Radioactivity of Rocks of the Kolar Gold-Fields. 45 



with alkaline carbonates. A thick copper flask A, of about 

 300 c.c. capacity, with a long neck upon which was soldered 

 an outer tube to form a water-jacket, was used to effect the 

 decomposition. 10 grams of the rock, powdered so as to 



pass through a 120-mesh sieve, were mixed with 2 grams of 

 anhydrous sodium carbonate and introduced into the flask, 

 and 50 grams of stick potassium hydroxide added. The last 

 was not fused to remove water previous to use, as it has been 

 shown that vigorous ebullition assists in the liberation of the 

 emanation. The flask was then connected to the rest of 

 the apparatus as shown, by a rubber stopper, and the whole 

 evacuated with a Fleuss pump to a pressure of about 1 cm., 

 as shown by the small manometer K. The tap B was then 

 closed and the flask and contents heated with a large Teclu 

 burner for 15 minutes, a very rapid stream of water being 

 passed through the neck. A certain amount of gas was 

 usually liberated, and in the earlier experiments the pressure 

 sometimes rose to such an extent that the cork was blown out 

 of the flask. To avoid this, a safety-valve was devised. The 

 tube E, slightly greater in length than the barometric height, 

 was attached to the apparatus, and bent round under the 

 wider tube C about 50 c.c. in capacity, the joint being under 

 mercury. If the pressure rose much above that of the 

 atmosphere, gas escaped into 0. The gas liberated was on 

 one occasion pumped off, and found to be almost perfectly 

 pure hydrogen. 



After heating, the copper flask was cooled in water and 

 the pressure fell sufficiently to cause C to fill with mercury 

 when the tap D was opened. The taps leading to the 

 electroscope were then very cautiously opened and the gas 

 washed out of the flask and drying-tubes which contained 

 calcium chloride, fused potassium hydroxide, and phosphoric 



