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CHEMICAL TECHNOLOGY

VOLUME 3

KIRK- OTHMER

ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY

THIRD EDITION

VOLUME 3

ANTIBIOTICS (PHENAZINES)

TO BLEACHING AGENTS

A WILEY- INTERSCIENCE PUBLICATION

John Wiley & Sons NEW YORK CHICHESTER BRISBANE TORONTO

The New Ybrk mec Library rte w ruas mural en

Copyright © 1978 by John Wiley & Sons, Inc.

All rights reserved. Published simultaneously in Canada.

Reproduction or translation of any part of this work beyond that permitted by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful. Requests for

permission or further information should be addressed to the Permissions Department, John Wiley & Sons, Inc.

Library of Congress Cataloging in Publication Data:

Main entry under title: Encyclopedia of chemical technology.

At head of title: Kirk -Othmer. "A Wiley -Interscience publication." Includes bibliographies. 1. Chemistry, Technical -Dictionaries. I. Kirk,

Raymond Eller, 1890 -1957. II. Othmer, Donald Frederick, 1904- III. Grayson, Martin. IV. Eckroth, David. V. Title: Kirk -Othmer encyclopedia of chemical technology.

TP9.E685 1978 660'.03 77- 15820 ISBN 0- 471- 02039 -7

Printed in the United States of America

CONTENTS

--- Antibiotics (continued), 1

Antifreezes and deicing fluids, 79 - -- Antimony and antimony alloys, 96

Antimony compounds, 105 Antioxidants and antiozonants, 128 Antistatic agents, 149

1-- Appetite- suppressing agents, 184 Aquaculture, 194

Aramid fibers, 213 Arsenic and arsenic alloys, 243 Arsenic compounds, 251

Asbestos, 267 Asphalt, 284 Aviation and other gas turbine

fuels, 328 Azeotropic and extractive

distillation, 352

Azine dyes, 378 Azo dyes, 387 Bagasse, 434 Bakery processes and leavening

agents, 438 Barium, 457 Barium compounds, 463

- Barrier polymers, 480

Batteries and electric cells, primary, 503

Batteries and electric cells,

secondary, 569

- Bearing materials, 670 Beer, 692 Benzaldehyde, 736 Benzene, 744 Benzidine and related

biphenyldiamines, 772 - Benzoic acid, 778

Benzyl alcohol and ß- phenethyl alcohol, 793

- Beryllium and beryllium alloys, 803 Beryllium compounds, 824 Beverage spirits, distilled, 830 Biomedical automated

instrumentation, 863 Biopolymers, 884 Bismuth and bismuth alloys, 912 Bismuth compounds, 921 Bleaching agents, 938

EDITORIAL STAFF FOR VOLUME 3

Executive Editor: Martin Grayson Associate Editor: David Eckroth Production Supervisor: Michalina Bickford Editors: Galen J. Bushey Loretta Campbell

Lorraine van Nes Anna Klingsberg

CONTRIBUTORS TO VOLUME 3

John Ballance, l3rush Wellman Inc., Cleveland, Ohio, Beryllium and beryllium alloys Burton M. Baum, FMC Corporation, Princeton, New Jersey, Bleaching agents Douglas N. Bennion, University of California, Los Angeles, California, Introduction; Primary

cells (both under Batteries and electric cells, primary) Julius Berger, Hoffmann-La Roche Inc., Nutley, New Jersey, Phenazines (under Antibiot-

ics)

John H. Blumbergs, FMC Corporation, Princeton, New Jersey, Bleaching agents E. R. Booser, General Electric Company, Schenectady, New York, Bearing materials James H. Boothe, Lederle Laboratories Division, American Cyanamid Company, Pearl River,

New York, Tetracyclines (under Antibiotics) Lester A. Brooks, R. T. Vanderbilt Co., Norwalk, Connecticut, Antioxidants and antizo-

nants Elton J. Cairns, General Motors Research Laboratories, Warren, Missouri, Fuels cells (under

Batteries and electric cells, primary)

vii

viii CONTRIBUTORS TO VOLUME 3

*S. C. Carapella, Jr., ASARCO Inc., South Plainfield, New Jersey, Arsenic and arsenic alloys;

Bismuth and bismuth alloys

Sigmund C. Catino, GAF Corp., Rensselaer, New York, Azo dyes

William B. Chess, Stauffer Chemical Co., Dobbs Ferry, New York, Chemical leavening agents

(under Bakery processes and leavening agents)

Margaret A. Clarke, Cane Sugar Refining Research Project, Inc., New Orleans, Louisiana,

Bagasse

Howard P. Clemens, University of Oklahoma, Norman, Oklahoma, Aquaculture

J. Clyde Conger, Sr., American Cyanamid Company, Bound Brook, New Jersey, Azine

dyes Michael Conway, University of Oklahoma, Norman, Oklahoma, Aquaculture

G. O. Doak, North Carolina State University, Raleigh, North Carolina, Antimony compounds;

Arsenic compounds; Bismuth compounds

James B. Doe, ESB Technology Co., Yardley, Pennsylvania, Introduction; Secondary cells,

lead -acid; Other cells (all under Batteries and electric cells, secondary)

W. G. Dukek, Exxon Research and Engineering Company, Linden, New Jersey, Aviation and

other gas turbine fuels

Edward J. Elliott, FMC Corporation, Princeton, New Jersey, Bleaching agents

James V. Evans, Amoco Oil Company, Chicago, Illinois, Asphalt

Russell E. Farris, GAF Corp., Rensselaer, New York, Azo dyes

R. H. Fay, Dow Chemical, U.S.A., Freeport, Texas, Antifreezes and deicing fluids

Kelvin H. Ferber, Allied Chemical Corp., Buffalo, New York, Benzidine and related bi-

phenyldiamines Joseph H. Finley, FMC Corporation, Princeton, New Jersey, Bleaching agents

Leon D. Freedman, North Carolina State University, Raleigh, North Carolina, Antimony

compounds; Arsenic compounds; Bismuth compounds

Hiram Gu, University of California, Los Angeles, California, Primary cells (under Batteries

and electric cells, primary)

