20 LABORATORY MANUAL 



to balance the globe evenly. Without disturbing the 

 weight pan, remove the globe from the other pan. 



Fig. 3. 



With an air pump exhaust the air from the globe and 

 then close the stop cock. Then replace the globe on 

 the pan of the balance from which it was removed. 

 Do the two sides now evenly balance each other ? 

 How do you account for this condition? Does air 

 then have weight? Air is a gas. From the definition 

 of matter, do experiments 1 and 3 prove that gas is 

 matter? Why? 



B. The bulb of an incandescent lamp is empty save 

 for the filament and a very slight trace of gas which 

 was not exhausted. Weigh the bulb carefully and 

 accurately With the aid of the blow-pipe direct a 



