Document rBrQyRRVvb62ma54K05L7oeVq

TjW* PLAINTIFF'S EXHIBIT DOW-2690 ENVrnONMtNTU, RESEARCH 2, 1G6-20S (1969) C/5 '--i CD CD Asbestos AAinerals in Modern Technology S. Spell and J. P. Leineweber Johns-Manuille Research and Engineering Center, Manvillc, New Jersey Received Avgust 6, J9G8 CD CJD Asbestos is a generic term for a variety of hydrated silicate minerals which have one common attribute, namely, the ability to be separated into relatively soft, silky fibers. Although the name is ordinarily associated with those varieties which have technologic importance, it is applicable to all minerals which fit the above description. The term "ashestiform minerals" is perhaps most descriptive. 1'he known varieties of asbestiform minerals can be divided into two main classes on the basis of their crystal structures: serpentine and amphiboles. The sole member of the serpentine class is chrysolile asbestos, which is by far the most common of the asbestiform minerals. It accounts for more than 953! of tlie asbestos fiber produced today. There are five recognized asbestiform varieties of amphibolc: crocidolite, amosite, anthopbyllile, treinolitc, and actinolite. Although the amphiboles are common rock-forming minerals, the asbestiform varieties are much less abundant than chrysotile. The physical and chemical properties of the asbestiform minerals can be directly related to their crystal structure and chemical composition. In turn, die physical and chemical properties are responsible for the commercial im portance of asbestos. It is understandable, therefore, that great emphasis has been placed on the elucidation of the structure and composition of these im portant minerals. Several comprehensive reviews on die asbestiform minerals have been pub lished in recent years, including Hendry (30), Gaze (25), Hodgson (33), and Deer, Howie, and Zussman (17). The objective of this paper is to bring this information up to date with particular emphasis on recent developments con cerning the physics and chemistry of the asbestiform minerals. In addition, die uses of asbestos will be discussed briefly in relation to the properties of the individual species. OCCURRENCE The epigenesis and occurrence of the asbestiform minerals have been the subject of considerable geologic and petrologic research. Chrysolile and amphi bolc fibers are found in entirely different geologic formations. Chrysotile was most probably formed as a result of two separate mctamorphic changes in ultrabasic rocks of volcanic origin. The fust stage involved (he fonnnlion of serpentine by the hydrothermal alteration of the original rock. At some later time the chrysotile was formed in cracks and fissure* in the rock by recryslallization of l) ic serpentine, again by an acpicous solution and rcprccipitatfon proc- IGG ST0011709 S T 0 0 I1710 iw t III l MINMIW.S IN M.rtHIlN 11 < IIV* >1 VK. V 107 i i 1 * 4 FiC. 1, Cross Vcm filur chrysolite. css. In most cases, chry.sotilc occurs as "cross fillers" which are oriented in a parallel array across the veins in tlic serpi ntne.' root: as *.Iio\vn in Fig. 1. Occa sional occurrences of "slip filler" arc fnuinl :n which the fiber is oriented parallel to the vein as shown in Fig. 2. A notable exception to the normal mode of occurrence of clirysolilc is the fiber found in the New ftlri.i sci pentinito of Western California and at Stragari, Yugoslavia (15). The New fdria fiber is generally referred to as Cnalmga fiber, rhe great bulk of (bis deposit consists of soft powdery pellet like agglomerates of chrysotilc as shown in Fig. The m.itciial may bo (be result of intensive t1i i it i . /* t/ ) it :| I inch Fie. 2. Slip fit*rr chrysolite. `* i *i ST0011710 S T 0 0 I1711 IGS 5. M'l II. AM* J I*. r i.im: . i.i Fic. 3. NoJnTt'5 of co.ilii)"a clirysotilc. crushing anti pu!vcii/nti<ui during or after serpentini/ation. In addition to Its unusual mode of occurrence, Coalinga chrysotilc is also unusual from (lie stand point of its physical structure. This feature will he discussed in the appropriate section or this paper. Tire g mesis of the aniplhhote fibers is not as clear-cut as that of chrysotilc. Their name*, tiilen from the Crt-eh v.uid tunt hifxjlos, meaning ambiguous, Is a vciy apt choice. 1'igme -1 is a typical example of the mode of occurrence for crocidolitc which is found in the banded ironstones of the Transvaal system of 'h ST0011711 S T 0 0 I1712 AM'I MlMHIV IN MMU* IIS' IIIII.VMI.III.V IfJO Sonlh Afliea. They .nr im t tmiMj'lii.1 il mds of st-ditneiil.ny urigill, which .ircmnls for the v.iri.tT*?!t\ in <; r*.itini of the host tee! s and inw.rtjucntly of I Ilf filter. *lhr oiK si-'i liflc .nit w'linciifv of a'lio-in- is also found ill (Iiis area. Crooitlolifc is found in other ;iir;n, including 1'nlivi.i nn<l West cm Australia. Iionatc neks. They air widely dMiihutcd in nature, lnit of little conuneicial significance. Tre inolite is a vciy common contaminant of commercial talc. ami Bragg (72) and filer elucidated liy Warren and Herring (CO). Tliese investigators determined tlial die mineral lias a layered-type structure similar to die minerals of the kaolinitc group. The basis of the structure is an infinite silica sheet (Si.Oi)* in which all the silica lehuhrdra arc pointing in the same direction. Attached to one side of this sheet is a Imitate Mg(OH)j layer in which two Out of ever)- three hydros) Is are replaced hy the apical oxygens of the silica tetrahedra. The result is a double sheet as shown in Fig. 5. The nvsmatch in the dimensions of the silica and hrncite sin els introduc es a strain in the stun.lure. Belter matching of the layers and relief of the strain can bo accomplished in three ways. 1. Substitution of larger ions in the silica sheet or smaller mis in the brucite sheet. 2. Distortion of the octahedral Inutile network or of the tetrahedral silica network. 3. Curvature of the sheet with the hriK itc layer on tin* outer surface. BUILD UP cr SHEETS INTO ruNOAMENTAL flQPILS Fir.. 5. KniKl.imrnt.il Tao<-| of rlirysoUlr:. w * * 7I 1 1 3 )70 S. M l It. AMI J. *. I.I INKWKm il Kver sine.- tlic first election micrographs were published showing tlic ap parent lnliul.li slim (me of clmsotile (7, 50, 70), there ha* been considerable controversy oxer llic moijiliulo^y of l!:c fillers. W hillakcr (70), 1>) mo.uis of careful X-ray clifFr.u tiuii studies, dcmonslralcd lh.it tlic Inlticc was definitely curved. Although he was unahle tn show whether the structure wns a cylindrical arc, a closed circular cylinder, or a cylindrical spiral, he favored R spiral structure. Tlic tubular concept was supported further when Maser, Rice, and Klug (44) puhlislicd the electron micrograph of Fig. 6 showing an end-011 view' of a ebrysolile fiber bundle. The fibrils were definitely cylindrical and included many which appeared to Ik* pairs of concentric cylinders. Kic. 6. Klvctroii inicroj'.i.ii'ti of clii}sotib sevlion. X195.000. Reprinted with per mission from American Mincrafop\t 45, CSO (1900). A recent pajicr by Yada (SI) has furnished what appears to be the final answer to the structure of chrysotilo fibrils. Hy means of high resolution electron microscopy, he was able to observe the actual crystal lattice planes both parallel and perpendicular to the fiber axis. These pictures, Figs, 7 and 8, show that most of the fihei have n hollow cylindrical form. The lattice planes have a* imdtispir.il nriaugerr.etit confiiming the prediction of Whittaker (70). Also ap parent in several of Yadas pictures is the presence of crystallographic disloca tions which sfiongly M that the basic structural unit consists of a single magnesia-silica sheet, rather than a double sheet as previously jxm tula ted by most authois. Midas oh .< i vatinm a ho confirm Whittaker's hvpotlicsis that the basic spiral tinner! M-. of foe silica magnesia units with approximately 10 silica in.igncsi.i units having t!,7(: \ v..,|| (lf single fibril. Occasional fibi i s u-n hIm in,! l.ieh v. cm solid latlcr than luiMt i-.-. . \| ST0011713 AMU.MOS MISI UMS IN modi'uN nTiisot.x.> 171 S T O O !1714 1 Fic. 7 aiiH Fin. 8. * #I Itir'h rr<o1nlion election mkrosr.ipU of cliry*ntik\ Tlrpniilril wllh pcrmfri'on fmm .\rlit Ccyif. 701 (10IT7). ST0011714 *, MTII. ANI> J. *' Sft f* SSSSn??28PSS8 oii f ^*r o c - d o o rj 1a os S E %% Ohprt0c>O0C0)^0O0^O^N0c*->C6C( S a 2% <s -* r# o o r> | ,sa^,..! s*' f I I I M I GO --i o CD cn - tO. I aJ sn II 3H p n fi y. r> f, n w o n M H S .8 d "b s KO* r9~i t *3 (N f *-7 s y " p p -<r ~ c5 ^ fc> c i ~ Sj* o * o *- fG* G- n %/"*ie-?S s? 0k f rt 2--I Ec -gft *5/. o-5 |; ^cr> vc6* ,S C ro~ $SSgS2Se p ** c*i d o' d d j; --* e_ v. t*?r c* c o r* *r c. c* -- ;. -r c -r "f *-?" C C' *r n j 6 V8 ;1 S cv?v V** * V x. >! :. ST0011715 A `.I'l s|i l\ MC.ill'I.S IN M'llMI.V il C IIVOI n*.Y 173 though (Jir.-st* /ili'jv .in- ii I.ilm Jy fnin 11 Kin iii I 111* '.iniples, the) are not enough to account for tfiv Ti*.f.i*^>;nn y between (In' measured and cals *11. t< J densities rcjvirled by Jv .ndvu k (5-j). One final point should lu: made about (be Yada iiicr*iiiriU>T,<:- 1 be ou,s<^ surface of most of tbc fibers shows the presence of highly disorganized or amorphous nirilciial. 