Zeev Gur- Arieh, Monsanto Textiles Company, Decatur, Alabama, Antistatic agents

Paul A. Hammes, Merck and Co., Rahway, New Jersey, Antioxidants and antiozonants

Frank N. Hepburn, U.S. Department of Agriculture, Hyattsville, Maryland, Yeast -raised

products (under Bakery processes and leavening agents)

Joseph J. Hlavka, Lederle Laboratories Division, American Cyanamid Company, Pearl River,

New York, Tetracyclines (under Antibiotics)

H. E. Howe, ASARCO Inc., South Plainfield, New Jersey, Bismuth and bismuth alloys

H. E. Hoyrup, Bryggeriforeningen, Copenhagen, Denmark, Beer

Truman Kirkpatrick, The Sherwin - Williams Company, Chicago, Illinois, Barium com-

pounds Karel Kulp, American institute of Baking, Chicago, Illinois, Yeast -raised products (under Bakery

processes and leavening agents) Charles J. Kunesh, Pfizer Inc., Easton, Pennsylvania, Barium G. Gilbert Long, North Carolina State University, Raleigh, North Carolina, Antimony com-

pounds; Arsenic compounds; Bismuth compounds Anthony M. Luxeder, The B. F. Goodrich Co., Chemical Division, Cleveland, Ohio, Antiox-

idants and antiozonants Alan K. Mallams, Schering- Plough Corporation, Bloomfield, New Jersey, Polyenes (under

Antibiotics)

Vol. 3 C Uti f Rlfill rt)it5 Tt) VOLUME 3 ix

Herman F. tiiark. j °t , 1't is 1, )rk t11, $1, A. 11 "it %.% 1 rte Hi( )1)01),(114:4's S. P. Nempho., ( orlt!.'sr, !,)I Pr f 11 hit to. ( t, Nh it 1rr1111)1, ( ()mu., trout Barrier

Paul P. Nicfx ic.. `'t ±; t i .414*A h t. r.! (.0(7x rtctf. RPNe.irrh ,.t ,li, r Ih1o. Artrrr,xirí.tnt ,

Donald F. t?thmer. fk)4.tek:lu is Iti tïtt,te of New York. Brooklyn, Nrw York AtPrtroptr f Ki tAtratilVe itit 4l t)n

Coe(r. e /tk Packow:ski, kAeph F Seagram & Sons, Inc ., New York, New York, BPvfir.fge o r (*st il ed

ugerpe Pearlman. [NB Te(hnok.)gy Co . }''ardlev. Pennsylvania, Secondary cells. alkaline under Batter. s and electrn Cells. secondary)

. Preston, N ortsanto T rangk' Park Development Center, Inc:., Research Triangle Park.. North Carolina .Aramid fibers

Waliarri P. Purcell, Union Oil Company of California, Brea, California, Benzene Glenn H. Rees, Brush Wellman Inc., Cleveland, Ohio, Beryllium compounds Sertie J. Reuben, A4onsanto Textiles Company, Decatur, Alabama, Antistatic agents 11Víiiam RingIc, Chemical Consultant, Westfield, New Jersey, Benzyl alcohol and 0- phenethyl

alcohol Stephen T. Ross, Smith Kline & French Laboratories, Philadelphiá, Pennsylvania, Appetite -

suppressing agents Salame, »onsanto Commercial Products Co., Bloomfield, Connecticut, Barrier poly-

mers Alvin 1. Salkind, ES8 Technology Co., Yardley, Pennsylvania, Secondary cells, alkaline (under

Batteries and electric cells, secondary) Fred Schuler. FMC Corporation, Princeton, New Jersey, Bleaching agents Morris H. Shamos, Technicon Instruments Corporation, Tarrytown, New York, Biomedical

automated instrumentation Lloyd R. Snyder, Technicon instruments Corporation, Tarrytown, New York, Biomedical

automated instrumentation S. Steiger, Monsanto Commercial Products Co., Bloomfield, Connecticut, Barrier poly -

mers A. tames Stonehouse, Brush Wellman Inc., Cleveland, Ohio, Beryllium and beryllium al-

rvv5

Wpm C. Streib, Johns - Manville Corporation, Denver, Colorado, Asbestos Ray Sweeney, Brush Wellman Inc.. Cleveland, Ohio, Beryllium and berllium alloys Ernst T Theifner, Consultant, Rumson, New Jersey, Benzyl alcohol arid ß- phenethyl alco-

kenneth Wes, Brush WeMnan inc... Cleveland, Ohio, Beryllium and beryllium alloys. Be- ryllium compounds

John W. WesUey, HOffrr;ar.vf -L a Roche /nc.-., Nutley, New Jersey, Polyethers (under Ant)br ois)

Arnold F. Wtlttarns, (ihr- rrik.a/ inr k'alarrra, Washington, Benzakicshyde Benzoic acid

Romeo R. Witherspoon, Genera/ Motorcc Research Laboratories. Warren, Missouri, Fuel cells (under Batteries and +.tri,. c, prunary)

Henry L. Wooten, f mK;; Corporation, Princeton, New Jersey, Bleaching agents

Vol. 3 ASBESTOS 267

ASBESTOS

Asbestos is a generic term describing a variety of naturally formed hydrated silicates that, upon mechanical processing, separate into mineral fibers. There are two fundamental varieties of asbestos: serpentine and the amphiboles. Serpentine asbestos is known as chrysotile and the amphiboles include five species identified as anthophyllite, amosite, crocidolite, actinolite, and tremolite. Each of these varieties of asbestos differ from each other chemically as illustrated in Table 1.

Asbestos fibers are unique minerals combining unusual physical and chemical properties which make them useful in the manufacture of a wide variety of residential and industrial products. Of mineral origin, asbestos does not burn, does not rot, and, dependent on variety, possesses extremely high tensile strength as well as resistance to acids, bases, and heat. Similarly, when processed into long, thin fibers, asbestos is sufficiently soft and flexible to be woven into fire- resistant fabrics.

