cibatool 5170 epoxy for use with helium-cadmium lasers and Cibatool 5180 for use with argon lasers Exactomer resins, of Allied Signal, use vinyl ethers and cationic photoinitiators

to start polymerization DTM Corp uses a low-power CO2laser beam

to trace part outlines in a thin layer of powder and to sinter the der particles Again, layer upon layer of material is built up on adescending platform until the model is completed Materials, called

pow-Laserite, include investment-casting wax, nylon, and bonate This system can also be used to form iron-matrix-compos- ite tools In this case, thermoplastic-coated carbon-steel powder

polycar-particles are tacked in place and transferred to a furnace where thecoating is burned off and the powder sintered to a porous shape, andthe shape infiltrated with copper A similar laser is used by Helisys

776 RAPID PROTOTYPING MATERIALS

Inc in what is called laminated object manufacturing Here the laser

cuts thin paper or film, dispensed on a roll, to the part outline, andthe cut pieces are deposited on a descending table until the model iscompleted The materials are heat-activated, adhesive-coated,

bleached kraft paper or polyester film in various colors The paper

results in a model resembling wood The film creates water-resistantmodels

In fused deposition modeling, by Stratasys, Inc., a thermoplastic orwax filament from a spool is heated, extruded, and deposited in thinlayers onto a base by a robot-held dispensing head The model is built

from the base up The materials, which include machinable wax,

investment-casting wax, Plastic P200 polyolefin, and nylonlike Plastic P300 and Plastic P301, are heated just sufficiently to flow,

and solidify instantly upon deposition

Acrylonitrile-butadiene-styrene parts, having a tensile strength of 3,000 lb/in2(21 MPa), and

polyester parts also have been made A robotic extrusion system

developed by IBM accepts thermoplastic pellets, including an tomer and a machinable nylonlike material In solid ground modeling,

elas-by Cubital Ltd (Israel) and Cubital America, successive layers of aliquid photopolymer are exposed and cured by an ultraviolet lampthrough a glass mask generated ionographically using toner and rep-resenting part cross sections The exposed resin is then removed, and

the cavity filled with water-soluble wax The layer is cooled and

milled to accurate thickness, and the next layer is formed When allthe layers have been built up, the wax is dissolved, leaving the modelshape Direct shell production casting, developed at theMassachusetts Institute of Technology and marketed by SoligenTechnology Inc., is based on three-dimensional printing This systembypasses the modeling stage and is used directly to make

metal-infiltrated, ceramic-matrix-composite cores and molds for casting parts A jet, similar to an ink jet but using a colloidal silica binder, sprays successive patterns of the part shape onto alumina

powder, which is compacted between powder charges When the finallayer is formed, the partially consolidated shape is removed, thebinder burned off, and the shape sintered and infiltrated with metal.Aluminum and stainless-steel parts have been cast using molds andcores made in this way

RARE-EARTH METALS. A group of trivalent metallic elements that

occur together They are also called rare earths, because of the

diffi-culty of extracting them, not because of their rarity They include

ele-ments 57 through 71, from lanthanum to luterium, and yttrium,

element 39, and thorium, element 90, because these are also

together in monazite, the chief ore The cerium metals are a group

of rare-earth metals consisting of elements with atomic numbers 57

through 63, including the metal cerium This group is also referred

to as the light rare earths The metal ytterbium (atomic number

70) also may be included in this group because of its light weight

Thorium is separated by a relatively easy process, and the others

remain grouped as the cerium metals, to be extracted as metals orcompounds for special purposes justifying high costs The separatemetals are regularly marketed in pellets and in 325-mesh powder of99.9% purity for pyrophoric and electronic uses, and as oxides of99.9% purity Cerium metal has an iron-gray color, is only slightlyharder than lead, and is malleable It has a specific gravity of 6.77and a melting point of 1480°F (804°C) Cerium-based pigments arebeing considered as alternatives to cadmium pigments for coloringplastics because of the toxicity of cadmium

After extraction of the thorium oxide from monazite, the chief earth ore, the residual matter is reduced by converting the oxides tochlorides and then removing the metals by electrolysis The productobtained is an alloy containing about 50% cerium together with lan-thanum, didymium, and the other rare-earth metals It is usually

rare-called mischmetal, the German name for mixed metal, and its nal use was for making pyrophoric alloys Cerium standard alloy of

origi-Cerium Metals Corp is a mischmetal containing 50 to 55% cerium, 22

to 25 lanthanum, 15 to 17 neodymium, and the balance a mixture ofyttrium, terbium, illinium, praseodymium, and samarium, with 0.5 to0.8 iron

Mischmetal is used in making aluminum alloys and in some steelsand irons In cast iron it opposes graphitization and produces a mal-leable iron It removes the sulfur and the oxides and completelydegasifies steel In stainless steel it is used as a precipitation-harden-ing agent An important use of mischmetal is in magnesium alloys forcastings From 3 to 4% of mischmetal is used with 0.2 to 0.6 zirco-nium, both of which refine the grain and give sound castings of com-plex shapes The cerium metals also add heat resistance tomagnesium castings

Ceria, cerium oxide, or ceric oxide, CeO2, is a pale-yellow,heavy powder of specific gravity 7.65, used in coloring ceramics andglass for producing distortion-free optical glass It is used also for de-colorizing crystal glass, but when the glass contains titania, it pro-

duces a canary-yellow color Cerious oxide, Ce2O3, is a greenishpowder of specific gravity 7.0 and refractive index 2.19 About 3% ofthe oxide in glass makes the glass completely absorbent to ultraviolet

rays It is also an excellent opacifier for ceramics Cerium fluoride,

CeF3, is used in arc carbons to increase brilliance Cerious nitrate,

Ce(No3)3 6H2O, is a red, crystalline powder used in gas-mantle

ufacture Cerium salts are used for coloring glass Ceric titanate,

Ce(TiO3)2, gives a golden-yellow color, and ceric molybdate gives a

blue color

Neodymium has a specific gravity of 7.01 and a melting point of

1875°F (1024°C) It is used in magnesium alloys to increase strength

at elevated temperatures and is used in some glasses to reduce glare

Neodymium glass, containing small amounts of neodymium oxide, is

used for color television filter plates since it transmits 90% of the blue,green, and red light rays and no more than 10% of the yellow It thusproduces truer colors and sharper contrasts in the pictures anddecreases the tendency toward gray tones Neodymium is also a

dopant for yttrium-aluminum-garnet, or YAG, lasers as well as for glass lasers Praseodymium has a specific gravity of 6.77 and a melt- ing point of 1715°F (935°C) Lanthanum is a white metal, malleable

and ductile, with a specific gravity of 6.16, and melts at 1688°F(919°C) Like the other cerium metals, it oxidizes easily in air and is

easily soluble in acids Lanthanum oxide, La2O3, is a white powder

used for absorbing gases in vacuum tubes Lanthanum boride, LaB6,

is a crystalline powder used as an electron emitter for maintaining aconstant, active cathode surface It has high electrical conductivity

Didymium is not an element, but is a mixture of rare earths

with-out cerium It averages 45% La2O3; 38 neodymium oxide, Nd2O3; 11

praseodymium oxide, Pr6O11; 4 samarium oxide, Sm2O3; and otheroxides It is really the basic material from which the rare metals areproduced In glass it gives a neutral gray color, and it is used in glassfor welders’ goggles, as it absorbs yellow light and reduces glare and

eye fatigue It is available as didymium carbonate, a pink powder soluble in acids; as didymium oxide, a brown acid-soluble powder; and as didymium chloride in pink lumps soluble in water and in

acids

Dysprosium has a specific gravity of 8.56 and a melting point of

2700°F (1482°C) Its corrosion resistance is higher than that of othercerium metals It also has good neutron-absorption ability, with aneutron cross section of 1,100 barns The metal is paramagnetic It isused in nuclear reactor control rods, in magnetic alloys, and in fer-rites for microwave use It is also used in mercury-vapor lamps Withargon gas in the arc area, it balances the color spectrum and gives a

higher light output Samarium has a higher neutron cross section,

5,500 barns, and is used for neutron absorption in reactors.Samarium has a specific gravity of 7.54 and a melting point of 1925°F

(1052°C) Terbium has a melting point of 2473°F (1356°C) and is

used as a phosphor, as a catalyst, and in alloys with dysprosium andiron for magnetostrictive devices or with cobalt for magneto-opticstorage devices

Ytterbium metal is produced in lumps and ingots It has a specific

gravity of 6.96 and a melting point of 1515°F (824°C) Yttrium is

more abundant in nature than lead, but is difficult to extract It isfound associated with elements 57 to 71, although its atomic number

is 39 It has a silvery luster, a specific gravity of 4.47, and a meltingpoint of 1550°F (843°C) It is the lightest of the cerium metals exceptscandium The metal is corrosion-resistant to 752°F (400°C) It has a

hexagonal, close-packed crystal structure Ytterbium oxide, Yb2O3,

and yttrium oxide, Y2O3, are the usual commercial forms of these

metals The two metals occur in the mineral gadolinite, or

ytter-bite, 4BeO FeO  Y2O3 2SiO2, which also contains gadolinium,

erbium, europium, holmium, and rhenium The mineral is found

in Greenland, Sweden, Norway, and Colorado Erbium has beenobtained only in small quantities as a dark-gray powder The metalhas a specific gravity of 9.06 and a melting point of about 2700°F

(1482°C) It forms the rose-red erbium oxide, or erbia, Er2O3, andother, highly colored, reddish salts At high temperatures erbia glowswith a greenish light

Yttrium also occurs in the scarce mineral nuevite found in

California The mineral also contains titanium, tantalum, iron, and

quartz, and is similar to the keilhauite found in Norway.

