356 Common Science 



these are used in advertising soaps. What is meant by 

 QQrVo % pure? What is free alkali? Why should any 

 soap injure fabrics? Wliat makes a soap " strong " ? 



The answer to all these questions is that there are 

 some substances called bases, which are the opposites 

 of acids, and some of which are as powerful as acids. 

 Lye, ammonia, caustic soda, and baking and washing 

 soda are common bases. The strong bases, like lye 

 and caustic soda, are also called alkalies. If you want 

 to see what a strong base an alkali will do to " the 

 most delicate of fabrics," and to fabrics that are not so 

 delicate, for that matter, try the following experiment : 



Experiment 108. To be done by the teacher. If you get any 

 alkali on your skin or clothes, wash it off immediately with 

 vinegar or lemon juice. 



Put half a teaspoonful of lye and a quarter of a cup of 

 water into a beaker, a small pan, or an evaporating dish. 

 Bring it to a gentle boil. Drop a small piece of woolen cloth 

 and a small piece of silk cloth into it and let them boil gently 

 for a couple of minutes. What happens to them? Try a 

 piece of plain cotton cloth, and then a piece of cloth that is 

 mixed wool and cotton or mixed silk and cotton. What 

 happens to them? This is a very good test to determine 

 whether any goods you buy are pure silk or wool, or whether 

 there is a cotton thread mixed with them. Drop one end 

 of a long hair into the hot lye solution. What happens to 

 it? Drop a speck of meat or a piece of finger nail into it. 



From this experiment you can readily see why lye 

 will burn your skin and ruin your clothes. You can 

 also see how it softens the food that sticks to the bottom 

 of the cooking pan and makes the pan easy to clean. 

 Lye is one of the strongest bases or alkalies in the world. 



