THE REFRIGERATOR 161 



increases rapidly, that is, its relative humidity is lessened; 

 it is no longer saturated. Since most of the provisions 

 usually placed in the refrigerator contain considerable mois- 

 ture, evaporation takes place and the foods become drier. 

 It is for this reason that fruits, such as apples, oranges and 

 lemons, as well as other lands of provisions, often dry up and 

 wither instead of suffering ordinary decay when placed in a 

 good refrigerator. Common table salt often absorbs so 

 much moisture in the summer that it can not be shaken from 

 a salt shaker. This can be prevented by placing the shaker 

 in the dry air of the refrigerator. 



189. Care of the Refrigerator. It is not possible to con- 

 struct a refrigerator of such material and in such a manner 

 as entirely to prevent heat from getting into it, even when 

 all doors are closed. If this were possible, very little ice 

 would be needed to operate it. Since heat is certain to 

 penetrate the refrigerator from every side, and at all times, 

 this heat must be taken up or absorbed by the ice. In Art. 

 150, we learned that heat used in melting ice is called HEAT 

 OF FUSION. The cooling of the refrigerator is due almost 

 entirely to the absorption by the ice of this heat of fusion; 

 that is, the heat is consumed simply in melting the ice. 

 Occasionally we hear of someone's wrapping the ice in paper, 

 to prevent melting, before placing it in the refrigerator. This, 

 of course, is an error. Just to the extent that wrapping 

 actually prevents melting as intended, the presence of the ice 

 in the refrigerator is useless. Nevertheless, good judgment 

 on the part of the operator may lessen considerably the 

 amount of ice required to operate the refrigerator. The re- 

 frigerator should be placed in the dryest and coolest place 

 possible, consistent with convenience. 



190. Rear-icing and Built-in Refrigerators. Most manu- 

 facturers, when requested, now furnish refrigerators with a 

 door to the ice compartment on the back, or rear, of the re- 

 frigerator. This device is often of great service, inasmuch 

 as it enables the ice man to fill the refrigerator without com- 



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