218 PKESENT PROBLEMS OF INORGANIC CHEMISTRY, 



oiiiaiiation, a most interestino; fact was observed, namely, that pre- 

 cipitation of the thorium as liydroxide by ammonia h'ft luiprecipi- 

 tated a substance, which they termed " tliorium-X." and which was 

 itself highly radio-active. Its radio-active life, however, was a short 

 one; and as it decayed, it was reproduced from its parent thorium at 

 an equal rate. Here is a case analogous to what was sought for with 

 radium and uranium; but evidently uranium is not the only parent 

 of radium; the operation is not one of parthenogenesis. Similar 

 facts have been elicited for uranium by Crookes. 



The ^I'-rays, caused by the disintegration of radium and of its em- 

 anation, are accompanied by rays of quite a dilferent character; 

 they are the /^-rays, identical wdth electrons, the mass of which has 

 been measured by J. J. Thomson and others. These particles are 

 projected with enormous velocity, and are capable of penetrating 

 glass and metal screens. The power of penetration appears to be 

 proportional to the amount of matter in the screen, estimated by its 

 density. These electrons are not matter; but, as I shall relate, they 

 are capable of causing profoimd changes in matter. 



For the past j'^ear a solution of radium bromide has been kept in 

 three glass bulbs, each connected to a Topler pump b}^ means of capil- 

 lary tubing. To insure these bulbs against accident each was sur- 

 rounded by a small beaker; it happened that one of these beakers 

 consisted mainly of potash glass; the other two were of soda glass. 

 The potash-glass beaker became brown, while the two soda -glass 

 beakers became purple. I think there is every probability that the 

 colors are due to liberation of the metals potassium and sodium in 

 the glass. They are contained in that very viscous litpiid, glass, in 

 the colorless ionic state ; but these ions are discharged by the yS-rays 

 or negative electrons, and each metal imparts its own peculiar color 

 to the glass, as has been shown by Maxwell Garnett. This phe- 

 nomenon, how^ever 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; o'-rays have never been in contact 

 with them; they have never been bombarded by what is usually 

 called matter, except by the molecules of the surrounding air. Now, 

 these colored beakers are radio-active, and the radio-active film dis- 

 solves in water. After careful washing, the glass Avas no longer 

 radio-active. The solution contains an emanation, for on l)ubbling 

 air through it, and cooling the issuing air with liquid air, part of the 

 radio-active matter was retained in the cooled tube. This substance 

 can be carried into an electroscoi)e by a current of air, after the liquid 

 air has been Avithdrawn, 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 



