COMPOSITION OF WATER 157 



d. 1707 : 59-65. Composition of Water. 



e. 1708 : 266-267. Water and Its Composition. 

 /. 1711:6-10. Composition of Water. 



Experiment 58. To Prepare Hydrogen. 



Apparatus: Test tube 8" X 1", rubber stopper with two 

 holes, thistle tube, evaporating dish, ring stand, asbestos mat, 

 burner; otherwise the same apparatus as in Experiment 3. 



Materials : Granulated zinc, hydrochloric acid, 1-4. 



a. Put a few pieces of zinc in the test tube and cover them 

 with water. Insert the stopper, placing the thistle tube so 

 that it reaches below the surface of the water in the tube. 

 The delivery tube should be in the other hole. Fill bottles as 

 in the Oxygen experiment. Add acid to the zinc through the 

 thistle tube, and collect four bottles of hydrogen. Keep the 

 bottles bottom side up; otherwise the hydrogen will escape. 



b. Light the hydrogen in one bottle, and describe its com- 

 bustion. Does hydrogen support the combustion of wood ? 



c. Place the mouth of a bottle filled with air against the 

 mouth of a bottle filled with hydrogen, and invert them several 

 times. Bring the mouths of the bottles near a flame. What 

 happens? Why? 



d. Turn a bottle of hydrogen right side up and try to light 

 it after one minute. What is the result? Explain. 



e. Boil to dryness the liquid from the hydrogen generator. 

 It is zinc chloride. Expose the dried salt to the air, and tell 

 what happens. 



EXPERIMENT FOR THE TEACHER 

 The Philosopher's Lamp 



Use a generator similar to the above, but in the place of the 

 delivery tube insert a tube which has been drawn out to form 

 a fine tip. After adding the acid, collect some of the hydrogen 



