Inference Exercise
Explain the following:
511. Sugar dissolves readily in hot coffee.
512. The sugar disappears, yet the coffee flavor remains and so does the sweetness of the sugar.
513. A tin spoon left overnight in apple sauce becomes black.
514. If one's clothes are on fire, rolling over on the ground is better than running.
515. Lemon juice bleaches straw hats.
516. Will-o'-the-wisps glow at night, deceiving travelers by their resemblance to moving lanterns.
517. Tomatoes should never be left in a tin can after it has been opened.
518. Boiled milk tastes different from ordinary milk.
519. Your hands become very cold after you have washed things in gasoline.
520. Wood decays more quickly when wet than when dry.
Section 55. Bases.
Why does strong soap make your face sting?
How is soap made?
"Contains no free alkali," "Will not injure the most delicate of fabrics," "99-44/100% pure,"—such phrases as these are used in advertising soaps. What is meant by 99-44/100% pure? What is free alkali? Why should any soap injure fabrics? What 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.
