374 Bolticood — Ionium, a New Radio-active Element. 



repeated. The final precipitate was dissolved in hydrochloric 

 acid and the solution was examined for the growth of radium. 

 In 14.0 days the amount of radium was seven times as great as 

 the amount present at the start. 



Solution 4£. The rare earths left after the separation of the 

 thorium used for the preparation of solution 4 were recovered 

 by treating the filtrates with an excess of ammonia. They 

 were reprecipitated four times as hydroxides in order to 

 remove radium and, as a solution of the chlorides, were sealed 

 up in a glass bulb. The amount of radium formed in this 

 solution in a period of over 140 days was too small to be 

 detected and could not have been as much as one one-hun- 

 dredth of the amount formed in solution 4 in the same interval. 



Solution 4c. The solution from which the thorium and 

 other, rare earths used in 4 and 4& had been separated was 

 evaporated to dryness and the residue was heated to destroy 

 the oxalic acid present. The residue was dissolved in dilute 

 hydrochloric acid and a solution of about two grams of rare 

 earths from cerite was added. The earths were then separated 

 as before, and, after removal of the radium, were obtained in 

 hydrochloric acid solution. No evidence of the growth of 

 radium in this solution could be obtained. It was apparent 

 that the substance from which the radium was formed had 

 been completely separated with the thorium. 



Activity of the Substances in Solutions. After the solutions 

 had been preserved for some time, during which observations 

 of the growth of radium were carried out, the solutions were 

 removed from the bulbs, diluted to a known volume and a 

 definite fraction removed. In this fraction the material 

 present was precipitated as hydroxide with ammonia, and the 

 hydroxide was strongly ignited to form the oxide. From the 

 oxides thus obtained thin films weighing a few milligrams 

 were prepared* and the activities of the films were determined 

 in an electroscope. The activities of the films were measured 

 at frequent intervals over a period of about 130 days. The 

 activity of the material from solutions 1, 2, 3 and 4 showed a 

 slight initial rise corresponding to the formation of thorium X 

 in "the thorium present, but the final maximum attained was 

 only about two per cent greater than the activity at the start. 

 From the known weights'of the films, which had been accu- 

 rately determined, the total activity of the substances present 

 in each of the solutions could be calculated. On comparing 

 these calculated activities with the amounts of radium produced 

 in the different solutions in equal periods, it was found that 

 these two quantities were closely related to one another. 



* The films were prepared by the method already described ; this Journal, 

 xxv, 274, 1908. 



