Document xjQpGMqo6bZoKQDVVNaE502JJ

TABLE 1 Instrum ental Methods -- C apabilities Instrum ents ______________ Method Morphology Optics D iffraction Chem ical Analysis* LM: light m icroscope DS: d is p e rsio n staining XRD: x -ra y diffraction SEM: scanning electron m icroscope TEM: transm ission electron m icroscope EMA: elec tro n m icroprobe EMMA: electro n m icro sco p em icroprobe analyzer IMA: ion m ic ro p ro b e >1 /on >5 /un NO >1 /un >1 /un NO ^ 0 . 005 m NO > 0. 001 /un NO >5 /un NO > 0 . 005 /un NO >5 /un NO NO NO YES NO YES NO YES NO NO NO YES YES NO** YES YES YES ^diffraction methods indirectly analyze chem ically by identifying the crystalline phase present; chem ical analysis by electron optical instrum ents may utilize energy o r wavelength dispersive x -ray analyzers **may be fitted with energy o r wavelength dispersive x -ray analyzers waiter c. mecrone associates, inc, @tmheicrosc pe Incorporating "Crystal Front" . Founded 1937 January-April 1970 Volume 18 No. 1 Annual Subscription: 5. $15. Second class postage paid at New York. Published by: Microscope Publications Ltd., 2 McCrone Mews, Belsize Lane, London, N.W.3., England. Identification of Asbestos Fibers by Microscopical Dispersion Staining* Y. JULIAN and W. C. McCRONE McCrone Associates, Inc., Chicago, Illinois, U S.A . Abstract The Cherkasov focal screening dispersion staining procedure has been successfully applied to the identification of asbestos. The various types of asbestos can be differentiated by noting the refractive index of the Cargille liquid giving matching wavelengths in the region near 550 nm. It is not necessary to use polarized light although the much more definitive data obtained with polarized light may eventually permit identification of the mine from which each asbestos came. Although too fewsamples of amosite and crocidolitehave been studied, it appears that these two types can be differentiated by dispersion staining. In Cargille liquid nffC 1-680 the central stop without polars will show colors in the blue magenta region (ko= 550-650 nm) for amosite and in the golden yellow region (A0= 400--500 nm) for crocidolite. Furthermore, with polarized light crocidolite will show lower birefringence than amosite; in terms of L0 difference in a given liquid amosite will show 160-190 nm and crocidolite 120--140 nm. Finally, the higher value of Jq, is observed for the vibration direction parallel to the length for crocidolite (three samples) but perpendicular to the length for amosite (two samples). * Presented at INTER/MICRO-69, London, England. 1 iS* Through publications1^3 and current research, the pneumoconiotic (lung hardening) and frequently cancer-producing hazards of asbestos are finally fully acknowledged. Hence, there is need of a method of determining qualitatively and quantitatively environmental pollution by respirable asbestos dust (1-7 prn). Asbestos is a fibrous form of silicate rock. There are six types: chrysotile, amosite, crocidolite, aclinolite, tremolite and anthophyllite; only the first three are of commercial importance. All are amphiboles (minerals with chains of silica tetrahedra as their basic structure) except chrysotile which is a serpentine (mineral made up of layers of silica tetrahedra). The property of asbestos that best lends itself to identification is refractive index. The fibers are so fine that electron microscopy would be necessary if morphology were to be used. There are no dependable differences in absorption color (except possibly for crocidolite) nor specific gravity (other than chrysotile) (Table I). If we wish to use chemical composition for identification of single asbestos fibers, we require highly sophisticated instruments and techniques--the electron microscope or an electron (or ion) microprobe. X-ray diffraction requires considerable sample and is not sensitive to small percentages in any sample (i.e., < 5-10%). Very small asbestos fibers can, however, be identified simply and quickly using dispersion staining. Experimental The McCrone dispersion staining objective, based on the focal screening method of Cherkasov4, was used in this study of asbestos (Figure 2). Figure 1. Dispersion staining data for a typical sample o f crocidolite. 