||Quantitative Separation of Asbestos in Environmental Samples.
Peters, Edward T. ;
Smith, Emmett M. ;
||Little (Arthur D.), Inc., Cambridge, MA.;Environmental Sciences Research Lab., Research Triangle Park, NC.
Chemical analysis ;
X ray diffraction ;
X ray analysis ;
Crystal growth ;
Air pollution detection
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Evaluations were made of a novel approach for separating chrysotile asbestos from other particulate matter to improve the application and detection limit of a broad beam x-ray diffraction analysis method developed by the Naval Research Laboratory. The separation method is based on Selective Nucleation of Crystal Growth (SNCG) whereby treatment of a particulate sample with a special reagent results in the nucleation and growth of crystals along asbestos fibers but not on other matter. The fibers can be thereby increased substantially in mass, volume and density. The reagent previously developed for chrysotile asbestos consists of mixed salts of AgI and KI in ethylene glycol-acetone-water solution, with AgI crystals (density of 5.67 g/cc) being the decorating agent. Attempts to develop a comparable reagent for amphibole asbestos were unsuccessful. Minerals structurally or chemically related to chrysotile gave no reagent response except for moderate response by lizardite and slight response from antigorite. Mixed mineral samples consisting of known amounts of chrysotile and quartz were reagent-treated, resulting in AgI overgrowths of up to 25 micrometers in diameter. Separation of the decorated asbestos from quartz by a high density liquid with and without centrifugation and by Stokes settling more unsuccessful; recoveries of about 50 percent of both chrysotile and quartz were found in the separated fraction. Further work is required to improve the separation process.