Document 2n40R7NeQ8wrnG4ZbvydQjra

I l u iJ I I l_ i 'w' III ) DOW CHEMICAL U.S.A. RESTRICTED: for use within The Dow Chemico! Compony on ly* ULPAHIMENT Central Laboratory - Texas Division 74 .tS#; L A DOH A T OM r *?> cT - c CCE TC-505 DATE ISSUED October 1. 1974 AU. riu. rHOHLCv E. TITLE A A Critical Evaluation of Current Analytical Methods for the 10 n Determination of Chrysotile Asbestos 14 PACE; IN FL__ REPC-.7 CRI NUMBER AUTHOR (Si S. I. Foster AUTHOR IS) SIGNATURE 15J ~' - s<fj IiEVIEIVER'S SIGNATURE DESCRIPTIVE SUMMARY WITH. CONCLUSIONS: (Include roporls, in this patents This report !s: (xj INTERIM | | FINAL space references to data and publications.) and mainly: fin review -- books, and to eeriier relc*:: This report outlines known analytical procedures for chrysotile (serpentine) asbestos fibers in various aqueous waste streams. Some of the topics covered are: Electron and Optical microscopy, chemical methods, infrared, ESCA, DTA, X-ray diffraction, etc. A bibliography of papers relating to currently used analytical procedures is included. The conclusions drawn from this review indicate that TEM (Transmission T?i *r: --------- - \ au - -- - a. u~ ...i. : _ i. f..u:n - -it .... ** .i i UIUl-U Uii iUiUA UDUU^J' y 1J Ullfc UaIC LC^C illlLV^U C3 (ViUCU XUi.XlXX& OrXl px UOQjll Uiiaiv ClCUi needs (i. e. identification, counting, and sizing). However, due to the complexity of the method and the cost of instrumentation, a rapid survey analysis which could give an order of magnitude of asbestos concentration and could be Implemented into a production facility is needed. The techniques discussed here, specifically, atomic absorption. I. R., light-scattering, ESCA, adsorption of dyes and tracers, and other chemical methods are being further evaluated as rapid scanning procedures and recommendations will be forthcoming. r Tg D t/ o rO CO XT <5 fsa 1374 CRI MtWAND DDIISSTTRRIIBBUUTTIIOONN.: dcpakimcnt fil.es C^C ^NTDR AALDRMEINPIOSRTTRATINIODNEX - 5 COPIES f 566 fi 1 d q -- Midland) FOUM ''I(IN1 to IM-/I -- ~ --1 1 -- Distribution Ini is continued on o I f o c fi e</ ri*. -2- cQ sn & zo is DISTRIBUTION Western Midland M. D. Yearn an *R. J. Moore Oyster Creek *D. A. Rilcard W. H. Caines Texas *1. C. Jones, B-1402 Bldg. F. W. Spillers, B-2224 Bldg. O. C. Taylor, B-2224 Bldg. F. P. Boer, B-1225 Bldg. E. H. Holt, B-2406 Bldg. L. C. Shepard, B-1219 Bldg. L. D. Martin, B-1225 Bldg. D. C. Benefiel, B-1219 Bldg. W. W. Henslee, B-1225 Bldg. *H. H. McClure, B-1210 Bldg. *W. H. Fletcher, B-101 Bldg. *L. J. Fourrier, A-1201 Bldg. J. A. VanWestenburg, A-606 Bldg. *0. N. Hollis, A-1201 Bldg. *S. F. Edquist, B-101 Bldg. G. E. Rademacher, B-2224 Bldg. J. D. Laman, B-1226 Bldg. F. C. Leavitt, 574 Bldg. D. R. Beaman, 574 Bldg. R. O. Kagel, 1603 Bldg. R. J. Moolenaar, 2020 Bldg. *D. P. Sheetz, 47 Bldg. *M. E. Pruitt, 2020 Bldg. *G. W. Pearson, 2020 Bldg. *M. E. Kelly; 2020 Bldg. K. W. Guebert, 474 Bldg. *D. D. Deline, 834 Bldg. R. G. Carlson, 2030 Bldg. Russellville *G. Miller Canada *R.'. C. Young, 726 Bldg. P. O. Box 1012 Sarnia, Ontario, Canada N7-T7-K7* *J. M. Pasnak Ft. Saskatchewan P. O. Box 759 Alberta, Canada TOB-IPO Louisiana G. W. Daigre, 2501 Bldg. H. A. Chagnard, 2501 Bldg. ,G. Liu, 2501 Bldg. *E. P. Edwards, 2601 Bldg. n o s n s z o is , -0- The Problem We are principally concerned with aqueous samples, some with high concentrations of NaCl and/or NaOH. These samples, in general, will contain 108 to 1010 asbestos fibers/liter (typical concentrations by weight encountered to date aje 0. 1 - 200 pg/1, the fibers being approximately 2 to 9 microns long and 200 to 400 A in cross section (i. e., 100 to 300 aspect ratio). Although this is the typical case, any particle with an aspect ratio 3 to 1 or larger will constitute a fiber. Representative samples may also be expected to contain additional suspended particulate matter such as: clay minerals (montmorillonite or kaolinite), diatoms, quartz, graphite, hydroxides, and minerals indigenous to the particular sample area. Important chemical and physical characteristics particular to chrysotile are summarized below: TABLE 1 Physical: 1. Large aspect ratios (100/1 typical). 