How soap is made. When lye and grease are boiled together, they form soap. You cannot very well make soap in the laboratory now, as the measurements must be exact and you need a good deal of strong lye to make it in a quantity large enough to use. But the fact that soap is made with oil, fat, or grease boiled with lye, or caustic soda, which is almost the same thing, shows why a soap must be 99-44/100% pure, or something like that, if it is not to injure "the most delicate fabric." If a little too much lye is used there will be free alkali in the soap, and it will make your hands harsh and sore and spoil the clothes you are washing. A "pure" soap is one with no free alkali in it. A "strong" soap is one that does have some free alkali in it; there is a little too much lye for the oil or fat, so some lye is left uncombined when the soap is made. This free alkali cleans things well, but it injures hands and clothes.
When the drainpipe of a kitchen sink is stopped up, you can often clear it by sprinkling lye down it, and then adding boiling water. If you ever do this, stand well back so that no lye will spatter into your face; it sputters when the boiling water strikes it. The grease in the drainpipe combines with the lye when the hot water comes down; then the soap that is formed is carried down the pipe, partly dissolved by the hot water.
When you sponge a grease spot with ammonia, the same sort of chemical action takes place. The ammonia is a base; it combines with the grease to form soap, and this soap rinses out of the cloth.
The litmus test. To tell what things are bases and what are acids, a piece of paper dyed with litmus is ordinarily used. Litmus is made from a plant (lichen). This paper is called litmus paper. Try the following experiment with litmus paper:
Experiment 109. Pour a few drops of ammonia, a base, into a cup. Into another cup pour a few drops of vinegar, an acid. Dip your litmus paper first into one, then into the other, and then back into the first. What color does the vinegar turn it? the ammonia? Try lemon juice; diluted hydrochloric acid; a very dilute lye solution.
This is called the litmus test. All ordinary acids, if not too strong, will turn litmus pink. All bases or alkalies will turn it blue. If it is already pink when you put it into an acid, it will stay pink, of course; if it is already blue when you put it into a base, it will stay blue. But if you put a piece of litmus paper into something that is neither an acid nor a base, like sugar or salt, it will still stay the same color. So, to test for a base, use a piece of litmus paper that is pink and see if it turns blue, or if you want to test for an acid, use blue litmus paper. Do this experiment:
Experiment 110. With pink and blue litmus paper, test the different substances named below to see which are acids and which are bases. Make a list of all the acids and another list for all the bases. Do not put down anything that is neither acid or base. You cannot be sure a thing is an acid unless it turns blue litmus pink. A piece of pink litmus would stay pink in an acid, but it would also stay pink in things that were neither acid nor base, like salt or water. In the same way you cannot be sure a thing is a base unless it turns pink litmus blue. Here is a list of things to try: 1, sugar; 2, orange; 3, dilute sulfuric acid; 4, baking soda in water; 5, alum in water; 6, washing soda in water; 7, ammonia; 8, dilute lye; 9, lemon juice; 10, vinegar; 11, washing powder in water; 12, sour milk; 13, cornstarch in water; 14, wet kitchen soap; 15, oil; 16, salt in water.
You may have to make the orange and sour milk test at home. You may take two pieces of litmus paper home with you and test anything else that you may care to. If you have a garden, try the soil in it. If it is acid it needs lime.
Application 81. A boy spilled some greasy soup on his best dark blue coat. Which of the following methods would have served to clean the coat? to sponge it (a) with cold water; (b) with water (hot) and ammonia; (c) with hot water and vinegar; (d) with concentrated nitric acid; to sprinkle lye on the spot and pour boiling water over it.
Application 82. A woman scorched the oatmeal she was cooking for breakfast. When she wanted to wash the pan, she found that the blackened cereal stuck fast to the bottom. Which of the following things would have served best to loosen the burned oatmeal from the pan: lye and hot water, ammonia, vinegar, salt water, lemon juice?
Inference Exercise
Explain the following:
521. After clothes have been washed with washing soda or strong soap, they should be thoroughly rinsed. Otherwise they will be badly eaten as they dry.
