| Summary: | This Test Guideline describes two methods. These tests are applicable only to water insoluble (solubility < 10-6 g/1) substances. The first method described (Method A) is designed to provide information on the transportation and sedimentation of insoluble particles in water and air. There are several standard methods available which meet the sensitivity requirements: the sedimentation, the centrifugation or the coulter counter. The sample should be subjected to a simple light microscopic examination to determine the approximate nature of the particles. Data are obtained for a 3 size ranges ›200µm, ‹2 µm and the region 2to 200µm. Method A, which determines the effective hydrodynamic radius, Rs (only in the range 2 μm < Rs < 100 μm), can be used for both fibrous and non-fibrous particulates. The Method B is used in the special case of materials which can form fibres, it is comparatively specialised, infrequently required and involves microscopic examination. Scanning (SEM) or transmission (TEM) electron microscopy are required. There is no standard procedure at present. The full length (l) and diameter (d) data are needed on fibre of dimensions d≥ 0.1µm and l≥ 5µm. Two histograms should be prepared based on examination of at least 50 fibres each
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