Fergusonite, a brown mineral with a vitreous fracture, found

sparsely in the Appalachian hills from New England to SouthCarolina, is a columbate and tantalate of yttrium with cerium,

erbium, and uranium In Europe it is known as bragite and tyrite The mineral known as bastnasite in California is a fluorocarbonate

of cerium and lanthanum, and the deposit at Mountain Pass,California, is sufficient to supply the commercial needs of all thecerium metals About 0.01% of rare-earth metals remain in the wasteafter apatite ores are processed in the making of phosphoric acid fer-tilizer These metals are extracted by solvent or ion-exchange meth-

ods Yttrium oxide is available as a fine, white powder Yttralox is a

transparent ceramic made from yttrium oxide and has a meltingpoint above 4000°F (2204°C) It is used for special high-temperaturelenses, infrared windows, lasers, and high-intensity lamps For thebrilliant reds for television phosphors, small amounts of europium are

added to yttrium vanadate.

Gadolinium oxide, or gadolinia, Gd2O3, has high neutron tion and is used for shields in atomic power plants As a moldedceramic, it has a specific gravity of 7.0, low thermal conductivity, and

absorp-a melting point of 4262°F (2350°C) Lutetium is absorp-a heabsorp-avy refrabsorp-actory

metal with a specific gravity of 9.85 and a melting point of about

3100°F (1704°C) Lutetium oxide, Lu2O3, of 99% purity, is produced

for atomic uses Holmium has a specific gravity of 8.8 and a melting

point of about 2700°F (1482°C) It is used in glass to transmit radiant

energy for wavelength-calibration instruments Thulium is a heavy

metal with a specific gravity of 9.32 and a melting point of about

2800°F (1538°C) It is used for radiographic applications Thulium

170 is a soft gamma-ray emitter and is used as a radiation source Thulium oxide, Tm2O3, is radioactive and is used as a power source

for small thermoelectric devices Scandium is a silvery-white metal found in the mineral thortveitite, (ScYt)2Si2O7, of Norway, which

contains 42% scandium oxide, Sc2O3 It also occurs in smallamounts in the fergusonite of Montana, and in lepidolite, muscovite,beryl, and the amphiboles The metal has a melting point of 2552°F(1400°C) and a specific gravity slightly higher than that of aluminum

RARE GASES Also known as inert gases in the metallurgical try, and as noble gases A general name applied to the five elements

indus-helium, neon, argon, krypton, and xenon They are rare in that theyare highly rarified gases at ordinary temperatures and are found dis-sipated in minute quantities in the atmosphere and in some sub-stances All have zero valence and normally make no chemicalcombinations, but by special catalyzations, except in the case of

helium, the outer proton bonding may be broken and compounds

pro-duced The rare gases are colorless, odorless, and tasteless at ambienttemperatures However, they exhibit very different properties whencooled to extremely low temperatures When saturated helium, or

helium 4, is cooled to below 2.17 K, it becomes a superfluid One

unique property of superfluids is the ability to pass undetected

through very small openings Helium 3, the unsaturated

counter-part, differs in that it is magnetic

Neon is procured from the air by liquefaction When it is energized,

it emits light and is used for signs and in glow lamps The specific ity, compared with air, is 0.674 It liquefies at 414°F (248°C) It iscolorless, but gives a reddish-orange glow in lamps to which an electriccurrent is applied Neon is also used in voltage-regulating tubes forradio apparatus and responds to low voltages In television the neonlamp gives fluctuations from full brilliancy to total darkness as many

grav-as 100,000 times per second Colored electric advertising signs areoften referred to as neon signs, but the colors other than orange are

produced by different gases Argon gives a purple light when an

elec-tric current is passed through it It occurs free in the atmosphere to theextent of 0.935% Its liquefying point is about 305°F (187°C) It isobtained by passing atmospheric nitrogen over red-hot magnesium,forming magnesium nitride and free argon It is also obtained by sepa-ration from industrial gases Argon is employed in incandescent lamps

to give increased light and to prevent vaporization of the filament It is

also used as a shielding gas in welding, as an assist gas in laser ting, as an inert blanket for nuclear fuels, and, at high pressure, inhybrid-type airbag inflators for cars.

cut-Krypton, which occurs in the air to the extent of 1 part in 1

mil-lion, gives a pale-violet light It is a heavy gas, with a specific gravity

of 2.896 It is used as a filler for fluorescent lamps to decrease ment evaporation and heat loss and to permit higher temperatures inthe lamp The 3109 candlepower aircraft-approach lights first used

fila-on the Berlin airlift cfila-ontained kryptfila-on Kryptfila-on 85, obtained from

atomic reactions, is a beta-ray emitter with a half-life of 9.4 years It

is used in luminous paints for activating phosphors and as a source ofradiation It comes combined in solid form with a hydroquinone togive higher concentration of energy and more convenience in use and

in disks of 0.23 and 0.5 in (0.58 and 1.27 cm) in diameter encased inacrylic plastic for use with phosphors as luminous sources The light

is yellow-green Xenon, another gas occurring in air to the extent of 1

part in 11 million, gives a sky-blue to green light It is the heaviest ofthe rare gases, with a specific gravity of 4.561 compared with 1 forair Its liquefying point is about 162°F (108°C) When atomic reac-tors are operated at high power, xenon tends to build up as a reaction

product, poisoning the fuel and reducing the reactivity Xenon lamps

for military use give a clear, white light known as sunlight plus

north-sky light This color does not change with the voltage, and thusthe lamps require no voltage regulators An 800-W xenon lamp deliv-ers 2,000 lm, 4 times as much as a 1,000-W incandescent lamp Thexenon lamp reflects each half cycle, so that shutterless projectors arepossible Krypton and xenon have lower thermal conductivity andlower electrical resistance than argon A helical arc of xenon is used toactivate ruby optical masers Xenon is a mild anesthetic, the accumu-lation from air helping to induce natural sleep, but it cannot be used

in surgery since the quantity needed produces asphyxiation

RARE METALS. A term given to metals that are rare in the sense thatthey are difficult to extract and are rare and expensive commercially

They include the elements astatine, technetium, and francium.

The silvery metal technetium, element 43, has been produced by bardment of molybdenum with neutrons It is available in the form of

bom-technetium carbonyl, Tc2(CO)10, which is stable in air and soluble

in most organic solvents but reacts with halogens Although radium

is a widely distributed metal, it is classified as a rare metal All of theultra-heavy metallic elements, such as plutonium, which are pro-duced synthetically, are classified as rare metals They are called

transuranic metals because they are above the heavy-metal

ura-nium in weight They are all radioactive

Element 99, called einsteinium, was originally named

eka-holmium because it appears to have chemical properties similar to

holmium It is produced by bombarding uranium 238 with stripped

nitrogen atoms It decays rapidly to form the lighter berkelium, or element 97 Neptunium, element 93, californium, element 98, and

illinium, element 61, are also made atomically The last also has the

names florentium and promethium.

Plutonium is made from uranium 238 by absorption of neutrons

from recycled fuel The metal, 99.8% pure, is obtained by reduction of

plutonium fluoride, PuF4, or plutonium chloride, PuCl3 It has amelting point of 147°F (64°C) The surface reacts in air to form the

nonadherent plutonium oxide, PuO2, which becomes airborne and

is pyrophoric and poisonous Plutonium 238, 239, and 240 emit

chiefly alpha rays Plutonium 238 has a low radiation level and isused as a heat source for small water-circulating heat exchangers fornaval undersea diving suits Heat generated by radioactive decay andconverted to electrical energy has been used to power spacecraft

Plutonium 241 emits beta and gamma rays Since all the

allotropic forms are radioactive, it is a pure nuclear fuel in contrast

to uranium, which is only 0.7% directly useful for fission It is thusnecessary to dilute plutonium for control For fuel elements it may

be dispersed in stainless steel and pressed into pellets at about

1600°F (871°C), or pellets may be made of plutonium carbide.

