62 Our Surroundings 



made a liquid by means of great pressure. This liquid is forced 

 into pipes running through a tank of brine water full of dissolved 

 salt and there it turns back to gas. This change of a liquid 

 to a gas requires heat, which is taken from the brine. In this 

 brine are suspended containers full of pure water. As the 

 temperature decreases, the pure water and the brine become 

 equally cold, but the brine having the lower freezing point of the 

 two remains a liquid while the pure water changes to pure, clear, 

 manufactured ice. 



Electric Refrigeration. The electric refrigerator is today 

 taking the place of the ice box. Its motor condenses a gas to a 

 liquid which later expands to a gas in pipes within the refrigera- 

 tor. This process absorbs heat and produces a low temperature. 

 At the same time ice for family use is made in partitioned drawers 

 near the pipes. 



Water as a Cleansing Agent. The best water for cleaning 

 is soft water, that is, water without any mineral matter in solu- 

 tion. Rain water is soft water. Water from wells and springs 

 usually contains mineral matter in solution taken from the soil. 

 Such water is called hard water. It does not readily combine 

 with soap and so is not as efficient for cleaning. 



Experiment to Show How Hard Water May Be Softened 

 by Means of Washing Soda, Borax, Etc. Put a half pint of 

 hard water in a beaker and stir in it a tablespoonful of borax 

 or washing soda. Allow the solution to settle and pour the clear 

 part into a bottle. Add a little soap and shake. In a second bottle 

 add soap to hard water and shake. Compare what occurs in the 

 two bottles and account for the different actions. 



Cleansing Agents Used with Water. Effective as water is 

 in cleansing, it can be made even more effective by the use of 

 certain materials. Among these are soaps and alkalis. 



Soap. Soap is a substance extensively used with water in 

 cleaning. Its great value lies in the fact that it will form an emul- 

 sion with grease or oil ; that is, it will break up the grease or oil 

 into small particles so that it becomes easy to remove it by the ap- 

 plication of soft water. Perhaps you have noticed how difficult 

 it is to remove grease from a piece of cloth by merely rubbing it 