Historical records show that asbestos has been known fór more than 2000 years. Applications of this noncombustible fiber are mentioned by Plutarch and Pliny, particularly with reference to asbestos textiles used for cremation cloths, oil lamp wicks, etc.

The asbestos industry per se had its inception in the 18th century in the Russian Ural mountains and by the mid -19th century both Italian chrysotile and tremolite varieties were mined and processed into commercial products. At the same time asbestos was discovered and mined on a commercial scale at Thetford Asbestos in Quebec, Canada. To this day, these Canadian and Russian locations are the major producers of chrysotile asbestos.

The amphibole asbestos industry is of more recent origin. Blue asbestos, crocidolite, was discovered in South Africa about 1803 to 1806, but it was not until 1893 that this variety was commercially exploited. Production, sale, and use of the amosite species from the Transvaal followed in the early 20th century (1).

Origin and Occurrence

Through the years, the origin of asbestos has been the subject of extensive geological research. Serpentine asbestos occurs under widely differing geological conditions from the amphiboles. Similarly, the modes of occurrence or the manner in which the fibers are physically imbedded in the host rock also differ widely. The current opinion is that chrysotile fiber resulted from two separate metamorphic'reactions in ultrabasic

Table 1. Asbestos

CAS Species Registry Number Variety Chemical composition

chrysotilea [12007 -29 -5] serpentine 3Mg0.2Si02.2H20 anthophyllite [17068 -78 -9] amphibole 7Mg0.8Si02.H20 amositea [12172 -73 -5] amphibole 11Fe0.3Mg0.16Si02.2H20 actinolite [13768 -00 -8] amphibole 2Ca0.4MgO.Fe0.8SiO2.H20 tremolite 114567 -73 -81 amphibole 2Ca0.5Mg0.8Si02.H20 crocidolitea [12001 -28 -4] amphibole Na20.Fe203.3Fe0.8 Si02.H20

a Asbestos species of major commercial significance.

268 ASBESTOS

rocks of igneous origin. The initial hydrothermal reaction altered the olivines and pyroxenes to serpentine. At a subsequent point the serpentine was redissolved and the mineral -rich solutions flowed into cracks and crevices in the host rock where chrysotile fiber was reprecipitated.

In this reprecipitation process, asbestos fiber was usually deposited in a cross -vein mode of occurrence; ie, the fiber is arranged perpendicular to the wall rock as illustrated in Figure 1.

In some cases, chrysotile was either deposited or affected by earth movements such that the fibers lie principally parallel to the wall rock as illustrated in Figure 2. This mode of occurrence is referred to as slip fiber.

The third and unusual mode of occurrence of chrysotile is referred to as a massive or agglomerated form wherein the fibers have been deposited as platelets having no specific fiber orientation. This unique formation has been found and commercially mined in the New Idria serpentine deposits of California (2) and at Stragari, Yugo- slavia. In these cases the asbestos content of the ore is abnormally high, but the fiber length is very short as compared to commercially useful cross -vein or slip fiber deposits. This mode of occurrence is illustrated in Figure 3.

The origin of the amphibole varieties of asbestos are not as clearly defined as those of chrysotile. The two commercially significant amphibole fibers, crocidolite and amosite, occur in metamorphosed sedimentary strata known as banded ironstones. These sedimentary formations vary considerably in composition which accounts for the compositional variations of the associated amphibole fibers (1).

.... ,. .......r... ....._. .y. wr.........._...

Figure 1. Cross -vein chrysotile (Courtesy of Johns -Manville Research Center).

Vol. 3

a

ASBESTOS 269

.( Y

)

y

. '`. nd` , <{AF ' ',.kl _ 1 Z n s 72. .,;7í

1 .? t. YI ÿ . r N M

r.

.P.,owr.-di+-u+1.:rE:4.»uaw.u-.._ ..-... -.. _...r:yauve.ww:,;a..,a.._.__.-.. . :._ . ., y; .,. .......n+rovs.swvnrass.wrw... .

Figure 2. Slip fiber chrysotile (Courtesy of Johns -Manville Research Center).

Crocidolite and amosite species of asbestos occur in cross -vein modes and the an-

thophyllite and tremolite species often occur in slip modes although both of the latter can also occur in a massive mode wherein the fibers are nonoriented. Actinolite, a

noncommercial species of amphibole asbestos, is most often found as brittle, acicular,

or bladed forms in a massive mode. In its generic connotation, asbestos is a mineral found all over the world. In most

cases, however, the asbestos species most easily located are those having limited or

no commercial utility such as actinolite, anthophyllite, or tremolite. In 1977, Canada and Russia are the major producers of chrysotile asbestos, and Africa, China, and the United States provide modest quantities. The major producing area of the important amphiboles, crocidolite, and amosite is Africa. In fact, the only deposits of amosite known to date are in the Eastern Transvaal.

Chrysotile Asbestos Crystal Structure. The mineral species associated with the serpentine group,

serpentine [12168- 92 -2], chrysotile, lizardite [12161-84-1], and antigorite [12135- 86 -3],

although differing structurally, are compositionally almost identical. All have the approximate chemical composition of Mg3(Si205) (OH)4. The crystal structure of

chrysotile is layered or sheeted similarly to the kaolinite group [1318 -74 -7] (3 -4). It is based on an infinite silica sheet (Si205)n in which all the silica tetrahedra point one

way (see Silica). On one side of the sheet structure, and joining the silica tetrahedra, is a layer of brucite, Mg(OH)2i in which two out of every three hydroxyls are replaced by oxygens at the apices of the tetrahedra. The result is a layered structure illustrated in Figure 4 (1,5).

270 ASBESTOS

SNFi.iiIP7IE

Y....Y.il 11 . .I.. _ --'rnv.wuwlaaw:.YwJ.ru4w ...Gti:taM..`1i+t<rK4rliia'N.wrlr 'Mrv.eAi: w+:!+i.'4.ii.+.aac.a

Figure 3. New Idria (Coalinga) chrysotile platelets (Courtesy of Johns -Manville Research Center).

