CONTROL OF FIRE 



79 



burning oil floats on the water and the expansion of any 

 generated steam throws the flaming oil about and thus 

 spreads the fire. In a case of this kind, sand or a woolen 

 blanket serves the purpose better. 



Wool does not readily burn, and when the blanket is 

 thrown over the burning oil, the air is shut off and the 

 fire put out. If one's clothing takes fire by accident, one 

 should never run. A rug or a blanket rolled about the 

 body is the most effective means of putting 

 out the fire. If one is outdoors, rolling in 

 the dust, or heaping dust on the flames, 

 will cut off the oxygen supply. The chief 

 thing to remember is to cut off the air 

 supply immediately. 



Experiment 26. (Teacher's Experiment.) 

 Get two or three bottles of carbon dioxide from 

 the chemical laboratory, or prepare it by pouring 

 dilute hydrochloric acid upon pieces of limestone 

 in a bottle and collecting the gas over water. 

 Does the appearance of this gas differ in any 

 way from that of air? Smell of one of the 

 bottles that has stood over water for some time. FI QURE 34. DIA- 



rrn T T T , i GRAM OF A FlRE 



The gas has no odor. Plunge a lighted match EXTINGUISHER 

 into one of the bottles containing the carbon 

 dioxide. What happens? Does the gas burn or support combus- 

 tion? Slowly overturn a bottle of the gas above a lighted candle. 

 The candle is extinguished. The gas falls out when the bottle 

 is overturned, thus showing that it is heavier than air. If the 

 amount of carbon dioxide in the air were largely increased, what 

 effect would it have upon combustion ? 



The ordinary chemical fire extinguisher (Figure 34) con- 

 sists of a strong metal cylinder nearly filled with a solution 

 of baking soda. Held firmly in the top of the cylinder is a 



