Abstract：The content of micro asbestos fiber in one unknown industrial mineral powder sample was determined by polarization microscope. The sample was treated by high-temperature heating at 450 ℃ followed by acid washing to remove most interference materials. After dispersion with ethanol, the sample was uniformly deposited on glass sheet to prepare test piece by dripping impregnation liquid with certain refractive index. The fibrous particles were observed in powder under orthogonal polarization system. Moreover, the fibers exhibited the characters of quartic parallel extinction. The interference colors were white, indicating the medium refraction index. After inserting the gypsum test plate, the positive elongation was evaluated according to the color of fibers in different quadrants. The fibers had no pleochroism in plane polarized light system. The impregnation liquid with different refractive indexes was investigated in dispersion staining colours. It was found that the refraction index of fiber was closed to 1.618 0. The analysis results of optical properties proved that the sample contained little tremolite asbestos fiber. Moreover, the mass fraction of this asbestos fiber was about 1%.
NIOSH 9000 method, Analysis was performed by XRD [S]. The National Institute for Occupational Safety and Health, 1994.
[12]
ISO 22262-1 Air quality-Bulk materials-Part 1: Sampling and qualitative determination of asbestos in commercial bulk materials [S]. The International Organization for Standardization, 2012.