Plutonium-iron alloy, with 9.5% iron, melts at 770°F (410°C) It is

encased in a tantalum tube for use as a reactor fuel

Plutonium-aluminum alloy is also used These alloys have hard compounds of

PuFe and PuAl in the matrix, and the plutonium is insoluble Whileplutonium 241 has a half-life of only 14 years, the beta emitters plu-tonium 239 and 240 have half-lives of 24,300 and 16,600 years,

respectively Element 102, called nobelium, has a half-life of only 0.2 h Other transuranic metals produced synthetically are ameri-

cium, element 95, and curium, element 96 Curium is used as a

heat source in remote applications Curium 244 is obtained as

curium nitrate in the reprocessing of spent reactor fuel It is

con-verted to curium oxide The by-product americium is used as a

component in neutron sources Other transuranic metals that have

been produced by nuclear reactions and synthesis include fermium (element 100), mendelevium (element 101), lawrencium (element 103), rutherfordium or kurchatovium (104), and hahnium or

nielsbohrium (105).

medicine as krameria The root of the shrub Krameria triandria,

which grows in Peru and is used for tanning leather and in medicine

as an astringent The root comes in diameters up to 1 in (2.5 cm) and

in pieces up to 3 ft (0.9 m) in length It contains about 40% tanninwhich is extracted by hot water It gives the leather a deep-browncolor and is usually mixed with other tannins

other species, of Sri Lanka, Malaya, and Laos There are more than

40 varieties The Malay word is rottan, meaning cane It is tough,

flexible, strong, and durable, and it is used for canes, umbrella dles, and furniture When split, it is used for car seats, baskets, baby-carriage bodies, furniture, whips, and heavy cordage.Commercial rattans are in pieces 5 to 20 ft (1.5 to 6.1 m) long A sub-

han-stitute for rattan is jacitará, from the plant Desmoncus

macroacan-thus, of Brazil It is used for seating Vinylidene chloride plastic is

now widely used as a substitute for rattan for seating

RAYON. A general name for artificial-silk textile fibers or yarns

made from cellulose nitrate, cellulose acetate, or cellulose

deriva-tives In general, the name rayon is limited to the viscose,

cupram-monium, and acetate fibers, or to fibers having a cellulose base.

Other synthetic fiber groups have their own group names, such as

azlon for the protein fibers and nylon for the polymeric amine fibers,

in addition to individual trade names

Viscose rayon is made by treating the cellulose with caustic

soda and then with carbon disulfide to form cellulose xanthate,which is dissolved in a weak caustic solution to form the viscose.With the cuprammonium process, the cellulose is digested in anammonia solution of copper sulfate, and the solution is forcedthrough the spinnerets into dilute acid for hardening Rayons man-ufactured by the different processes vary both chemically andphysically They are resistant to caustic solutions which woulddestroy natural silk They are also mildewproof, durable, and eas-ily cleaned But they do not have the permeability and soft feel of

silk The acetate rayons are more resistant than the viscose or

cuprammonium The lack of permeability of the fibers is partlyovercome by having superfine fibers so that the yarns are perme-able The one-denier viscose staple produced by FMC Corp bystretching the fiber after it leaves the spinnerets is finer thanEgyptian cotton and can thus be made into yarns that are perme-able between the fibers Fabrics made from the superfine yarns

have the appearance of sheer silk Multicell rayon of this

com-pany, for making nonwoven fabrics and lining and filter papers onregular papermaking machines without the addition of a binder, is

a multicellular, short-staple fiber cut to uniform 0.25-in (0.64-cm)

length The fibers lock themselves firmly in place with contactingfibers, and the 1.5-denier fiber makes a soft, opaque sheet of paper.The density of the sheets and the strength per unit weight

decrease with increase in fiber denier Fiber 40, of this company,

is a type of rayon called Avril, made by a special pulping process

which decreases the tendency to shrink or felt when the fiber is

wet Avlin is a multicellular rayon fiber that gives a tight, firm bulk to fabrics Fabray, of Stearnes Technical Textiles Co., is a

thin, lightweight, porous, nonwoven fabric of rayon fiber used forthrowaway garments

The objectionable high gloss of synthetic fibers is reduced by

pig-mentation Glos was an early name for rayon because of this gloss,

but the name now has been abandoned Mixtures of rayon and otherfibers have some use for dress fabrics as well as underwear Thematerial is also used for automotive tire fabrics because of its

strength Stable fiber is fiber cut to length for the spinning system

to be used

High-tenacity rayon is produced by stretching the fibers so that

the molecular chains run parallel to the filament axis, and a number

of small crystalline regions act as anchors for the cellulose chains

Tire cord stretched in this way has greater tensile strength.

RECYCLATE PLASTICS. Resins made at least partially from recycledthermoplastics In 1996, about 17% of the 225  106lb (102  106kg) ofplastic processed by a major U.S automaker was recyclate.Polyurethane-bonded foam made from flexible polyurethane scrap isused for carpet underlays, gymnasium mats, auto sound damping andmud guards, particleboards, and, mixed with rubber chips, adhesivepavements on athletic fields Caprolactam, a nylon feedstock, is recover-able from carpets and reusable in carpets, textiles, and molded parts.Polystyrene foam with as much as 50% recycled polystyrene is used forextruded food trays and containers Polyethylene film scrap and stretchand shrink wrap, bottles, and trash, dry-cleaning, and merchandizingbags are reprocessed into film products and used as fillers in molded

products Petra 140, of Allied Signal, is a 40% glass-reinforced

polyeth-ylene terephthalate (PET) made from recycled soda bottles It has a sile strength of 26,000 lb/in2 (179 MPa) and a heat-deflectiontemperature of 437°F (225°C) at 264 lb/in2 (1.8 MPa) Another PET

ten-polyester, Hoechst Celanese’s Impet 830R, is made from 100% recycled

bottle scrap and used for auto parts; 35% glass- and mineral-filled, ithas a tensile strength of 15,000 lb/in2(103 MPa), a notched Izod impactstrength of 1 ft lb/in (53 J/m) and a heat-deflection temperature of420°F (216°C) at 264 lb/in2 (1.8 MPa) Also based totally on recycled

PET is Du Pont’s Rynite PCR (postconsumer recyclate) line The three

grades differ only in reinforcement material: PCR130 BK503 (30% glassfiber), PCR140 BK504 (45% glass fiber), and PCR230 BK505 (35% glassand mica) Much of recycled PET also ends up as polyester fiber or film.

Envirez Q6215, a low-profile polyester sheet molding compound (SMC)

from Ashland Chemical, contains 25% reclaimed PET Altek 14-70

RCP, from Alpha/Owens Corning LLP, contains 14% PET recyclate and

is used as bulk molding compound as well as SMC and for pultrusion.Discarded plastic bottles are also reduced to green and white flakes,melted, and spun into yarn for Synchilla sweaters by Patagonia DowPlastics has a method for incorporating as much as 10% process scrap inurethane reaction-injection-molded (RIM) auto body panels Miles Inc.has a process for compression-molding parts from 100% RIM scrapregrind Polyvinyl chloride recycled from flexible PVC wire and cable isused to mold hidden auto parts that dampen noise and resist water

Recyclates are widely used for plastic lumber, or synthetic

wood Advantages over natural wood include weight reduction,

especially by foaming, and rot resistance They also resist

splinter-ing and color fade Replex, of RPE of Italy, is a recyclate of 60% by

weight polyolefins and 40% polyethylene terephthalate, polyvinylchloride, and polystyrene It is used for tabletops and lighting units

of desktop furniture In England, decorative building panels aremade from packaging waste, largely low- and high-density polyeth-ylene (HDPE), polypropylene, and rigid polyvinyl chloride Sheet,made by Stanley Smith & Co from recycled HDPE, is similar intensile strength and creep resistance to that made of virgin mater-ial Also in England, Plexite Ltd converts reclaimed polystyrenefoam to synthetic wood that looks like rain forest hardwoods

Tectan, made by Tetra Pak subsidiary EVD of Germany, is a form

of chipboard made from recycled, multilayer beverage cartons.

This machinable and thermoformable sheet contains about 20%polyethylene and is used for desks, cupboards, and bar stools MobilChemical uses all recycled material—50% polyethylene film (gro-cery sacks and stretch wrap) and 50% sawdust—to extrude profiles

12 ft (3.7 m) long They are colorable and paintable, resist moistureand ultraviolet, feel like wood, and can be machined with wood-working tools

Polycarbonate (PC)-acrylonitrile-butadiene-styrene (ABS) blends, oralloys, using 25% recyclate are used for personal-computer housings

PC23MS-200, of MRC Polymers, contains at least 25% recyclate from

PC compact disks and polyethylene terephthalate beverage bottles Asmuch as 25% PC recyclate goes into PC headlamp housings at one

automaker About this amount goes into Dow Chemical’s Retain

8209 glass-filled PC-ABS alloy or blend, and at least 25% accounts for

MRC Polymers’ Virgaloy VG101 PC-polymethyl methacrylate

(PMMA) VG101 has a tensile strength at yield of 9000 lb/in2 (62MPa), a flexural strength of 13,400 lb/in2 (92 MPa), a flexural modu-lus of 345,000 lb/in2 (2,379 MPa), and a heat-deflection temperature

of 200°F (93°C) at 264 lb/in2 (1.8 MPa) Retain 7490 ABS from Dow

averages about 25% recyclate and has a tensile strength at yield of6,830 lb/in (47 MPa), a flexural modulus of 363,000 lb/in2 (2,503MPa), a notched Izod impact strength of 3.4 ft lb/in (181 J/m) and a heat-deflection temperature of 174°F (79°C) at 264 lb/in2 Dylark 378

P20A, from Arco Chemicals, consists of styrene maleic anhydride

blended with 20% glass and as much as 10% recycled acrylic—the

recyclate improving toughness DMDA-1343 NT polyethylene, of

Union Carbide, contains 28% color-sorted recyclate and has physical

properties similar to those of virgin stock NPP05, of Newplast SA of

Switzerland, is a thermoplastic amalgam of heterogeneous polymers inpellet form made from unsorted domestic plastic waste and is suitablefor extrusion, compression-molding, and injection-molding machines

Encore resins, of Hoechst Celanese, are a family of plastics based on

100% reclaimed thermoplastics such as acetal, polyester, polyphenylene

sulfide, Nylon 6/6, and liquid-crystal polymer Unfilled DR-1000 acetal,

an Encore resin, has a specific gravity of 1.41, a tensile strength at yield

of 7,900 lb/in2(54 MPa), 18% elongation at break, a flexural modulus of342,000 lb/in2 (2,358 MPa), a notched Izod impact strength of 1.3 ftlb/in (69 J/m), and a heat-deflection temperature of 230°F (110°C) at 264lb/in2(1.8 MPa)

Glass fibers used to reinforce plastics are also recyclable CSX

hybrid fibers, of Phoenix Fiberglass, are reclaimed from sheet

molding compound waste and suitable for mixing with virgin fibers.Deja Inc makes footware from recycled tire rubber, wetsuit trim-mings, old file folders, coffee filters, seat cushions, soda bottles, andother materials Used Rubber USA makes wallets and belts from oldinner tubes and scrap rubber Michelin Americas can incorporate asmuch as 10% cured rubber from discarded tires in new ones withoutaffecting their performance Up to 60% recycled rubber from tires is

used in Symar-T, a thermoplastic vulcanizate from NRI Industries,

which provides performance and processing quality comparable tothat of conventional thermoplastic elastomers Discarded tires arealso used to produce methanol, liquid petroleum gas, and gas oil

EEKO recyclable synthetic leather is used for handbags.

