202 PROFESSOR E. RUTHERFORD ON THE 



24. Connection of Slowly Decaying Product with Raflio-Tcllnrium.Sinne evidence 

 will now he considered which points to the strong probability that one of these slowly 

 changing products of radium is tbe same as the active constituent present in radio- 

 tellurium, separated from pitchblende by MARCKWALD. 



It will be recalled that the polonium of Mme. CURIE is always obtained with 

 bismuth, but can be partially separated from it by several distinct methods. GIESEL 

 early observed that a bismuth plate dipped into a radium solution became per- 

 manently active and gave out only a rays, and in this respect resembled the polonium 

 of Mme. CURIE. 



GIESEL has throughout insisted that polonium was nothing more than ' induced 

 bismuth ' apparently considering that the bismuth acquired the radioactive property 

 by mixture with a radium solution. Taking the point of view that radioactivity is 

 always the result of changes occurring in special kinds of matter, the experiments of 

 GIESEL indicate that a radioactive product is deposited from the radium solution on 

 to the bismuth plate, and that the activity of the plate is not due to the bismuth at 

 all, but to radioactive matter deposited on its surface. 



MARCKWALD found that a bismuth plate dipped into a solution of pitchblende was 

 coated with a radioactive deposit. He at first thought this activity was due to the 

 tellurium which was deposited on the plate, and consequently gave it the name 

 radio-tellurium. Later results have, however, shown that the activity has nothing 

 whatever to do with the tellurium, and by suitable chemical methods he has separated 

 an extremely active substance. MARCKWALD states that the radio-tellurium gives 

 out only a rays, and has not appreciably changed during six months after separation. 

 Mme. CURIE found that the active constituent present in bismuth, which had been 

 made active by placing it in a radium solution, could be fractionated in the same way 

 as polonium, and in that way was able to obtain bismuth 2000 times as active as 

 uranium, but this activity decreased with the time. 



An account will now be given of some experiments to ascertain if there is any 

 connection between this slowly decaying product of radium and radio-tellurium or 

 polonium. 



The active matter deposited on the glass tube, in which a large amount of radium 

 emanation had been stored for a month, was dissolved in sulphuric acid. A bismuth 

 plate was introduced into the solution and left for several hours. The bismuth plate 

 was found to be strongly active and to give out only a rays. On adding a second 

 bismuth plate, very little active matter was deposited iipon it. The remaining 

 solution was then evaporated, and the residue was found to be about as active as the 

 bismuth plate, and to give out both a and /8 rays. There is thus no doubt that the 

 matter dissolved off the glass is complex, and one part is deposited on bismuth and 



transformed in 40 years and E in about 1 year. This modification has been introduced into the subsequent 

 schedules in the text. A full account of these experiments was communicated to the Electrical Congress 

 at St. Louis (September 16, 1904) in a paper entitled " Further Transformation Products of Radium."] 