522. Carbon will burn; oxygen will support combustion; yet carbon dioxid (CO2), which is made of both these elements, will neither burn nor support combustion.
523. You can clean silver by putting it in hot soda solution in contact with aluminum.
524. When you stub your toe while walking, you tend to fall forward.
525. Electric lamps glow when you turn on the switch.
526. If you use much ammonia in washing clothes or cleaning, your hands become harsh and dry.
527. If a person swallows lye or caustic soda, he should immediately drink as much vegetable oil or animal oil as possible.
528. Water is made of hydrogen and oxygen; air is made of nitrogen and oxygen; yet while things will not burn in water, they will burn easily in air.
529. The backs of books that have been kept in cases for several years are not as bright colored as the side covers.
530. If you try to burn a book or magazine in a grate, only the outer pages and edges burn.
Section 56. Neutralization.
When you put soda in vinegar, what makes the vinegar less sour?
When we use sour milk for cooking, why does the food not taste sour?
One of the most interesting and important facts about acids and bases is that if they are put together in the right proportions they turn to salt and water. Strong hydrochloric acid (HCl), for instance, will attack the skin and clothes, as you know; if you should drink it, it would kill you. Caustic soda (NaOH), a kind of lye, is such a strong alkali that it would dissolve the skin of your mouth in the way that lye dissolved hair in Experiment 108. Yet if you put these two strongly poisonous chemicals together, they promptly turn to ordinary table salt (NaCl) and water (H2O). Or, as the chemists write it:
You can make this happen yourself in the following experiment, using the acid and base dilute enough so that they will not hurt you:
Experiment 111. Although strong hydrochloric acid and strong caustic soda are dangerous, if they are diluted with enough water they are perfectly harmless. You will find two bottles, one labeled "caustic soda (NaOH) diluted for tasting," and the other labeled "hydrochloric acid (HCl) diluted for tasting." From one bottle take a little in the medicine dropper and let a drop fall on your tongue. Taste the contents of the other bottle in the same way. It is not usually safe to taste things in the laboratory. Taste only those things which are marked "for tasting."
Now put a teaspoonful of the same hydrochloric acid into a clean evaporating dish. Lay a piece of litmus paper in the bottom of the dish. With a medicine dropper gradually add the dilute caustic soda (NaOH), stirring as you add it. Watch the litmus paper. When the litmus paper begins to turn blue, add the dilute caustic soda drop by drop until the litmus paper stays blue when you stir the mixture. Now add a drop or two more of the acid until the litmus turns pink again. Taste the mixture.
Put the evaporating dish on the wire gauze over a Bunsen burner, and bring the liquid to a boil. Boil it gently until it begins to sputter. Then take the Bunsen burner in your hand and hold it under the dish for a couple of seconds; remove it for a few seconds, and then again hold it under the dish for a couple of seconds; remove it once more, and keep this up until the water has all evaporated and left dry white crystals and powder in the bottom of the dish. As soon as the dish is cool, taste the crystals and powder. What are they?
Is salt an acid or a base?
Whenever you put acids and bases together, you get some kind of salt and water. Thus the chlorine (Cl) of the hydrochloric acid (HCl) combines with the sodium (Na) of caustic soda (NaOH) to form ordinary table salt, sodium chloride (NaCl), while the hydrogen (H) of the hydrochloric acid (HCl) combines with the oxygen and hydrogen (OH) of the caustic soda (NaOH) to form water (H2O). Chemists write this as follows:
Why sour milk pancakes are not sour. It is because bases neutralize acids that you put baking soda with sour milk when you make sour milk pancakes or muffins. The soda is a weak base. The sour milk is a weak acid. The soda neutralizes the acid, changing it into a kind of salt and plain water. Therefore the sour milk pancakes or muffins do not taste sour.
In the same way a little soda keeps tomatoes from curdling the milk when it is added to make cream of tomato soup. It is the acid in the tomatoes that curdles milk. If you neutralize the acid by adding a base, there is no acid left to curdle the milk; the acid and base turn to water and a kind of salt.
