602 Dr. B. B. Boltwood on 



the flask C. The quantity taken depended on the percentage 

 of uranium contained in the substance and varied from O'l 

 gram to 5 grams, the smallest quantities being taken of 

 those minerals in which the content of uranium was high. 

 The flask C had an approximate capacity of 200 c.c. and was 

 closed with a tight-fitting rubber stopper which carried two 

 tubes, one extending almost to the bottom of the flask, and 

 the other only a short distance below the stopper. The air 

 in this flask was largely displaced by a slow current of carbon- 

 dioxide gas introduced through the longer of the tubes *. 

 The tubes were connected by short lengths of rubber tubing 

 to the rest of the apparatus as shown in the diagram, the 

 stopper of the flask was removed and about 50 c.c. of the 

 reagent used for the decomposition of the mineral was quickly 

 introduced. The pinchcock b was closed and the flask was 

 shaken with a rotary motion in order to thoroughly mix the 

 reagent and the powdered mineral. The flask was warmed 

 gently, the agitation of the liquid being continued without 

 interruption, until the decomposition of the mineral was 

 complete. During the heating operation the pinchcock c 

 was opened, and the gas displaced by expansion was allowed 

 to accumulate in the burette D, from which it was transferred 

 to a second storage burette connected with the latter. The 

 heating was discontinued and the pinchcock c was closed. 

 The next step depended on the nature of the reagent used to 

 decompose the mineral. If the reagent was concentrated 

 sulphuric acid, a substance employed in a number of cases, 

 the rubber tube at a was connected with a carbon-dioxide 

 generator, the pinchcocks a and b were opened, and the gas 

 was allowed to flow into C as the gaseous contents of the 

 latter contracted on cooling. When the acid mixture in 

 had become quite cold, a process which could be greatly 

 hastened toward the latter end by the cautious application of 

 cold water, the pinchcocks a and b were closed, the carbon- 

 dioxide generator was disconnected, and the tube at a was 

 connected with the reservoir B containing water. The 

 cock a was opened, permitting the water to fill the shorter 

 limb of the tube Ab, and about 100 c.c. of water were admitted 

 to the flask C through the cock b. The contents of the flask 

 were agitated by shaking during the process of dilution, and 

 the cock c was opened to allow the gas to escape into the 

 burette D. When the reagent used in the flask C was a 

 dilute acid, the dilution of the solution could be carried out 



* The object in using- the carbon dioxide was that by absorbing it 

 later the final volume of gas obtained was of convenient volume for 

 introduction into the electroscope. 