Unit cell composition Mg6(OH)8Si4Oto

Build -up of sheets into fundamental fibrils

r...ii.

Figure 4. Fundamental sheet of a chrysotile structure.

Mismatches and strains between the layers cause the structure to curve and form cylinders or fibers (6 -7). Individual chrysotile fibers have ultimate diameters of 0.02 -0.03 Am. X -ray and electron microscope studies have confirmed this cylindrical form and diameter range. In fact, the first electron microphotographs indicated a tubular structure as illustrated in Figure 5 (8-10). This characteristic appearance has now become one of the more definitive identification techniques for chrysotile.

Vol. 3 ASBESTOS 271

Figure 5. Electron photomicrograph (80,000X) of chrysotile (Courtesy of Johns -Manville Research Center).

Electron microphotographs have shown most chrysotile fibers with a hollow cylindrical form and a single magnesia -silica sheet rather than the earlier double -layer concept (11_ -12). The lattice planes have a multispiral arrangement as suggested by earlier x -ray studies (13).

272 ASBESTOS

Chemical and Surface Properties. Chrysotile asbestos is a naturally formed mineral. The chemical compositions vary somewhat, depending on deposit location, from the idealized composition of Mg3(Si205)(OH)4. Chemical analyses of chrysotile range approximately as follows: Si02, 37-44%; MgO, 39 -44 %; FeO, 0 -6.0%; Fe203, 0.1 -5.0%; A1203, 0.2 -1.5 %; CaO, trace -5.0 %; H20, 12.0 -15.0%. Variations in chemical analyses may be due to either associated mineral impurities or to isomorphic substitutions in the crystal lattice. Common mineral impurities found in commercial grades of chrysotile from various locations include magnetite, chromite, brucite, calcite, dolomite, and awaruite. Within the chrysotile lattice, nickel and iron can occur as minor isomorphic substitutions for magnesium (14 -17). Chrysotile, a hydrated silicate, is subject to thermal decomposition at elevated temperatures. This thermal decomposition is a two -stage reaction consisting first of a dehydroxylation phase and then a structure phase change. Dehydroxylation or the loss of water occurs at 600 -780 °C. At 800 -850 °C the anhydride breaks down to forsterite and silica. These reactions are irreversible and are illustrated by the typical differential thermal analysis shown in Figure 6.

Structural changes in chrysotile can occur under conditions of intense grinding. As a result of these effects the structure can become amorphous and no longer iden- tifiable by either x -ray diffraction or electron microscopy. These structural changes apparently occur because of localized temperature surges in the fibrils with accom- panying dehydroxylation as they absorb the tremendous impact energies, eg, extensive dry ball milling results in an amorphous mass and wet ball milling results in short fibrils that retain their crystallinity (16).

Because of its hydroxyl outer layer, chrysotile is readily attacked by acid and will, ultimately, completely dissolve the magnesium component, leaving essentially a fibrous, but fragile, silica structure. Similarly, because of its alkaline surface, chrysotile is not readily attacked by caustic solutions except under conditions of extreme alkali concentration and elevated temperatures (18 -19).

Dispersions of chrysotile fiber in carbon dioxide -free distilled water exhibit al-

DTA -Z

/ Thermobaiance run?

_-------r- +' 100 200 300 400 500 600 700 800

Temperature (C °)

Figure 6. Typical differential thermal analysis of chrysotile.

14

12

10

8

4

2

0

900 1000

i

Vol. 3 ASBESTOS 273

kaline properties. Such suspensions will reach a pH of 10.33 as with magnesium hy-

droxide suspensions tested under the same conditions. Solubility product constants for chrysotile fibers range from 1.0 X 10 -11 to 3 X 10 -12, indicative of the magnesium hydroxide outer layer (20 -22).

The electrokinetic behavior of chrysotile is also related to its surface characteristics. Normally, below its isoelectric point of approximately pH 11 -12, chrysotile exhibits a positive charge. Above this pH range, it demonstrates a negative charge. Exceptions to this general behavior have been noted with chrysotile fibers from certain locations (23).

Because of its very small fiber diameter, its high specific surface area and its relatively reactive surface, chrysotile is a selectively adsorptive material. Commercial grades of chrysotile adsorb as much as 2 -3 wt % moisture from saturated air. Ad-

sorption studies of a variety of organic compounds from both vapor and liquid media show that chrysotile has a greater affinity for polar molecules. Heats of adsorption have been measured ranging from 38 kJ /g (9 kcal /g) for hexane to 67 kJ /g (16 kcal /g)

for water (5,24 -27). Chrysotile also adsorbs iodine from solutions in a manner similar

to magnesium hydroxide or brucite. This adsorption characteristic is often used as

a staining technique for the detection of chrysotile asbestos (28). Physical Properties. The common physical properties of chrysotile asbestos are

given in Table 2. Asbestos fibers are used in composite materials (qv) to provide reinforcement.

Tensile strength of the fiber is, therefore, an important and highly significant physical

property. Unfortunately, because of their extremely fine diameter and the complicating

factor of the effect of sample length on strength determinations, it is extremely difficult

to measure the tensile strengths of asbestos with precision. Most recent information indicates typical chrysotiles have tensile strengths in the order of 3727 MPa (5.4 X

105 psi) which exceeds corresponding values for steel piano wire and fiber glass. A

comparison of typical strength values for the different asbestos varieties is given in

Table 3. Since all these measured values are far less than the theoretical value of over

10,000 MPa (1.45 X 106 psi) attributable to silicate chain structures, the values given

should be considered as relative for the different varieties rather than specific

(1,29 -31). Physical strengths of asbestos are adversely affected by elevated temperatures.

Table 4 shows decreasing tensile strength as dehydroxylation takes place (1).

What visually appears to be a single fiber in commercial grades of asbestos is in

actuality a bundle of a large number of individual fibrils. These bundles can be sub-

divided into a multitude of finer bundles, but only with special processing can a large

portion of fiber mass be divided to its ultimate fibril diameter. The specific surface

areas of commercial asbestos fibers vary with the extent of mechanical defibrillation.