2 MICROSCOPE (1970) 18 SERPENTINES Composition Chrysotile 3Mg0.2Si02. 2 H 20 Spec. Gray. Cryst. Syst. Extinction Sign (elong.) 2.36 2.5 Monoclmic t a l * = oc + TABLE 1 ASBESTOS AMPHIBOLES Actinolite Tremo lite Anthophyllite Amosite 2Ca0.4Mg0. 2Ca0.5Mg0. 7Mg0.8Si02. Fe0.8Si02.H20 8Si02.H20 H 20 5-5Fe0. 1-5Mg0. 8Si02.H 20 3.03-3.5 2.9-3.2 2.85-3.4T 2.6-3.0 Monoclinic Monoclinic Orthorhombic Monoclinic y A L = 10-15 y A L = 10-21 y A L = 0 y A L = 14-21 ++ + Crocidolite N a20.Fe->03. 3Fe0.8Si02 H 20 3.0-3.45 Monoclinic a A L = 3-15 __ *L= long direction of fibers . JULIAN & W. C. McCRONE Figure 2. The arrangement for focal screening; the annular stop permits passage o f the matching wavelength and the central stop white light minus the matching wavelength. 5 Figures 4-7. Central stop colors for chrysotile (Figure 4), anthophyllite (5). amosite (6) and crocidolite (7) each with the appropriate Cargille refractive index liquid, 1.560 (Figure 4), 1.610 (Figure 5), 1.670 (Figure 6), 1.700 (Figure 7). The vibration direction of the polar is east-west in each figure. 4 MICROSCOPE (1970) 18 Dispersion Staining Colors >rs observed Annular stop dark-blue blue-violet blue blue-green \ green yellow-green yellow orange orange-red brownish-red lumination are often used for these methods are empirical, nixture of colors observed is tern used. With the Cherkasov d and hence essentially pure was determined as a function each of 26 asbestos samples, ible II was found to be most better resolution and contrast; bers. The procedure involved: ly in those Cargille refractive 'dors to it. oth polarized and unpolarized ibration direction of the polar other asbestos fibers'). (3 and y (crocidolite) or a and (3 ndom orientations under these (3 n y positions and all ^ a positions. The two extreme ations are designated a (highest ;stos fibers other than crocidolite t X0) for crocidolite. often observed with asbestos Figure 1 shows the data for one s way. bestos fibers show nominally a re wavelengths observed during due to polarization by reflection MICROSCOPE 0970) 18 J<aEJ/> o CO Mo <v .Ea z3 Figure 3 The range o f matching wavelengths shown by anthophylhte and chrysotile with unpolarized light The Cargille liquid was chosen so that most samples o f each asbestos show a Kq in the blue magenta region with the central stop___________________________ ___ 8I9 Figures 8-11 Central stop colors for chrysotile {Figure 8) anthophylhte (9) amosite {10) and crocidohte (11) in the same Cargille liquids as Figures 4-7 respectively Unpolarized light was used for this series 5 Y. J U L I A N & W. C M c C R O N E from the microscope mirror, there is a slight change in color when the stage is rotated. All our data were taken with the fibers normal to the mirror reflection vibration direction. Figures 4-7 show the dispersion staining colors of representative samples of chrysotile, anthophyllite, amosite and crocidolite res pectively. Each is shown in the various orientations (relative to the polarizer vibration direction) necessary for determination of a, P and y. Careful study of these figures may indicate the simplified procedure used to orient the fibers at precise 90 degree angles to each other. To determine if the simpler application of dispersion staining without a polarizer is adequate for identifying asbestos, the fields of view of Figures 