80 EXPERIMENTAL GENERAL SCIENCE 



19. The filament in certain electric light bulbs is made of carbon. 

 Why is it not consumed when the electricity is turned on? 



20. Dissolve a piece of phosphorus, half the size of a pea, in about 3 

 cubic centimeters of carbon disulphide. (Do not touch the phosphorus 

 with the hands.) Support a piece of blotting paper or filter paper on a 

 ring stand and pour the solution over it. What happens when the liquid 

 evaporates, leaving the phosphorus? 



21. What form of combustion is illustrated by the foregoing 

 experiment? 



22. Is the kindling temperature of wood higher or lower than the 

 temperature of the school-room? 



23. Why do gasoline engines require that a certain amount of air be 

 admitted to the cylinders with the gasoline? 



24. Why cannot sodium be preserved under water? 



25. Examine the bunsen burner and find the hole at the base for the 

 admission of air. Close this opening, turn on the gas and light it. 

 What color is the flame? Why? 



26. Admit air to the burner. What effect has this on the color of the 

 flame? Why? 



27. Press a sheet of metal down upon the orange flame for a few 

 seconds. What is deposited on the metal? 



28. Make the same experiment with the blue flame. How do you 

 account for the difference. 



29. Why does a candle or lamp smoke when not well supplied with 

 air? 



