Page:Popular Science Monthly Volume 88.djvu/919

 Ice Making at Home

��Bv Jav F. Bancroft

��THERE is no sound scientific reason why a household refriger- ating machine should not be a commercial success and go into very general use in private homes. There is a wide demand for such ma- chines, and much money and engineering skill have been expended in their de- velopment. Notwithstand- ing this, it must be ad- mitted that they have not gone into use very exten- sively in private house- holds.

The use of refrigeration to cool and preserve our food and drinks is so general that it has now come to be regarded as an essential factor in our daily life. Nevertheless it is surprising how few users of such re- frigeration there are who could accurately explain even the principles on which the ice-cooled re- frigerator works. Ev- erybody knows that in order to cool a sub- stance it must be placed in proximity to a cold body, such as ice. There are numerous ways in which cold bodies can be produced mechani- cally, but the only way in practical use in household refrigerators is by the evapora- tion of a licjuid. If the hand is plunged into warm water and then exposed to a draft of air the hand dries, but also be- comes very cool. This cooling effect is more pronounced if ether or alcohol is used instead of water, for such liquids evaporate more readily. The cooling effect is due to the fact that the liquid has changed to a vapor, and in doing so has absorbed a perceptible amount of heat from the hand, which heat disap- pears with the vapor. This principle is

���The re- frigerat- ing ap- paratus here de- s cr ib ed can be conven- iently lo- cated in the base- ment be- low the kitchen. The prin- cipal fea- ture of this ma- chine is thedumb- bell con- t a i n e r shown in its relation to the other parts of the machine. This ma- chine is 'so nearly automatic that the services of an expert attendant are not necessary

��extensively used in dry climates for cool- ing water which is placed in porous- walled vessels exposed to the air. The small amount of water that seeps through the porous walls and is evaporated will cool down the remainder of the water within the vessel.

Should water be placed in a pan under the receiver of an air-pump such water can be very much cooled, or even con- verted into ice, by removing the vapor as fast as it is formed. Only a small fraction of the liquid is evaporated, but in the evaporation of this small fraction a

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