Chemistry and Physics. 415 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Atomic Weight of C cesium. — An elaborate revision of 

 the atomic weight of caesium has been made by Richards and 

 Archibald. The material used in this investigation was chiefly 

 a large quantity of csesium salts from the pollucite of Paris, 

 Maine, which Wells of the Sheffield Scientific School had purified 

 by his method of recrystallizing the salt CsClJ, and which was 

 so pure that the authors were unable to improve upon its purity. 

 Three methods of atomic weight determination were used ; the 

 analysis of the chloride, which consisted in comparing csesium 

 chloride with silver chloride and with silver; the analysis of 

 caesium bromide, with analogous comparisons ; and the ignition 

 of caesium nitrate with an excess of pure silica, where caesium 

 nitrate was compared with N 2 B . Indirect comparisons with 

 potassium chloride and oxide were also made. The close agree- 

 ment of the individual results and of the results by the different 

 methods is very remarkable, and there is no doubt that the 

 atomic weight of this rare element is now known with the highest 

 degree of accuracy. As an outcome of forty-two analyses involv- 

 ing seven different ratios and three compounds of caesium (the 

 chloride, bromide and nitrate), the authors calculate the atomic 

 weight of caesium to be 132*879, if oxygen is 16. The result 

 shows that the early work done upon this atomic weight in the 

 Sheffield Laboratory by Johnson and Allen,. was remarkably 

 exact. — Proceedings Amer. Acad., xxxviii, 443. h. l. w. 



2. Conductivity Produced in Gases by the aid of Ultra- Violet 

 Light. — In a former paper Professor Townsend confirmed the 

 results previously published by him, on the theory of the genesis 

 of ions by collision. It was shown that the negative ions thus 

 produced in a gas are identical with the negative ions set free 

 from the negative electrode by the action of ultra-violet light. 

 Professor Townsend has now extended his results in experiments 

 with hydrochloric acid gas and water vapor, with the result 

 that the same theory of genesis affords an explanation of the 

 phenomena and we are led to conclude that negative ions are 

 generated in air, carbonic acid gas, hydrogen, water vapor, or 

 hydrochloric acid gas, which are all identical with the negative 

 ions set free from a zinc plate by the action of ultra-violet light. 

 It is shown that a negative ion may pass inside the sphere of 

 action of a moucule without producing new ions. — Phil. Mag., 

 April, 1903, pp. 390-398. J. T. 



3. Absorption of Gravitation Energy by Radio-active Sub- 

 stances. — EI. R. Geigel published in the Ann. der Physik, 10, p. 

 429, 1903, some results tending to show evidence of this absorp- 

 tion. W. Kaufmanx, of the Physik. Inst. d. Univ. Gottingen, 



Am. Jour. Sci.— Fourth Series, Vol. XV, No. 89. — May, 1903. 

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