Societies and Academies

Abstract

LONDON Physical Society, July 7. F. TWYMAN and G. F. LOTHIAN: Conditions for securing accuracy in spectrophotometry. The first section deals with absorption spectrophotometry in application to chemistry and includes consideration of the various methods in use, namely, photographic, visual and photoelectric, the optimum conditions for each method being stated; and the three types of method are compared. The second section is concerned with spectrophotometry as a means of describing a radiation, for example in connexion with colorimetry, the comparison of light-sources, and quantitative spectrum analysis. W. E. WILLIAMS: Studies in interferometry (2). The construction, testing and use of reflection echelons for the visible and ultraviolet regions. The various methods of mounting are compared. A method is described whereby the instrument can be used for wave-length measurements. It is further shown that the echelon provides an alternative means of standardising length units in terms of a wave-length of light. E. V. APPLETON: Two methods of ionospheric investigation. Both methods involve measurements of the equivalent height of reflection for a number of electric wave frequencies. Different relations are expected and found to exist between the equivalent height and the frequency for the ordinary and extraordinary magneto-ionic components. It is found that magneto-ionic double refraction is caused by region E. For daytime conditions, and more frequently in summer than in winter, evidence of the existence of a protuberance or ledge on region F is found. Evidence of the existence of ionisation between regions E and F (?intermediate region?) has also occasionally been obtained at noon, so that the whole ionospheric configuration may be regarded as a composite structure of four components, regions E1, E11, F1 and F11. Usually only regions E1 and F11 are of importance (see NATURE, June 17, p. 872). A. H. JAY: A high-temperature X-ray camera for precision measurements. A high-temperature X-ray camera has been designed for taking powder photographs which show well-resolved Ka doublets at high angles of reflection, enabling an accurate estimate of line position to be made. The temperature of the specimen was found in the following way. Photographs of silver, from which the lattice dimensions were calculated, were taken with varying heating-currents. The coefficient of expansion of silver was used to convert lattice-spacing measurements to degrees centigrade. A curve relating the watts in the furnaces to the temperature of the specimens was thus obtained. A. ELLIOTT: The intensities of bands in the spectrum of boron monoxide. The intensities of the a bands of boron monoxide have been measured by means of an arrangement which gives the intensity of a whole band. Precautions for the detection of systematic errors are described, and the probable error is estimated at about ±5 per cent. The intensity ratio of the B11O and B10O bands has been measured for two of the? bands. The result, 3?5: 1, is in satisfactory agreement with a previous determination of the isotope intensity ratio in the (3 bands of boron monoxide, 3?66: 1. J. F. HEARD: Pressure effects in the spectra Xe I and Xe ii. The first and second spectra of xenon have been examined for pressure effects. At high pressure, lines of the Xe I spectrum show broadenings which correspond qualitatively to their respective Stark effects. This points to the existence of strong interionic electric fields within the discharge. Many pressure displacements in the Xe II spectrum are also found, and it is suggested that these too have their origin in interionic fields. E. GWYNNE JONES: Hyperfine structure in the spark spectrum of cadmium. The Cd II spectrum has been investigated in the region??4200-8500 with Fabry-Perot etalons. Of the 13 lines examined, only?8067 has any structure. From the structure of the 62S1/2 term it is calculated that the g(I) factor of the odd isotopes is?1?25 proton magnetons.