386 Boltwood — Radio-activity of Natural Waters. 



flask and about 500 cc of water added. The water was boiled 

 for three hours. The mineral was then filtered off and the 

 filtrate boiled for one-half hour. The filtrate was diluted, 

 sealed up for four days and then boiled again. The gases 

 given off were tested for radio-activity in the electroscope and 

 the observed leak was 0*034: division per minute. 



About 80 grams of the same mineral mixture but in coarser 

 powder had been shut up in a flask for about eight days. A 

 sample of the gas in the flask withdrawn and separately tested 

 showed that the total accumulated emanation in the flask had 

 an activity equivalent to approximately 1700 divisions per 

 minute. The gas was drawn from the flask into a 4-liter bot- 

 tle by allowing the water with which the bottle was filled to 

 run out until only about two liters remained. The bottle was 

 then closed and shaken vigorously for about five minutes, and 

 was then allowed to stand undisturbed for about thirty min- 

 utes. Water was then run into the bottle until all of the gas 

 was displaced, the gas being collected in a second bottle (see 

 below). Care was taken to remove any small bubbles of gas 

 adhering to the neck of the bottle, and the water it contained 

 was then introduced into the boiling can. The gases were 

 boiled out of the water and tested in the electroscope. The 

 activity of the gas obtained was equivalent to 80 divisions per 

 minute. 



The second bottle mentioned above, having a capacity of 

 four liters, was filled one-half full of the gas from the first 

 bottle, the gas being introduced at the top, while the water 

 with which it was at first filled was permitted to flow out 

 through a tube reaching to the bottom. Care was taken to 

 avoid any agitation of the water and the gas was allowed to 

 stand in contact with it for about two hours. The bottle was 

 then completely filled with water by means of a tube reaching 

 to the bottom and the gas was displaced. The activity of the 

 gas obtained from the water on boiling was equivalent to a 

 leak of 0*40 division per minute. 



Summary. 

 From the results of these experiments it is apparent that by 

 the action of cold, pure water on the uranium minerals used 

 only a very slight trace of the radium contained in them is 

 dissolved. The action of hot water is only slightly greater 

 than that of cold water. Even brief contact with uranium 

 minerals can impart to water very marked radio-active proper- 

 ties due to dissolved radium emanation. Water can also 

 acquire very readily measurable quantities of radium emana- 

 tion by simple contact with gaseous mixtures containing the 

 emanation. 