When you did an experiment with strong acid, you were advised to have some ammonia at hand to wash off any acid that might get on your skin or clothes. The ammonia, being a base, would immediately neutralize the acid and therefore keep it from doing any damage. Lye also would neutralize the acid, but if you used the least bit too much, the lye would do as much harm as the acid. That is why you should use a weak base, like ammonia or baking soda or washing soda, to neutralize any acid that spills on you. Then if you get too much on, it will not do any harm.
In the same way you were warned to have vinegar near at hand while you worked with lye. Strong nitric acid also would neutralize the lye, but if you happened to use a drop too much, the acid would be worse than the lye. Vinegar, of course, would not hurt you, no matter how much you put on.
Any acid will neutralize any base. But it would take a great deal of a weak acid to neutralize a strong base or alkali; you would have to use a great deal of vinegar to neutralize concentrated lye. In the same way it would take a great deal of a weak base to neutralize a strong acid; you would have to use a large amount of baking soda or ammonia to neutralize concentrated nitric acid.
Application 83. A woman was cleaning kettles with lye. Her little boy was playing near, and some lye splashed on his hand. She looked swiftly around and saw the following things: soap, oil, lemon, flour, peroxide, ammonia, iodine, baking soda, essence of peppermint. Which should she have put on the boy's hand?
Application 84. A teacher spilled some nitric acid on her apron. On the shelf there were: hydrochloric acid, vinegar, lye, caustic soda, baking soda, ammonia, salt, alcohol, kerosene, salad oil. Which should she have put on her apron?
Application 85. A boy had "sour stomach." His sister said, "Chew some gum." His aunt said, "Drink hot water with a little peppermint in it." His mother told him to take a little baking soda in water. His brother said, "Try some hot lemonade." Which advice should he have followed?
Application 86. Two women were bleaching a faded pair of curtains. The Javelle water which they had used was made of bleaching powder and washing soda. Before hanging the curtains out to dry, one of them said that she was afraid the Javelle water would become so strong as the water evaporated from the curtains that it would eat the curtains. They decided they had better rinse them out with something that would counteract the soda and lime in the Javelle water, and in the laundry and pantry they found: ammonia, blueing, starch, washing powder, soap, vinegar, and gasoline. Which of them, if any, would it have been well to put in the rinsing water?
Inference Exercise
Explain the following:
531. Solid pieces of washing soda disappear in hot water.
532. Greasy clothes put into hot water with washing soda become clean.
533. If you hang these clothes up to dry without rinsing them, the soda will weaken the cloth.
534. Lemon juice in the rinsing water will prevent washing soda from injuring the clothes.
535. If you hang them in the sun, the color will fade.
536. A piece of soot blown against them will stick.
537. A drop of oil that may spatter against them will spread.
538. The clothes will be easier to iron if dampened.
539. The creases made in ironing the clothes will reappear even if you flatten the creases out with your hand.
540. After they have been worn, washed, and ironed a number of times, clothes are thinner than they were when they were new.
Section 57. Effervescence.
What makes baking powder bubble?
What makes the foam on soda water?
Did you ever make soda lemonade? It is easy to make and is rather good. Try making it at home. Here are the directions:
Experiment 112. Make a glass of ordinary lemonade (half a lemon, 1-1/2 teaspoonfuls of sugar; fill the glass with water). Pour half of this lemonade into another cup or glass. Into the remaining half glass stir half a teaspoonful of soda. Drink it while it fizzes. Does it taste sour?
When anything fizzes or bubbles up like this, we say that it effervesces. Effervescence is the bubbling up of a gas from a liquid. The gas that bubbled up from your lemonade was carbon dioxid (CO2), and this is the gas that usually bubbles up out of things when they effervesce.
When you make bread, the yeast turns the sugar into carbon dioxid (CO2) and alcohol. The carbon dioxid tries to bubble up out of the dough, and the bubbles make little holes all through the dough. This makes the bread light. When bread rises, it really is slowly effervescing.
How soda water is made. Certain firms make pure carbon dioxid (commercially known as carbonic acid gas) and compress it in iron tanks. These iron tanks of carbon dioxid (CO2) are shipped to soda-water fountains and soda-bottling works. Here the compressed carbon dioxid is dissolved in water under pressure,—this is called "charging" the water. When the charged water comes out of the faucet in the soda fountains, or out of the spout of a seltzer siphon, or out of a bottle of soda pop, the carbon dioxid that was dissolved in the water under pressure bubbles up and escapes,—the soda water effervesces.