'tins is the result of damage to the outer la)or of fibrils by the electron beam under the conditions of observation. There arc two other serpentine materials found in chrysotile-1x.nring rockl Itzardite and antigorite (20). They both liux-c the same chemical compodtfc**;--ami the same fundamental sheet structure as clirysotile. Hie differences betwrcwtrfc^' these minerals reflects the way the strain in the crystal Lattice hat been idfeWil%: Lfznrdile, which is the principal constituent of massive serpentine, generally hs-.-v an extremely fine grained, platy morphology, visible only untlcr the electron ,?V, microscope in most s(>ccimcns, Its slmciure has not yet been elucidated, btit X-ray diffraction patterns indicate flat rather than etirved sheet*. Antigorfte^ n*r~;"C the other hand, docs show evidence of curved sheets. Two of fts unit mensions arc equal to clirysotile, but the third is much larger and variabto'H^v Tills third (h) dimension can vary from JS.5A to as largo ns 100 A, compares! to the 9.2 A value for clirysotile. It is lwdicvcd that the structure consists of ; undulating sheets the periodicity of which corresponds to the variable unit cell dimension. .jCr * j AmphiboJes The basic crystal form of the nmphibolc minerals is less complicated than that of the serpentines. The basic structural unit is a double silica chain (Si.O,,). As in the clirysotile sheets, all of the silica tclrahcdra point in one direction. These chains arc paired, 'back-to-back,1' with n layer of hydrated cr.tions In between to satisfy the negative charges of the silica chains. The -flnal structure is formed l>y flic slacking of these sandwich ribbons in an ordcicd array.. pictorial concept of this structure is shown in Fig. 9. The various mineral* fcir ^ V: the amplnbolc groups arc rh.nvicleri/vd by the cations vi Irich occur in the structure. The principal cations arc magnesium, iron, calcium, and sodium. Since the bonding between these ribbons is rather weak, (he crystals are easily cleaved parallel to the ribbons along A-A. If the cleavage is very facile, (he result It an ; asbeslifnrm mineral. bor each variety of ashcstiforin amphibolo, there is a corresponding massiirtB form with a different mineral name. Normally the asbesttform varieties arc not found along with the massive counterparts. Undoubtedly, the local gcochcmk*! conditions extant at the time of formation contributed to the relative ease of cleavage of any specific deposit and, therefore, to its commercial utility. The ^ massive and ashcstiforin varieties have the same chemical compositions and q X-ray crystal structures. They can be distinguished by their physic:.! properties and by petrographic examination. O -- Cin:\HCU. COMPOSITION Hie chemical oompodtinit of rnimncrcially avaiFalilc chrjsotile* frrm various locations are ilioun in Table t. I'or (ompun.m ........t......... ..... ..sill- .l||(|- -----I cr> ST0011716 174 . StTIC AN'O J. P. LUXKWi.BKH S T O O I1717 Fig. 9. Amphtbolc structure. gorite are included. In all cases, it is apparent that the composition differs very bom, thcJdcaUzcd composition ,bf Mg{SirO) (OH),. The impuritterwhich may be part of the crystal structure or due to assort*tcdmfnier*hr. most common impurity Is Iron. This can be in the form of ferrous fFe**) or (Fcv) Ions. It is generally assumed that the Fe* can be substituted for silicon in the silica sheets, and the Fcf* can be substituted for tlie magnesium in the bruciti' layer. The next most common Impurity In chrysotile is aluminum. Since aluminum can assume either tetrahedral or octahedral coordination it can be substituted in either the silica or brudtc layers. Other impurities*, generally found to be associated with chrysotile in lesser amounts than iron or tlrtmfnum, are calcium, chromium, nickel, manganese, sodium, and potassium. T1c ionic radii of the ions commonly associated with chrysotile are given in Table II. Since these ions vary considerably in sire, they can have an effect on tlm strains which exist in the chrysotile lAttkcLIons which are larger titan silicon and smaller than magnesium will tOfnd' tb telievu the Straln%WfafcfpIstitutrd in the respective layers. Aluminum Blit this requirement fttraHNwHir, since it is intermediate in size between silicon and magnesimn. larger than silicon so it will help relieve the slfain when substituted',&t' the silica layer. Ferrous iron in the hrudto layer will increase the strain because of TABLE II Io.vrc IlAr.ii kor Ki.emrxt Avoo.m hth Chrymuuc Element .X ! W*4 0.41 Mr" O.M Al*' O.M IV` o.;o tv*- O.lH NV iv(i*'<' n.;s 0 7S 0M .Mu'' c-.i- n.so n.r.tt ST0011717 ASBESTOS MIXKIIM.S IN MODKIW TKaiXOLOCY 175 ils larger size. Finally, it is improbable that the very brgo lon^ weh ns the .-I. alkali or alkaline earths, can truly be substituted to any significant extent in tbo brocite layer; and when present in appreciable quantities may exist as Inter* liyef* eatfont between the primary layers. Various authors have "normalized dwDiksl analyses of chrysotile, indicating the probable location of the impurity tons in the crystal structure. The chemical composition of the asbesttform amphlbolcs is mote complex ": than that of chrysotOo. The idealized chemical fonmalas Tor the various speciaa ~ - aro given below. In these formulas, when cations, are written la parentheses ' ~ without subscripts, a variable composition is indicated with the most abundant species first. CroodoIHe...............(X*TV*FV*)8Me<0ID, Amoit....................... (FV% M|)iSI/)a(OR)i Anthotthylfite...............(Mfc Fe^bSkOii(OH), 1Vnnte............................ 0*MstSWb{OII)j Actinofite...............................I**NSiOe(OH) The range of chemical analyses for these varieties of amphiboles are listed In Table Ilf. Detailed analyses can be found in various publications (17, 23, 32), SiOl MgO PM> r*Oi AhO, CaO k,o Na,0 1LO TABLE HI Chemical Couro*mox or .VtrannroMi Amphiboles* Aibcptiform amphlbolo (rang* %) Croeitlofite 49-53 0-3 13-20 17-90 0-0.2 0.3-2.7 0-0.4 4.0-S.5 2.4-4.5 A motile 49-53 t-7 34-44 -- -- -- 0-0 4 tr 2.5-4 5 Anlhophyilite 50-58 2S-34 3-12 0.5-1.5 -- -- ' -1.56.0 r Actinolita 51-50 15-20 5-15 o- 1.5-3 10-12 0-0.5 0.5-1.5 1.5-2.5 TremoUte 55-00 21-26 0-4 * 0-0.5 . 0-2.5 11-13 0-0.0 0-1.5 0.5-2.5 The considerable variation In composition which cma cxxor iSAUedfly noted. The actual identification of a particular amphibole species ma^^fejreijd Oh which ofh the idealized compositions the sample in question most cloody^represonts. This variability In composition is n direct consequence bf the facNfakt the structure can accommodate many different ions in the space between the siDon ribbons, and tho vnrinblo nature of the host rocks can contribute different Jons to this structure. Accessory Minerals The analysis of asbesliform minerals is often complicated by the fact that lire .... ^ of tho host rock and its associated minerals, nmi nfo that other m.Wrafs may 1* intimately lntcrt'm\vn in the i.i* r immllc*. ISTO O !7 IG STOO11718 176 s. asv ). \ i-KwcEwr.imn Contamination duo to host rock fragments Is common In comincrcinl fillers. Jn the cpe of chrysotile asbestos, tho most common contaminants nre tho other terpentine minerals- lizarditc and antigoritc. While tlicse species haw similar Over-all compositions, tlic trace element analyses could be influenced by their GO --I CD CD presence. Ot1rr minerals which are found in serpentino masses, and which could be found In commercial chrysotile fillers, trot magnetite, brueite, chromite, caJdte, magnesite, olivine, pyroxene, tremollte, actfnolite, chlorite, talc, and chalcedony. The proportions of these minerals will vary considerably with (ho CD location and nature of the deposit. For a specific commercial mine, the nature and content erf the impurities in the ore will be relatively constant. Neighboring deposits In the same serpentine belt may differ considerably in their impurities. Several good publications arc available (19, 27, 45) which describe the geology and mineralogy of tltc various chrysotlle producing areas. Other than lizarditc and anligprite, tho roost common minerals associated with . ehrvsotfle are inaDietite and brueite. Both of these species often are found fillip v* v* v m vim im\< iiimv * ^uowv* Using a combination of chemical dispersion and magnetic separation, the asbes tos was divided into fibrillar chrysotlle, serpentine, and magnetic concentrates. Ail of the chromium was found to be associated with the magnetite phnsc, most probably as an isomorphous substitute for ferric iron. When chromium appeared in the chrysotile or serpentine fractions, it was associated with the last traces of magnetite which were impossible to remove.' Most of the nickel in the ore is also found in the magnetic fraction. A. small amount may lc associated with tho magnetito, but the majority occurs as a separate phase. This phase is tire iron-nickel alloy, awnnittc, whoso composition ranges from FeNi_. to FeNi,. It can be separated by a differential solution method proposed by Nickel (49). Finally, a small amount of nickel, about 0.00S7, is found to be present in the chrysotile lattice, most probably as a substitute for magnesium. Organic