2. Specific gravity 2. 5; density 2. 56 g/cc. 3. Loss of crystalline water at 695C (14 %by wt.). 4. Irreversible change of crystal structure at 840C. 5. Characteristic I. R. spectrum. 6. Isoelectric point - 10. 3. Chemical: A i.-. ns _ i.: _ . a. tO oi iauu! Empirical composition: 3MgO- 2Si02- 2H,,0 or Mg6(OH)6Si4Ou-H20, i. e., 43. 5%MgO; 43. 5% Si02; 13%H20. Typical impurities are:1 Fe, 0-1% ; Al, Ca, Cr (light; Cu, Na (trace); nickel (medium). 2. pH-- 9 to 10. 3. Soluble in strong acids to 56 % by wt. 1Sample analyzed by emission spectroscopy on asbestos from Chlor-Alkali department. The analytical problems associated with asbestos fibers are fourfold: concentration and separation, identification, sizing, and counting. These areas will be. dealt with separately with the objective of describing available techniques and evaluating their usefulness. Filtration: CONCENTRATION AND SEPARATION Of the concentration methods, filtration seems to be the most universal. Typically, a millipore(- -type membrane made of cellulose esters and having a pore-size between o. 2 - 0. 8 pm is employed either in a pressure of vacuum filtration -3- &06H8201* assembly.3> 9> 27, 33 57_ 60, 67, 68 . These membranes can then be ashed at relatively low temperatures (350C)59>07, dissolved, or extracted in order to free the insoluble fraction. The currently used technique employs a EFFA condensation washer wherein the filter is bathed in acetone vapors and condensate until it dissolves. This procedure takes approximately one hour if a 2 mm (dia.) filter is used. An added benefit is that it is possible to wash from the filter soluble material which may interfere with successive analysis. An average filtering time for 1 liter of solution is approximately 10 min/in2 of filter. This time will depend on how much clogging is experienced. Centrifugation: Centrifugation offers an attractive alternative to filtration in that it is relatively fast and does not involve additional steps to free the filtering agent. It is routinely used as a technique to ''spin-down" fibers onto an electron micro scope grid57 and also as a prefiltering aid to reduce clogging by large particles59!60. The use of an ultracentrifuge and density gradient may prove helpful in separating unwanted suspended material from the asbestos fibers. On the other hand, a continuous centrifuge (e. g., Sharpless might aid in concentration of the particulate matter from a large sample. Agglom eration and Extraction: It is well known that hydroxyl groups on the asbestos fibers are subject to attack U/rjry uiiiui *> ^ 1 Ip P 1A n V- /-* A A A M ppn C4.ii.Cl U.XXWJwjf U 4.J.O.UC. J Cjyx tuuuc Cp Ui /> Jai. 42 UC1 IVAUVCd 9 9 > K4 . PO It has also been found that agglomeration or graft-polymerization will occur if the silane contains more than one reactive site. If the silane contains bulky organic substituents it may make the asbestos more soluble in organic solvents and thus extraction may be feasible34. Evaporation: Th disadvantage of this approach is that both soluble and insoluble material will be simultaneously concentrated. If, however, the soluble species can be extracted or perhaps dialyzed, evaporation may still provide a useful concentration method. Electrokinetic Effect: Asbestos fibers have been shown to carry a large surface charge (isoelectric point 10. 3)2>3!hnd thus, electrophoresis may be applied in separation and concen tration38. Whether or not the majority of fibers can be collected by this technique or if the fibers will be lost when the electrode is withdrawn is net presently known. 