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EXPERIMENTAL GENERAL SCIENCE 



the liquid by filtration, matter in solution passing through 

 unchanged. In many cities, the water for household use is 

 filtered through beds of sand. This gives clear water, but not 

 necessarily pure water, since it does not remove dissolved 

 matter. 



121. Distillation. When it is desired to recover the solid 

 matter in a solution, this is easily accomplished by evaporating 

 the solvent. The solvent may also be obtained in its original 



FIG. 46. Apparatus used in filtering. (Rockwood.) 



state by catching the vapor as it rises, and cooling it to the 

 liquid state again. The latter process is called distillation. 

 The distilling apparatus consists essentially of a closed vessel 

 in which the matter to be distilled is heated, with a coil of 

 pipe for cooling and condensing the vapor produced. The 

 coil of pipe, often called the "worm," may be kept cool by 

 being immersed in a tank or stream of running water. The 

 condensed vapor which slowly drops from the coil of pipe, 