4-7 were also taken with no polar (Figures 8-11). The curves obtained without polar were plotted in a single graph (Figure 12). The bunching of the curves of each different type of asbestos indicates that for identification purposes a liquid can be chosen that will impart a characteristic color to one species of asbestos only. A polarizing microscope is not, therefore, required. However, we can anticipate that with additional samples of crocidolite and amosite there might be some overlap. For this reason, the distinction between the signs of elongation (Figures 6 and 7) and the crocidolite blue absorption color are mentioned as special aids for differentiation. In this case a polarizer is useful. Figure 12. Matching wavelengths shown by different samples o f four types of asbestos when mounted in the Cargdle refractive index liquids shown and observed with unpolanzed light. 7 a cs The characteristic color will vary somewhat for different samples of the same type of asbestos. So, the problem arose of determining the ranges of colors for each asbestos in the chosen liquid (the liquid in which most samples of any asbestos type give a color of wavelength 580-620 nanometers). To determine this range of colors for any type of asbestos, the matching wavelengths observed in the chosen liquid are plotted against the number of different samples showing that X0. The area under the resulting curve (colored in Figure 3 as per Table II) shows all the colors shown by our samples of anthophyllite and chrysotile. Too few samples of amosite or crocidolite have been studied to justify their inclusion in Figure 3. Conclusion The limited results obtained indicate that asbestos can be identified by dispersion staining. More work on many more samples will establish the full range of X0values for each asbestos. Relating X0data to asbestos source may then also pinpoint the mine source of unknown asbestos samples. Acknowledgement The authors are grateful to Dr. Bertram G. Woodland, Curator of Igneous and Metamorphic Petrology of the Field Museum of Natural Flistory in Chicago for the samples of asbestos from various sources. REFERENCES 1 H.M. Factory Inspectorate, (1968). Problems arising from the use o f asbestos, Memorandum of the Senior Medical Inspector's Advisory Panel, Department of Employment and Productivity, London, Her Majesty's Stationery Office. 2 Smith, K. W., (1955). Pulmonary disability in asbestos workers. Arch. Ind. Health, 12 198-203. 3 Brodeur, P., (1968). The Magic Mineral, New Yorker Magazine, 12 October. 4 Brown, K. M., and McCrone, W. C., (1963). Dispersion Staining, Parts I and II, Microscope, 13 311 and 14 39. MICROSCOPE (1970) 18 Lincoln Co., Nevada El 101 APPENDIX (Continued) *Y 1.609 1.611 1.616 1.602 1 605 1.609 1.596 1.599 1.602 a 1.589 1.592 1.595 Rio Grande de Sul, Brazil E l4494 Y* a 1.610 1.605 1.603 1.596 1.615 1.610 1.607 1.600 1.620 1.615 1.611 1.604 California E14464 Y* 1.619 1.624 1.630 1.614 1.619 1.624 1.612 1.616 1.622 a 1.601 1.605 1.610 Pine Mt., Georgia *Y 1.607 1.613 1.619 1.602 1.608 1.614 1.597 1.602 1.607 a 1.589 1.593 1.597 Encampment, Wyoming Y# a 1.619 1.61.1 1.609 1.598 1.620 1.616 1.612 1.600 1.626 1.619 1.615 1.603 Bedford, Virginia E l2790 Y* 1.614 1.619 1.622 1.609 1.613 1.618 1.606 1.610 1.615 a 1.599 1.603 1.607 1.623 1.615 1.609 1.600 1.630 1.624 1.620 1.611 1.642 1.635 1.632 1.618 1.632 1.625 1.617 1.606 1.630 1.625 1.621 1.607 1.634 1.628 1.624 1.614 1.630 1.621 1.615 1.606 1.641 1.635 1.628 1.618 1.656 1.646 1.642 1.627 1.647 1.638 1.628 1.614 1.638 1.630 1.626 1.611 1.644 1.638 1.633 1.622 Orange River, South Africa Y* a Westerburg, South Africa Y* a South Africa Y* a Crocidolites 1.688 1.684 1.680 1.674 1.694 1.690 1.686 1.678 1.686 1.682 1.679 1.674 1.692 1.687 1.683 1.678 1.691 1.685 1.680 1.674 