Impurities The association of benzofo)pyrene and other organic impurities with nsbesti- form minerals from various sources was investigated by Jleimschussel (00) The total amount nr cxtnictnblo orgnnfe matter was determined by long-term Soshlct extraction with cyclohexane. After drying and weighing, the organic residue was analyzed for l>en*o(e)|>yrene by thin-layer chro:.,atoran!ifc techniques, ** 1 an and African elnysottles, cro: ruut.n'ned nvasur.ihh- antnunj*- ST0011719 4 *"' . i * at* ! AsmsiOS MIXI.lt \IA JN MCMHtnN 1l.rilNOt.OCY 177 of extractable organic malt<r, ranging from '10 lo ^00 ppm. iluic was, hots ever, no correlation between the amount of organic matter and the amount of benzo (fl)pyrcnc present. The Canadian and United States fibers (It chrysotilcs and one antlropliyllitc) contained no detectable l>cnzo(rt) pyrene. fbo detection limit varied with the amount and complexity of composition of tbc extracted organic matter. It wa as low as 0.02 pa its per billion and generally below 5 ppb. All of tbc flbcTS from Africa and Finland, on tlic other hand, did contain bcnzo(rt)pyrene. The highest concentration (150 parts per billion) was found in crocidotfte from the Cape Province, South Africa. Crocirlollte and nmosltc from tho Tmiwtud Province contained 12-1S ppb; Rhodesian clirysolllc and Finnish anthophyltilc contalnctl less tlum 10 ppb. These results are In general agreement with those reported by Harington (28) except that Harington found no bcnzo(a)pyrene in African chrysolilcs. The explanation of this difference may lie in the fact that Harington used virgin samples collected in the field, whereas RcimschusscI analyzed typical commer cial products. This could mean that at least some of the benzo (tr) pyrene is fntrodneed during the processing or shipping of the fiber. SURFACE CHARACTERISTICS Tho surface characteristics of the nsbestiform minerals arc very important in relation to their commercial uses and to their interaction with whatever cnvlronTi&nt they may be exposed to. Most of the discussion relates to chrysotile because the surface characteristics of the nsbestiform nmphibolc minerals have received much less attention. The external surface of chrysotile fillers consists of magnesium hydroxide nnd, therefore, it is not surprising that the fibers behave in some respects as though they were magnesium hydroxide. For example, Pundsack (53) determined that the pH of ft suspension of chrysotile in carbon dioxide-free distilled water is 10.33. This compares to a value of 10.37 for a magnesium hydroxide suspension under the same conditions. Pundsack nnd Peimschussc! also determined the "solubility product constants" for various chrysotile fibers (56). The vnlucs ranged from 1.0 X 10 " to 3 X 10 and correspond quite closely to a value of 1.9 X 10 M reported for magnesium hydroxide (04). Surface Charges The clcctrokinctic behavior of chrysotile is another manifestation of the mag nesium hydroxide surface. Martinez and Zuckor (42) studied the effect of pll on the surface charge, or /eta jxif initial. of aslrcstos ore Iiody minerals by the streaming potential method, figure 10 shows the complete pH vs zcla potential eurve obtained by these authors. They found the isoelectric point of chrysotile to l>c H.8. At lower pH values, tlie surface charge is positive; nlxivc tho iso electric point, the charge becomes negative. They attributed the sharp increase in potential which was obtained s,, ihc pH was lowered from 7 to 3 to removal of hydioxyl .groups frmn the surface and resultant espuMne of the magnesium ions. IMow pfl 3, the magnesium ions arc removed and the silica surface ex posed, accounting for (he <?, . ,,-an- in /. ta potential in this i.mgc. A'*' ST0 0 {1 7 2 0 ST0011720 178 (. SJXJL. ANJJ J. \ IJOXKWtBWI C/5 --I O CD ro The electrokmctic behavior of lizardite, also shown in Fig. 10, is significantly different from that of ebrysotile. it has an isoelectric point of 9.7 with a much smaller charge than chrysotile. Furthermore, the sharp rise in potential, between pi I 7 and 3, is not found. This would be in accord with the proposed undulating . structure in which l>oth silica and magnesium hydroxide surfaces are exposed.' . Chemically, the surface of the amphiboles is similar to that of silica^ It ili;. polar in nature, but not as highly polar as chrysolite. The electrokinetics is negative and smaller in magnitude than the positive charge of ebryitofiKg Isoelectric points have not been ss ell established, although It 1$ presumed the charge would become positive at very low pH. Most materials have a negative surface charge in aqueous systems. SlttCUv chrysotile has a positive charge, it will attract or be attracted to most dispersed^ materials. This characteristic or chrysotile manifests itself in many of thcoom-" mcrcinl applications. In addition, the highly reactive surface causes many Inters csting surface reactions to take place which arc intermediate botwecn tfmpl* adsorption and true chemical reaction. For the sake of better continuity, tboso interactions will Ik* discussed along with the chemical properties of the fiber*. Surface Area The specific sn.huv area or chrysotile nslxntlos ns determined by gas adsorp tion measurements has l.vn found to vaiy considerably with the physical con dition of the fillers. For example*, ]*uwls.ick (51) reported that jndling fiber* from a bhv-k of crude Jiflrey rhrysotifo fiber with tweeters gave products with surface nroLis, a <T ti-miMinl Ia* nliro^m adsorption, ran^fnj* fn>m 4 to ISmVS j i ST0011721 STOOI I 722 ASV5TOI Ml.vmiA IN MOUKIlN |3tSOLOCTf 179 dcpcndinj' on bow Ihorou^lily the liber* were pulled apart. When the fiber* were opened (urtlicr in a Wiley Mill, the comparable surface area was more .'r.-iipte than 30 Value* in of 30 mr/j were obtained when the fibers were '.IT . mdeed in an Aerosol OT solution to separate Individual fibrils. ^ Neumann and Dmher (48) studied the surface areas of various chrysotfle*'^: In more detail. They also found a considerable variation in surface area with the^ degree of fiber opening for most fibers. Tlic two exceptions were the diryJOtlb,,?a| from New Idria (Cbalmga) ami Stragari. In these cases, there was very little variation with the degree of opening. Theoretical surface areas of the chemically dispersed fibers calculated from measurements of fibril diameter distribution*--**, were in good agreement with the measured values, ns shown below. Fiber* from Obenrd SA Calculated SA Averaje fibril diameter Canadian Cr.uJo 7R Kmr Mrk 50 m'/j 7* mV* 45 m*/* 78 m'/* 375 Ji mk The autlion proposed, that for those fiber* whose surface areas arc sensitive to' the degree of opening, the voids between fibers are partially filled with solid; material, and llicrefore not accessible to nitrogen or other gases. In the case of';? the New Idria fibers, these intcrfibril voids arc available for adsorption. In either case, die futrafibril voids arc not available. Several workers (18, 48, SI) have attempted measurements of the pore-size r^^<fistributkm of various asbestos fibers, including chrysolite and amphibole*. The. methods have included water vapor adsorption, nitrogen adsorption, and mer- ' ^ cury penetration. Most nitrogen adsorption results show a peak in the vicinity of 20 A which has been interpreted as a measure of die radius of the pores within the fibrils. Harris (29), however, pointed out that this may be an artifact^ of the measuring method and is open to serious question; The surface area of amphibole asbestos is considerably lower than chry*otQ it docs not exhibit any unusual porosity. Patterson and TTiompson (52) reporter that sawn blocks of Witfenoom crocidolite have surface areas around 5m*/g^j This increases to between 7 and S on teasing fillers from the block. The fully, flberixed material had n value of M.8m*/g* Adsorption The adsorption of various materials on the surface of chiysotflo has been/ta studied from both the liquid and vapor states; Yotmg and Hcaly (84) studied? the adsorption of several vapors on chrysolite. They found that nitrogen. Argon, carbon monoxide, acetylene, n-bmnne, trimethyl nmfne, and dimethyl amino all: gave surface areas of 0.7 mVg on grade 7R Canadian fiber. Ammonia and water vapor, however, gave surface areas of 17.8 m'/g for the same sample. The difference could not be explained in terms of chemisorption or other specific interactions because ail the isotherms were completely reversible. Their con* elusion was that the extremely polar water owl ammonia molecules could bo adsorbed on portions of the surface which are not available to less polar molecule*. They further concluded that -nme of the pores in chrysolite may be ST0011722 ^*3 100 i i / 23 180 i. wkii. A\n j, r, ii:ink\vmwi plugged with water, am! that these plugs arc porutcahle lo polar vapor* only. Young and Ilcaly also )t|X)rlt (l a similar nnomotous sorplion of water vapor on antigoritc, a nonfibrous serpentine. Anthopliyllitc and trcinolitc, the only amphibolcs studied, did not exhibit this behavior. The adsorption of various organic compounds on chrysolile from both the liquid and vapor phases is currently being studied by Weeks awl Loineweber (75). The fiber used in this study was specially air cleaned to remove most of the nonfibrous material and extracted with carbon tetrachloride to remove or* ganic contaminants. Ethanol, benzene, and hexane all exhibit normal isotherms on chrysotile. The surface areas, estimated from the isotherms are ethanol, 18.8 m*/g; benzene, llJim'/g: and hexane, 9.0 ro'/g- Tire' nitrogen surface area is 21.2 m*/g- The corresponding heats of adsorption are ethanol, 13 keal/g; boaot^f cnc, 11 k'-al/g; and hexane 9 keal/g. Zcltlcmoycr el at (85), reporte<l 16 keal/g for the heal of adsorption of water on chrysotile. J Ihcsc adsorption data support the obvious premise that the polar surface of'-:;. ^ chrysotile has a greater affinity for polar molecules than for nonpolar, in gcmeraKs^~ agreement wflli the findings of Young and Ilealy. Adsorption from solution is complicated by the concurrent adsorption of sol of,wlvfnt,.making the interpretation of tbo isotherms quite difficult. We studied the following binary systems on the same liber -- adsorption studies: benzene-ethanol; benzcno-tcrt-butanol; benzene-naphthalene; benzene-anthracene; hexano-naplithal Typical adsorption isotherms obtnined from these systems are shown In ITg. ) These isotherms of concentration change are plots of the "apparent" or cnttal adsorption of the "solute" (the component whose concentration k catcd on the abscissa) ct. concentration. These concentration changes determined by means of a differential rcfractometcr. The extremes in the of isotherms obtnined arc illustrated by the benzene-ethanol system and' FC. 11. - tl fiction .oloto *t r Snrptimi of nrj;.infc on c1n>wl1r. ST0011723 aotts'ios Mixmui is Mom-.iis iM.usoi.ncr 131 ;`-*V hexanc-licnzcoe system. In llic former, the apparent adsorption of ethanol l* positive at lovr concentrations and negative at high concentrations, whereas fn the latter systematise apparent adsorption of hexane is negative throughout. A qualitative lalciptefation of these cfTccts is that the affinity of tlic surface for ethanol and beMMe arc csscntLilly equal, while benzene is more strongly atl* sorbed than.hdjpfifc^Thc affinity of the surface for the compoumls studied can be listed in ibe^tjipdpg decreasing order: - Leiueue > naphthalene > anthraeeno > hexane Quantitative* bfnmcCation of these Dthemis by the methods proposed by Kipling and T8^v (3S) was impossible because sufficient information was not available to be able to extract the individual isotherms. CHKMICAL CHARACTERISTICS Asbestos has often been touted as the "indestructible mineral.* In reality, this is far from the case. As far back as 18S5 (67) the reactivity of chrysolilo with acids was recognized and in 1S90 Clark and Schneider (16) found that chrysotile was the most susceptible to acid attack of all the serpentine minerals. Nagy and Bates (47) and Nagy (40) confirmed this conclusion with electron microscopic and X-ray diffraction studies on acid-treated chrysotile and antigoritc. After treatment with 1 x 1IC1 for 1 hour at 100C, the chrysotile X-ray diffraction pattern completely disappeared while that of antigoritc was relatively un changed. Electron micrographs of the reaction products showed that chrysotile was very severely etched and had lost its tubular morphology. Faust and Nagy (21, 22) studied the differential solubility of chrysotile and serpentine In more detail. They confirmed that chiysolifc is almost completely destroyer! in lx IIC1 for 1 hour at 95C, while antigoritc is almost untouched under the same condi tions. The reactivity of Ifznrdltc Is intermediate between that of chrysotilo and antigoritc. Badollct (2, 3) summarized tho available information on the stability of asbestifonn minerals. Strong acids decompose chrysolilo rapidly with the re moval of all MgO and a total weight loss of GOT. Tho residue which remains after acid attack consists of amorphous silica which retains a very fragile fibrous morphology. In contrast to the sensitivity of chrysotilo, the amphibclc fibers arc much more resistant to acids. Them are, howovor, significant dlfToroncct between these fil>eis. The data in Table IV shows that anthophyllitc, crocfdolfto, and tromolitc nro significantly more resistant to acid attack than nmosito and actinolito. Twenty-two days at room temperature had essentially tho samo effect as tho 2-hour reflux exposure. All of tho fibers were relatively stable in 2oX sodium hydroxido solutions. Hie high solubility of actinolito was attributed to Impurities in tho sample. Hiscock (33) more recently studied the rate of decomposition of asbestifonn fibers in lolling 4 k hydrochloric neid. No feuml tho following relative order of stability as shown in Fig. 12: Irrmotitr > nnl'iopliynife > -r..ci.?..rile > nctinolile > nm.Titr chrysolite oo -- 1 O CD PO `.laSSfe.-; ST0011724 182 s. am> ). r. ir.ixr.wr.tir.n TOO!I 725 After aw initial rapid weight loss, the rale of attack decreases radically with trcmolito and atilhophyllite showing extremely low rates. Recently Week* (74) studied the rate of decomposition of ehrysolilo fibers less than 1 ft In diameter in 0.12 n hydrochloric acid at 37C. Decomposition mas determined by analysis for magnesium which bad gono into solution. The decomposition is relatively slow under these conditions as shown in Fig. 13. The straight line indicate* that TAlthK iv Soi.uiui.m or AsnrsTOs Mivemis ix 75% Acip on Cactic* Clnysolite AhthojhyJ)ilr iVn* *Jrtc f.Yjmi'lnr**1 v.| Per cent loss In weight, refluxing 2 hours J1C1 CH,COOU ll.l-o. HtSO, N.Oll 45.GO 1.3? 12. M 2 CA .**1 at t 77 23.42 0.01 2.G3 O.CO 12. 1.00 . Jsi {* ' *! t M Ji*it7 55. ?8 4.37 11.07 3. If. ?n io 1 00 35.75 3.GO 11.35 2.73 20 3S 4 .VJ 0.00 1.35 8.07 1 0.25 t.SO JMl M. l .tl.l.;. ii .1 lOiIl-tin, April, IOM. A\ltl'j|*i' mi:. i mh !; m*i>i UN i * < 11 S'>1 nr:Y 1E3 STODI 1726 0 imo min)^ Fic. 13. Rcactian of chrysolite with 0.12 n IlCl VIC. the decomposition is diffusion controlled. This conclusion is justifiable because extraction of the magnesium from the chrysolite structure leaves a residue of silica through which both the acid and magnesium ions must diffuse for the decomposition to continue. It is also interesting to note that extrapolation to zero lime indicates an initial decomposition of approximately 6". This decomposition probably represents the immediate dissolution of the surface magnesium hydroxide. X-ray difTraetion analysis of the GJi-hour icac'ion product showed no difference from the original material in spite of the fact that it was more than 50iJ decomposed. The acid apparently attacks the surface1 of the fibrils leaving an unrcacted core which diffracts X-rays the same as chiysotile. This is in accord with tho observation that clirysotilc fibers can he readily fihrillizcd by agitation in weak acid. Electron micrographs of the reaction product show' an etched surface on typical clirysotilc tubes. The residual silica on these partially decomposed fibrils is probably re sponsible for this etched cfTcct. The very rapid initial reaction of the surface hydroxyls was also noted by Pundsnek (EG) during the stepwise titration of clirysotilc with 0.5X hydro chloric acid at I00C. Ample time was allowed for equilibrium to he attained *ftcr each increment of acid. The titration curve, Fig. I f, exhibits several in flection points. T1ic first mcmiM-iils of ncul con sc n s1>nrp tlccrcj.se in pTI from an initial value of 10 to about G.S. This point corresponds to the reaction of about 4.5% of the filler w ith acid. After the first inflection the curve levels off until nlioiit 67S of the fiber is reacted and finally tails off to a pTI of 2.3 as the reaction (s completed. Pundsack estimated that alwut 1Z of the total hydroxyls exist on the surface, and flint fir!* decomposition represents reaction of all the structural hydroxyls. The final .3-3'I reaction represents reaction with the .silica grl formed by lire process. The chemical reactivity of ciocidolite has b< en stndird in eoi.si.h r,,,| ST0011726 )K1 S M J M . \m ] r. m im.vvi STOOI I 727 Kj'-. 1 ). Titr.i!it >:i <f t l.i) .'utile*. by Thompson (CS) using films in the diameter range of 0.03 to 0.15/i. In a Soxhlcl extractor, w.iter nmoicd J. of the silica and G7 of the' sodium rons. These values con esp< ml l<i a dip'll of attack of 1 and lb imil cells, ri spec-lively. Similarly, in boiling alkali the attack is limited to the: surface layer. In 5 \ liydroclilo! ic acid at 100'C., ?0V of the structure is disrupted within 3 minutes, conresponding In a 57 A penetration. After 3 minutes, tin- rate drops rapidly with less (h.m twice the aho\<- p-r-nctration ; ftcr G horns, agreeing generally with lliseoek's findings (13). Thompson proposed tli.il the foimation of a tough floating of pub ,n i i .! si! ea pmtic-ts the crystals from further attack. This hypothesis is .supposed b) tin- fad that the fillers are again susceptible to acid attack if the sili< a I.ijei i> ie.-nosed by leuclinu willi alkali. In the pn '-t net- of O il \ JiUTA at pll m3 and 100'C, lire late of decomposition of the fiber appears to be cliflusicn cmitmlled. In this case at least a portion of the silic a Ik comes dispeim d in tbe n action ntedium. Thompson concluded that the amphiholc slimline is not inti iie-ic alls lesblant to acid attack, 'the nppnrent reset.mr-e is a imnlt of the piot.