Surface areas by nitrogen adsorption tests on samples teased by hand from chrysotile

crude are 4-12 m2 /g; however, when aggressively milled or fiberized, surface areas of

30 -50 m2 /g result (32). Chrysotile asbestos can be separated into smaller diameter fibrils (higher specific area) more readily under wet processing conditions than under dry mechanical milling. For this reason many asbestos product manufacturing processes utilize wet opening techniques to provide improved fiber reinforcing efficien-

cies. The term harshness in the asbestos industry refers to the fiber's brittleness,

flexibility, form, and modulus of elasticity. Commercial grades of chrysotile are usually

Tab

le 2

. Pr

oper

ties

of A

sbes

tos

Fibe

rs

Chr

ysot

ile

Ant

hoph

yllit

e A

nios

ite

(fer

roan

thop

hylli

te)

Cro

cido

lite

Tre

mol

ite

Act

inol

ite

stru

ctur

e

N :

min

eral

as

soci

atio

n

orig

in

vein

ing

esse

ntia

l co

mpo

sitio

n

crys

tal

stru

ctur

e

crys

tal

syst

em

in v

eins

of s

erpe

ntin

e, e

tc

in a

ltere

d pe

rido

tite

adja

cent

to

serp

entin

e, a

nd l

imes

tone

nea

r co

ntac

t with

bas

ic ig

neou

s ro

cks

alte

ratio

n an

d m

etam

orph

ism

of

basi

c ig

neou

s ro

cks

rich

in

mag

nesi

um s

ilica

tes

cros

s an

d sl

ip fi

bers

hydr

ous

silic

ates

of m

agne

sia

fibr

ous

and

asbe

stif

orm

mon

oclin

ic

(pse

udoo

rtho

rhom

bic?

)

lam

ella

r, f

ibro

us

asbe

stif

orm

in c

ryst

allin

e sc

hist

e an

d gn

eiss

es

met

amor

phic

, us

ually

from

ol

ivin

e

slip

, mas

s fi

ber

unor

ient

ed a

nd

inte

rlac

ing

Mg

silic

ate

with

ir

on

pris

mat

ic,

lam

ella

r to

fi

brou

s or

thor

hom

bic

lam

ella

r, c

oars

e to

fin

e fi

brou

s in

iro

n -s

tone

s fi

brou

s an

d as

best

ifor

m

in c

ryst

allin

e sc

hist

s,

etc

met

amor

phic

cros

s fi

ber

long

, pr

ism

atic

and

fib

rous

ag

greg

ates

in ir

on -r

ich

silic

ious

in

Mg

limes

tone

s as

alte

ra-

argi

llite

in q

uart

zose

tio

n pr

oduc

t of

high

ly

schi

ste

mag

nesi

an r

ocks

, m

etam

orph

ic a

nd i

gneo

us

rock

s re

gion

al

met

amor

phic

m

etam

orph

ism

cros

s fi

ber

silic

ate

of F

e an

d M

g,

silic

ate

of N

a an

d Fe

hi

gher

iron

than

w

ater

an

thop

hylli

te

pris

mat

ic,

to

fibr

ous

fibr

ous

mon

oclin

ic

mon

oclin

ic

slip

or

mas

s fi

ber

retic

ulat

ed l

ong

pris

mat

ic c

ryst

als

and

fibe

rs

in

limes

tone

and

in

crys

talli

ne s

chis

te

resu

lts o

f con

tact

m

etam

orph

ism

slip

or

mas

s fi

ber

Ca

and

Mg

silic

ate

with

som

e C

a, M

g, F

e,

wat

er

silic

ates

, wat

er

up t

o 5%

long

and

thi

n co

lum

nar t

o lo

ng a

nd th

in

fibr

ous

colu

mna

r to

fi

brou

s m

onoc

linic

m

onoc

linic

colo

r

lust

er

hard

ness

, Moh

s sp

ecif

ic g

ravi

ty

clea

vage

op

tical

pro

pert

ies

refr

activ

e in

dex

fusi

bilit

y, S

eger

co

nes

flex

ibili

ty

leng

th

J1

text

ure

acid

res

ista

nce

spin

nabi

lity

spec

ific

hea

t, J /

(kgK

) [o

r B

tu /(

lb °F

)]

whi

te, g

ray,

gre

en,

yello

w

silk

y

gray

-whi

te,

brow

n, g

ray,

or

gree

n vi

treo

us t

o pe

arly

ash

gray

, gr

een,

or

brow

n

vitr

eous

, som

ewha

t pe

arly

lave

nder

, blu

e

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at

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276 ASBESTOS

Table 3. Tensile Strength of Asbestos a

chrysotile, Arizona, USA chrysotile, Thetford, Canada crocidolite, Koegas, Cape Province, Africa crocidolite, Koegas, Cape Province, Africa crocidolite, Pomfret, Cape Province, Africa crocidolite, Pomfret, Cape Province, Africa crocidolite, Cochabambo, Bolivia amosite, Penge; Transvaal, Africa amosite, Penge, Transvaal, Africa anthophyllite, Paakilla, Finland

a See ref. 1.

Tensile strength, MPa (psi X 103)

Young's modulus, GPa (psi X 106)

3780 (548) 145 (21.1) 3640 (528) 146 (21.2) 2840 (413) 147 (21.3) 3090 (448) 151 (21.9) 4660 (675) 169 (24.5) 3550 (515) 175 (25.3) 1440 (209) 170 (24.6) 2580 (374) 143 (20.8) 1980 (287) 143 (20.8) 2450 (356) 156 (22.6)

Table 4. Effect of Temperature on Tensile Strength of Asbestosa

Percentage of original tensile strength Temperature, °C Chrysotile Crocidolite Amosite

200 100 100 320 91.6 70 58 430 73.3 32 32 550 59.5 20 15 670 32.0 period of heat soak 3 min 4 h 4 h

a See ref. 1.

classed as soft or nonharsh. Commonly, they are silky, of fine diameter, and extremely flexible. Contrary to chrysotile, the commercial amphiboles are harsh fibers. They are relatively stiff, brittle, coarser in diameter, and rodlike in appearance under the microscope. These differing physical characteristics account for the different operating characteristics exhibited in the manufacture of various asbestos -containing products. For example, soft chrysotiles can be more readily spun into textiles than the amphiboles but they have poorer drainage properties when used in wet manufacturing processes. However, several fiber treatments have been developed to improve the filtration or drainage properties of chrysotile and thereby increase the production rate of wet machines manufacturing asbestos -cement products (33 -37).

