6 



GENERAL SCIENCE 



The ice manufacturing plants have a compressor, B, Fig. 5, 

 and cooling coils, C, over which cold water is running, since gaseous 

 ammonia changing into a liquid gives off large quantities of heat. 

 Every person is familiar with the compressing of air with a pump 

 to fill bicycle tires or automobile tires. We know air gets very 

 warm as it is compressed; so does the ammonia. The liquid 

 ammonia, after it has been cooled by the water, is allowed to run 

 through pipes which are surrounded with brine. In this brine 

 are cans of water, G. The ammonia liquid, when entering the 



ABOUT 34 LB3. 



FIG. 5. 



pipes at E, changes by evaporation from a liquid to a gas, but in 

 order to change into a gas it requires a large amount of heat. 

 This heat is removed from the brine, which in turn removes heat 

 enough from the water to freeze it. 



Fig. 6 shows a refrigerator for home use. Instead of ammonia 

 gas, sulphur dioxide gas is used. 



What is the motor A used for? 



Why is the compressor B necessary? 



Why are the coils at C called the cooling coils? 



Why are the coils in the ice chamber called the refrigerating coils? 



