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1. The form of the absorption curves of homogeneous β-rays in aluminium has been investigated by means of a Geiger counter. It is found, in agreement with Schonland, that the main portion of the curve is linear, with pronounced initial and final flattenings. Similar initial flattenings were found for copper and silver, but not for gold.2. The range of β-rays emergent at different angles has been determined, and it appears that the loss of range is due to the increased path consequent upon scattering.3. Some evidence has been obtained of the angular distribution of plurally scattered particles, and of the existence of a most probable angle of scattering, similar to that found for α-rays by Geiger.

[Plate 1.] Summary.The previous work of the authors on analysis by X-ray spectroscopy, which was shown to be highly sensitive and capable of general application, has been developed as a method of quantitative analysis. It has been tested in the first place on alloys of elements of nearly equal atomic number with widely varying concentrations, and is found to have an accuracy of about 1 in 200 ; successful preliminary experiments have been made with alloys of elements of unequal atomic number.It is assumed that the ratio of the number of atoms of two elements in an alloy of metals of nearly equal atomic number is equal to the ratio of the intensities of corresponding lines (say the Kcq lines) in the spectra of the elements provided the lines are excited under equivalent conditions. The intensities have been determined photographically, and the great advantages of the photographic method for line intensity measurements are pointed out.The effect on the assumption stated above of (a) the potential applied to the X-ray tube, ( b)the variation with wave-length of the absorption an photographic action of the lines measured, and (c) the inhomogeneity of some of the targets used are discussed and tested by experiment.The results obtained are not in agreement in certain respects with those of previous workers. Coster and Nishina found that the presence of a third element affected the results of an X-ray analysis, which we have not confirmed for alloys, and came to conclusions unfavourable to the direct method used successfully in this investigation. The ratio of the intensities of two lines of a given element is found to be independent of their absolute intensities, con trary to the results of Gunther and Stranski.The X-ray method of analysis has been applied to alloys obtainable only in small amounts, in which the element to be estimated was present in from 0 • 1 to 0-01 per cent. In such cases it is difficult to apply other methods. The X-ray method was tested in a series of alloys containing traces of lead in zinc.on May 10, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from As these elements differ widely in atomic number, the method described above was replaced by one in which a comparison was made of the intensity of the lead Loq lines from each alloy with those obtained with an equal exposure from an alloy of known composition.X-ray analysis should be of value in testing the purity of metals to be used in the accurate determination of their physical properties. Introduction.In a previous paper* the qualitative detection of elements by X-rays was discussed and the method, although involving a complicated technique, was shown to be very sensitive and generally applicable. In this paper,f experi ments will be described which had as their aim the investigation of the possibilities of quantitative analysis by X-ray spectroscopy. In order to have, in the initial experiments, conditions to which existing theory is applicable alloys of metals of nearly equal atomic number were studied ; some results, however, ar...

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