Amphibole Asbestos

Crystal Structure. The structure of all the amphiboles consists of two chains or ribbons based on Si4011units separated by a band of cations. Seven cations form the basal unit. Two hydroxyl groups are attached to the central cation in each unit cell. These hydroxyls, unlike the chrysotile structure, are contained entirely within the amphibole structure. The final structure is composed of stacks of these sandwich ribbons as illustrated in Figure 7 (1,5). The bonding between these ribbons is rather weak and the crystals are easily cleaved parallel to the ribbons along cleavage line A -A. If the cleavage is very facile, the result is an asbestiform mineral (1,5). Amphiboles

Vol. 3 ASBESTOS 277

8 Oxygens 4 Silicons 3 Ox 'ens + 1 hydroxyl

Cation layer O O O

Silica ribbon

Figure 7. Amphibole structure.

can also occur in nonfibrous forms (38) which may result because of structural disorder (39). The dominant cations are Mg2+, Fe2 +, Fe3 +, Na +, and Ca2+ (see Table 1). Minor isomorphic substitutions of Ala +, Ti4 +, K +, and Li+ also occur. Because of the wide compositional range, the amphiboles are often assigned to three generic series; le, the anthophyllite-cummingtonite [17499 -08 -0] series, the calcic amphiboles and the soda amphiboles.

Chemical and Surface Properties. The chemical compositions of the amphibole fibers are more complex and variable than chrysotile. Typical compositions are shown in Table 5.

Like chrysotile, the amphibole asbestos fibers dehydroxylate and decompose at elevated temperatures. The presence of large quantities of iron (particularly ferrous iron) makes the decomposition or thermal analysis determinations particularly complex and very dependent on the composition of the atmosphere. Table 6 is an

Table 5. Typical Chemical Compositions of Amphibole Asbestos

Crocidolite, Amosite, Anthophyllite, Actinolite, Tremolite, 96 96 96 96 96

Si02 49 -53 49 -53 56-58 51 -52 55 -60 Mg0 0-3 1 -7 28-34 15-20 21 -26 Fe0 13 -20 34-44 3 -12 5-15 0-4 Fe203 17 -20 0-3 0-0.5 A1203 0-0.2 0.5 -1.5 1.5-3 0 -2.5 Ca0 0.3 -2.7 10 -12 11 -13 K20 0-0.4 0-0.4 0-0.5 0-0.6 Na20 4-8.5 trace 0.5 -1.5 0 -1.5 H20 2.5 -4.5 2.5 -4.5 1-6 1.5 -2.5 0.5 -2.5

278 ASBESTOS

Table 6. Decomposition Reactions of Amphiboles Under Neutral Conditionsa

Amphibole Dehydroxylation Structural Decomposition variety DTA peak, °C breakdown, °C products

crocidolite 610 800 Na -Fe pyroxene, magnetite, silica

amosite 780 600 -900 Fe-Mg pyroxene, silica

anthophyllite 950 950 Mg -Fe pyroxene, magnetite, silica

actinolite 1040 1040 CaMgFe pyroxene, silica

a See ref. 1.

oversimplification of the thermal decomposition reactions of the amphibole fibers (1,40).

Compared to chrysotile, the amphibole fibers are relatively acid resistant. How- ever, under boiling conditions and high acid concentrations the amphiboles can exhibit weight losses of approximately 2 -20%. Relative order of acid resistance is:

tremolite > anthophyllite > crocidolite > actinolite >

amosite >» chrÿsotile

Amphibole fibers have a negative charge as contrasted to chrysotile's usual positive charge. The magnitude of the charge exhibited by the amphiboles is substantially lower than chrysotile's.

Physical Properties. See Table 2 for the more common physical properties and characteristics of the various amphibole fibers. In general, amphibole fibers are harsh, springy, and brittle as compared to the chrysotile variety. These physical properties make the amphiboles fast draining and bulky when used in manufacturing processes.

As illustrated in Table 3, the tensile strengths of amphibole asbestos fibers differ widely. The typical tensile strengths of asbestos fibers have the order:

crocidolite > chrysotile > amosite > anthophyllite >

tremolite > actinolite

As shown in Table 4, the amphiboles also lose their strength with increasing temperature.

Amphibole fibers do not divide into fibrils as fine in diameter or as symmetrical as the chrysotile variety. Ultimate diameters of amphiboles have been reported to be about 0.1 pm (1) and the surface areas of amphibole asbestos are considerably smaller than chrysotile. Fully fiberized commercial grades of crocidolite, for example, have surface areas by gas adsorption of 3 -15 m2 /g compared to the 30 -50 m2 /g values of chrysotile (2,41).

Vol. 3

Milling

ASBESTOS 279

Imbedded asbestos fibers are removed from the ore by a repeated series of crushing, fiberizing, screening, aspirating, and grading operations (milling). A typical, greatly simplified asbestos mill is shown in Figure 8. The ore is crushed, dried, and fiberized in a variety of impact mills. The short fiber and granular material is removed by screening the fiberized mass. The oversized fractions are stratified on a screen where the spherical, granular material of high density seeks the screen's surface and the fluffy, low- density fiber rises to the top of the bed. At the end of the screen, the fiber is separated from the rock by an aspirating hood. The coarse granular fractions that still contain veins of chrysotile fiber, are refiberized and rescreened to recover shorter fibers. Fibers recovered from these primary screening operations are rescreened to remove entrapped granular material and classified into grades by fiber length.

The recovery of milled asbestos fiber from ore is fairly low. In general, a 5% recovery is typical. The chrysotile mines in California are notable exceptions where 50% recoveries are common from agglomerated ores (Fig. 3). The fibers, however, are very short and are normally sold as reinforcing fillers (qv).

