ACIDS, BASES, AND SALTS 57 



monia water may be used in a number of different ways to 

 help remove grease from various kinds of fabrics, and that 

 lye will act upon grease in such a way that water will dis- 

 solve it. Lye is therefore used for " cutting " the grease 

 in drain pipes leading from sinks. But since lye and other 

 strong bases which " cut " grease will also ruin most fabrics 

 and will do harm to the skin, a milder cleansing agent must 

 be found for laundry and personal use. Soap is one of 

 those substances which chemists call salts, and is made by 

 mixing or boiling fats with lye. 



The neutralizing of acids by means of some mild base is 

 a part of the daily experience of many people, even though 

 they may not realize what the chemical action is. We put 

 ammonia or damp baking soda on a bee-sting to neutralize 

 the acid that the bee has injected into the flesh. Baking 

 soda is used by housewives to sweeten sour milk. Frugal 

 cooks sprinkle baking soda lightly over rhubarb, gooseberry, 

 or cherry pie in order partly to neutralize the acids and 

 thus to save sugar. 



The farmer uses lime to " sweeten "a " sour " or acid 

 soil. Physicians often prescribe limewater or a solution of 

 baking soda to neutralize acidity (sourness) of the stomach. 

 Fruit stains are caused by fruit acids. For that reason, 

 the stains may usually be removed by soaking the linen in a 

 weak solution of ammonia or borax. 



The wonderful progress that man has made in the last 

 century in manufacturing, transportation, agriculture, build- 

 ing, sanitation, and comfortable living conditions, has come 

 out of his greatly increased scientific knowledge, and out 

 of his increasing ability to control forms of energy which 

 produce desired chemical and physical changes. 



