Abstract
LONDON Royal Society, Nov. 10.—Lord Rutherford, C. E. Wynn-Williams, W. B Lewis and B. V. Bowden: Analysis of α-rays by an annular magnetic field. With the assistance of Dr. J. Cockroft, an electromagnet has been designed which provides a uniform magnetic field, of the order of 10,000 gauss, in an annular gap in which α-rays can be bent into a circle of 40 cm. radius. The particles are emitted from a source placed in the gap, and are detected by a small ionisation chamber symmetrically situated on the opposite end of a diameter! The interior of the whole magnet is exhausted to a low pressure (0–001 mm. mercury). As in previous experiments the ionisation chamber is connected to an amplifier, and individual a-particles are automatically counted by a system of thyratrons. The analysis is carried out by adjusting the magnetic field so as to bring groups of different velocities successively en to the slit of the counting chamber, the high velocity edge of a group being very sharply defined. Moreover, it is necessary to measure small changes of the magnetic field with great accuracy. A special method has been developed for this purpose, and the relative velocities of a number of α-particle groups have already been determined with an accuracy of about 1 in 3,000. The weak group of α-particles from radium C, numbering only 1 in 4,000 of the main radium C' group, comprises two distinct components.—W. A. Bone, D. M. Newitt and D. T. A. Townend: Gaseous combustion at high pressures (14). Explosions of hydrogen-air and carbonic oxide-air mixtures at initial pressures up to 1,000 atmospheres. With regard to the actual explosions it was found that: (1) In those of theoretical hydrogen-air media there was a quite definite increase in the explosion times with density at initial pressures exceeding 250 atmospheres; although at 750 atmospheres detonation was instantaneously set up at the firing point with such violence as to preclude work at any higher pressures; (2) in explosions of theoretical carbon monoxide-air media the characteristic lag in the explosion time, as well as the exothermic effects observed during the cooling period—both of which had hitherto consistently increased with the density reached their maxima at an initial pressure somewhere between 350 and 500 atmospheres, and thereafter remained constant up to 1,000 atmospheres, indicating that the nitrogen activation effect had reached maximum within this density range; (3) in 2CO + O2 + 3.76CO explosions the explosion times, which were always very much shorter than in the corresponding 2CO + O2 + 3.76N2 explosions and had remained nearly constant up to initial pressures of 250 atmospheres, began definitely to increase thereafter with the density, and about the same point some slight carbon deposition began to be manifest during the explosions, the two circumstances probably being connected. The rates of pressure fall during the first second of the cooling period immediately after the attainment of maximum pressure were always much faster than in the corresponding 2CO + O2 + 3.76N2 experiments.
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Societies and Academies. Nature 130, 786–787 (1932). https://doi.org/10.1038/130786b0
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DOI: https://doi.org/10.1038/130786b0