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CHEMISTRY. (CHEMICAL PHYSICS.) 



pearing to be more directly connected with radio- 

 activity than with luminosity. Very luminous 

 radium produces less ozone than radium chloride, 

 which is much less luminous, but more strongly 

 radio-active. Again, if a radium salt is contained 

 in. a glass vessel, a violet coloration is seen in the 

 glass, which proceeds from the interior to the 

 exterior surface. At the end of about ten days 

 the bottom of the flask is almost black. With a 

 less active product the tint is less deep, and re- 

 quires a longer time to develop. The phenomenon 

 is not due to the reduction of lead, as it occurs in 

 glass containing no lead. All these phenomena in- 

 dicate that the rays emitted by radium represent 

 a continual development of energy. In another 

 paper on the subject Mine. Curie cited both 

 her experiments and the spectrum examinations 

 as seeming to prove that radium exists as a sub- 

 stance, and possesses an atomic weight slightly 

 higher than that of barium. In the course of 

 furt her experiments with radium, Mme. and M. 

 Curie found that the radiant emission charged 

 bodies which received it negatively, while the ra- 

 dium itself was charged positively. In the light 

 of these and other experiments, M. Becquerel 

 declared, in March, 1900, that only one interpre- 

 tation seemed possible, at least for that part of 

 the emission comprising the deviating rays, and 

 that was that the emission was composed of ma- 

 terial particles carrying negative charges. He 

 did not consider the objection to this view based 

 upon the loss of mass of the radium valid, be- 

 cause, as the Curies had shown, the charges car- 

 ried off were so feeble " that if we admit the same 

 proportions as with cathodic rays, some millions 

 of years would be required to remove one milli- 

 gramme in the case of the most intense radiation 

 that has yet been observed." This author added, 

 as a thing that could be said with certainty, that 

 " the new discoveries singularly limit the field for 

 hypotheses, and by fixing the direction for re- 

 search, permit us to foresee a generalization of 

 great magnitude, which will be of great attraction 

 in the study of certain properties of matter to 

 which in the last few years a large body of scien- 

 tific men have turned." 



Throughout the researches of Mme. and M. 

 Curie on the isolation of radium, the progress of 

 the condensation of the element was controlled by 

 examination of the spectrum and by determina- 

 tions of atomic weights. In all the separations a 

 part of the product was kept for spectroscopic 

 studies, and a part for atomic weight. The spec- 

 troscopic studies have been made by M. Demar- 

 gay. Tho last of his products apparently con- 

 tained only a trace of barium, and might be con- 

 feidered almost a pure radium chloride. It was not 

 in large enough quantity for atomic weight investi- 

 gation, and Mme. Curie was obliged to deal with 

 the less concentrated product. Her determina- 

 tions gave 138 as the atomic weight of pure bari- 

 um in barium chloride, while two determinations 

 carried out on the radio-active chloride gave 174.1 

 and 173.0 as tho numbers for the atomic weight 

 of the metals in this chloride. The author had 

 no moans of distinguishing the relative quantities 

 of radium and barium in this product, but M. 

 Demargay thinks, from the aspect of the spec- 

 trum, that thore is rather more radium than 

 barium. In any case, it appears to be certain that 

 the atomic weight of radium is much higher than 

 174. The quantity of radium chloride isolated has 

 been insufficient for an examination of the proper- 

 ties of pure radium. Mme. and M. Curie, however, 

 express themselves much pleased at having ob- 

 tained a proof of the existence of this element, and 



at having confirmed the idea which guided them 

 in their researches on radio-active materials. 



A fundamental difference has been found by 

 M. Henri Becquerel to exist between the rays 

 emitted by radium and those of polonium, in that 

 a part of the radium rays are deflected by an 

 electro-magnet. The deviation appears to be the 

 same in the air and in a vacuum. The rays given 

 off appear to be the same in nature, but to differ 

 only in intensity. Herr F. Geisel has observed a 

 considerable difference in the penetrating power 

 of the rays of the two bodies: while the rays 

 from radium penetrate fairly well a silver thaler, 

 those from polonium, although more intense, are 

 absorbed by thinner metallic plates. The shadows 

 of the band and of metallic objects thrown by the 

 polonium rays on a fluorescent screen are stronger 

 in contrast than those produced by the radium 

 rays. Experiments by M. Henri Becquerel on the 

 velocity of propagation of the rays emitted by 

 radium indicate that this factor is of the same 

 order as that of the cathode rays. The spon- 

 taneous luminosity of radium compounds was an- 

 nounced by Mme. Curie in March, 1899. M. 

 A. Debierne, experimenting with pitchblende, 

 found associated with titanium a substance show- 

 ing 100,000 times more radiant power than ura- 

 nium, and having chemical properties distinct 

 from radium and polonium. The rays emitted by 

 this body, which was named actinium, had the 

 same manifold action as those from the other sub- 

 stances, except that it was not self-luminous. 

 M. Debierne found the new substance analogous 

 to thorium, and suggests that the radio-activity 

 of the latter is due to its presence. Other ex- 

 periments have been made with these radio-active 

 substances by some German chemists and by Mr. 

 Bolton. The primary source of the energy mani- 

 fested by them is still unknown. B. von Lengel, 

 of Buda-Pesth, has pointed out that the chemical 

 evidence is insufficient to establish their elemen- 

 tary character, and claims, in a preliminary paper, 

 to have prepared radio-active barium synthet- 

 ically. By treating uranium nitrate and barium 

 nitrate fused in the electric arc with nitric acid, 

 water, and sulphuric acid successively, he ob- 

 tained radio-active barium sulphate possessing 

 all the characteristic physical properties observed 

 in that substance. 



The property of becoming luminous under the 

 influence of the Becquerel rays has been observed 

 by M. Paul Bary to be acquired by certain metals 

 of the alkalies and the alkaline earths by sodium, 

 potassium, lithium, rubidium, caesium, magne- 

 sium, calcium, strontium, and barium. Of other 

 metals, only phosphorescent salts of uranium ex- 

 hibited this property. These results lead the au- 

 thor to the conclusion that the same class of bodies 

 which yield salts phosphorescent to light yield 

 also compounds which become luminous under the . 

 influence of the X and the Becquerel rays. From 

 this point of view, at least, these latter rays behave 

 like luminous rays of shorter wave length. 



At the conclusion of an article in Nature, on 

 the nature and properties of the Becquerel rays. 

 Mr. G. H. Bryan observed that before 189(5 physi- 

 cists were just beginning to grasp Maxwell's theme 

 ;ni(l to realize more clearly the simplification into 

 the notions of electric and optical phenomena by 

 the conception of the ether. The discovery of rays 

 capable of discharging electrified bodies in the air 

 had not only shown the fallacy of our preconceived 

 dogmatic notions as to the division of substances 

 into conductors and dielectrics, but had taught us 

 that the properties of the ether are not so simple 

 as we had anticipated. 





