EXPLOSION 



223 



FIG. 145 



Experiment 140. Into a large test tube fit a bent delivery 

 tube (of small size), as in Fig. 144. Put bits of marble into the 

 test tube and pour upon them strong HC1, so as to make a good 

 flow of CO 2 (Experiment 129). Direct this stream of CO 2 gas 

 upon a candle flame or a small fire made of chips. 

 Note the effect, and explain. 



Experiment 141. Cut holes in a piece of 

 cardboard and fit it into a small glass chimney. 

 Stick a lighted candle on the card (Fig. 145). 

 Now cover the chimney tightly at the top for a 

 moment. Light the candle and set the chimney 

 upon some flat surface that will close it at the 

 bottom. Explain. 



261. Explosion. An explosion is a sort 

 of combustion that takes place very rap- 

 idly in a confined space. Two or more 

 substances that may easily unite are mixed together ; 

 a mere spark at some point in the mixture will often 

 cause action throughout the whole mass in a moment. 

 If the mixture is confined in a small space, the gases 

 that are formed by the chemical action will have so 

 much larger natural volume that they will expand and 

 burst the walls that confined them. 



262. Flames. A burning gas gives rise to a flame; 

 burning solids usually glow and are luminous ( 126), 

 but without flame. When a solid substance, such as 

 wood, burns with a flame, it is because the substance is 

 being decomposed by the heat, and the gases that are 

 given off cause the flames. 



Experiment 142. Make some H as in Experiment 121, using 

 care in lighting the gas. The flame is usually somewhat colored 

 by solid particles from the heated glass tube ; but if the end be 