1.696 1.690 1.685 1.679 1.700 1.696 1.692 1.682 1.697 1.692 1.688 1.683 1.701 1.695 1.690 1.683 1.712 1.707 1.702 1.690 1.708 1.701 1.697 1.691 1.712 1.705 1.700 1.692 1.726 1.721 1.713 1.698 1.718 1.710 1.706 1.699 1.723 1.714 1.710 1.700 Lydenburg Dist., Transvaal Amosites Y* 1.676 1.682 1.665 1.670 1.658 1.663 a 1.652 1.657 Penge, Transvaal Y* 1.672 1.677 1.665 1.669 P 1.660 1.664 a 1.653 1.657 OEC 11973 1.687 1.676 1.668 1.662 1.682 1.674 1.668 1.661 1.699 1.687 1.678 1.672 1.692 1.682 1.676 1.669 1.712 1.698 1.689 1.682 1.701 1.691 1.684 1.676 MICROSCOPE (1970) 18 Y. J U L I A N & Vy. C. M c C R O N E APPENDIX Dispersion Staining D ata, n |j c o f Cargille refractive index liquid Chrysotil es Sample Orientation 450 Thetford Mines, Quebec y* 1.539 1.535 1.533 a 1.528 Matching wavelength, %0, nm 486(F) 520 590(D) 656(C) 1.542 1.546 1.553 1.559 1.539 1.543 1.550 1.556 1.539 1.543 1.547 1.556 1.531 1.534 1.541 1.546 Eden, Vermont El 9048** 1.549 1.553 1.558 1.566 1.574 I 1.543 1.547 1.551 1.559 1.566 P 1.543 1.547 1.551 1.559 1.566 a 1.534 1.539 1.543 1.550 1.557 Thetford Mines, Quebec E20436 y * P a 1.545 1.540 1.538 1.536 1.549 1.546 1.541 1.539 1.552 1.547 1.544 1.542 1.559 1.553 1.550 1.548 1.565 1.558 1.554 1.552 Thetford Mines, Quebec El 2 185 y * CP 1.543 1.540 1.536 1.531 1.547 1.543 1.540 1.534 1.550 1.546 1.543 1.537 1.556 1.552 1.549 1.543 1.563 1.558 1.555 1.548 King's Mine, Quebec 7 1.543 1.547 1.551 1.559 1.566 * 1.539 1.543 1.547 1.554 1.561 P 1.535 1.539 1.543 1.550 1.557 a 1.529 1.532 1.535 1.542 1.547 Barquisimento, Venezuela *y P a 1.536 1 530 1.530 1.524 1.541 1.537 1.534 1 528 1.546 1.541 1.539 1.532 1.556 1.550 1.547 1.540 1.566 1.559 1.555 1.548 * no polars were used. ** sample identification number of the Field Museum of Natural History, Chicago, Illinois, U.S.A. Minas Gerais, Brazil El 6696 Maryland E3713 New Mexico E3709 Macon Co., N. Carolina E3700 Anthophylhtes 7* 1.604 ?.613 1.602 1.608 1.599 1.606 a 1.582 1.588 y* 1.617 1.623 1.613 J.618 1.609 1.614 a 1.599 1.604 *7 1 620 1.625 1.616 1.621 1.609 1.612 a 1.601 1.604 7* 1.614 1.618 1.610 1 614 P 1.606 1 610 a 1.594 1 597 1.620 1.614 1.612 1.594 1.630 1.624 1.619 1.609 1.629 1.625 1.616 1.607 1.623 1.619 1.614 1.604 1.633 1.628 1.625 1.606 1.642 1.636 1.630 1.620 1.638 1.634 1.620 1.613 1.632 1.627 1.622 1.607 1.645 1.638 1.636 1.616 1.658 1.649 1.642 1.630 1.648 1.642 1.628 1.618 1.641 1.635 1.629 1.613 9 # + . Detection and Identification of A sbestos by M icroscopical D ispersion Staining W alter C. M cCrone, M cCrone A ssociates, Inc. C hicago, IL C061G T here is a g reat need for a dependable, sensitive and rapid method for the detection and identification of asbestos. M icroscopical dispersion staining satisfies all of these re q u ire m e n ts. It is dependable because it is based on the m easurem ent of th ree refractiv e indices as well as the dispersion of those indices. R efractive indices are among the m ost valuable identifying ch aracteristics for sm all p articles. It is sensitive because the refractiv e indices are "read" as bright dispersion staining colors against a black background. T hese colors can be observed on p a rtic le s well below one m ic ro m e te r in d ia m e te r . It is ra p id b e ca u se any p a rtic le in th e m ic ro scopical preparation showing the optical p ro p erties of asbestos signals its presence by a unique color com bination with polarized light. One p article of asbestos in a field of view containing many thousands of other p a rtic le s w ill be im m ediately apparent on scanning the eye acro ss the field of view. . B esides optical cry stallo g rap h ic m ethods like d isp ersio n staining only DTA and diffraction have th is ability to tag a p a rtic u la r cry stallin e phase in a m ixture. X -rajr