HARD AND SOFT WATER 103 



already in solution it will not dissolve other substances 

 as readily as will pure water. If water has very little 

 dissolved material in it, it will cleanse easily. We call 

 such water soft. Rain water which has fallen after it 

 has been raining for some time, is very soft. Why? 

 Water obtains its dissolved .material from the ground. 

 Water which contains dissolved substances is called 

 hard. Soft water makes suds with soap very easily 

 while hard water does not. Since soap has the power of 

 acting with the water to dissolve or loosen dirt, if it does 

 not dissolve in the water and form suds, the water is 

 hard to use for washing. Cleansing is much easier with 

 soft water than with hard water. 



Experiment 51. *Hard and Soft Water. Soap. 



Apparatus: Burner, ring stand, tin cup, pint bottle 

 with stopper. 



Materials: Distilled water, powdered or shaved 

 soap. 



a. Measure the smallest amount of soap which will 

 just begin to make suds when shaken with a half pint 

 of distilled water in a pint bottle. This will give you a 

 standard, for distilled water is absolutely pure and will 

 make suds with the least amount of soap. Any other 

 water will use more soap. 



b. See how much soap is necessary to produce suds 

 with a half pint of ordinary water. Take another "half 

 pint of the same kind of water which has been boiled for 

 at least five minutes. Does it take more or less soap to 

 make suds with the boiled water than with the unboiled 

 water? Hard water which can be made soft by boiling 



* See Experiment 79. Distillation. 