RED BRASS. A series of copper alloys including one wrought alloy

(C23000) and several cast alloys (C83300 to C84800) Red brass

C23000 contains 84 to 86% copper and the balance zinc except for

small amounts (0.05 maximum) of lead and iron The cast alloys,

which include leaded red brasses, have a zinc content that can

range from 1.0 to 2.5% (C83500) to 13 to 17% (C84800), and all butC83400, which is limited to 0.20 tin, contain substantial amounts ofthis element: 1.0 to 6.5, depending on the alloy Lead content of thecast alloys can be as little as 0.50% maximum (C83400) or as much as8.0 (C84400) Some of these alloys also contain about 1% nickel, andmost contain smaller amounts of other metals

C23000 is available in most wrought mill forms and is used forcondenser and heat-exchanger tubing, plumbing lines, electricalconduit, fasteners, and architectural and ornamental applications

It is quite ductile in the annealed condition, and can be appreciablyhardened by cold work Annealed, thin, flat products have tensileproperties of 39,000 to 45,000 lb/in2 (269 to 310 MPa) ultimatestrength, 10,000 to 18,000 lb/in2 (69 to 124 MPa) yield strength,and 42 to 48% elongation When it is cold-worked to the spring tem-per, ultimate strength increases to 84,000 lb/in2 (579 MPa) andyield strength to 62,000 lb/in2 (427 MPa), while elongationdecreases to 3% The alloy has a density of 0.316 lb/in3 (8,747kg/m3) and, annealed, has an electrical conductivity about 37% that

of copper It has good resistance to fresh and seawaters and is notprone to dezincification

All of the cast alloys are suitable for sand casting, and some for trifugal and/or investment casting As cast, the ultimate tensilestrength is typically 32,000 to 37,000 lb/in2 (221 to 255 MPa), yieldstrength is 10,000 to 17,000 lb/in2(69 to 117 MPa), and elongation 25

cen-to 35% C83300 is used for terminal ends for electrical cables, andC83400 is used for rotating bands The other cast alloys find broaderapplications, including pump parts and housings, valves, flanges, pipefittings, general plumbing hardware, and fasteners

Standard gilding metal (C21000), used for making cheap jewelry and

small-arms ammunition, contains 94 to 96% copper It has a golden-redcolor, is stronger and harder than copper, but has only about half the

electrical conductivity The English cap copper, used for cartridge caps, has 97% copper and 3 zinc BES gilding metal comes in three grades,

80, 85, and 90% copper, but the 80–20 alloy has a definite golden-yellowcolor and is not in the class of red brasses The 80–20 brass (C24000) is

one of the standard alloys of the brass mills under the name of low

brass It was early used for jewelry under the name of Dutch metal It

is very ductile and is easily drawn, takes a high polish, and has high

strength It is still much used for cheap jewelry Chain bronze, used for

flat-link jack chains and for costume jewelry, contains 87 to 89% copper,0.60 to 1.25 tin, and the balance zinc The tin increases the hardness,and the alloy has good strength and corrosion resistance

Many old names used for designating the golden or reddish copper brasses, especially for cheap jewelry making, are still in

high-occasional use Pinchbeck metal, originally made by C.

Pinchbeck, an English jeweler, contained 88% copper and 12 zinc

This is the same as the Guinea gold used for traders’ jewelry.

Manila gold, or traders’ gold, was about the same with some lead

to heighten the color Ormolu gold, a name still used by brass platers, was any composition that would give a golden color Rich

gold metal was the 90–10 alloy, and this alloy is still being used

for decorative purposes under the name of copper-rich brass.

Manheim gold, containing 83% copper, 10 zinc, and 7 tin, was a

German alloy for cheap jewelry It is a considerably harder alloy

than ordinary red brasses Tournay metal was a French alloy

widely used for buttons when brass buttons were in vogue It was

essentially the same as the original tombac metal used by the

Chinese for buttons, and was the 85–15 alloy containing able arsenic to give a brilliant grayish tone to the metal The alloy

consider-is quite brittle The name tombac consider-is the Malay word tombaga used

to designate gold-colored jewelry alloys Chrysochalk is another

old name for gilding metal containing enough lead to give a dullgold tone Japanese low-priced jewelry alloys often contained silver

or gold to balance the color and make them resistant to tarnishing

Shadke was a high-copper alloy with some gold, and Shakudo

contained about 4% gold and 1 silver The gold color of the redbrasses is enhanced by pickling in nitric acid

minium It is a lead tetroxide, Pb3O4, forming a bright-red ororange-red powder of specific gravity 0.096, insoluble in water As apigment, it has great covering power and brilliancy, but red lead thathas not been completely oxidized and contains litharge must beapplied immediately after mixing to avoid combining with the oil It isused as a heavy protective paint for iron and steel Red lead is alsoused in storage-battery plates and leaded glass With linseed oil it is

used as a lute in pipe fitting Orange mineral is a pure form of red

lead made from white lead and has an orange color Chemically it isthe same as red lead, but it has a different structure, giving it a morebrilliant color Red lead is made from lead metal by drossing and then

heating in a furnace Fume red lead is a fine grade made from fume

litharge, which is made by oxidizing molten lead and is passed off as

a yellow smoke or fume Fume red lead is notable for the extremefineness of its particles, and it bulks greater than ordinary red lead

Fume red lead is marketed for pigment as superfine red lead.

REDWOOD Also called sequoia, California redwood, and

Humboldt redwood The wood of the tree Sequoia sempervirens,

native to the west coast of the United States The wood is light,soft, and spongy but has comparatively high strength and is resis-tant to decay and insect attack The trees grow in a narrow coastalstrip in California and are immense, reaching a diameter of 20 ft(6.1 m) and a height of 350 ft (107 m) in 2,000 years The so-called

Big tree, however, is the S gigantea or S washingtoniana It grows

in the mountains at elevations of 5,000 to 8,500 ft (1,524 to 2,591m), but is not cut for lumber Planks of redwood can be readilyobtained 6 ft (1.8 m) in width The specific gravity is 0.374 to 0.387

It has a tensile strength of 7,000 to 11,000 lb/in2 (48 to 76 MPa).The heartwood varies from light-cherry to dark-mahogany in color,and the narrow sapwood is almost white The wood is used in all

kinds of common construction Redwood bark fiber is the

shred-ded fiber of the bark of the redwood It has excellent felting ties, is water-resistant and fire-resistant, and is an excellentinsulator for house walls and refrigerators It is also used in woolmixtures for blankets and overcoatings The fiber is short, but has

proper-a nproper-aturproper-al twist thproper-at fproper-acilitproper-ates spinning The fiber contproper-ains proper-a highcontent of lignin and makes a good filler for heat-curing plastics

Palco wool is redwood bark fiber, and Palco board is a

light-weight insulation board for cold-storage chambers made from the

shredded bark fibers Palcotan is a sodium salt of palcotannic

acid, a weak sulfonated tannic acid, used as a binder in ceramic

clays, a stabilizer for asphalt emulsions, and in latex and paste

adhesives Redwood tannin, produced by soaking redwood chips

in hot water and dissolving out the tannin with ethyl acetate, isused as an oxidation inhibitor in hydrocarbons

resistance to very high temperature is required, as for furnace ings and metal-melting pots Materials with a melting point above

lin-2876°F (1580°C) are called refractory, and those with melting points above Seger cone 36, or 3254°F (1790°C), are called highly refractory But, in addition to the ability to resist softening and

deformation at the operating temperatures, other factors are sidered in the choice of a refractory, especially load-bearing capac-ity and resistance to slag attack and spalling Heat transfer andelectrical resistivity are sometimes also important Many of therefractories are derived directly from natural minerals, but syn-thetic materials are much used To manufacture refractory prod-ucts, powders of the raw materials are mixed and usuallydry-pressed to form the desired shape

