300 



Introduction to the Study of Science 



of rubber tubing ; this will serve as an escape valve. A pinchcock 

 on the rubber tubing will aid in regulating the escape of steam. Place 

 the boiler thus equipped and about two thirds full of water on a stand 

 and secure it with a clamp. Apply heat. 



Observe the thermometer and pressure gage as the water is being 

 brought to boiling. When the water boils vigorously and steam 



issues freely from the escape 

 valve, close the valve partly 

 to prevent the free escape of 

 steam. The pressure is in- 

 creased, as the mercury in 

 the gage shows, and the ther- 

 mometer indicates a change 

 in the temperature of the 

 water. Apply carefully dif- 

 ferent degrees of pressure by 

 closing the valve more and 

 more, and note the corre- 

 sponding changes in boiling 

 temperature. 



Boiling tempjerature 

 raised with increase in 

 pressure. The tempera- 

 ture of boiling water 

 (page 87) is not changed 

 with any amount of added 

 heat so long as the pres- 

 sure remains unchanged ; 

 the water boils more 

 violently or is converted 

 more rapidly into steam. 

 In this experiment an 

 increase in pressure is 

 followed immediately by a rise in the temperature, which shows 

 that the boiling temperature of water is raised. The table (page 

 312) gives the boiling temperatures for certain pressures above 

 and below atmospheric pressure, and may be consulted for fur- 

 ther emphasis of the fact brought out in your experiment. 



FIG. 94. Apparatus for demonstrating 

 changes in boiling point due to changes in 

 pressure. 