diffraction, however, is several o rd ers of magnitude less sensitive than dis p e rs io n stain in g and x*c .uires m uch m o re tim e . T h e re a r e , h o w ev er, com pounds whose d ispersion staining colors a re , at least at first glance, confused with ehrysotile c o lo rs. H ere, fortunately, p article morphology is able to differentiate between these interfering substances. Q uartz is one exam ple, lizardile another. The latter, however, is a tabular talelike m ineral and quartz shows conchoidal frac tu re into usually thin flak es. Both a rc easily differentiated from fibrous asb esto s by m orphology. D ispersion staining is, th erefo re, a straightforw ard technique easily applied by any m icro sco p ist with som e knowledge of optical cry stallo g rap h y . We have found it extrem ely useful for the rapid and routine exam ination of any particulate sam ples fo r any of the various kinds of asbestos"*". The n e c e ssa ry background inform ation for applying the method is given in Figure 1 which plots the m atching wavelength, as a function of refractiv e index of the C argille refractiv e index liquids used in these determ inations. M ost of the asbestos m in erals have distinctive indices without overlap, saniesVs F ig u re l^ehow s, h o w ev er, th a t a m o site and c ro c id o lite 'sr o v e rla p p a r tia lly . T h e re should be no confusion in this situation, how ever, since gam m a for am osite overlaps only with alpha for crocidolite. The data in Figure 1 a re plotted as the averages of a c o n sid e ra b l num ber of valu es fo r individual m ine sa m p le s p re v io u sly published"*". It is in terestin g to look a little bit m ore closely at this variation in d ispersion stabling C x 'O . v -* ' data/fox mine to mine and Table I lists the matching wavelength, X ^, for gam m a^paral- lel to the fiber lengtli^and alpha ^perpendicular to the fib er length} for a group of m ore than thirty asbestos sam ples from different p a rts of the w orld. T here is som e variation fro m sam p le to sa m p le , in d icatin g co m p o sitio n v a ria tio n s . H ow ever, a ll of the d ata liG. in the sam e c h a ra c te ris tic c h ry so tile region and show no overlap w ith any of the fibrous am phiboles. Since d isp ersio n staining is a relatively new technique requiring a certain amount of sk ill, not only in reading the m atching wavelengths but also in adjusting the m icroscope for best d isp ersio n staining co lo rs, it seem s well to sum m arize a few of the common difficulties. 1. The re fra c tiv e indices given in d isp ersio n staining tables a re not dispersion data for that compound. To illu stra te this we can cite the data for the u index of q u artz. - 2- tru e re fra c tiv e indices* O dispersion staining data 486 nm 1.550 1.538 589 nm 1.544 1.544 65G rtm 1.542 1.547 T he value 1 .538 for w at 486 nm is for th e C a rg ille liquid th a t m a tch es q u a rtz co at 486 nm . The acb 'al re fra c tiv e index of that liquid at 486 nm is 1.550, the sam e as q u a rtz co. T his o p e ra tio n , which s im p lifie s the a n a ly tic a l p ro c e d u re , is u sed fo r a ll dispersion staining data. One can, of co u rse, calculate the tru e refractiv e indices of any substance from the d isp ersio n staining d ata. The n e ce ssa ry data to do th is can be found in the table of dispersion of refractiv e index data for the C argille liquids. 2. True refractiv e index data and dispersion staining data are idc. Teal at 589 nm , hence re fra c tiv e index data at 589 nm for any substance becom es dispersu staining data for that substance. Chryso' ery l, for exam ple, does not appear in the 2 d is p e rsio n stain in g ta b le s but V /inchell g iv es n ^ = 1.746 (oj> 1.748 (3) and 7.5 6 (y). ^) s F ro m th e se d ata one would m ount a su sp e c ted c h ry s o b e ry l in C a rg ille liquidA1.750 and expect to se e an n u lar stop c o lo rs ran g in g fro m o ran g e (a) to g re e n ish -y e llo w (y) o r g re e n ish -b lu e (a) to m a g en ta-b lu e (y) with the c e n tr a l sto p . T h is g re a tly extends the usefulness of dispersion staining. 