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b X-ray spectrometric methods have been developed for the determination of magnesium, aluminum, silicon, potassium, calcium, titanium, iron, and barium in forsterite and in the materials used in making it (talc, magnesium oxide, feldspar, and clay). Major constituents are determined by comparison with standards using a glass disk technique. Minor constituents (less than 5%) are determined as powders by a standard-addition method. The precision in most cases appears to b e excellent.The accuracy, although difficult to evaluate, compares favorably with that of classical wet methods.

During the normal operation of conventional receiving-type electron tubes, certain metallic elements, such as barium, strontium, nickel, and manganese, sublime from the hot cathode and deposit on cooler parts of the tube. This process gradually impairs the performance of the tube and may eventually limit its useful life. This paper describes some applications of a variety of X-ray spectrometric techniques to the qualitative and quantitative analysis of these sublimates and to the mapping of their distribution on various surfaces in the tubes.All work was done on a standard commercial X-ray spectrometer, but specially designed accessories are described for mounting and rotating small parts in the primary X-ray beam and for confining the beam to these parts. Procedures are given for analysis of microgram deposits on electron-tube cathodes, grids, plates, micas, and bulbs by both nondestructive and filter-paper-disk techniques. Procedures are given for point-by-point mapping of the distribution of sublimates over the surfaces of these parts by use of a commercial “X-ray probe” selectedarea accessory in conjunction with a curved crystal to give increased intensity. Procedures are given for various techniques for calibrating all the analytical methods, including preparation of thin films of known composition.The results of some typical electron tube studies are described and illustrated. The approximate sensitivity of the methods for determination of total sublimate is, in micrograms per part, 0.1 for barium, strontium, and manganese and 0.05 for nickel. The approximate sensitivity for mapping sublimate distribution with a 1-mm aperture is, in micrograms per square centimeter, 1 for barium, strontium, and manganese and 0.5 for nickel. Although the techniques described are applied specifically to sublimates in electron tubes, they are also readily applicable to analysis of specks and films on other small parts and to thin-film studies in general

y = 1 + al -5,' and the integration limits are Y and Yo . The integral form df Equation 9, alsd'derived by Lee and Kolthoff ( I ) , was not used for the example calculations below because it is not applicable a t integral values of 8.