HEAT 



73 



Slowly heat it to a very high temperature to drive out 

 all moisture. Slip a cork tube over the open end and 

 have the cork tube tight on the glass and extend- 

 ing about a half inch above the end of the glass 

 tube. Fasten the tube securely on a ring-stand 

 in a vertical position and fill the cork cup at 

 the top almost full of mercury. Slowly heat 

 the bulb at the bottom to drive out some of the 

 air by expansion. After a few air bubbles 

 escape through the mercury, allow the bulb to 

 cool and the mercury will flow down as the air 

 contracts while it is cooling. After the mercury 

 stops flowing down heat the bulb again as be- 

 fore, and then let it cool. Continue this process 



until the bulb and tube 

 are both full of mer- 

 cury and all the air 

 out. 



Take the thermo- 

 meter tube, now full 

 of mercury, and slip it 

 through one of the two 

 holes of a rubber stop- 

 per and put it into a 

 flask containing some water. 

 Do not let the bulb touch the 

 water. Put a tube into the 

 other hole of the rubber stopper 

 to direct the escaping steam 

 away from the thermometer, 

 and heat the water to the boil- 

 ing point. After the mercury in the tube ceases to flow 

 out, seal the top by directing a gas flame against it to 



THERMOM- 

 ETER 

 TUBE 



How TO LOCATE THE BOILING 

 POINT 



