16 LABORATORY EXERCISES. 



drawn out until the opening is small. 

 Stand away from the tube and apply a 

 lighted match. (See Fig. 3.) 



a. What do you observe? How does 



the color of the flame differ from 

 that of B, 2, b above? (This dif- 

 ference is due to the heated glass 

 tube.) 



b. Hold a dry glass tumbler over the 



mouth of the delivery -tube. What 

 do you see on the sides of the 

 glass? What, therefore, is formed 

 when hydrogen burns? 



c. What was formed when wood first be- 



gan to burn? What was probably 

 one of the ingredients of wood? 

 (See experiment J, C, 2.) 



6. STUDY OF EVAPORATION. 



A. Pour a wine-glass of water into a saucer and 



place it near a heated stove or radiator. Ex- 

 amine at the end of several (6-12) hours. 

 What do you observe? 



B. Pour the same amount of water into a second 



saucer, put it in a cool place, and compare 

 with (A) above at the end of several hours. 



C. Into a third saucer put another wine-glass of 



water, cover with a glass dish, and place be- 

 side (A). What do you find on examining the 

 dishes at the end of several hours? Explain. 



D. Fill the wine-glass with water and place it beside 



