The x-ray line broadening method of determining particle size was compared with direct measurement on electron micrographs. By controlled heating of the carbonate, magnesium oxide particles were prepared from 50 to 1000A in diameter. Particle size calculated from x-ray data taken on a Geiger counter spectrometer agreed to ±10 percent with the microscope measurements. Mechanical mixtures of two different sizes were examined by the x-ray method, but the particle sizes could not be determined unless the two maxima of the distribution curve were completely resolved.

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A computer program, called nrlxrf, which employs a combination approach utilizing both fundamental-parameter expressions and empirical coefficients has demonstrated versatility and accuracy for multicomponent x-ray analysis. The program takes advantage of all standard reference materials that have been measured. Analysis can also be accomplished with only one multicomponent standard and no pure-element standards. Results agree with National Bureau of Standards certified values within 1.2 % relative for major constituents and 1.6% relative for minor constitutents. The computer program can calculate primary spectra if given the x-ray tube target material and operating voltage. Thin samples as well as thick samples, either homogeneous or heterogeneous, can be analyzed.

X-Ray fluorescence spectrometry is well suited to the determination of elemental composition of air pollution particulate samples because no sample preparation is required for filter collections, 1 00-second detection limits are 1 to 100 ng/cmz for most elements of interest, the technique is nondestructive, and 10 or 20 elements can be measured simultaneously using presently available commercial equipment. The best detection limits are achieved by reducing the background primary radiation scattered into the measuring system by the sample and its filter substrate. In this work, comparisons were made among various excitation sources, X-ray tubes, fluorescers, radioisotopes and 5-MeV protons and alpha particles, and between wavelength dispersion using a crystal spectrometer and energy dispersion using a Si(Li) solid state detector. Incinerator and other actual samples are analyzed to show application of the method.