Conventional asbestos milling uses large quantities of air both for separating the fibers as they are freed from the ore and for dust control. Approximately 130 m3 /s (275,000 cfm) are used to process one metric ton of ore (42). Preconcentration of ore includes selective grinding, screening, and magnetic techniques (43 -45).

Travelling conveyor,..-

Fiberizer

Vibrating screen

Gyrating crusher

Long fiber

collector

To Shaking graders screen and

packers

Dry rock storage

I INi I M..

!11114 , r- Sly dust filter I'ilt'I l n IIIi t, 45P;tn

Hot gases to collecter and stack

Shaking screens

Gyrating crusher

Vertical dryer and

furnace

Sly dust Exhaust air ducts -1

Medium fiber

\ / collector

Fiberizer

To graders

and packers

Short fiber collector

Shaking screens

Fiberizer

Shaking r- screen I l

To tailings

Figure 8. Schematic of a typical asbestos milling flowline.

To graders

and packers

280 ASBESTOS

Production and Usage

In 1977, 80% of the world's chrysotile was produced by Canada and Russia. Most of the Canadian production is from Quebec and the balance from Newfoundland, British Columbia, and the Yukon Territory. Russian production is predominantly in the Bazhenovo District in the Central Urals, the Dzhetygara area northwest of Kazakhstan, and the Aktourak deposits near the Yenisei River.

Crocidolite and Amosite are produced in significant quantities only in South Africa. Main producing areas are at Bosrand, Cornheim, Ouplaas, Owendale, the Kuruman area in the Cape Province, and the Lydenburg District in the Transvaal (46).

Production statistics vary widely with the source of information. Table 7 sum- marizes ranges given by various authorities (47 -53).

The largest use of asbestos is in asbestos- cement for products such as pipes, ducts, and flat and corrugated sheets. Pipe products find use in water supply, sewage disposal, and irrigation systems. Asbestos -cement sheets are used in a wide variety of con- struction applications. Othér uses of asbestos include fire -resistant textiles, friction materials (see Brake linings), underlayment and roofing papers, and floor tiles. Table 8 shows the uses of asbestos in the United States (the largest consumer) and the world. The United States usage patterns differ considerably from the rest of the world (54 -56).

Standards and Test Methods

Classification. Canadian chrysotile crudes are classified as follows:

crude # 1:

crude # 2: crude run of mine:

Table 7. 1976 Asbestos Production

1.9 cm staple and longer 0.95 cm to 1.9 cm staple unsorted crudes

Type and location Thousands of

metric tons

Chrysotile Canada 1537 USSR. 2285 South Africa 111 Rhodesia (estimate) 239 China (estimate) 150 Europe 321 USA 104 South America 69 Australia 66 others 45 Total chrysotile 4927

Amphiboles (South Africa) crocidolite 178 amosite 79 anthophyllite 2 Total amphiboles 259 Total asbestos 5186

Vol. 3

Table 8. Asbestos Usage by Product line Estimated Percent of Production

ASBESTOS 281

Product line United States

consumption, %

World consumption, %

asbestos -cement 23 -30 65-70 asbestos papers 26-38 7 -8

floor tile 13 -21 4-7 friction materials 6-8 2 -3 roof coatings 4 -7 2 -3 textiles 1 -2 1-4

plastics 1 -2 trace -1 miscellaneous 12 -20 13 -15

Milled Canadian fibers sold from Quebec are classified by a dry screen technique known as the Quebec Standard Asbestos Test. This test method grades fibers roughly by fiber or staple length. Minimum test values are guaranteed for each grade and a numerical classification system has been established for fibers ranging from Group 3, the longest grade, to Group 7, the shortest grade.

Chrysotile fibers produced outside Quebec are graded or controlled by screening test methods differing from the Quebec Screen Test; however, these basically identify grade by staple length.

Test Methods. The major properties of concern are length, granular content, degree of openness or effective surface area, drainage or filtration rate, color, ab- sorption, electrical resistivity, bulk density, and strength -giving properties (57).

Fiber length is most reliably measured by wet screening techniques. Fiber openness is commonly measured by air permeability surface area methods. A variety of filtration tests are used to estimate a fiber's operating performance in asbestos - cement wet machines or paper machines. Granular content is often determined by a dry screening test where the fibrous material is aspirated from the granular impurity remaining on the various screen meshes.

The most complex measurement is the determination of the strength -giving property of a fiber for use in asbestos- cement products. In this case, small pressed sheets are made from a slurry of fiber and cement. After curing, the sheet strength is determined and the reinforcing effectiveness or value of the fiber is calculated.

Health and Safety Factors

The inhalation of excessive quantities of free asbestos fibers over prolonged pe- riods of time can increase the risk of developing certain diseases of the lung within 20 or 30 years. The three diseases associated with the inhalation of asbestos are: asbestosis, a nonmalignant fibrotic lung condition; bronchogenic (lung) carcinoma; and mesothelioma, a rare cancer of the lining of the chest or abdominal cavities (58) .

Reduction of asbestos dust exposure is at present the only known method of preventing disease among asbestos industry workmen. When dust levels are low, risk to employees and the incidence of asbestos -related disease drop sharply. Cigarette smoking greatly increases the risk of developing bronchogenic cancer among persons encountering heavy asbestos exposure. Nonsmoking asbestos workers show no greater incidence of bronchogenic cancer than the average nonsmoker.

282 ASBESTOS

There are governmental regulations (OSHA) that describe the allowable airborne fiber levels in work areas. Extensive dust control together with corrective work prac- tices are used to implement these regulations and medical examinations are regularly provided to assure worker protection (see Air pollution control methods; Industrial hygiene and toxicology).

BIBLIOGRAPHY

"Asbestos" in ECT 1st ed., Vol. 2, pp. 134 -142, by M. S. Badollet, Johns -Manville Research Center; "As- bestos" in ECT 2nd ed., Vol. 2, pp. 734 -747 by M. S. Badollet, Consultant.

