il6 SCIENCE OF HOME AND COMMUNITY 



stance thus formed is an insoluble chemical which further 

 interferes with the cleansing. When the drinking water is 

 hard, another supply of soft water is frequently provided in 

 cisterns. This water may be pumped by hand or it may be 

 made to circulate throughout the house by means of pressure 

 tanks as already explained in Chapter IV. 



LABORATORY EXERCISE 16 



Purpose. To learn the effect of soap on hard water. 



Materials. Soap, test tubes, calcium sulfate, soft water, 

 washing soda. 



Directions, i. To procure hard water, add calcium sulfate 

 to some water. Shake and filter. Make a soap solution by 

 heating a little soap in soft water in a test tube. 



2. Take a little of the hard water and add to it a measured 

 quantity of soap solution. Shake the test tube. Take the 

 same quantity of soft water and add the same amount of soap 

 solution as in the previous experiment. How do the rer.ilts 

 differ from those in the previous experiment? Why is hard 

 water not satisfactory for cleansing purposes ? 



3. To hard water, add a little washing soda and shake the 

 mixture. Then add some soap solution. What was the effect 

 of the soda on the hard water ? 



Removing stains. A stain may usually be removed by / 

 one of the following methods : by dissolving it ; by bleach- 

 ing it; by neutralizing it ; or by absorbing it. The following 

 table shows what may be used to remove various stains. 



Kind of stain How removed 



Grease Dissolved in naphtha. 



Fresh paint Dissolved in turpentine. 



Grass Dissolved in alcohol. 



Iron rust Weak hydrochloric acid for cotton 



or linen. Oxalic acid for silk. 



Mildew Bleach with Javelle water. 



Lemonade Neutralize with ammonia. 



