[satterly-burton] 



HYDROGEN AND HELIUM 



213 



Figure 1 



The soap bubbles were now replaced by thin india-rubber bal- 

 loons, such as are sold at the common drug stores for twopence apiece. 

 The balloon was tied to the glass apparatus shown in the figure. The 

 volume of the glass tube was 44 cc. All the air was first removed from 

 the balloon and the tube partially filled with helium. On depressing it in 

 mercury and opening the tap, the helium was sent into the balloon B. 

 A measured quantity of hydrogen was now delivered into the tube, 

 and by depression this also was sent into the balloon. The balloon 

 was now nearly a sphere of about 23^ inches in diameter. A lighted 

 match or a white hot platinum spiral, S, was now brought up to the 

 thin walled fabric, the wall burnt through and the action of the gases 

 issuing through the vent observed. The temperature of the spiral 

 would be above that of the match. The fabric itself did not burn. 