Sometimes there is compressed carbon dioxid down in the ground. This dissolves in the underground water, and when the water bubbles up from the ground and the pressure is released, the carbon dioxid foams out of the water; it effervesces like the charged water at a soda fountain.
But the most useful and best-known effervescence is the kind you got when you stirred the baking soda in the lemonade. Baking soda is made of the same elements as caustic soda (NaOH), with carbon dioxid (CO2) combined with them. The formula for baking soda could be written NaOHCO2, but usually chemists put all of the O's together at the end and write it NaHCO3. Whenever baking soda is mixed with any kind of acid, the caustic soda part (NaOH) is used up in neutralizing the acid. This leaves the carbon dioxid (CO2) part free, so that it bubbles off and we have effervescence. Baking soda mixed with an acid always effervesces. That is why sour milk muffins and pancakes are light as well as not sour. The effervescing carbon dioxid makes bubbles all through the batter, while the caustic soda (NaOH) in the baking soda neutralizes the acid of the sour milk.
Effervescence generally due to the freeing of carbon dioxid. Since baking soda is so much used in the home for neutralizing acids, people sometimes get the idea that whenever there is neutralization there is effervescence. Of course this is not true. Whenever you neutralize an acid with baking soda or washing soda, the carbon dioxid in the soda bubbles up and you have effervescence. But if you neutralize an acid with ammonia, lye, or plain caustic soda, there is not a bit of effervescence. Ammonia, lye, and plain caustic soda have no carbon dioxid in them to bubble out.
Baking powder is merely a mixture of baking soda and dry acid (cream of tartar or phosphates in the better baking powders, alum in the cheap ones). These dry acids cannot act on the soda until they go into solution. As long as the baking powder remains dry in the can, there is no effervescence. But when the baking powder is stirred into the moist biscuit dough or cake batter, the baking powder dissolves; so the acid in it can act on the baking soda and set free the carbon dioxid.
In most cases it is the freeing of carbon dioxid that constitutes effervescence, but the freeing of any gas from liquid is effervescence. When you made hydrogen by pouring hydrochloric acid (HCl) on zinc shavings, the acid effervesced,—the hydrogen gas was set free and it bubbled up.
Stirring or shaking helps effervescence, just as it does crystallization. As the little bubbles form, the stirring or shaking brings them together and lets them join to form big bubbles that pass quickly up through the liquid. That is why soda pop will foam so much if you shake it before you pour it, or if you stir it in your glass.
Application 87. Explain why we do not neutralize the acid in sour milk gingerbread with weak caustic soda instead of with baking soda; why soda water which is drawn with considerable force from the fine opening at a soda fountain makes so much more foam than does the same charged water if it is drawn from a large opening, from which it flows gently; why there is always baking soda and dry acid in baking powder.
Application 88. A woman wanted to make gingerbread. She had no baking powder and no sour milk, but she had sweet milk and all the other articles necessary for making gingerbread. She had also baking soda, caustic soda, lemons, oranges, vanilla, salad oil, vinegar, and lye. Was there any way in which she might have made the gingerbread light without spoiling it?
Inference Exercise
Explain the following:
541. Harness is oiled to keep it flexible.
542. When you pour nitric acid on copper filings, there is a bubbling up of gas.
543. The flask or dish in which the action takes place becomes very hot.
544. The copper disappears and a clear green solution is left.
545. In making cream of tomato soup, soda is added to the tomatoes before the milk is, so that the milk will not curdle How does the soda prevent curdling?
546. The soda makes the soup froth up.
547. A wagon squeaks when an axle needs greasing.
548. Seidlitz powders are mixed in only half a glass of water.
549. The work of developing photographs is all done with a ruby light for illumination.
550. Coal slides forward off the shovel into a furnace when you stop the shovel at the furnace door.
CHAPTER TWELVE
ANALYSIS
Section 58. Analysis.
How can people tell what things are made of?