3. We a re often asked if the dispersion staining objective can be supplied with a h ig h er m a g n ificatio n . T his g iv es u s the opportunity to point out th a t hi; ' e r m agnifi cation is not d e sira b le . One is try in g to " re so lv e " color of the p a rtic le s not the p a r ticles them selves. C entral stop dispersion staining is a darkficld procedure, hence a strong light source will show points of light for p:irticlcs sm aller than the resolving power fe lim it of the m ic ro sco p e s y s te m , i . e . , 1 .2 2 pm for|kN A --- 0 .2 5 , 10X o b je ctiv e. T hese points of light will be colored for p a rtic le s showing dispersion in that liquid. The lower lim it of detection is a function of light intensity and co n trast. - 3- # 4 . T here a re a num ber of points of technique which greatly im prove the sensitivity of the disp sion staining p ro ced u re. These include: a . The p articles m ust be well separated in the mounting liquid since nonstained p articles close to or overlapping stained asbestos can mask their presence. b . The d isp ersio n staining co lo rs for ch ry so tile and the fih^r** am phiboles a re m ore b rillian t if one uses the high dispersion C argille set of refractiv e index liquids. c . In sp ite of the above injunction concerning high m agnification, it is so m etim es u seful to u se a 20-25X o cu lar w ith the 10X dispersion staining objective. d . The optics for the die .ersion staining objective, the axis of stage rotation, the substage apertures and lenses m ust be well aligned on the sam e optical a x is . It is a good idea to take special pains to align the optical system and to m aintain that m icroscope for dispersion staining exam ination only. e . The proble m of g lare from other p a rtic le s in the field of view is solved to a g re a t extent by having a cen tered and nearly closed field diaplr'-'un in the optical sy stem . This concentrates attention on p a rtic le s in the center of the field and elim inates well over 90% of the g la re which m ak es it d ifficu lt to see v ery fine a sb e sto s fib e rs . f . It is d e s ira b le to be ab le to cha> ge ih c o rie n ta tio n of any p a rtic le s which appear at firs t sight to give the distinctive dispersion stain ing c o lo rs c h a r a c te r is tic of chpys^jtile or o th er fib ro u s am phi b o le s). R olling the ptauj t i d e by ,1iVe\V:o.ovveerr slip wi-iiflt-fltr-rYi-Sis'emis liquid_pxeji-ia-t-he-i deal.-way-~of-ckkng4.his--nd-helps g re a tly in dif ferentiating quartz, paper fibers and m ineral wool from chrysotile. g . The slides and cover slips used for dispersion staining prc.ps should be unusually clean since any optical discontinuities on any surface of the prop cause g lare and interfcreSvith visibility of the dispersion staining c o lo rs. h . Finally, it is d e sirab le to have standards of the substance you are looking for mounted in the sam e re fra c tiv e index liquid. If one is looking for ch ry so tile, it is also useful to have standard p reparations of q u artz, paper fib ers and talc in o rd er to rem ind oneself quickly of the essen tial differences in appearance and color for these substances. - 4- . . ` The color plates show the general nature of the dispersion staining colors and the specific appearance of the various kinds of asbestos in their specific liquids. Figure 2 shows the arrangem ent of annular and central stops in the objective back focal plane. These may be a centered 