44 POPULAR SCIENCE MONTHLY. 



electrons, and each metal imparts its own peculiar color to the glass, 

 as has been shown by Maxwell Garnett. This phenomenon, however 

 interesting, is not the one to which I desire to draw special attention. 

 It must be remembered that the beakers have been exposed only to /?- 

 rays; a-rays have never been in contact with them; they have never 

 been bombarded by what is usually called matter, except by the mole- 

 cules of the surrounding air. Now these colored beakers are radio- 

 active, and the radioactive film dissolves in water. After careful 

 washing, the glass was no longer radioactive. The solution contains 

 an emanation, for on bubbling air through it, and cooling the issuing 

 air with liquid air, part of the radioactive matter was retained in the 

 cooled tube. This substance can be carried into an electroscope by a 

 current of air, after the liquid air has been withdrawn, and as long 

 as the air-current passes, the electroscope is discharged; the period of 

 decay of this emanation, however, is very rapid, and on ceasing the 

 current of air, the leaves of the electroscope cease to be discharged. 

 In having such a short period of existence, this emanation resembles 

 the one from actinium. 



Owing to the recess, only a commencement has been made with the 

 investigation of the residue left on evaporation of the aqueous solu- 

 tion. On evaporation, the residue is strongly active. Some mercur- 

 ous nitrate was then added to the dissolved residue, and it was treated 

 with hydrochloric acid in excess, to precipitate mercurous chloride. 

 The greater part of the active matter was thrown down with the mer- 

 curous chloride, hence it appears to form an insoluble chloride. The 

 mercurous chloride retained its activity unchanged in amount for ten 

 days. The filtrate from the mercurous chloride, on evaporation, 

 turned out to be active; and on precipitating mercuric sulphide in it, 

 the sulphide precipitate was also active; but its activity decayed in one 

 day. The filtrate from the mercuric sulphide gave inactive precipita- 

 tates with ferric salts and ammonia, with zinc salts and ammonium 

 sulphide, with calcium salts and ammonium carbonate; and on final 

 evaporation, the residue was not radioactive. Hence the active mat- 

 ter forms an insoluble chloride and sulphide. The precipitated mer- 

 curous chloride and mercuric sulphide were dissolved in aqua regia, 

 and the solution was evaporated. The residue was dissolved in water, 

 and left the dish inactive. But the solution gave an insoluble sul- 

 phate, when barium chloride and sulphuric acid were added to it, 

 hence the radioactive element forms an insoluble sulphate, as well as 

 an insoluble chloride and sulphide. 



This is a sample of the experiments which have been made. It 

 may be remarked that the above results were obtained from a mixture 

 of the potash and soda glass; somewhat different results were obtained 

 from the potash glass alone. These changes appear to be due to the 

 conversion of one or more of the constituents of the glass into other 