If it were not for chemical analysis, most of the big factories would have to shut down, much of our agricultural experimentation would stop, the Pure Food Law would be impossible to enforce, mining would be paralyzed, and the science of chemistry would almost vanish.
Analysis is finding out what things are made of. In order to make steel from ore, the ore has to be analyzed; and factories could not run very well without steel. In order to test soil, to test cow's milk, or to find the food value of different kinds of feed, analysis is essential. As to the Pure Food Law, how could the government find out that a firm was using artificial coloring matter or preservatives if there were no way of analyzing the food? In mining, the ore must be assayed; that is, it must be analyzed to show what part of it is gold, for instance, and what part consists of other minerals. Also, the analysis must show what these substances are, so that they can be treated properly. And the science of chemistry is largely the science of analyzing—finding out what things are made of and how they will act on each other.
The subject of chemical analysis is extremely important. But in this course it is impossible and unnecessary for you to learn to analyze everything; the main thing is for you to know what analysis is and to have a general notion of how a chemist analyzes things.
When you tested a number of substances with litmus paper to find out which of them were acids, you were really doing some work in chemical analysis. Chemists actually use litmus paper in this way to find out whether a substance is an acid or a base.
The borax bead test. This is another chemical test, by which certain substances can be recognized:
Experiment 113. Make a loop of wire about a quarter of an inch across, using light-weight platinum wire (about No. 30). Seal the straight end of the wire into the end of a piece of glass tubing by melting the end of the tube around the wire.
Hold the loop of wire in the flame of a Bunsen burner for a few seconds, then dip the looped end in borax powder. Be careful not to get borax on the upper part of the wire or on the handle. Some of the borax will stick to the hot loop. Hold this in the flame until it melts into a glassy bead in the loop. You may have to dip it into the borax once or twice more to get a good-sized bead.
When the bead is all glassy, and while it is melted, touch it lightly to one small grain of one of the chemicals on the "jewel-making plate." This jewel-making plate is a plate with six small heaps of chemicals on it. They are: manganese dioxid, copper sulfate, cobalt chlorid, nickel salts, chrome alum, and silver nitrate. Put the bead back into the flame and let it melt until the color of the chemical has run all through it. Then while it is still melted, shake the bead out of the loop on to a clean plate. If it is dark colored and cloudy, try again, getting a still smaller grain of the chemical. You should get a bead that is transparent, but clearly colored, like an emerald, topaz, or sapphire.
Repeat with each of the six chemicals, so that you have a set of six different-colored beads.
This is a regular chemical test for certain elements when they are combined with oxygen. The cobalt will always change the borax bead to the blue you got; the chromium will make the bead emerald green or, in certain kinds of flame, ruby red; etc. If you wanted to know whether or not certain substances contained cobalt combined with oxygen, you could really find out by taking a grain on a borax bead and seeing if it turned blue.
The hydrochloric acid test for silver. The experiment in which you tested the action of light in effecting chemical change, and in which you made a white powder or precipitate in a silver nitrate solution by adding hydrochloric acid (page 327), is a regular chemical test to find out whether or not a thing has silver in it. If any silver is dissolved in nitric acid, you will get a precipitate (powder) when hydrochloric acid is added. Make the test in the following experiment:
Experiment 114. Use distilled water all through this experiment if possible. First wash two test tubes and an evaporating dish thoroughly, rinsing them several times. Into one test tube pour some nitric acid diluted 1 to 4. Heat this to boiling, then add a few drops of hydrochloric acid diluted 1 to 10. Does anything happen? Pour out this acid and rinse the dish thoroughly. Now put a piece of silver or anything partly made of silver into the bottom of the evaporating dish. Do not use anything for the appearance of which you care. Cover the silver with some of the dilute nitric acid, put the dish over the Bunsen burner on a wire gauze, and bring the acid to a gentle boil. As soon as it boils, take the dish off, pour some clean, cold water into it to stop the action, and pour the liquid off into the clean test tube. Add a few drops of the dilute hydrochloric acid to the liquid in the test tube. What happens? What does this show must have been in the liquid?
You can detect very small amounts of silver in a liquid by this test. It is a regular test in chemical analysis.