Clay is the oldest and most common of the refractories The ural refractories are kaolin, chromite, bauxite, zirconia, and magne-site, often marketed under trade names Refractories may be acid,such as silica, or basic, such as magnesite or bauxite, for use inacid- or basic-process steel furnaces Graphite and chromite areneutral refractories Magnesia is insoluble in the slag of open-hearth furnaces and is used for linings Magnesia fuses at 3929°F(2165°C), chromite at 3722°F (2050°C), and alumina at 3670°F(2021°C) The fusing point of the refractory, however, is usuallydependent on the binder, as all binders or impurities lower the

nat-melting point Arco refractory brick, of General Refractories Co.,

with 60 to 80% alumina, withstands temperatures from 3290 to3335°F (1810 to 1835°C) The melting point of a 99.5% pure alu-mina is given as 3725°F (2052°C), and the decomposing point of a

98% pure silicon carbide as 4175°F (2301°C) Chrome-magnesite

bricks are made usually with 75% chrome ore and 25 dead-burned

magnesite

The chief artificial refractories are silicon carbide and aluminum

oxide Refrax, of Carborundum Co., is silicon carbide held together

by crystallization without a binder It withstands temperatures to4064°F (2240°C), at which point it decomposes The crushingstrength of the brick is 12,500 lb/in2(85 MPa) This type of materialcan be made only in simple shapes, but is also made into rolls for

roller-type furnaces Refrax FS is fused silica bonded with silicon

nitride It is used for formed parts up to 23 in (58 cm) in diameterfor such applications as brazing fixtures, and has dimensional sta-

bility and thermal shock resistance to 2250°F (1232°C) Silfrax is in grades with 40 to 78% SiC, and porosities from 9 to 18% Monofrax,

of the same company, is a refractory block for lining glass furnaces

It is composed of 98% alpha and beta alumina crystals interlocked

in a dense structure of 200 lb/ft3 (3,204 kg/m3), with only a smallamount of bond and impurities A grade with more open structurehas a density of 175 lb/ft3 (2,804 kg/m3), and Monofrax K contains

80% alumina and the balance chromite crystals saturated with mina These materials are resistant to abrasion to temperaturesabove 3000°F (1649°C) They have porosities from 20 to 29%

alu-Aluminite is furnished in blocks for temperatures to 2000°F

(1093°C) Korundal XD brick, of Harbison-Walker Refractories

Co., is corundum bonded with mullite For open-hearth and furnace roofs it will withstand a 25-lb/in2 (0.17-MPa) load at a tem-

electric-perature of 3000°F (1649°C) without spalling Lo-Sil brick of

Kaiser Aluminum, for aluminum-melting furnaces, is made with ahigh alumina content with very low silica to avoid pickup of silicon

in the molten aluminum Phosphate-bonded refractories having atleast 50% alumina content, relatively low density, and 3 to 5-in (76- to 127-mm) thickness are used to thermally insulate steel ductsand bypass stacks of incinerators.

The silica brick used in coke ovens has a high coefficient of

expansion below about 155°F (68°C), so that ovens must be heatedgradually over a period of 6 to 8 weeks to prevent cracking of the

brick Fire sand is a sand composed of 98% silica and is very

refractory The natural silica refractories used to replace fireclayfor high temperatures should contain at least 97% silica and notyield too fine a powder on crushing In order of merit, the materialsused are chalcedony, old quartzites, and vein quartz The refractory

known in Europe as klebsand, used for steel furnace linings, has

87% SiO2, 8.6 Al2O3, 0.3 TiO2, and some ferric oxide Ganister is a

natural refractory mineral used for furnace linings In compactform it was used for furnace hearths It contains about 95% silica,about 1.5 Al2O3, and a small amount of lime as a binder The chiefdeposits are in the quartzites of Wisconsin, Alabama, and Colorado

An artificial ganister is made with silica and clay Ganisand is a ganister having a fusing point at 3250°F (1788°C) Dinas silica is

an English ganister with about 97% silica, having a melting point

of 1680°C Silica brick made from quartzite containing 98% silicahas lime added as bond, and the resulting brick usually containsabout 96% silica, 2 lime, and 2 alumina and ferric oxide The bricksare rigid under load and are resistant to attack by acid slags and to

spalling under rapid temperature changes Vega silica brick, of

Harbison-Walker Refractories Co., has no more than 0.4% of oxidesother than lime and withstands temperatures of 3090°F (1699°C)

under load Foamed silica blocks for lining tanks and for

refrac-tory insulation are made from pure fused silica They have a sity of 10 to 15 lb/ft3 (160 to 240 kg/m3) with an impermeableclosed-cell structure, have a compressive strength of 130 to 210lb/in2 (0.9 to 1.4 MPa), and withstand temperatures to 2200°F

den-(1204°C) Foamsil, of Pittsburgh Corning Corp., is this material.

Pinite, from Nevada, is a secondary material derived from the

alteration of feldspar and other rocks, and it is used for kiln linings incement plants It is a hydrous silicate of alumina and potash, and themassive material resembles steatite It will bond alone as clay doesand has low shrinkage At 2057°F (1125°C), the mineral inverts to

mullite Agalmatolite is a massive pinite and can be used in the same way Bull-dog is an old name for a refractory which is a mix-

ture of ferric oxide and silica made by roasting tap cinder (a basic cate of iron) with free access of air

REFRACTORY CEMENT. A large proportion of the commercial tory cements used for furnace and oven linings and for fillers are fire-clay-silica-ganister mixtures with a refractory range of 2600 to2800°F (1427 to 1538°C) Cheaper varieties may be mixtures of fire-clay and crushed brick, fireclay and sodium silicate, or fireclay andsilica sand An important class of refractory cements is made of sili-con carbide grains or silicon carbide–fire sand with clay bonds or syn-thetic mineral bonds The temperature range of these cements is 2700

refrac-to 3400°F (1482 refrac-to 1871°C) Silicon carbide cements are

acid-resis-tant and have high thermal and electric conductivity For crucible naces the silicon carbide cements are widely used except for molten

fur-iron Alumina and alumina-silica cements are very refractory and

have high thermal conductivity Calcined kaolin, diaspore clay, lite, sillimanite, and combinations of these make cements that areneutral to most slags and to metal attacks They are electrical insula-

mul-tors Chrome-ore cements are difficult to bond unless mixed with magnesite Plastic 695 is a chrome-magnesite cement made of

treated magnesite and high-grade chrome ore It sets quickly andforms a hard, dense structure The melting point is above 3600°F(1982°C) It is used particularly for hot repairs in open-hearth fur-

naces Magnefer is the name of a dead-burned dolomite refractory, while Basifrit is a magnesia refractory for resurfacing Zircon-mag-

nesite cement is made with 25% refined zircon sand, 10 milled

zir-con, 15 fused magnesia, and 50 low-iron dead-burned magnesitebonded with sodium silicate A wide range of refractory cements ofvarying compositions and characteristics are sold under trade names,and these are usually selected by their rated temperature resistance

For example, Hadesite is composed of refractory clay and aggregates,

mineral wool, and a binder, and is recommended for temperatures up

to 1900°F (1038°C) Carbofrax cement, of Carborundum Co., is

sili-con carbide with a small amount of binder in various grades for peratures from 1600 to 3200°F (871 to 1760°C), depending on the

tem-fineness and the bond Firefrax cement of the same company is an

aluminum silicate, sometimes used in mixtures with ganister for

lin-ing furnaces It is for temperatures to 3000°F (1649°C) Alfrax

cement is fused silica also in various grades for temperatures from

1650 to 3300°F (899 to 1816°C) Mullfrax cement has a base of

elec-tric-furnace mullite and is for temperatures from 2200 to 3200°F

(1204 to 1760°C), while Mullite S cement is of converted kyanite for

ferrous and nonferrous melting furnaces for temperatures to 3150°F

(1732°C) Ankorite, of Harbison-Walker Refractories Co., is a

high-alumina hot-setting refractory mortar for laying superduty

fire-brick Thermolith, of this company, is chrome-based cold-setting

mortar for laying magnesite, chrome, and forsterite brick

REFRACTORY HARD METALS. True chemical compounds of two or moremetals in the form of crystals of very high melting point and high hard-ness Because of their ceramiclike nature, they are often classified as

ceramics These materials were originally called Hartstoffe in

Germany, and they do not include the hard, metallic carbides, some ofwhich, with metal binders, have similar uses; nor do they include thehard cermets The refractory hard metals may be single large crystals,

or crystalline powder bonded to itself by recrystallization under heatand pressure In general, parts made from them do not have binders or

contain only a small percentage of stabilizing binder The

intermetal-lic compounds, or intermetals, are marketed regularly as powders

of particle size from 150 to 325 mesh for pressing into mechanical parts

or for plasma-arc deposition as refractory coatings, and the powders are referred to chemically, such as borides, beryllides, and silicides.