90648Z01S. -5- IDEKTIFICATION METHODS Methods of low-specificity Chemical Methods: Chemical techniques rely on the analysis of both Mg and Si in the bulk sample of suspended matter. The typical procedure is to analyze for both Mg and Si using whichever value is found to be lowest to calculate an upper limit of asbestos present. The particulate matter is solubilized with HF and HC104 or by Na2C03 fusion and the Mg and Si are then analyzed by any of a number of wet chemical or Instrumental methods. This approach is presently being carried out with atomic absorption spectroscopy at B-2406 of the Texas Central Laboratory (E. H. Holt, private communications). X-Ray Spectroscopy: X-ray fluorescence, whether X-ray or electron induced, exhibits a rather low sensitivity for either Mg or Si. It would therefore be doubtful if this technique would be applied successfully. Atomic Emission Spectroscopy: Emission spectroscopy does not lend itself easily to quantitative analysis. How ever, it has been estimated that a lower limit of 20 ng of asbestos can be determined if the sample is fused with NagCOj. Again, it must be recognized, that any foreign silicate or magnesium containing compound will interfere. Radioactive or Chemical Tagging: It is known that coupling reagents modified to contain a radioactive or fluorescent tag can be affixed to the asbestos fibers. Some of the more likely candidates are the chloro- and alkoxy silanes which contain a grouping which might chelate an easily monitored metal ion. It has been reported that some dyes43*31 can be adsorbed in aqueous solution and also that titrated chrysotile has been synthesized23. Tagging represents an important concept in the identification of chrysotile. If metal ions, dyes, or other surface active agents can be found to bond specifically to chrysotile this could give a major increment in analytical sensitivity and possibly specificity. Some reports indicate that a degree of specificity has already been observed10*lc* 2234*3S* 40>43. Infrared: It has been estimated that chrysotile in the range 20 to 700 ng46 can be determined by using the 2. 72 n-m hydroxyl adsorption. However, this method is non-specific since other hydroxyl containing compounds may interfere. The specificity may be improved by monitoring the 9-10 inn silicate adsorption. Even with its drawbacks, I. R. represents a simple, cheap, and relatively fast method by which an upper limit could be obtained and thus may constitute a quick survey technique. A sensitivity of 0. 5 Fg is readily attained in the absence cf interferences. ESCA: ESCA can provide a quick semi-quantitative Mg and Si analysis. Its advantage may lie in its ability to look only at the first 50 A or so of the surface. Thus, if the asbestos can be distributed on the top of a filtering agent, ESCA may be able to do the analysis without removing the filter. Methods of Moderate to High Selectivity TGA and DTA: Chrysotile gives a characteristic endotherm at 695C associated W'ith its loss of ILjO (13%wt). It also exotherms at temperatures above 800C which is indicative of a change in crystal structure37*41. It has been reported that chrysotile in talc can be detected in the 1. 0% range on samples as low as 10 milligrams. Consequently, sample handling would constitute its main liability since the asbestos concentration is expected to be in the micro gram/liter range. 106*182018 Thermohygrometric analysis28 relies on the detection of evolved water at 695C using a sensitive hygrometer. If we assume 10 Fg of chrysotile is contained in a 10 cc volume of dry gas, the water evolved would be in the parts/1000 range. This could be easily monitored by existing hygrometers. However, it is not known if other compounds will also evolve water at this temperature and thus the specificity of this technique remains in question. Silicate Extraction: Silicate minerals can act as sources of trim ethyls ilyl silicates when reacted with chlorotrimethyl silanes02. The particular silicate evolved can be characteristic of the mineral reacted. The trimethylsilyl silicate can be determined by G. C. in some cases. Sensitivity may be a problem, but this technique should be further researched. Optical Microscopy: Optical microscopy is considered useful for particles larger than 1 Fm in smallest dimension. Since most individual asbestos fibers have been found to have a cross section of less than 0. 