2-3 mm opening in any opaque film or a 3-4 m m dot of India ink on an 18 m m cover slip , re sp ectiv ely ? although a d isp ersio n staining objective is availabl com m ercially . Note that the substage iris is closed to allow only an axial beam of light to strik e the object. The color s e rie s obtained with each stop a re shown in F ig u re 3. C h ry so tile is shown in F ig u res 4-5 m ounted in two different standard C argille refractiv e index m edia. P olarized light is used with an E-W vibj ation d irection for F igure 4 and N-S for F igure 5. O bserved X values are given in Table II. Table II. Matching W avelengths for C krysot'' . R efractive index, n ^ , of C argille liquid P a ra lle l to fiber length C rossw ise of fiber 1.550 1.560 500 570 610 640 F igures 6-8 show anthophyllite,all with E-W p o la r. Figure.s G and 7 show the fib e rs mounted in 1.610 and 1 .620, re sp e c tiv e ly . F ig u re 8 shows two different antho- phyllites (M aryland and North C arolina) mounted in 1 .627. This figure, like the o th ers, a r e double e x p o su res with the stag e ro ta te d 90 betw een e x p o s u re s . The two d ifferen t so u rces re su lt in sm all variations in X . A m osite is shown in F ig u re s 9-11 m ounted in C arg ille li . uds 1 .6 7 0 , 1.680 and 1 .6 9 0 , re s p e c t) o.ly. F ig u re 12 show s c ro c id o lite in C a rg ille liquid n - 1.700 and F ig u re 13 show s one p a rtic le of c h ry s o tile in a ta le sam p le m ounted in C a rg ille liquid, n - 1.550. - ;> # CONCLUSION The com bination of p article morphology and optics uniquely identifies any of the fibrous asbestos eompounds. The m ost rapid method for obtaining this inform ati' , is through the use of dispersion staining. Pm pcrly c a rrie d out, the dispersion stain ing method is capable to sensitivity in the ppm ran g e. REFERENCES 1 . J u lia n , Y and W . C . M cC rone, M icro sco p e 18, 1-10 (1970) 2 . Wine he 11, A .N . and H . W inchell, M icro sc o p ic al C h a ra c te rs of A rtific ia l Inorganic Solid S ub stan ces, A cadem ic P r e s s , 1964, p . 78 - G- Table I M atching W avelength (XQ) in II. D . 1 .5 5 0 Liquid II lg Quebec; Lake Asbestos Quebec; King, A sbestos C orp. Quebec; A sbestos Corp. Quebec; B ell Mines Quebec; Johnsons Quebec; C areys, Bradford Quebec; Flintkote Quebec; Normandie Ontario; Beeves Ontario; Munro Vermont; Hyde P ark , GAF Vermont; Jeffery New Foundland; Advocate New Foundland; Yukon; Clinton Creek B ritish Columbia; C assiar California; Pacific Asbestos Corp. C alifornia; Coalings A rizona; Venezuela; Rhodesian; Rhodesian; Shabina Rhodesian; Havelock C and G Rhodesian; Havelock HVL R hodesian; Havelock VRA Cyprus; G reece; Zandini Y u g o slav ia; Italian; B alengera R u ssian ; A ustralia; W oodsreef 510 510 500 510 500 480 500 570 480 560 510 500 510 590 500 500 480 590 600 610 520 (460)* 480 490 490 500 600 580 520 500 (4C0) 500 610 i lg 610 610 610 600 600 590 610 610 590 610 620 580 610 620 580 580 610 630 620 680 620 (550) 580 590 590 630 660 620 590 600 (510) 600 680 Figure Captions 1. Asbestos dispersion staining curves. 2. Schematic arrangem ent for annular and central stop dispersion staining. . 3. Color series for annular and central stop dispersion staining. 4. C hrysotile in C argille liquid n ^ = 1.550. 5. C h ry so tile in C a rg ille liquid njQ = 1 .5 6 0 . 6. Anthophyllite in C argille liquid n^ = 1.610. 7. Anthophyllite in C argille liquid = 1.620. 8. Two differc t anthopliyllites in C argille liquid nD = 1 .6 2 7 . 9. A m ositc in C argille liquid n ^ = 1.670. 10. A m osite in C argille liquid n^ = 1.680. 11. A m osite in C argille liquid n ^ = 1 .6 9 0 . 12. Crocidolite in C argille liquid n^ = 1.700. 13. One m agenta ch ry so tile fiber in talc mounted in C argille liquid n^ = 1.555.