[Refinement of the methods of diffractometric analysis in relation to the preparation surface exposed to X rays]

The aim of the study was to assess the degree of X-ray diffractometric response using preparations having a surface exposed to X-rays other than 2 cm2, which is standard for sample-holders supplied with a goniometer, coupled to a commercially available analytic apparatus. Two samples of commercial talc were examined with dust size below 30 microns (and having different content of "respirable" or "alveolar" dust classes), as regards chlorate, talc and asbestos constituents and quartz. Twelve different experimental conditions of the preparations permitted X-ray exposure of surfaces between 6.25 and 500 mm2. For the low angle positions it was possible to obtain a substantial improvement in the overall diffractometric response by increasing the surface of the preparations; however, in each case, a reduction in the surface produced, in addition to a better definition of the peaks, an increase in the diffracted intensities per unit of surface of the preparation; this is clearly related to the collection spectrum of the radiant energy of the incident beam in space, and leads to the possibility of reducing to an order of magnitude of milligrams the mass of samples that can still be submitted to qualitative and quantitative diffractometric analysis.