5 Fm, this technique will not be applicable except for looking ST0284988 -7- at large bundles of fibers. Optical microscopy is widely used for analysis of asbestos in air samples9 >4055. Transmission Electron Microscopy: TEM combined with selected area electron diffraction (SAED) and energy dispersive X-ray analysis (EDX) can identify, count, and size individual asbestos fibers. Its liability lies in involved sample preparation, small field of view, tediousness, and considerable capital investment. The usual technique is to filter the fibers onto a filtering membrane. The membrane is then ashed or dissolved and the residue dispersed onto a microscope grid (see filtering techniques). This technique is presently the standard method for chrysotile analysis. It can be successfully used to detect chrysotile in the ng range3* 27> 33> 51 57-B1> ? Scanning Electron Microscopy: As far as sample preparation, SEM offers an advantage over TEM in that the filter does not have to be removed. Aside from this advantage, the inherently lower resolution and lesser degree of contrast should make SEM inferior to TEM as a method for asbestos analysis and fiber counting. However, recent literature from the Kevex Corp. indicates that X-ray spec troscopy, in conjunction with scanning electron microscopy (SEM), can be used to analyze individual asbestos fibers. X-Ray Diffraction:* 1 X-ray analysis is probably tire most specific technique. It is not easily quantified except by elaborate standardization, and under normal circumstances is not very sensitive. Sensitivity is in the range 10 to 100 mg21, but claims have been made of analyses in the 50 to 100 ug range24. The standard lines used for this analysis are the 7. 36 A and 3. 66 A lines. COUNTING AND SIZING The only direct method of counting fibers seems to be electron microscopy. How ever, if the asbestos fibers are found to fall within a certain size range, then bulk measurements of asbestos in a sample can be extrapolated to fibers present. Indirect measurements of the number of particles may be realized by applying one of the following concepts: 1- Light scattering: This technique offers a possible avenue for counting and sizing. The major problems arise from interference by other suspended particles,absorption of light by colored solutions, and in not knowing how these fibers will scatter. It is also unknown at present if light scattering can detect asbestos in the ppm or ppb concentration range. 60648281$. -82. Centrifugation: The Joyce-Loebl disc centrifuge will allow for sedimentation and separation of particles based mainly on specific gravity differences. Its use of light scattering as a detection technique will also depend on whether or not these fibers will scatter in the visible light region. Summary At present, TEM stands as the one technique which fulfills all analytical needs (i. e., identification, counting, and sizing). However, a complimentary, rapid survey analysis which can give an order of magnitude asbestos concentration and could be implemented into a production facility is needed. The techniques discussed here, especially atomic absorption, I. R., light-scattering, adsorption of dyes and tracers, and other chemical methods are being further evaluated as rapid analytical procedures and recommendations will be forthcoming. dv -9- Bibliography 1967 - Present (Sept., 1974) This bibliography has been compiled from the following sources: A. Chem ical Abstracts-- 1967 to September, 1974. B. Dow Computer Search which lists: Engineering Index NT IS Chemical Abstracts (1972-Present) . . ,C. . Dow CRI 016*18201$ 1. 