-ctim, avoided by the silica layer. The lesser resistance of annule to at id attack can possibly be attributed to faults in the structure. 3 he n sist mes of the us!k stifor: mitmals to attack by reagents other tlnn acids is p.i nc lulls consult n il excellent at temperatures up to 100'C, blit dc- teiiorates rapidly at higher It mpe lafmcv Jkdl and Taylur (G) studied the re actions of cht)so!ile with .usual materials under hydrothermal condition-:. lb cent studies by Vang (S3) indicate that reaction between cluysotile and caleinin bydjo.id<- is T*(< t.iblr in 2 dues at ?aOnC. Similarly I'riniw bussed (GO) hum.! cfnssii'ile was crimp!. ! K decomposed in (oiif-rnli.i!. J potassium h) it>.i\.<!.- .1! ?()') ('. w ,l!n,. 'I h'KMs 1 limit;!-:,.! (f'l) slum eel that Cto Molite is nit -r ' r im t . |, w ! 0! T ( ' ,m I Si, e ' >>!.. tl--M I ... , I'n I- ; c . ' . f t. b I- m - . . ' : . .. V . I. .-f . ,1 . Is f i !. i \ - .111.1 ,is! - i s1.1. . 1 .' ! :. --: . !;. i:'. . - |) ST0011727 STOOI172 .\Sr.lNlC>> \ll\l i:\IN IN Mwl>l lt\ 185 demonstrated lint fatly acid; ;'.d other weak organic acids when dissolved ill nonarpicous solvents icat t with tin* filter mu face In fuini a monmnulei nfar "chemisorbed' layer, 'Ilie ;init of (hi'ii\isorl>cil arid is afFeited by the |)ic5cncc of sorlrcd water on the filter. `1 Iiis is illustrated below. Ciiriiij'jiirTKiv or Oi uc Ac;o i hum Hcmiak bt CMiti.">Tii.t Filer coruliiit'itrtl for IS 'hi*iu at is:c 20% mi 100% rh Mj, acid forbcvl/g, filter 10.8 7.4 0.5 Equilibrium in these reactions is established very rapidly, probably within seconds. It was also noted that above a concentration of 0.003 moles of oleic ftrid/kg of benzene, the amount of acid chemisorbed by the fiber is constant and has a value of about \"< by weight of the fiber. This value could vary with the exposed surface area of the fiber. Even after 15 extractions wTh hot benzene, 803 ot more of the original oleic acid remains fixed '!n the filter surface. Fiber which contains chemisorbed fatly acid is somewhat hydrophobic and markedly orgnnophillic. 'Hie h) drophobic diameter of the fiber is of a limited nature, since the fiber can he wet by vigorous stirring in water. Jn general, organic compov'tions possessing acidic functional groups dissolved In nonpolar or slightly polar sob cuts, such as benzene and methyl ethyl ketone, exhibit a strong tendency either to chemisorb or to slowly react with ebrysotile. f.ongchnin aliphatic acids, such as . fraric acid, oleic .acid, and palmitic acid, arc chemisorbed by div filter. Atoma'ic-lypc acids, such as benzoic acid and related compounds, arc also cheiuisorb',d as are dibasic aliphatic acids, such as adipic acid. Although die uns.i'.urated six-carbon sorbic acid appears to bo chemisorbed by' ebrysotile, die related shorter carbon chain acrylic, crotonic acids show some evidence of slow reaction with the dry ebrysotile even in non polar solvents and there is a tendi ncy for die adsorbed layer to show* an affinity for water. Maleic acid reacts w illi die bulk fiber. If the fiber contains rubni!u d water, the interaction of an organic acid in benzene or MFK solutions differs maikt.illy from that with the dry fiber. The long chain aliphatic acids, e g., stearic, oleic, when dissolved in nonpolar or slightly polar solvents, show little or no tendency to sorb on fibers containing adsorbed water. Acids such ns adipic, benzoic or sorbic, which have some slight affinity for water, tenet with the hulk fiber structure instead of chemisorbing ns they do on dry fibers. The reaction of cluysotilc with certain anionic wetting agents, such as Aerosol Ol, is peculiar m that they cause the fiber bundles to separate into ultimate fibrils. This reaction is accompanied by strong chrmisoqrtiun of tho agents with permanent modification of the suifaec (51). ttlien cluysotilc filler is decomposed by strong l.ydrochloric acid in the prescnee of chtorotrimethyl silane (21) a very interesting reaction oocmx. Normally die decomposition by acid leaves a le i.lue of amorphous .silica which polymer! ' i. - *<.. JjSfaSSffiTrt 'tj ST0011728 STOOI 1729 186 g. trui. axp j. r. unoiwmn Izc* in Jhc shape of (lie original fiber. The chJoreMmdbyl sHiM^ bowc^l with tho siUca sliect as the magncsfnm is removed and prevents further ~ crizaUon of the silica. The final prodoct of Ibo resctioft ii iA elTjct sn sHteoa potyiner in sheet form. The sheets am wBad:lBle.lwBwr?toj exhibit typical dtij-sotile morphology show a;J5A spocing between the layers r tho jwljnws swells and the X-ray (MiacUoe'jptUeM thotutabr sheet? fr rnrofled. ThlrprocfcsctfsfW----- w,, the baafcr cbrysotilc structure is a spiral mther dam a closed CMWilrfb Reaction with Water In addition to being vulnerable to attack by . cuinstances alkalies, asbestos fillers are also suhfaet to at cbnrsotfle with water, has;been: studtedbir/Holtftgtct1 IliMNMtoQtaW jmtyhwao: ebrysotfle decomposcdby tow 6f ihagrtesltfai tens 1 1 silica. lie oho suggested that the colloidal silica is I s results confirm that chrysotile ft decomposed by waC ^^vJdund that the concentration of magnesium in tho extract was relative^ ^ during the first 3-d hours of Soxhlet extraction ind thm bOgaiKto dc decrease fin magnesium concentration was precipitate of amorphous magnesium silicate^Aftcrlhe iftftfidnipid' magnesium and silica arc removed In amounts proportional to the composition. Whether (lie removal of silica proceeds bjr way of the-formation of colloidal silica Is yet to be>determlood. .TheroJ that efirysoldc b slowly `'solabW^Sfcev extraction. For crocidoh'te, Thompson (6S) ieported flat-ftl sodlwn are removed by Soxlilct extraction with watctl' was equivalent to that of alkalies at corresponding - ` :\v* snmuts^? ftfri-'ww-Wsf'" - ' * Chryaotif* kj: :& Numerous Investigators have studied the synthesis of chiyaotAe fi tine minerals. Tlicso studies were motivated cft&efct or by the desire to grow large synthetic crystah. lt tH.___ ^________ tile was synlliesircd as early as 1927 (31) but before the j microscopy and sophisticated X-ray dilTrnrfkm techniques, ft was *w to distinguish among the minerals of the serpentine group. The roc*w3 lire chemical analysis of the unction products mafcltcd ttat of not be considered distinctly diagnostic for chrysotile. Chrysntite has Ik-co synthesized only under Ikydtoihcmtal^fOtM^tO^ ' *-- v--'w- -- - STOO11729 -wv-" r ' *,< s 'J.$-,r-^ ` ;. ASBESTOS MDiDIMt W MOMCBK HOWOWCtS .-$pr naSte' HI tlW pCOOSM QSTOUn^. ttof^Hiid tUtjr (03) canted tort tine-minerals with magnesium toherJ6M.RepIaccnwttof product which wm either ptetjr or ^(ho pwe-wo ot sodium chloride hteti* .iiwdbnjnfe^ (host*** the tetrahedml layer by subrtRutfcg^sflteoi^vrtth genrtanfuirr resulted; fapenifoe nhenl which formed partial substitution of aluminum fabothhryeir yielded-platy "ftlurofmmfc ie!^ pentlneT (Mg*AI)(AlSf>0,,)(OII)i. ArKJthcrserpcnthiephase was afioiyn*: . thesized from nickel and gennanium Ni,Cc,0(0II), which also had a pWj structure. It was not possible to produce serpentine-typo pluses substRvt&g^^ manganese, zinc, cobalt, iron, chromium, or gallium for magnesium. Thts,iiOin^ ^ ever, docs not preclude the possibility of tn>QO amounts of these ions b present In natural or synthetic materials. The authors concluded that the fol structure of chrysotile is not only a consequence of the ion sizes, bat external influences ns well. AmpltlMer - The amphibolc minerals can be synthesized by efther pjrrogenic or thermal methods. Recent studies nt the Institute for SQicat&rCbembtiy^ grad, arc probably the most comprehensive In this CoId."AmphIboIes cori fluorine substituted for hydroxyl were produced by hcatftjga mixtureoft and fluorides to 000-1100*0 in tightly closed pinthrum Orccrarolc vuneft The mineral phase and the morphologic cha^iswffii|E^ on the composition of the initial mixtures, th#? __ turn. The fsomorphous series of fibrous flooro-amphiboleS; included a wide?; variety of cations comprising a mixture Ttr1' flftldhtf plus Cither Mg'% Fc'*, Cr1*, Cu'% Co, NP\ Mn\ or CH*BVIthJi* the reaettoo ^ mix, crystals of 0.5-1.0 m.n in length, amt 0.1-2.0 * ht diameter were fbmred with crystals ns long as 20 mm on the surface of tho reaction mesa..The physical.. properties of the synthetic flttoroamphiboles were stated h> be superior TO the best natural varldlrs with temilo strength of 20,000-/0,000 Ig/on*. Thermal decomposition did not occur until the temperature exceeded 000*C. Hydroxy amphiholes containing combinations of NTa or Ca plus cither Mg* ST0011730 trt'- S. SPKIL. ANO J. I*. I.WNKWWIKn "ft***' Nj'or KP* were formed under hydrothermal conditions (39). litkms were 35CW300*C with pressures ranging from 300-2 times of 6 bona to 3 days, filers ns Jong ns 4 mm were o __ s ranging from 0.1-1.0,u The hydrothermal fillers wore too _ > tliefr njccjionical properties. Their thermal stability was of tlie onle^rwgnil wle ns the natural materials. PHYSICAL I'ROPliUTItiS Ti strength Is used primarily as n reinforcing fil>cr. Its tensile strength is, tls fore, of prime significance. Tire measurement of tensile properties is compF by the combination of short length and small diameters resulting in a wide i of values from the same type of fiber as reported by Badollct (2). Zukos and Coze (86) sliowcd a strong dependence of strength on fiber length maximum values of 61,000 Jcg/cin* and 58,000 kg/cm* for notidol ito and rIfle^ropectivcly, with a fiber length of approximately 2 mm. Motion .