244 Intelligence and Miscellaneous Articles. 



of utilizable energy. The production of ozone by the action of the 

 rays emitted by radium is thus a proof that this radiation represents 

 a continual freeiDg of energy. — Comptes Rendus, t. cxxix. p. 823. 



ON THE CHEMICAL ACTION OF THE X-RAYS. BY P. VILLARD. 



The interesting results which M. and Mme. Curie * have lately 

 made known will perhaps render the following observation, which 

 I have not ventured to publish before, of some interest. 



When a Crookes tube has been in action for some time, the 

 glass of the bulb acquires, as is well known, a very marked violet 

 tint over the part above the plane of the anticathode, that is to say, 

 on the side where the latter receives the cathode-rays. This region 

 of the bulb is struck at the same time by the #-rays and by the 

 diffused cathode-rays ; the following experiment enables us to 

 determine to which of the two radiations the action observed should 

 be attributed. 



In a focus-tube, I surrounded the anticathode by a wide tube, 

 either of ordinary glass or of flint glass, the inner wall of which 

 could be protected against the cathode-rays by very thin aluminium 

 leaf, very transparent to the #-rays. A silhouette cut out of opaque 

 metal, platinum for example, could be interposed at will in the path 

 of these latter. After action had gone on for about half an hour I 

 obtained the following results : 



When there is no aluminium leaf the tube becomes strongly 

 blackened if it is of flint glass, and acquires the bluish tint with 

 metallic reflexion of flint glass that has been reduced. When it is 

 of ordinary glass, which always contains a little lead, it only becomes 

 brown. This is the ordinary cathodic reduction, similar to that 

 produced in a reducing flame. The interposition of the aluminium 

 leaf, stopping the cathode-rays, does away altogether with this re- 

 duction ; and then a violet coloration is obtained, both with flint 

 glass and with ordinary glass. This modification is evidently due 

 to the cV-rays ? it is only produced above the plane of the anti- 

 cathode, and if a little plate of platinum be interposed in the path 

 of these rays, the region protected by it remains uncoloured. It 

 was to this phenomenon that I alluded in a discussion at the Easter 

 meeting of the Societe de Physique, when I said that it was strictly 

 speaking possible to obtain a radiograph by taking for the sensitive 

 compound a simple glass plate. 



This transformation of glass or flint glass is certainly due to oxid- 

 ation, as it is equally well obtained on warming the flint glass in a 

 strongly oxidizing flame. Very probably the violet coloration is 

 produced by manganese ; this metal, in its fully oxidized combi- 

 nations, is known to colour glass violet. 



These results moreover establish an analogy between the .r-rays 

 and the radiations emitted by radioactive substances. For this 

 reason I propose to repeat the foregoing experiments, but substi- 

 tuting for ordinary glass a silicate containing, in considerable 

 quantity, some substance whose oxidation will be easy to recognize. 

 — Comptes Rendus, cxxix. p. 882. 



* Comptes Bendus, cxxix. p. 823 ; supra, p. 242. 