80-2343q1 Fed. Registr. 28 Sept. 1973, 27076-81. Gives specifications and limits for asbestos in air. 2. 80-64137] J. Appl. Chem. and Biotechnol, 3 (9), 675 (1973). Talks about different surface charge concentrations of asbestos minerals. 3. 80-51909n Int. Symp, Indent. Meas. Environ. Pollut., 1971, 154-7. Asbestos in air is detected by low temp, ashing, ultrasonic breakdown, and TEM gives levels found. 4. 80-137024g Fed. Registr. 26 Feb., 1971, 38(39) 7526-33. Limits and regulations. 5. 80-99654c Report 1973 UCRL- 51422 5-7. Radio induced thermoluminescence of asbestos can be used as detection technique but there are interferences from quartz, etc. 6. 80-90702j Thermochimica Acta., 8 (1-2), 197 (1974). DTA was used to detect chrysotile in talc down to l%by wt. 7. 81- J. Occup. Med. 15 (2), 92 (1973). Review of toxicological effects. 8. 81-16279f U.S. Nat. Tech. Inform. Serv., PB Reb. 1973 No. 226471/IGA. Avail. NTIS from Gov. Rep. Announce 1974, 74 (6) 81. Using SEM with microprobe the gov. has developed a method to scan air samples. 1Chemical Abstract No. r- -10- i tfr'itm s 9. 78-9295p Proc. Elect. Microsc. Soc. Amer., 30, 356 (1972). Atlas including diffraction patterns and description of fibers using light and electron microscopy. 10. 79-68556x Zh. Prikl. Spettrosk., j_8 (5), 914 (1973)Russ, Showed all asbestos luminesced when excited by U. V. in 370-620 nm. Samples displayed thermoluminescence when excited by X-rays. 11. 79-81607j Ustar. Jad. Vyzk., Cesk. Alcad. Ved., 1972, No. 2851-F-Ch 86 pp. (Eng.). X-ray spectra of asbestos. 12. 78-33508k Proc., Elect. Microsc. Soc. Amer., 30, 546 (1972). SAED patterns for various minerals including chrysotile. 13. 78-143447 Staub.-Reinhalt. Luft., 33 (2), 66-70 (1973) Ger. Quant, detection of asbestos by optical, chemical X-ray, and I. R. techniques. 14. 78-150831w TNO Nieuws., 27 (11), 661 (1972) Eng. Discusses nattem of filtration nViO Pfl o TEM, I. R.^ XRD, Elect. Diff.' 4 cf rv^ 1X4 XV*X nmr Jj 15. 77-20074v Bull. Soc. Chim. Fr., 1, 54 (1972) Fr. Reaction of chrysotile with dichlorosilanes for grafting. 16. 79-58074Z Patent - Pol 67, 335, 20 Feb. 1973. Asbestos impregnated with rare earths, etc., for ion exchange membranes. 17. 70-108184x Sb. Nar. Mus. Praze, 24b (1), 61 (1968) (Eng. ). Mineral identification of chrysotile by chemical, optical, DTA, XRD. 18. 74-102752s Proc. Int. Conf. 3rd 1969 (pub. 1970), 52 (Eng. ). Neutron-activation technique to investigate biological effects of asbestos. 19. 75-9103Gd Atmos. Environ., 5 (7) 565 (1971). I. R. for airborne asbestos. 20. 80-148609(1 Lyon Pharm., 1973, 24 (5) 627 (1973) Fr. Industrial micropollutants. m *a m s. -11- 21. Analyst (London), 94 (1124) 985 (1969) (Eng.). Quant. XRD for chrysotile. 22. 70-132503Z Vzainodeisfuse Vodora. Policle. Disp. Sist., 83 (1970) Russ. Coagulation and bonding in asbestos suspensions in the presence of electrolyte K-4. 23. 70-45539x Environ. Res., 4_ (2), 86 (1971). Synthesis of 3H-labeled chrysotile. 24. Analytical Chem., 44 (11), 1872 (1972). . by XRD 50-100 ng of chrysotile can be detected. 25. 70-123172X Zem.-Kalk-Gips, 23 (8) 390 (1970) (Ger.). TGA of chrysotile. 26. 69-22881q Acta. Cryst., 24 (3) 374 (1968). Measurement of position and 1/2 height width of some reflections of chrysotile. 27. 69-1556664 Dokl. Akad. Nauk. SSSR, 200 (4) 953 (1971) (Russ. ). TEM of natural and synthetic chrysotile. 28. 69-142677y Clay Miner., 9 (1) 19 (1971). Thermohygrometric analysis (water evolved) of clay minerals. 29. 69-560736 U. S. Geol. Surv. Prof. Papers, No. 384-B, 93, 1967. Different solution methods for discriminating asbestos. 30. 69-305975 Geochim. Cosmochim. Acta., 32 (5) 485 (1968). Solubility of chrysotile. 31. 69-24053u Hokkaido. Daigaku. Kogakuku Kenkyu Hohoku, 1967, (45), 81 (1967) Russ. " Synthesis chrysotile with fluoride substituted for OH". 32. 70- 108823e IZV. Akad. Naulc. SSSR, Neorg. Mater., 5 (1) 143 (1967) Russ. Reactions of chrysotile with various chlorosilanes. 