The oxides and carbides of the metals are also used for sintering andfor coatings, and to make cermets

Zirconium boride is a microcrystalline, gray powder of

composi-tion ZrB2 When compressed and sintered to a specific gravity ofabout 5.3, it has a Rockwell A hardness of 90, a melting point of5396°F (2980°C), and a tensile strength of 35,000 to 40,000 lb/in2(241

to 276 MPa) It is resistant to nitric and hydrochloric acids, to moltenaluminum and silicon, and to oxidation At 2200°F (1204°C) it has atransverse rupture strength of 55,000 lb/in2 (379 MPa) It is used forcrucibles and rocket nozzles

Chromium boride occurs as very hard crystalline powder in

sev-eral phases: the orthorhombic crystal CrB melting at 2732°F(1500°C), the hexagonal crystal Cr2B melting at 3362°F (1850°C), andthe tetragonal crystal Cr3B2 melting at 3560°F (1960°C) Chromiumboride parts produced by powder metallurgy have a specific gravity of6.20 to 7.31, with a Rockwell A hardness of 77 to 88 They have goodresistance to oxidation at high temperatures, are stable to strongacids, and have high heat-shock resistance up to 2400°F (1316°C).The transverse rupture strength is from 80,000 to 135,000 lb/in2(552

to 931 MPa) Colmonoy, of Wall Colmonoy Corp., is chromium

boride, CrB, used for oil-well drilling A sintered material, used forgas-turbine blades, contains 85% CrB with 15 nickel binder It has aRockwell A hardness of 87 and a transverse rupture strength of123,000 lb/in2 (848 MPa) CKS-36, from AE Goetze North America,

comprises layers of hard chromium containing microcracks filled withceramic particles Engine tests indicate substantially less wear andsurface cracks than for hard chromium coatings and improved scuffand thermal-fatigue resistance

Molybdenum boride, Mo2B, has a specific gravity of 9.3, a Knoophardness of 1,660, and a melting point of about 3020°F (1660°C)

Tungsten boride, W2B, has a specific gravity of 16.7 and a melting

point of 5018°F (2770°C) Titanium boride, TiB2, is lightweight with

a specific gravity of 4.5 It has a melting point of about 4700°F(2593°C) Molded parts made from the powder have a Knoop hardness

of 3,300 and a flexural strength of 35,000 lb/in2 (241 MPa), and theyare resistant to oxidation to 1800°F (982°C) with a very low oxidationrate above that point to about 2500°F (1371°C) They are inert tomolten aluminum

Conventional TiB2 production relies on a solid-state diffusionprocess to heat boron carbide and titanium dioxide to 3632°F(2000°C), resulting in carbide contamination which necessitates hotpressing at high temperatures and pressures for parts manufactur-ing However, adapting a process developed at the Georgia Institute

of Technology, Advanced Engineered Materials uses magnesium oraluminum powder mixed with titanium oxide and boron oxide.Ignition of the mixture initiates reaction of the oxides at tempera-tures above 3632°F, leaving residual magnesium oxide that can beleached out and submicrometer particles of titanium boride The TiB2has a melting point of 5400°F (3000°C) and is suitable for cuttingtools and dies of extreme hardness and good thermal conductivity.Titanium boride coatings, deposited by laser surface modification, areattractive for their wear-, heat- and corrosion-resistant qualities.Potential applications include metal- and rock-cutting tools, pipes forconveying molten metal, instruments for use in molten metals, theinert cathode in the Hall-Heroult aluminum-electrolysis cell, and alu-minum casting molds

Intermetal powders of beryllium-tantalum,

beryllium-zirco-nium, and beryllium-columbium are also marketed, and they are

lightweight and have high strength Sintered parts resist oxidation to3000°F (1649°C)

Molybdenum disilicide, MoSi2, has a crystalline structure intetragonal prisms, a Knoop hardness of 1,240, and excellent oxidationresistance up to at least 2912°F (1600°C) It is a potential candidatefor high-temperature composites for aircraft-turbine parts Thedecomposition point is above 3398°F (1870°C) It can be produced bysintering molybdenum and silicon powders or by growing single crys-tals from an arc melt The specific gravity of the single crystal is 6.24.The tensile strength of sintered parts is 40,000 lb/in2(276 MPa), andcompressive strength is 333,000 lb/in2 (2,296 MPa) The resistivity is11.3
  in (29
  cm) It is used in rod form for heating elements

in furnaces The material is brittle, but can be bent to shape at

tem-peratures above 2000°F (1093°C) Super Hot Rod, of Norton Co., is molybdenum disilicide rod Kanthal Super, of Kanthal Corp., is a

similar material In an inert atmosphere the operating temperature

is 2912°F (1600°C) Furnace gases containing active oxygen raise theoperating temperature to about 3092°F (1700°C), while gases contain-ing active hydrogen lower it to about 2462°F (1350°C).

Boron-doped pentamolybdenum trisilicide, Mo5Si3B, is cally conductive, as strong as many ceramics, oxidation resistant attemperatures up to 2372°F (1300°C), and retains a low creep rate atthis temperature and a compressive stress of 17,400 lb/in2(120 MPa).Developed at Ames Laboratory of the U.S Department of Energy, it ismade by arc melting the three elemental constituents, and can beground into powder, pressed into shapes, and inert sintered at 2912 to3272°F (1600 to 1800°C)

electri-Tungsten disilicide, WSi2, is not as hard and not as resistant tooxidation at high temperatures, but has a higher melting point,

3722°F (2050°C) Titanium nitride, TiN, is a light-brown powder

with a cubic lattice crystal structure Sintered bars are extremelyhard and brittle, with a Mohs hardness above 9 and a melting point of5342°F (2950°C) It is not attacked by nitric, sulfuric, or hydrochloricacids, and it is resistant to oxidation at high temperatures In recent

years, titanium nitride coatings have been used to markedly

extend the life of tool-steel cutters and forming tools The coatings,golden in color, are deposited by chemical or physical vapor deposi-

tion Titanium carbonitride, TiCN, and chromium nitride, CrN,

are also used to increase wear resistance

Tribaloy intermetallic materials, developed by Du Pont, are

com-posed of various combinations of nickel, cobalt, molybdenum,chromium, and silicon For example, one composition is 50% nickel,

32 molybdenum, 15 chromium, and 3 silicon Another is 52% cobalt,

28 molybdenum, 17 chromium, and 3 silicon The structure consists of

a hard intermetallic Laves phase in a softer matrix Supplied as alloy-metal powder, welding rod, or casting stock, they can be cast,deposited as a hard-facing surface, plasma-sprayed, or consolidated

by powder metallurgy The materials have exceptional wear and rosion resistance properties in corrosive media and in air up to2000°F (1093°C) Typical applications are in pumps, valves, bearings,seals, and other parts for chemical process equipment Also, the mate-rials are suited for marine and saltwater applications and for partssubject to wear in atomic energy plants

cor-REFRIGERANTS. Gases, or very-low-boiling-point liquids, used for theheat-absorbent cycle in refrigerating machines The ideal refrigerant,besides having a low boiling point, should be noncorrosive, nonflam-mable, and nontoxic It must be free of water, since as little as 40parts per million of water may cause freezing in the system.Ammonia is a common refrigerant Ethyl chloride, methyl ether, car-

bon dioxide, and various chlorinated and fluorinated hydrocarbons

marketed under trade names such as the Freons of Du Pont Co and the Genetrons of Allied Chemical Corp are also used Dichloro-

difluoromethane, a nonflammable, colorless, odorless gas of

compo-sition CCl2F2 is Freon 12 It liquefies at 21.7°F (30°C) Freon E3

is a fluorated hydrocarbon which boils at 306°F (152°C) and is stable

to 570°F (299°C) It is pourable at 175°F (79°C) It is used for

dielec-tric insulating in electronic equipment

Trichloro-monofluo-romethane, CCl3F, is used as a refrigerant in industrial systemsemploying centrifugal compressors, and in indirect expansion-typeair-conditioning systems The boiling point is 74.7°F (24°C), andfreezing point 168°F (111°C) The condensing pressure at 86°F(30°C) is 18.3 lb/in2(0.13 MPa), and the net refrigerating effect of the

liquid is 67.5 Btu/lb (157 kJ/kg) Genetron 11 is this material.

Genetron 101 has composition CH3:CClF2, with boiling point at15.4°F (9.2°C) and freezing point at 203°F (131°C) The chlori-nated constituent of these chlorofluorocarbons has been implicated inthe depletion of stratospheric ozone, and alternatives are now beingsought that are less environmentally harmful

Of the chlorofluorocarbons, CFC-11 (CCl3) and CFC-12 have thehighest ozone-depletion potential (ODP), with CFC-11 having an ODP

of 1.0 Hydrochlorofluorocarbons (HCFCs) are also

ozone-deplet-ing but much less so and, thus, are viewed as temporary ments HCFC-22 (CHClF2), for example, has an ODP of 0.055, andHCFC-123 (CHCl2CF3) has an ODP of 0.02 Hydrofluorocarbons

replace-(HFCs), being chlorine-free, have no ozone-depletion potential Alarge variety of HFC mixtures are viewed as possible replacements

for HCFCs and CFCs Allied Signal’s Genetron AZ-50 is an azeotropic mixture of HFC-125 and HFC-143a, and Du Pont’s Suva

HP 62 is a blend of HFC-125, HFC-134a (CF3CH2F), and HFC-143a

Suva Blend-MP is a blend of HFC-152a (CHF2CH3), HCFC-22, andHCFC-124

RESINS Historically, resins is the term applied to an important

group of substances obtained as gums from trees or manufacturedsynthetically It is also frequently used interchangeably with the term

plastics The common resin of the pine tree is called rosin The

nat-ural resins are soluble in most organic solvents and are used in

var-nishes, adhesives, and various compounds Oleoresins are natural resins containing essential oils of the plants Gum resins are natural

mixtures of true gums and resins and are not as soluble in alcohol.They include rubber, gutta percha, gamboge, myrrh, and olibanum.Some of the more common natural resins are rosin, dammar, mastic,

sandarac, lac, and animi Fossil resins, such as amber and copal, are

natural resins from ancient trees, which have been chemically altered

by long exposure The synthetic resins differ chemically from naturalresins, and few of the natural resins have physical properties thatmake them suitable for mechanical parts

Galbanum, used in medicine, is a gum resin from the perennial

herb Ferula galbaniflua of western Asia It comes in yellowish to

brownish tears Myrrh is a yellow-reddish, aromatic gum resin from

Commiphora malmol and other species of small trees of India, Arabia,

and northeast Africa There are more than 80 species The Hebrew

word mur means bitter, and the gum has a bitter taste It consists of

a mixture of complex acids and alcohols but mainly the mucilaginous

arabin, with from 3 to 8% of a volatile oil of formula C10H14O It isused in incense and perfumes, and in medicine as a tonic The gum is

called mulmul and ogo in eastern Africa and herabol in India.