^showed that fiber failure nonnally occurred by rupture of weak lute ,.j bonds, rather than true tensile failure of a fiber. Using a newly developed (ensile machine, comparable data were obtained by Borman on n vnrief ; asbestos /Hkt* 4 mm long and 10-20 n fn diameter (33). Crocklolitc and chr tile hod the greatest strength followed closely by amosftc, with the amphihoVs significantly weaker. More recent work by Bunnan (13) in Tat TAm.K V PnvatCAi. Pcoi'KKrn.s or Attr.<mutni Mi\kk\ia Ort Nunptr* Tcnriie ttrcnglu (X10\ kt/em*) Chrysolite, Arhmut, U.R.A. Chry**tib, Thothmi, Cnimdn Crocklolllc, Korfyi*, Cm* Provider CrocMlolltc, Cnpe Province Crodslnfile, Poinfrvt, Cnjw Province Crocidulilc, Pumfret, Cnj* Province Croeiditlite, CMhilnnilju, Holivi.v Amobile, PttiRc, Transvaal Airvwitr, Pcnur, Tniti*vi:(l AlilltoithyUilc, Pintkilln, l'lnlatwl 3*.5 37.1 20 0 31.3 47.3 30 2 117 20.3 20.2 23 0 Yourif* modulus (XIO* kB/crn*) 1.43 1.40 l.ftd 1.54 1.72 1.78 1.73 1.40' 1.40 1.50 A\Tmee ardloiMl if fibon i (XI0"r a.orfl C/> 2.13 o l.CSf.J CD 1.38 _ l.M -e'-g _ --J 2 43 CO 2.71 ^ -- t.tt 0.05 <JgK&v** costs doubt on the validity of assigning specific tensile strength values to asbestiform mineral, although the same relative order is maintained. Alt appear to have strengths Jess than tl.e theorcliral value of over IfO.OOO attributable to silieate chain strurtuics. The fact that chrysolile and ; tbe nmpbiboles give so nearly tjir same values lias Jed Uliittnkcr (77) to that tlte fiU-r strength is affected more by the iTyvlal Imperfection* tut during fihc i formation rath r by (hc atomic arrangement nr sfri ST0011731 ST00 I 1732 ASHKSTOS MINriMIJ IX MOOWtX 'mnivucoor ISO consistent with the hypothec!* thnt ninphibotc fillers nrc built crystallites held together by II--O--II coordinate linkages or `orces. Clirysotilc fibers, on the other hand, are bundles of fundarelatively constant diameter, but varying length. The difference chrysolites is best exemplified by* Coalingn fiber (Kig. IS) consist of overlapping fibrils approximately 0.5-2 n long V and Jeffrey chrysolite which has long individual fibrils can also explain the gradual time-dependent loss in strength . Vv ^ /> *] r V- i^V:?-,V4 ,v , f\ . rfl-' .s// /*>c'' , 'V- 0\ N A" /w -<v; -'"tv Y sfZ WZWm-. ; ,. .0/ >> . .'/ , A-, .. /V?'- .^Z /'-fZsrk fry,;./ ' (- '/yf i,/ ... Ls-/ io .vA'7*- .. '' lV** \ 1 `;v- '>/ /!/ ' f> \ -- - 7 r 1 I Fir.. I.'S. Fkttrnn imVir-r.ipti of mating.) dir).<oli!o. XG000. ' '/** -3* - re- K. ST0011732 J90 s. si'iji- and j. r. i Ki.M WtJim e c l11oois of Asbestos. /iF>ors with increasing temperature 1>clow the decomposition tem perature of the crystal. Small loss-s of water in tbo early stages oT dehydration for both c-Tiryvotilc: nml amphiholcs are probably associated with reducird edge wise bonding between tin- fibrils nr ciyst.dfitci comprising the asbestos fibers, resulting in redured "tensile Mi< ngth"' of the fiber. U ttrxhnrti *1 be fein> `"li.nslniess i-, 11 T.r < 1 to tin- flexural modulus of the rislicMifmni fl..... ' I ' . II. `............................................ ............. I' I* M .. . .11. I 1 1 1 , i . ` " .* ................... * !> .-sm: ST0011733 AUCTRS MiM IULt IN MOW.BX Tit ILS'OI.OCt 101 even in the finest fiber* shown in llc electron micrograph of Fig. 1" Although most chrysotde fibers art* soft, scmihnrsh fibers are also commercially available. Ihnh rhiysotiie is not usually commercially significant The difference in the appearance of fiber, masses is well illustrated bv tftc photomicrogrspl* of Figs. lSandl. IbnhcJIbm yield an open, bulky, fost'filterfng mass* Flexible soft.fibers form stringy, dense- manes with slow' filtration characteristics. This-specifier at* '> .i.*****~fc`.-1 . *' . < -?. STOOII 734 Htc. )7. Klcvifon imcrri';i ij,it >,' ST0011734 )92 (ft a. amc A?*o j. Pr uowiovnwMt --rrvi ^ ** ./T'**? rH-ii'r-< -./I > /'* . V 4. * : , `-V : iV^." r,\ ^ <*" V; Hk >#:# --'TJT*** " " ''-v "}'; : --'Aw-:.' /./.\>. *x.. 'iTM. -y& wN.' . .* .. / 'VV V% /V / - `-V. "b` . .'U ' 'j V > V" V :- ** . ^ v:*vw<r^it-x-v./vsy:^. 'V v' -V* .-'.*\ vjS*v:.:. ... ,.. 4;r.*'< > S.*- /....V . - xs.'-sv.; , *.,. K* V- s\ f,`/^sr* ; vv/c .- />i - V* ' >v\\*S-V V , ;I. **' ,,y ' y* .; -* '* *^- ' -n v- i * *-j < vv. , *>. * .v .sl.tfjY ' . M * , ' ,,... m J':f: ,.. : v&., >:-.>.;V\-.U..^;t%.l -::,.v^*>:>-!*.-?/-.a.- eG//4^3y % y- ... M -;r =>Ay >U: \ it. v*' ";-y. 7'. . 1 `-^v .> V| '-'-v - c# ryr>* '-;r > \\V/ is.:'... :vvw',-'. Via. 18. Soft dir>iotllc. XI50. . tribute of aoft clirj-jotflc is often a serious nfques cmpIo>*cri in iKe ntnnufActtiro of jwbcstos-ccmefit jw>docts. ebrysotile fibers, u lien economically available, or crocidolfte con plaec soft chryjotilc to improve filtniffon. Clicmical techniques rrmy nl be used to nccomplish the same objective either by adding polyclectrolytcs (l)for bjr ' treating the fil*`r w:l Mxlium lilimtv (58). :- ConsldcraMe rv'senrih h.tv Ihcii desoted to correlate harrimess mental jihysir-.d or ehi inir.il f.ulnnc. N\'o<xlri>ofr (SO) has indicated a reTatfon- ^hin wet. it.r. <_ ; ,IK. in liiu* with this, Ibhlnllct ambiStlOlb ' . .' ># . # STOOI1735 ST0011735 .% 11 i . i'% *}>;**.% i (*.'i ,i *fV i 03 <) a\e jvit'-uti-il .1 (i < hin'.pie for in'.-rcasing the !i.n dmtvs of ihryj'otilc Ijy Qnvli calcining in (fir i.inge t>f f> drive i>lf part of ihe chemically min* Iiliicd seat* r More recently, !~iw'tf .-mil Kerr (37) have indicat'd a correlation ft'illi fine mineral Intergron Ihs In Ilie bundles of fibrili comprising thry.otllc. Another hjpothesis is lb.it harshness is related to the relative contents of the two crystallographic forms, clino-chrysolite and ortho chrysotile in the fiber from specific source (Whittaker and Zussmnn (77)). ""V V iA*, *4 'P >. f /f '// ' / / ' v:v a - */ f[ /* \ V* f.i. ) t . tI II 'l -jr- 7t ra U! / * ; \i >;' i s' X.f; ,'S*.* .*. \ \\ s. h\'.' *.vv- r.; -- , ,r- ' ,-r ->*>' J , ' .^ * ./Vt" X s. e. , />V*\ .V s' s' > t -1I. * * * v-..J..:i. ' - i , ` ' ^ \- [ : % * // f,v >/ / ->* >, /V ' V r z' ;.r` . j - > r-x'-- i / 'iljl;i ' ( !>. 'i! - V. , \ v'v: |:v [ ''St I i \V i .i . * - -^c ' . . .t vI\ \ *1 - -' fI//;// v- -7 ' ...... rM<.A^ i ?. 1 V '// ; w--.-w > --^ICO J-V.. I'J. tlnrtir cnryjo*iie. X i' f STOOII 736 ST0011736 ID I . cmi. anit j. r. u:iNKWiiiM-;u Thermal Decomposition Asbestos minerals, despite their relatively high fusion temperature, arc ^ plctcly decomposed nl temperatures of 1000C or lower, depending on mineral species. __ -r i} The course of the thermal decomposition can be followed by three dilFeran^ - ' but interrelated techniques: differential thermal annlysis (DTA), llicnr metric analysis (TGA), and static dehydration. The actual decomposition phenomena in nmpliiboles are extremely ealed and depeml on the type of atmosphere and particularly on the amphtbolc involved. Typical curves for the l>chavior of crocidolitc in rfrj given in Fig. 20 from Hodgson (33). Tire first chemical change, cortc - .1fttir -no*, v:. STOO I 1737 500 *00 TOO Temperature (*C) too iio Fie. 20. Tlirnn.il analyse* of cvocidolitc in oxygen. to nn apparent loss of water, occurs at 420t>G with .the final dccomposi the nmphiliolo into a pyroxene mineral, cristohalitc, nnd iron oxide occur__ 900C. Tin's water is formed by migration of protons which arc oxidized atJ surface by oxygen in the air. 'flic other amphiholcr lose water primarily by condensation of hydroxy? Oxidation of divalent iron has a profound effect on the thermal bchnviu.,.,^,., these minerals and this becomes very evident by comparing the reactions hiafe and in nn Inert atmosphere Noth the drhydroxylntfon temperature and d00*^' jKisilton tempor.it.i^e appear to Jnmnso with Inere.ised MgO content In the- different amphfhnlc species. Ihidgsnn (32) gave a d, t,dice! experimental an^ theoretical review of these phenomena, which include loss of pin xicv.Uy i.iovd o.... :..,s of vl...........? m: ,.l I... ,l,1........................................................... ,,t,J, decomposition products. T iiesc thermal iin.rhxis fe* hmVpu k Jem- proved ppr ST0011737 m MINWVW.S IN' MOM'UN I M;>IN*I.OCV m t categorizing amphilnilc snnples front different locales. 