33. 67~7044h ICristallografiya, ^2 (3) 430 (1967) Russ. Study of wall thickness of fibers of chrysotile. f -12- e i e n v o is 34. 67-100166 Patent (US) 3, 346, 111 Oct., 1967. Asbestos coated with fluorescent dye is made selectively fluorescent. 35. 66-21861j Patent (Ger.) 1, 226, 505 Oct. 13, 1966. Surfactants can be used to precip. asbestos suspensions with organic solvents. 36. 68-80358m Vop. Min. Osad. Obrazov., 7, 48 (1966) Russ. I. R. spectra of chrysotile. 37. 67-74039z Plast. Inst. Trans. J., 35 (117) 525 (1967). 38. 69-29885c Patent (Brit.) 1,115, 221. Anionic asbestos fibers are drawn to anode for continuous stripping. 39. 74-6242e Af\ *70 OAOCCi* txU9 i U. K. At. Energy Auth., At. Weapons Res. Estab., Rep. 1970 AWRE 028/70 Avail. IiMSO 95. Discusses membrane filters, impingers, cascade irapacters, horizontal elutriators. *5 ^ -- in /i \ non \ JVi.iOAUOUVJpC, 1U L Dispersion staining discussed. 41. 73-59034b Atmos. Environ., 4 (2) 125 (1970). Internal reflection used to determine chrysotile. 42. 66-115792q Patent (USSR) 185, 858. Organic derivatives of silicates using colloidal nickel catalyst. 43. 66-67812x Tr. Inst. Geol. Nauk., Akad. Nauk. Kaz. S.S.R., 16, 201 (1966) Russ. " Applying organic dyes to asbestos. 44. 75-54544x Kristallografiya, U3 (3) 544 (1971) Russ. TGA and DTA shows endotherm 695C releasing 2 mol of II20 and exotherm 840C assoc, with transition to MgSiOz. 45. 72-6029 Arbeitsschutz (Cologne), 7, 161 (1969) Ger. I. R. spectra of chrysotile. -13- S T02849IU 46. 74-102730h Atmos. Environ., 4 (16) 667 (1970). Uses the 2.72 fim absorption to detect 20 ng of chrysotile, some interference is also experienced. . 47. 72-8812y Khim. Prakt. Primen. Kremniiorg. Soedin., Tr. Sovesch. 186 (1966). Ethoxy silanes react with chrysotile in the presence of Ni catalyst. 48. 72-112662k J. Appl. Chem., 20 (3) 76 (1970). I. R. study of silanes coupled to chrysotile. 49. 71-93424v Clays and Clay Minerals, H, 367 (1964) (Pub. 1966). Neutron inelastic scattering cf chrysotile shows peaks at 620-650 cm-1 and 460-510 cm-1. 50. 73-17270x Amer. Mineral, 55 (5-6) 1025 (1970). Chemical differences of asbestoses. 51. 68-72576 Acta. Cryst., 23 (5) 704 (1967). High resolution TEM. 52. 70-87028q Patent (USSR) 228, 947. Organic derivatives of silicates. 53. 68--302711c U. S. Clearinghouse Fed. Sci. Tech. Inform. AD 649281, 1967. Chrysotile reacts with HC1 and Me3SiCl to form curled ribbons. 54. 69-7908k Bull. Soc. Chim. Fr., 2, 483 (1968). In acidic solution Mg was removed from chrysotile. Hexamethyldisiloxane was added to give chrysotile polymer. 55. Arch. Environ. Health, 20, 571 (1970). Describes asbestos fibers under TEM. 56. Toxic Materials News, Aug. 15, 1974. i How EPA plans to move on asbestos pollution. 57. Science, 185 (4154x 853 (1974). Chrysotile by TEM. 58. Science, F77, 171 (1972). Asbestos in drugs. TEM .analysis described. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. -14- Nature, 219, 93 (1968). Asbestos in beer. TEM analysis described. Nature, 233, 332 (1971). Asbestos in beverages. TEM analysis described. Water Pollut. Control, 111, 33 (1973). Search for asbestos in drinking water; analytical techniques described. Inorganic Chem., 3, 574 (1964). Organic derivatives of silicates as means for identification. Science, 173, 1141 (1971). Talc treated rice and Japanese stomach cancer. American Lab., 13, April, 1974. Optical microscopic techniques. TDI - TC-347 Dow Report. Dissolving of asbestos. Analytical Chem., 45 (4) 609 (1973). TEM analysis. Amer. Industrial Hy. Assoc. J.', 31, 587 (1970). Techniques for the detection, identification and analysis of fibers. Proc. 67th meeting of APCA, June (1974), Denver, Colo. Note on filtering samples from air using two nucleopore filters. Inorg. Chem., 6 (9), 1693 (1967). Reaction of chrysotile with HC1 and trimethyl chlorosilane to form a fibrous polymer. S16*182015