242 Boltwood — Production of Radium from Uranium. 



(a) The employment of a method for the determination of 

 radium which gives positive and quantitative results. The 

 method must be suitable for the determination of very small 

 quantities of radium and must be capable of indicating the 

 maximum quantity present at all times. 



(b) The preparation of a pure compound of uranium and the 

 demonstration that the compound is initially free from radium. 



(c) Proper conditions for testing and preserving the uranium 

 salt in order to preclude the introduction of radium or radium 

 emanation from external sources, so that if the presence of 

 radium is noted it can be assumed with certainty that the 

 radium found has actually been formed in the solution. 



It would appear that none of these essential conditions has 

 been fulfilled in the experiment described by Mr. Soddy. 



The writer of the present paper has been conducting an 

 experiment on the growth of radium in a uranium solution for 

 the past thirteen months. The conditions of the experiment 

 were the following: In May, 1904, a kilogram of "purest 

 uranium nitrate " was purchased from Eimer & Amend of 

 New York City. This material was tested qualitatively for 

 radium (through the emanation) and readily detectable quanti- 

 ties of this element were found to be present. The salt was 

 dissolved in distilled water and the solution was filtered. The 

 compound was then recrystallized five separate times, the con- 

 ditions being so chosen that the separate crystals of each of the 

 different crops were not over two millimeters in cross-section. 

 The mother liquors were each time removed from the crystals 

 on a suction filter, and the crystals were washed with a small 

 quantity of ice-cold water. 



The final yield of purified material was a little in excess of 

 200 grams. Of this 100 grams were taken and dissolved in 

 pure, distilled water. This solution was introduced into a 

 glass bulb with a capacity of approximately 400 cc , diluted to 

 about 250 cc , and the neck of the bulb was drawn out into a 

 short capillary and sealed in the flame of the blowpipe. The 

 solution was sealed up on July 8, 1904. Thirty days later the 

 bulb was opened under conditions which precluded the escape 

 of any portion of the contained gases and the entire gaseous 

 contents were removed and transferred to an electroscope. In 

 order to completely displace the dissolved gases and any radium 

 emanation which might have been present the solution was 

 boiled vigorously for about fifteen minutes.* 



* The removal and collection *of the gaseous contents of the bulb was 

 accomplished by the use of the apparatus which has been described in a 

 previous paper (this Journal, xviii, 379). The neck of the bulb containing 

 the uranium solution having been first notched with a file, it was inserted 

 in the rubber tube D, the point was broken off within the tube, and the 

 gases displaced from the bulb on heating were collected in the burette D, 

 which was filled at the start with boiling water. 