1 or rociJolilc exhibits characteristics of loth nnlliopliyllHo and Transvaal species is often an Intimate mixture of cjtjcUIo- of duysotilc is ntueft simpler and independent of at omic heating conditions (l>TA), clcUyc1roxylntk.it occurs MC with formation of forstcrite and silica, about SI0*0, as i*static deliydmlion experiments, tbc initial water loss below I S i_____t -- -J------------ too >00 500 400 509 #00 teWPt*ATWU Km, 21. Thermal tfrtiTyi 800 900 1000 :j\C--v: 500C is time-dependent with no dc tcctablttrcitange in the X-ray diffraction pattern (J2, SO). Martinez. (*fl) lias summarized tbc various theories for the atomic rearrangement during tbc dehydration and formation of forstorfln. llio i , simplest approach to describing the decomposition above 500C (static) Is to consider it as a three-step process: tbc solid residue of the first step ( <000*0) Is a slightly hydrated amorphous magnesium silicate with n minor amount of poorly crystallized forstcrite. Tin's is followed by the formation of well-crystal lized forstcrite with some residual amorphous material at COO-fOOtFC, Finally, beating above t JOlFC yields a mixture of cnslalile and forslcrite. This generalized sellerne has been confirmed by comparisons of Infrared spectra of licntix! cbrysotile with those of mixtures of pure synthetic minerals (01). Many investigators have studied the thermal deesimposition of clnysotile OO --I o o from a wide variety nf sources, and all have Ihtii found to yield essentially the same DTA curves. Recent studies with nil extremely sensitive dul'out |)fffcrcntial Thermal .\nafyzer have disclosed significant differencs .< botwr'co fiber from cfifTcrent sources. For many chrysofiles, the 6o0 dehydruxylation peak is CO CO realty a doublet (.TJ). Tin's doublet phenomenon m -u ft-'1 ..... ]. Mr,.-. STOO11738 I*J0 S. MT.lt. ANI) J. I*. I.UM.WI Ill'.H tinr/ ( iOJ in a mixture of l\\o sampV i of the same fiber which lt.ul joclcd to different degrees of intensive grinding. The dependence of d'lt at ion temperature on particle size in tin.* analogous mineral kaolinitc retried by Spoil (fifl). It lias not yd bent determined whether theso ol*>cived doublet peals in specific chrysolites correspond to two fiber* populations or to some other phenomenon. ..U'.fc; Mechanical Disintegration l'or cfTcdivc reinforcement, the astioslifoim mineral should Ixi the degree required by the specific application. Mechanical milling is the Ikisic inelhod of fil>eiizing oslxrstos minerals. Ideally, the fiber' should be opened without reducing the fiber length. In practice, llic shoi toned to a degree controlled not only by the severity of the action, but even more, by the brittleness or harshness of the mineral,., ehrysotilcs show minimum length disintegration during Opening wh same mechanical attrition, the semiharsh and harsh clnysolilcs arc significantly, Amphiboles are even more susceptible to length at mechanical impact, and are usually given their final opening by the.; ^'^';>^'Ot>muincr, often in the actual mixing or processing operations. Normally as the fillers become more open, the additional energy for further opening increases rapidly, imposing a practical limit on the; of subdivision attainable in commercial milled products. Recently, W grinding tests with an intensive dry grinder1 showed that it is possible t destroy the structure of chrysolite so that it is no longer identifiable X-ray diffraction or by the electron micrograph of big. 93, (CO). Jeffrey healed to TCXTC for t boor jtelds an amoqihous material with exactly appearance when viewed by the electron microscope. Ill is suggests^' changes observed will intensive grinding were actually caused by localized temperature surges in a fibril as it alrsorlcd the tremend energy. To substantiate this hypothesis, chrysolite was subjected to dry ball milling which yielded a similar appearing amorphous mass. \V< which precluded the possibility of attaining localized high temporal duecd short ultimate fibrils which maintained their crystalline fo easily identifiable as ebrysotile. These observations have been used to explain the result* of cont wear tests peiTomucl at the Jolms-Manville Hosearch ami Knginccring^ (Go). Wear dust was collected from passenger car brake linings subj series of stops simulating normal traffic and highway driving. Afrl and debris in the brake drams were collected separately and analyzed The composition of the inorganic fraction of these residues matched original brake lining wlrieh contained a total of 707 chrysotile. No was oliscrvable in the wc.tr <lust by tidier X-ray or optical microsixipy. Iron mic rograph of (be du<t |% slam n in ITg. ?.:l. The .vscmhk.mv 1**1 w and ebrysotile, which bad been an thanically (mid, pr*Mimahly, tl * S'P"1 Mis- ./Mill. ..I II,Ilf.,, fir. .1 t.y S(>. x I. i. tn.li m Xcw Jersey OSS If). |r,,-. avno I'.rl. \\,Mlrr y ' oo --I o CD OJ CD ST0011739 S T 0 0 I1740 ASIU-MOS MINKH.MS IN' -irCHN'OUJCr m 1 l1-. I' <> -t I# " l** 4 *> * '? tr */ i 0. .. H ' k' * * n <r s' I A c> 0 .o .* * , n t t o' * o At *K* _* * * <i V *i * . b*. '.'.-cyr.-J.'.V. ^- i V -J.. f \ ' - -* * . ; | c -3 (!ccom(imn), is Apparent. Despile llw facl tint tltcnnocotipje measumnents of the brake drum temperature did not exceed 273*C, [hwnstle>TwltnlHorn ftxHented (hat the temperatures at localized point* of contact^exceeded 1000*Cl Minute fraj'incnts of clirvsolilc fibrils could be observed in someol the electron micrographs and a modified point count technique svas devised to determine the chrysotile content. Conservative estimates of tin; chrysotile content by this method showed th.it more than OSf of die chrysotilc i destroyed during ikxiimiI hmke-usnjje. Similar studies by the U-S. Public Health Se*rvoc substantiated these results for normal drivim; conditions (3S). ST0011740 STOO!1741. Fin. 2X Klcclmn rmcrogruph of brake ftaibf Aot * IDKNTIFICATION Tho positive idcntinr.ition of the nslxrstlform mfnetah highly impendent upon such factors as the physical form* the presence of contaminants, prior mechanical, tlicrmal or chemical treatment. The variable nature of tins nmphiholes makes it necessary' to classify a particular sample as "most closely re sembling" a specific mineral species. It is obvious that, even if sufficient material is available, simple chemical anal ysis is not sufficient to characterize an asbestiform mineral lxxnwse nil asbesth form mineral* haw massive rmmterparts with the same ehcmicol compositionr I ST0011741 r** I.-v. -g-ey A)M31M MIMHAI.S IN MCHHUtN UCCIINOLOCY i One must, therefore, rely on a combination of molliods. Ilio ihclliods most fro* qncnlly used arc thcmk.il analysis, petrographic microscopy, X-ray clifTrod*on, electron microscopy, electron diffraction, and differential thermal analy Is. co Perhaps the most reliable method of identification for particles down to a few microns fn diameter fs petrographic microscopy. Using this technique, tl*B Ubroos nature of tlic species is evident and the .optica! properties con be used to a CD determine which species 1s present Among the amphibolcs however, the vari able composition may also effect the optical properties, to that again posf&tot . fdentificatfov-inay be difficult In such casc*,iX-ray diffraction and chemical '*ahalyab br DTA can be used for confthnatio&^'^y:'- ro Jr the size b below (lie pmctical 'WOrldttgeBm^ microscopy, . election microscope is the proper tooiTWs tatrttocttt*^ bout the shae and shape so that posittve id^atlsfiitlon informations$ speciBe amphibolcs. The tatmlrnpfcaM microscope is specific. WTicn elc<irOT d!ffractld^ bscxl Iron microscopy a lictler, but tof" arapIflWifei#/?-.. is possible. iT Tlic electron miemprobe is a relatively recerit^dcvelopinent which Is proving of great value for the characterization of -sntall^moants. of. material. With this., instrument ft fs possible to obtain a complete chemical analysts on a particle as small os I f. It is nlso possible to study the same particles with both (lie electron microprobe and the electron microscope, thus molting a more complete chnmctcri'/nlion possible. Table VI Is a listing of the properties of the asbcsUlbim minerals used for* their characterization. * " SOURCES OF FIBER S Ilcmlry (30) at the JC63 Conference on HioTogfc Effeeb df Asbestoa sdW^^'V marized the pertinent aspects of the occurrcrico, pitxTrtCtl6ili'flnd commeretot'^?; applications of asbestos fiber. j .; Table VII presents the world production of robestro Iri^Kff (<43). Prod4e^%*^ lion has increased with few changes fn the relative standTriM of the nroduefnjr countries. The major difference is the great incrense fri nussian production which now * outranks Canada ns the major producer. The Increased jgwNddHftlttbto ll United ' ' Stales over lire past few years is due to the redout development of tile Coating* fiber deposits in California. One important change sincT90(^h the dosingsof the Australian crocfdolite mines and the eHmihatfon of TiMS tomre from (he market. Thus, South Africa remains ns the one significant area producing crocidolitc and nmcsitc. Chrysolite accounts for approximately 03Z of commercial asbestos. Chrysolite asbestos from Quc!>cc Is available tn more than 5D standntd or specialized grades to meet specific requirements. Some 6f tho larger asbestos mtlH, such ns that of Che Jeffrey mine fn Asbestos, Quebec, prodi.ee many of these grades slimd* tnnromle by n complex system of continuous crushing, screening, nnd aspiration from the smne mill food materia!. ST0011742 200 I II 3. srKJf. AND J. P. IJJXMVKni'lt .ski .s*< * - - SSF^fcSSS 3 5. 5 1MX ro. 5 ** <?. 3 2 fm * o 5 p M si ^5 a 2 a .3 in7 71 < * *! I ao s5 fri *2 8 J*< ss?sw- s2i`SJ: ?. ^ lb 8 OK Nm l*- 1 .....s..s......e3s I e8* w 1 **4i&s| ^ 4 t) SS23 2 ? o c. r* O 9 * 9 . O fi V all I m p; o iJ SX.o0 I 1743 ST0011743 )lirMOS MIXUlMJ IN MOlnnS HI.IIXWOCY 201 CO TAHfi: VII r(ntir>:ruN or A-m.