162 GENERAL SCIENCE 



Acetylene Gas. This gas is produced by adding water to cal- 

 cium carbide. It is especially rich in carbon, and gives a very white 

 light. The gas is used for automobiles and stereopticons and, to 

 some extent, for lighting houses. It is, however, very explosive 

 when mixed with air, and because of its richness in carbon a special 

 burner is required. 



Prest-o-Lite. Prest-o-lite is acetylene dissolved in acetone. 

 A tank is filled with asbestos soaked in acetone. Acetylene is forced 

 into the tank under pressure. The gas is dissolved in the acetone. 

 When the gas is turned on for the lights, the pressure is reduced 

 inside, and the acetylene passes from the solution. 



Gasoline. Gasoline is used for lighting and cooking. The 

 tank of a gasoline stove is a little higher than the burner to which 

 the gasoline runs. The heat changes the gasoline into a gas which 

 burns as a blue flame. 



Gasoline vapor is very explosive if mixed with air. Accidents 

 have occurred through trying to fill the tank of a gasoline stove when 

 the stove was lighted. The modern gasoline stove is so con- 

 structed that the tank cannot be filled while the stove is lighted. 



Gasoline Engine. The gas of gasoline is used in gasoline 

 engines because of its explosiveness when mixed with large quanti- 

 ties of air. The gasoline is allowed to enter a carburetor where it is 

 changed to a gas and mixed with air. From the carburetor the gas 

 enters the' cylinders of the engine, and is exploded by means of an 

 electric spark. 



All small and medium size gas engines operate on the four- 

 stroke cycle principle. A four-stroke cycle engine completes one 

 cycle of events in four strokes of the piston, i.e., the suction, compres- 

 sion, power and exhaust strokes. 



First or Suction Stroke. 



Gas and air, constituting the fuel charge, are sucked into the cylinder (A) 

 through the inlet valve (H ) as the piston (B) moves outwards, away from the 

 cylinder head (Al). The exhaust valve (HI) is closed. 



Second or Compression Stroke. 



The piston (5) moving inward, towards the cylinder head (AY), compresses 

 the fuel charge. Both inlet and exhaust valves (H) and (HI), respectively, 

 are closed. 