1. A. A. Hodgson, "Fibrous Silicates," The Royal Institute of Chemistry, London, Lecture, Series No. 41965.

2. F. A. Mumpton, H. W. Jaffe, and C. S. Thompson, Am. Mineral. 50,1893 (1965). 3. B. E. Warren and W. L. Bragg, Krist. 76, 201 (1930). 4. B. E. Warren and K. W. Hearing, Phys. Rev. 59, 925 (1941). 5. S. Speil and J. P. Leineweber, Environ. Res. 2(3), (1969). 6. F. J. Wicks and E. J. W. Whittaker, Can. Mineral. 13, 227 (1975). 7. F. J. Wicks and J. Zussman, Can. Mineral. 13, 244 (1975). 8. T. F. Bates, L. P. Sand, and J. F. Mink, Science 111, 512 (1950). 9. W. Noll and H. Kercher, Naturwissenschaften 37, 540 (1950).

10. J. Turkevich and J. Hillier, Anal. Chem. 21, 475 (1949). 11. M. Maser, R. V. Rice, and H. P. Klug, Am. Mineral. 45, 680 (1960). 12. K. Yada, Acta Crystallogr. 23, 704 (1967). 13. E. J. W. Whittaker, Acta Crystallogr. 6, 747 (1953); 8, 571 (1955); 9, 855 (1956); 10, 149 (1957). 14. H. Berman, Am. Mineral. 17, 313 (1932). 15. E. H. Nickel, Can. Mineral. 6, 307 (1959). 16. G. P. Reimschussel, unpublished information, Johns -Manville Research Center, Denver, Colo. 17. P. Hahn -Weinheimer and A. Hirner, 3rd International Conference on the Physics and Chemistry

of Asbestos Minerals, Quebec, Canada, 1975. 18. M. S. Badollet, Can. Min. Metall. Bull. I (1951). 19. D. G. Hiscock, unpublished information, Cape Asbestos Ltd., 1964. 20. F. L. Pundsack, J. Phys. Chem. 59, 892 (1955). 21. F. L. Pundsack and G. P. Reimschussel, J. Phys. Chem. 60,1218 (1956). 22. J. W. Ryznar, J. Greon, and M. G. Winterstein, Ind. Eng. Chem. 38,1057 (1946). 23. E. Martinez and G. L. Zucker, J. Phys. Chem. 64, 924 (1960). 24. L. M. Pidgeon and A. van Wissen, Can. J. Res. 9,153 (1933). 25. G. J. Young and F. H. Healy, J. Phys. Chem. 58, 881 (1954). 26. A. C. Zettlemoyer, G. J. Young, and F. H. Healey, J. Phys. Chem. 57, 649 (1953). 27. C. H. Gorski and L. E. Stettler, Amer. Ind. Hyg. Assoc. J. 36, (1975). 28. M. Morton and W. G. Baker, Can. Inst. Min. Metall. Trans. XLIV, (1941). 29. M. S. Badollet, Can. Min. Metall. Bull. 1 (1951). 30. R. Zukowski and R. Gaze, Nature (London) 183, 35 (1959). 31. D. R. Burman, Paper No. 2-8, 1st International Conference on the Physics and Chemistry of Asbestos

Minerals, Oxford, Eng., 1967. 32. F. L. Pundsack, J. Phys. Chem. 65, 30 (1961). 33. M. S. Badollet and W. C. Streib, Can. Min. Metall. Bull. 48, (1955). 34. U.S. Pat. 2,616,801 (Nov. 1952), M. S. Badollet and W. C. Streib (to Johns -Manville). 35. U.S. Pat. 3,173,831 (Mar. 1965), F. L. Pundsack and G. P. Reimschussel (to Johns -Manville). 36. U.S. Pat. 3,891,498 (June 24, 1975), T. H. Sadler (to Johns -Manville). 37. U.S. Pat. 3,715,230 (Feb. 6, 1973), T. H. Sadler (to Johns- Manville). 38. J. E. Chisholm, J. Mater. Sci. 8, 475 (1973). 39. D. R. Veblen, R. R. Buseck, and C. W. Burnhem, Science 198, 359 (1977). 40. J. J. Cilliers and co- workers, Econ. Geol. 56, (1961). 41. J. H. Patterson and R. L. Thompson, Paper No. 2 -5, 1st International Conference on the Physics and

Chemistry of Asbestos Minerals, Oxford, Eng., 1967. 42. J. Goldfield, Min. Eng. 7, (Nov. 1955).

Vol. 3 ASPARTIC ACID 283

43. H. Berger, CIM Bull. 68, (Feb. 1975). 44. R. G. Evans, CIM Bull. 68, (July 1975). 45. E. Martinez, Trans. Soc. Min. Eng. 255, (1974). 46. H. H. Gossling, 2nd Industrial Minerals International Conference, Munich, Ger., 1976. 47. Asbestos 58, (Dec. 1976). 48. Asbestos 58, (Mar. 1977). 49. Asbestos 59, (Nov. 1977). 50. Mineral Industries of the USSR, U.S. Bureau of Mines, MP2, July 1977. 51. Asbestos -197, U.S. Bureau of Mines, MCP6, Sept. 1977. 52. Mineral Trade Notes, 74(6), (June 1977). 53. World Mining Magazine 30, June 25, 1977. 54. Ind. Min. (June 1975). 55. B. Lincoln, Ind. Min., (Oct. 1975). 56. N. W. Hendry, unpublished information, Johns -Manville Corporation, Denver, Colo. 57. Chrysotile Asbestos Test Manual, 3rd ed., Asbestos Textile Institute and the Quebec Asbestos Mining

Association, 1974. 58. Chem. Week,, 16 (May 3, 1978).

WILLIAM C. STREIB Johns - Manville Corporation

ASBESTOS- CEMENT PRODUCTS. See Cement.

ASBESTOSIS. See Industrial hygiene and toxicology.

ASCORBIC ACID. See Vitamins.

ASPARAGINE. See Amino acids.

ASPARTIC ACID. See Amino acids.

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