Sweet myrrh, or bisabol myrrh, is a very ancient perfume and

incense It comes from the tree C erythraea of Arabia Herabol

myrrh is from the small tree C myrrha of India and is a brown to

black solid It is used in medicine as a stimulant and antiseptic and in

perfumes and incense Asafetida is a gum resin with a foul odor and

acrid taste obtained from the roots of the perennial herb F assafoetida and other species It is used in Asia for flavoring foods,

but in the United States it is employed in medicines and perfumes

Creosote bush resin is amber-colored, soft, and sticky, from the

leaves and small twigs of the greasewood bush, Larrae tridentata,

or creosote bush, L divaricata, of the desert regions of Mexico and

the southwestern United States It is used in adhesives, insecticides,core binders, insulating compounds, and pharmaceuticals When dis-

tilled, the resin yields nordihydroguaiaretic acid, (C6H3 Cl COOH)2CH2, called NDGA, formerly used as a preservative but now

prohibited by the FDA for use in foods It is a white, crystalline solidmelting at 363°F (184°C), soluble in fats and slightly soluble in hot

water Okra gum is from the pods of the plant Hibiscus esculentus,

native to Africa but now grown in many countries It is edible and isused as a thickening agent in foodstuffs and pharmaceuticals It hasantioxidant properties and also acts as a stabilizer As a gellingagent, it forms a network molecular structure with branched chains,giving slipperiness valued for foodstuff spreads It is a tan-colored,water-soluble powder Okra gum is also used in plating baths as abrightener

Ammoniac is a gum resin from the stems of Dorema

ammoni-acum, a desert perennial plant of Persia and India It forms in hard,

brittle, brownish-yellow tears, and has a peculiar fetid odor and anacrid taste It is used in adhesives, in perfumery, and as a stimulant

in medicine In pharmacy it is called ammoniacum Oil ammoniac

is a yellow liquid distilled from the gum The specific gravity is 0.890,boiling point is 527°F (275°C), and it is soluble in alcohol and benzol.

C6H4(OH)2 and melting point 230°F (110°C) It is very soluble inwater and in alcohol It is used in the production of plastics; in themanufacture of fluorescein; in the production of xanthene and azo

dyes, particularly the fast Alsace green; in medicine as an

antisep-tic; and in making the explosive lead styphnate Resorcinol

polymer-izes with formaldehyde to form the resorcinol-formaldehyde

plastics that will cure at room temperature and with only slight

pressure They are used in strong adhesives for plywood and woodproducts, and do not deteriorate from acid action as some other plas-

tics do Resorcinol adhesives remain water-soluble during the

working period for 2 to 4 h and are then insoluble and tant Derivatives of resorcinol are used in medicine as specific bacteri-

chemical-resis-cides, such as diverinol, which is propyl resorcinol, and olivertol,

which is amyl resorcinol

present in small quantities in many minerals Rhenium has a specificgravity of 21.04, being almost twice as heavy as lead The meltingpoint is 5756°F (3180°C) It is a hard, silvery-white metal and takes ahigh polish As a plating metal, the white color is darker than that ofrhodium It has good chemical resistance, but is soluble in nitric acidand oxidizes in air at temperatures of about 1112°F (600°C) andgreater The crystal structure is closely packed hexagonal, making itmore difficult to work than the cubic-structured tungsten; but thecrystal grains are tiny, and small amounts of rhenium added to tung-sten improve ductility and increase high-temperature strength oftungsten used for lamp filaments and wire

Rhenium is among the strongest and most rigid of metals, having

an ultimate tensile strength of about 155,000 lb/in2 (1,069 MPa) and

a tensile modulus of 68  106lb/in2(469,000 MPa) at room ture, with good ductility (35% reduction of area) Also, it is quiteheat-resistant, having an ultimate tensile strength of 134,000 lb/in2

tempera-(924 MPa) and a tensile modulus of 54  106 lb/in2 (372,000 MPa) at1600°F (871°C) The metal is used mainly for electrical contacts,thermocouples, filaments in electronic components, and as an alloy-ing element to increase the ductility of tungsten and molybdenum forelectrical and electronic applications At 70°F (21°C), rhenium has anelectrical resistivity of 7.5
  in (19
  cm), a coefficient of thermalexpansion of 3.7  106/°F (6.7/K), and a specific heat of 0.035Btu/(lb  °F) [0.147 kJ/(kg  K)] Rhenium can be obtained from

molybdenite, which contains 0.0001 to 0.05% of the metal But the

usual source is from the flue dusts and from the sublimed rhenium

oxide, Re2O7, of stack gases in the smelting of copper and other ores

It is precipitated from the flue dust of molybdenum-bearing copper

ores in the form of potassium perrhenate, KReO4, or of

ammo-nium perrhenate, NH4ReO4 The Russians also obtain some

rhe-nium from the Ural platinum ores The stable rhenia, used in alloying, is rhenium trioxide, ReO3, which comes as a red powder.The metal is obtained as a dense, silvery powder which can be com-pacted, sintered, and cold-rolled with frequent annealing It is mar-keted in the form of rod, strip, foil, and wire

At the Technical University of Munich in Germany, pure, cally conductive ReO3 ceramic films have been made by heating the

electri-polymer methyl-trioxorhenium Ch3ReO3, above 460°F (240°C),causing it to lose its methyl groups and water

Rhenium has a higher electrical resistivity than tungsten, has higharc resistance, and does not become brittle after prolonged heating, astungsten does Rhenium is used as an undercoat for tungsten coat-ings on graphite nozzles to prevent the formation of tungsten carbideand thus give the full heat resistance of the tungsten Rhenium andrhenium-tungsten alloys used for electric contacts give very long ser-vice life Rhenium-tungsten versus tungsten thermocouples are goodfor service to 5072°F (2800°C) Substantial amounts of rhenium areused in select tungsten- and molybdenum-base alloys

RHODIUM. A rare metal, symbol Rh, found in platinum ores such as

the nickel-copper ores of Canada and pyroxenite of South Africa It is

very hard and is one of the most infusible of the metals The meltingpoint is 3565°F (1963°C) It is insoluble in most acids, including aquaregia, but is attacked by chlorine at elevated temperatures and by hotfuming sulfuric acid Liquid rhodium dissolves oxygen, and ingots aremade by argon-arc melting At temperatures above 2192°F (1200°C),

rhodium reacts with oxygen to form rhodium oxide, Rh2O3 The cific gravity is 12.44 Rhodium is used to make the nibs of writingpens, to make resistance windings in high-temperature furnaces, forhigh-temperature thermocouples, as a catalyst, and for laboratorydishes As a catalyst, it is used with platinum and palladium in autocatalytic converters to convert nitrogen oxide emission to nitrogen gas

spe-It is the hardest of the platinum-group metals, the annealed metalhaving a Brinell hardness of 135 Rhodium also has considerablestrength and rigidity, ultimate tensile strengths ranging from 138,000

to 300,000 lb/in2 (952 to 2,068 MPa), and tensile modulus from 42 

106 to 55  106lb/in2 (290,000 to 379,000 MPa), depending on tion or hardness Rhodium is also valued for electroplating jewelry,

electric contacts, hospital and surgical instruments, and especially

reflectors For electrodepositing rhodium, an electrolyte of rhodium

sulfate, Rh2(SO4)3, is used The coatings are wear-resistant and tarnish-resistant The plated metal has a pinkish-white luster of highcorrosion resistance and a light reflectivity of 80% Decorative fin-ishes are seldom more than 0.0002 in (0.0005 cm) thick, but plates for

electric contacts may be up to 0.005 in (0.013 cm) Rhodium

car-bonyl has the general formula Rh(CO), but with several variations in

the number of CO groups They are used for depositing rhodium

coatings.

The most important alloys of rhodium are rhodium-platinum.

