Intelligence and Miscellaneous Articles. 243 



very active product, at the end of ten days the bottom of the flask, 

 viewed from the side, is almost black where in contact with the 

 salt. This tint diminishes in proportion as it extends into the glass, 

 and at some millimetres depth it appears violet. With a less active 

 product the tint is less intense and requires more time for its 

 production. The glass of the flasks in which this phenomenon 

 manifests itself is not blackened in the reducing flame, whence we 

 conclude that it does not contain any lead. 



The change produced in barium platinocyanide by the radium 

 rays is probably also a chemical effect. When submitted to the 

 action of the radium rays, barium platinocyanide begins to grow 

 yellow, then it becomes brown, and this brown variety is less sen- 

 sitive to the excitation of fluorescence. To restore the platino- 

 cyanide to its original condition it is sufficient to expose it to sun- 

 light. This phenomenon is the same as that which has been 

 described for the Eontgen rays by M. Villard*. 



When a layer of barium platinocyanide is placed in the dark 

 above a layer of a radioactive salt, the platinocyanide becomes 

 strongly luminous under the influence of the Becquerel rays ; but 

 little by little the platinocyanide is converted into the brown 

 variety and the luminosity gradually diminishes. On exposing the 

 system to light, the platinocyanide is partially restored, and if 

 then the system is brought back into the dark the light emitted is 

 again very brilliant. 



Thus is realized the synthesis of a phosphorescent body with 

 long duration of phosphorescence by means of a fluorescent body 

 and a radioactive body. 



M. Griesel has prepared a radiferous platinocyanide of barium, 

 very luminous at the moment of its preparation, which under the 

 action of its own Becquerel rays is converted into the less luminous 

 brown variety f. 



When the chloride of barium and radium is crystallized out of 

 a solution which has been saturated when hot, the crystals are 

 colourless at the moment of deposit. Little by little these crystals 

 acquire a rose colour w T hich becomes gradually more pronounced. 

 This coloration appears the more rapidly and is the more intense 

 as the salt contains more radium. If the rose crystals are dissolved 

 the solution is colourless, and if it be caused to crystallize, it 

 deposits crystals which are at first colourless. The development 

 of the coloration seems to accompany that of the radioactivity, 

 which after the deposition increases with time. 



Dry chloride of barium and radium is white quite at first, it 

 grows yellow gradually at the same time that its radioactivity 

 develops. 



It is probable that these changes of colour correspond to mole- 

 cular modifications which are produced in the barium salts by the 

 action of the radium rays. 



The conversion of oxygen into ozone necessitates the expenditure 



* Soc. de Phys., 18 May, 1898. t Wied. Ann. lxix. p. 91. 



