Relation between Uranium and Radium. 285 



observed, the yellow precipitate formed as before, and the 

 liquid gave off oxides of nitrogen freely. In the first 

 purification in Experiment II. the first extraction was made 

 on the solid crystals as supplied by the maker, and in the 

 other purification in this experiment and those in Experi- 

 ment III. the crystals obtained by evaporating the solution 

 to dryness were employed in the first extraction. 



The residues were worked up by evaporation with concen- 

 trated nitric acid, and then diluted and purified from radium 

 as described under Experiment VII. Owing to accidents 

 and various other causes, these residues do not represent the 

 whole of the three kilograms employed. The residues from 

 the old kilogram (Experiments III. to V.) contained barium 

 and were unfortunately rejected. Probably the greater portion 

 of the residues from the other two kilograms is present. 



Experiment I. 



This experiment is the one that has been longest started of 

 those with the new method of purification. A kilogram of 

 commercial uranyl nitrate was employed, and in its original 

 state when tested for radium by the bubbling test produced 

 a leak of 190 in the electroscope, equivalent to between 10 _s 

 and 10 -9 gram radium. On June 20th, 1905, after the first 

 purification with ether a bubbling test gave a leak of 5" 5. 

 After a second purification in the same way it gave (July 3rd, 

 1905) a leak of 0"4, and on Sept. 12th, 19057 0'45, both by 

 the bubbling test. Two tests performed by the mercury- 

 pump method gave (Oct. 3rd, 1905) 4' 7, and (Oct. 10th, 

 1905) 5*5. 



At this stage the solution contained by analysis 280 grams 

 of uranium (element). The solution was purified a third and 

 last time with ether and finally set up in a closed flask 

 connected to the mercury pump on October 24th, 1905. 

 Unfortunately the record of the final analysis has been mis- 

 laid, but it may be assumed for present purposes that about 

 250 grams of uranium is present. The determination will be 

 done again at the first opportunity. The first test in the 

 series of measurements af the quantity of radium present, 

 which has been continued uninterruptedly since, was done on 

 October 31st, 1905, and the leak obtained was 1*4. 



In the table (p. 2^) the results up to date are collected. 

 It has been thought advisable to record every time the gas 

 has been pumped out of the flask even though the tost was a 

 failure. 