They form solid solutions in any proportion, but alloys of more than40% rhodium are rare Rhodium is not a potent hardener of platinumbut increases its high-temperature strength It is easily workable anddoes not tarnish or oxidize at high temperatures These alloys are

used for thermocouples and in the glass industry A rhodium-iron

alloy with equiatomic proportions of the metal has an ordered crystalstructure and changes from antiferromagnetic to ferromagnetic in anelectric field Rhodium is sold by the troy ounce (31 g), 1 in3 (16 cm3)weighing 6.56 troy oz (204 g)

RICE. The white seed of the large annual grass Oryza sativa,

grow-ing to a height of 2 to 4 ft (0.6 to 1.2 m) It is a tropical plant native toAsia, but grows in hot, moist regions well into the temperate zonesand is cultivated in many parts of the world Rice fields are floodedafter planting to control weeds The rice seed grows in an inflores-cence composed of a number of fine branches, each terminating in asingle grain enclosed in a brown husk Rice forms the staple food of

more than half the populations of the world Wild rice was used by

the Indians of North America before the first Asiatic rice was brought

to South Carolina in 1694 Rice is high in starch and low in proteins

It is used as a direct food, also as flour, as cereal, in puddings, and for

the manufacture of starch and for alcoholic beverages Rice hulls are used as stock feed, and rice straw is used for packing, hats, and other articles Maxflo and Profix, of EnviroGuard, Inc., are filtration aids made from rice hull ash, a by-product of rice milling The tex-

tured surface of the ash speeds solids separation from wastestreams

A low-ash version has some caloric value so that it can be used to sop

up waste oils during filtering and produce a recyclable waste fuel.Rice in the husk before hulling is known by the Hindu name of

paddy Brown rice is rice that has been cleaned but not polished.

Broken grains are sold in the India trade as coodie or khood, and about 20% of the rice produced from paddy is broken Patna rice

does not refer to the Patna district of India, but to a variety of rice

with bold and hard grains especially suited for soups, as it holds its

shape in boiling Malekized rice, developed by General American

Transportation Co., is produced by steaming unpolished rice to forcethe soluble part of the bran and the vitamins into the core of thegrain, and then sealing the rice kernal by gelatinization, after which

it is polished The treated rice holds its shape and does not becomegummy when cooked, and the nutritional value is improved The bev-

erage known in Japan as saké is rice wine containing 14% alcohol, made by fermenting rice with the mold tané koji Rice bran oil,

used as a salad and cooking oil and in lubricants, is produced fromrice bran By wet-milling whole rice in a rice oil solutions, a higheryield of oil and wax is obtained together with a yield of proteins It isclear, odorless, and neutral, with a pleasant flavor, and is resistant to

oxidation and rancidity Rice wax is produced from rice bran by hot

hexane extraction after cold extraction of the oil It is a hard, brown,lustrous wax with a melting point of 174°F (79°C) used in polishes

Synthetic rice, used in Japan as a rice extender, is made from wheat

flour, potato starch, and powdered rice

ROSEWOOD. The wood of several species of Dalbergia of northern

South America, but chiefly from the jacaranda tree, D nigra It is

used for fine cabinetwork, pianos, novelties, and expensive furniture

It should not be confused with the wood of the tree Physocalymma

floridum, which also comes from Brazil and is there called pao rosa

or rosewood The color of rosewood is dark brown to purple, and ittakes a beautiful polish It has a characteristic fragrance Very hardwith a coarse, even grain, it has a density of 54 lb/ft3(865 kg/m3) The

tree grows to a height of 125 ft (38 m) Brazilian rosewood is the

preferred wood for guitar bodies, but its use was banned in 1969 bythe Convention on International Trade in Endangered Species

Another Brazilian wood, caroba, from the large tree Jacaranda copaia, is also called jacaranda and is sometimes confused with rose-

wood The tree has purple flowers while the true rosewood has whiteflowers Caroba wood is chocolate-colored and is used for fine furni-

ture and knife handles Indian rosewood is from the tree D sissoo

of India It is also called sissoo and is a beautiful, brown hardwood

employed for carvings In Europe it is used for parquet floors

Borneo rosewood, also known as ringas, is the wood of several

species of trees of genus Melanorrhoea of Borneo The wood has a

deep-red color with light and dark streaks It has a close texture

suit-able for carving Satinee is a type of rosewood from the tree Ferolia

guianensis of the order Rosaceae, native to tropical America,

particu-larly the Guianas The wood is reddish brown, has a density of 54lb/ft3(865 kg/m3), is fairly hard, has a fine grain, and takes a lustrous

polish It is used for cabinetwork Bois de rose oil, or rosewood oil,

is not from rosewood, but is extracted from the heartwood of the tree

Aniba panurensis of Brazil and the Guianas, though the wood of this

tree is also used as a cabinet wood The oil is also called Cayenne

linaloe, or Cayenne oil It has a delicate rose odor with a suggestion

of orange and mignonette valued in perfumes It contains a high

per-centage of linalol, a colorless alcohol with a soft, sweet odor, also

found in the rose, lilac, lily, lavender, petitgrain, and other plants It

also contains geraniol Linaloe oil, or Mexican linaloe, is distilled

from the heartwood of the trees Bursera delpechianum and B aloeoxylon It contains less linalol and also terpineol and geraniol.

Linalol is closely related to geraniol and nerol Bois de rose is also

made synthetically from geraniol Oriental linaloe is distilled from

selected, highly perfumed parts of the wood of the large tree

Aquilaria agollocha of eastern India, Burma, and Java The odor of

the oil is like rose, ambergris, and sandalwood Like the linaloes ofthe American continent, the oil is a pathological product and comes

only from old trees It is also called aloe wood oil and agar attar,

and is a very ancient perfume The beautifully figured and fragrant,

reddish wood of this tree, called aloes wood, eagle wood, and

par-adise wood, is used for ornamental articles True original rosewood

oil known as rhodium oil was distilled from the wood of the plant

Convolvulus scoparius of the Canary Islands.

ROSIN. The common resin of several varieties of pine tree, foundwidely distributed in North America and Europe It is obtained bycutting a longitudinal slice in the tree and allowing the exudation todrip into containers The liquid resin is then distilled to remove the

turpentine, and the residue forms what is known as gum rosin, or

pine gum Wood rosin is obtained by distillation of old pine stumps.

It is darker than gum rosin and is inferior for general use

Rosin contains seven acids with very similar characteristics, but

consists chiefly of abietic acid, C19H29COOH Normally, when gum

rosin is heated, the natural pimaric acid isomerizes to form abietic

acid; but in the production of turpentine and rosin from pine sap, theturpentine is removed by steam distillation, and various acids arethen extracted Pimaric acid is closely related to abietic acid It reacts

with maleic and anhydride, and maleopimaric acid is used in

print-ing inks and coatprint-ings Rosin has a specific gravity of about 1.08 and amelting point of about 180°F (82°C), and it is soluble in alcohol, tur-pentine, and alkalis It is used in varnishes, paint driers, soluble oils,paper sizing, and belt dressings; for compounding with rubber andother resins; and for producing many chemicals

Rosin is generally graded commercially by letters according tocolor The darkest grade is B, and the lightest is W Extra grades are

A, nearly black, and WW, water-white Thirteen color grades are

designated under the Naval Stores Act The dark grades of woodrosin are considered inferior They have a high melting point andlow acid number and are used for making rosin oil; for battery wax,thermoplastics, and dark varnish; and for linoleum manufacture.The ruby-red wood rosin, obtained by extraction from fat pine wood,has high acid number, 155, and low melting point, 175°F (79°C) It

is used for printing inks, paper size, and adhesives Rosin is usually

marketed in barrels of 280 lb (127 kg) Naval stores is an old name for rosin and turpentine Pexite and Pamite are rosin grades from

Hercules Inc that cover the various color standards set by the U.S

Department of Agriculture Pelletized rosin consists of

free-flow-ing, dustless pellets produced by coating droplets of molten rosin

with inert powder Colophony is an old pharmacy name for rosin

before distillation of rosin oil Rosin was referred to by early writers

as Greek pitch, but the ancient incendiary known as Greek fire

was tow or pine sawdust impregnated with rosin, pitch, and sulfur

Burgundy pitch was originally the resin of the Norway spruce,

Picea abies, used in medicine, but the name was later applied to a

rosin, rubber, and mineral oil compound used for friction tape

Hardened rosin is a weak resinate made by adding 6 to 8%

high-calcium lime to melted rosin It is used in some varnishes

Fosfo rosin, of Newport Industries, Inc., is a lime-hardened rosin.

It is an FF rosin treated with 4.75% calcium hydrate, which raisesthe melting point, decreases the free rosin acids, and decreases thetendency to crystallize It is used in paints, varnishes, and molded

products Soda-treated rosins, with about 1% Na2O, but no free

alkali, are used for soap, paper size, and disinfectants Rosin size is

alkali-treated rosin in dry powder or emulsion form for sizing paper

Dresinite is such a sodium or potassium salt of rosin Cyfor, of

American Cyanamid Co., is a rosin size fortified with a synthetic

resin to give increased water and acid resistance to paper Rosin

ester, or ester gum, is prepared by heating rosin with glycerin It is

lighter in color than rosin, has a higher softening point, and has amuch lower acid number, usually 7 to 9 It is used with tung oil in

enamels and varnishes and in adhesives Resin V is a rosin glycerin

ester gum Rosin esterified with glycerin has lower molecular weightand is not as stable as rosin esterified with pentaerythritol or othertetrahydric alcohol; but modified rosin ester gums develop hardnessquickly in nitrocellulose and are used for such purposes as furniture

lacquers Cellolyn 102, of Hercules Inc., is a modified ester gum of this type, and Lewisol 28 is a maleic alkyd modified rosin ester used for hard, glossy furniture lacquers Hydroabietyl alcohol, used as

a plasticizer and tackifier for rubber and for sizing textiles, is a less, tacky liquid made by reduction of rosin The 85% alcohol has a