-iv* in lOCft O CO Count!/ North , CariMiU (mfon) SUtM (rlktpnamtn) SmiIi Aikim AqnrtiM Bolivia fespncft) Braid Ptnnpo Amtiit Bnlpm Finhiwf Prance Greece JUJy Tortnc*! tr* U-S.S.R. YuforUvi* Africa l Botswana Krnya 'Mors mLi<(tie nh<xkis, ,'v.uihem South Africa, Republic of Swaailand United Arab RctmbJic (Rfa'l'1) Aim China I Cjrjina l I India Japan Korea, South PfciMipmee Taiwan Turkey Oceania i- Ami rafta New Zmhnrf TVorW Total* No. of ibirt lofit 1,479,2*1 I2S.9K 740* 4 two 1130* 13,250 7720* 85* w.iot 10 I,872,fW Mil sso* 73 173,000* 270,307 36,112 2057 140,000* 21,449 7616 17,067 OCT 721 I2 13,472 4^57,000 / --I 4-~ ... - >' tur.v..-``T'-V ; J^l: ' i; ' "flo* * 1'npuftJbhc*! ilnta coiv>l<1<-rcil to bo u-IiaMo (not front Mbveraln Yearbook). AH fibers from Quebec are classified by a standardised system which, with sonic modifications, forms the basis for other classification systems in uso througfiout t!c world. TIc longest fibers are Croups I and 2, with fiber lengtlw of over X in. and from !S to X in., respectively. Tlicse consist of hand-selected crossvcfn fiticr and arc termed "crude" asbestos grades since they arc normally given final preparation by the ultimate user. Cioups 3 through 7 are classified as "milled" filler with decreasin'; fiber length, ns measured by die Qucliec Standard Cor.-...i Tr<.t (iT)). I'nr li t'loup is fin .`her subdivided Into a mnnlier of sub- '.j ST0011744 S T 0 0 I1745 2**2 S. *. ANO'J. f. UaNKWIOMW- gnalr* according to their "cmJlucWy'* eootmt of bulking. A* and plwir])(l>Ki [m^xirtlcs. Subgnop^ f!bon- front different souroi iKtcfwity iMwIiangcable for ipodfie cndippKcttioiOklft tho**bes \twJjT filter h one which contofw** largemwnbOr of wwopcood ^b those liber snhgr.Klcs In which ihc CSen haw been welt Ctwrleed or are inown at "opened* grade*. Table VIII gives die approximate distribution by grades of ehr) produced m Canada and the United States*, as compared to that p the USSR in ffJG& TABUS YU! Ammxtxi.vrc Pkoocctiox or Cunrsomae Fikkim ir Graors is I1 (Irwle UitAlt. Xo. 1 finite No. 2 (indie 18.000 130.000 180,000 650.000 300.000 830,000 Appflattfoni Tlie commercial applications of asbestos arc so numerous that thi can do no In-iter than refer the reader to the many excellent texts wl cpmtely cover this subject (8, G2). Tlie uses range from asbestos-cement: or fl>or tile, which consume hundreds of thousands of tons, to specialty applications which may consume only several tons annually. Asbestorfl a great variety of products n combination of properties wltteb^i attaint'd by using other materials. Its strong fibrous form rrlnForces otB stifh as plastics or cement, or controls viscosity of many systetrw; nature is (mpuitmii for resistance to hent and chemical or environment Its fine si/e contributes filtration efficiency and Insulating cfllcfencyj|! dance and low- cost are significant factors in promoting oommerdal ap| On the basis of relative abundance alone, chrysotfle will be uscd| possible in preference to other forms of aslreslos. Where a comblhljH treme bulking cliaracferlstfcs plus low water content and high lempw slstancp arc desirable, e.g., thermal Insulations, nmosltc Iras iminDy^ furred. Application* mjuiring resistance to nckls usually take ad' relatively good arid resistance of crocldolilc. Textile proslucts silky, long* ! grade of ehrysotilc although crocidolitc has also acid-resistant textile forms. Ceographic considerations may exert ' flucnee to increase the usage of sj>ocific nmphfljolex, such ns ant Finland i*r tlie c-roc-ldolllps In South Africa. Anlhnphylllto hft* sll advantages over oilier asl)c\tiform minerals In reinforcing polypm ud and U used extensively for this purpose. ST0011745 AsmcsTus uixrnu ix momom ufCiiNoroor 203 In gmrral, specific gr.ulu* or chrysotile have been ilmloiHil by the AslolOI Industry for each innriot. Alllxnigii the longer fibers nrc considered to be of better quality It would be just as impractical to uso ruinlively long `1-grade fiber fa floor tile as It would be lo attempt to male salisfactory asbestos paper or nsbesto*. cement products with 7-grade fibers. In fact; some applications may even roqoirer the presence of a considerable amount of the nonfiforous, fine-grained portleolatesctpentiw which is contained* In some of the 7-grade subgroups. ^;> Nortnany^ tho cwuomcr selects tlc least expensive grade of fiber which will meet htrnceds. ... S T 0 0 I 1*746 3*.- fTc?.. '.* { 1 . r yi .. **-&c '***V>.; <V*. -%v'N'* S'J*' . . - cr 'A . /V ' ' * - ; . * 'u * < \ Vv.'*: Kk. 24. H kx-tron nikrngnipti of ctMinm-iil Ulc. X22S0. ST0011746 STOOI 1747 201 s. m'mi, and j. \ i.i:ixwi;nffl production ami applications of asbinlos fibers arc usually (he only significant sources of asbestos fibers entering lle V on closer examination it becomes* evident that wo the quwtkw of fiapuriBB to sboato^ but abo (he are an Fw. 2-7. I^rctmn mf. mginpli of \V.nm County. New Yortc, wtrx-wtfcwv ST0011747 STOOI1748 A5BKVTOS MIMRAUS IN' MODERN IKOINOl.OtiY 205 cosmetic applications. Figure 24, an electrimmicrogmph of a typical bene* ficiafcd industrial talc, reveals the presence of considerable fibrous treinolitc. Approximately S0C0 tons of talc arc used armually as a currier for pesticides (71). Whxloin et at. (79) investigated the distribution of talc in the atmosphere and in glacier and snow samples to study the migration of pesticides, Tlicir samples covered a world-wilc geographic distribution. In practically every sample, amphibolcs were detected along with the talc, as might be .anticipated from the common occurrence of amphibolcs in talc. . *" Cndley(M) et at. have recently investigated 22 cosmetic talcum products. All had significant fiber contents ranging from S'to 305 by count of tbc total talc particulates, and averaging 195. The fibrons tale included tretnolite, antliophynit^," andchrysotile. They made special note of the. fact that cosmetic talcum pioi< . nets should be included as a source of fibers, from which may be. derived ferru ginous bodies observes! in the lungs of humans. . In another investigation by the UiS. PubIic.IfOaIth Seniee ot the source fdentUkurion of respirable fibers, Cralk^Cl^w*^ thwag^ lOO 'diflcrcnt natural minerals with swnetKpiifi^ fibrous structure.which occur in respirable sizes. In addition to the asbestos minerals, these included ^ fidlcr's'carth, zeolite, xcrroicnlitc, calcium carbonate, g>psum, pyrophyllite, tale, ,;i kyanite, hornblende, mica, magnesite," a* tlntany others. Pure serpentine is considered lo be composed of nonfibrous anllgorito or prBanlite based on petrographic and X-ray examination. However, electron microscopy reveals the fact that all serpentine rocks contain significant amounts of chrysolite. Figure 23 is an electron micrograph of a practically translucent "museum grade" serpentine specimen from Warren County, New York, obtained through Wards Natural Science Establishment. Despite its apparent content of approximately 201 of Hirers, optical microscopy showed no chrysotilo whatsoever. Examination of many other authenticated sample* of "pure-serpentine" v" revealed the presence of chrvsotile. Serpentine?rock depoaftii'irief- wkl throughout the world. In the United States they form the Franciscan serpen belt along the entire length of California, Just as they form much of tlc Appa lachian range on the East Const. They ore used as the basis for many large-scale applications, such ns ballast, road construction, aggregate, building stone. Dur ing grinding and preparation for such commercial usage, there could be oppor tunity for escape of fibrous material. / * - * V' 'f'v COXCf.t'SIOXS It is important for the medical investigator of tho bfologiejeffccts of asbestfform minerals to properly understand the wide dNr^boW^M srreral In dividual nsfiextos minerals, the ubiquitous nature of their oceurrence, both In coinmercirtlly vahinblc form and ns Impurities in othermaterials, am! (lie widesprend existence of many other minerals with fibrous form. It Is only by relating experimental biologic evidence " ith the variations in phjslcal sire and form, in physical strength attributes, in phj-steoehcmkul surface renctfona, in rhemfcnl renelfvHy, and tn associated impurities that we can ultimately arrix-e at x-alld medical cnorfuttons. '-x,-i-*i ST0011748 STOO!!7 4 9 j, spkji- ano j. r. lkikkwkukh ACKNCnTTJlDCMKNTS' _ thefr fcmtnmlo to J. W. Axcborv D. A. BoOey. C. P. HcIimdiMlI, (he Johm-ManviBe Research and Rncfnerrfag Center foe their invaluftMD (he pn-poration of thb paper. * REFERENCES S, V. S, Patent 2j068lfe SL Cam MMmg Wet- Raff,! (11). 3, "Kncydepedla Chemical Tadmoloyy VoL 2, p. 734. (IMS). S, axd STiucia; \V. C, U. S. ratent-2,618301. and Tatm*, IL r. Mr, Wtelng Meg. London X 7*4 (1961); . e'*"' . 0. Bju^ mTc, akdTayiahi. II. F. W,/. Aw*. C/iem. London 13,143 (1963). 7. Batw^T. F, Saxiv L P, axd Mink; J. F, Science 111, 512 (1950). 8. Bkmco^ If, "A'lifiloi Fundamentals," Chem.-Pnbl. Co, New Tort (1963). 9. Beaman, II, Am. 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