HOW WE MAY MAKE WATER PURE 



water, while rain water and other waters that have little 

 or no dissolved mineral matter in them are known as 

 soft waters. We can usually tell hard water because soap 

 does not readily make a good lather, or suds, with it. We 

 find that the soap comes to the top in a sticky, insoluble 

 scum. Hard water leaves a deposit in kettles, feels harsh 

 to the hands, and requires much 

 w r ashing powder, else it is very 

 wasteful of soap. Such waters 

 are perfectly good to drink, but 

 must be treated with chemicals 

 before using them for washing 

 purposes. Washing soda added 

 to the water before soap is used 

 will usually make the water bet- 

 ter suited for washing. 



How we may make water 

 pure. We have already seen 

 that harmful water contains 

 germs. Germs are living organ- Notice the bubbles of air which es- 



. , fit cape when water is first heated. 



ISmS, and many Of them do Why is boiling water sometimes 



recommended? . 



harm when they are alive. Any 



method which will kill them and will not harm the water 

 will therefore render it safe to drink. Boiling water for a 

 period of at least ten minutes will kill practically all harmful 

 germs, so that we may- safely drink such water. Unfortu- 

 nately, boiled water has a flat and unpleasant taste, due to the 

 fact that the air which was held in solution has been forced 

 out of it. In order to make such water palatable we may 

 shake it up in a bottle half full of air or allow it to stand 

 exposed to the air. Such water dissolves some of the air 

 and again assumes its palatable taste, and is good to drink. 