The iodine test for starch. A very simple test for starch, but one that is thoroughly reliable, is the following:
Experiment 115. Mix a little starch with water. Add a drop of iodine. What color does the starch turn? Repeat with sugar. You can tell what foods have starch in them by testing them with iodine. If they turn black, blue, or purple instead of brown, you may be sure there is starch in them. And if they do not turn black, blue, or purple, you can be equally sure that they have no starch in them. Some baking powders contain starch to keep them dry. Test the baking powder in the laboratory for starch. Often a little cornstarch is mixed with powdered sugar to keep it from lumping. Test the powdered sugar in the laboratory to see if it contains starch.
Test the following or any other ten foods to see if any of them are partly made of starch: salt, potatoes, milk, meat, sausage, butter, eggs, rice, oatmeal, cornmeal, onions.
The limewater test for carbon dioxid. In crowded and badly ventilated rooms carbon dioxid in unusual amounts is in the air. It can be detected by the limewater test.
Experiment 116. Pour an inch or two of limewater into a glass. Does it turn milky? Pump ordinary air through it with a bicycle pump. Now blow air from your lungs through a glass tube into some fresh limewater until it turns milky. By this test you can always tell if carbon dioxid (CO2) is present.
Carbon dioxid turns limewater milky as it combines with the lime in the limewater to make tiny particles (a precipitate) of limestone. If you pour seltzer water or soda pop into limewater, you get the same milkiness, for the bubbles of carbon dioxid in the charged water act as the carbon dioxid in your breath did. If you pumped enough air through the limewater you would produce some milkiness in it, for there is always some carbon dioxid in the air.
The purpose of these experiments is only to give you a general notion of how a chemist analyzes things,—by putting an unknown substance through a series of tests he can tell just what that substance contains; and by accurately weighing and measuring everything he puts in and everything he gets out, he can determine how much of each thing is present in the compound or mixture. To learn to do this accurately takes years of training. But the men who go through this training and analyze substances for us are among the most useful members of the human race.
Inference Exercise
Explain the following:
551. A little soda used in canning an acid fruit will save sugar.
552. The fats you eat are mostly digested in the small intestine, where there is a large excess of alkali.
553. The dissolved food in the liquid part of the blood gets out of the blood vessels and in among the cells of the body, and it is finally taken into the cells through their walls.
554. Ammonia takes the color out of delicate fabrics.
555. Dishes in which cheese has been cooked can be cleaned quickly by boiling vinegar in them.
556. Prepared pancake flour contains baking powder. It keeps indefinitely when dry, but if the box gets wet, it spoils.
557. When water or milk is added to prepared pancake flour to make a batter, bubbles appear all through it.
558. When a roof leaks a little, a large spot appears on the ceiling.
559. Gasoline burns quietly enough in a stove, but if a spark gets into a can containing gasoline vapor, there is a violent explosion.
560. Turpentine will remove fresh paint.
General Review Inference Exercise
Explain the following:
561. We can remove fresh stains by pouring boiling water through them.
562. A ship can be more heavily laden in salt water than in fresh water.
563. Water flies off a wet dog when he shakes himself.
564. In cooking molasses candy, baking soda is often added to make it lighter.
565. An egg will not stand on end.
566. Women who carry bundles on their heads stand up very straight.
567. To get all crayon marks off a blackboard, the janitor uses vinegar in water.
568. Sunlight makes your skin darker.
569. Water puts out a fire.
570. You get a much worse shock from a live wire when your hands are wet than when they are dry.
571. Stone or brick buildings are cool in summer but warm in winter.
572. If you take the handle off a faucet, it is almost impossible to turn the valve with your fingers.
573. Sparks fly from a grindstone when you are sharpening a knife.
574. Violin strings are spoiled by getting wet.
575. The oxygen of the air gets into the blood from the lungs, although there are no holes from the blood vessels into the lungs.
576. You push a button or turn a key switch and an electric lamp lights.
577. A rubber comb, rubbed on a piece of wool cloth, will attract bits of paper to it.
578. People whose eyes no longer adjust themselves have to have "reading glasses" and "distance glasses" to see clearly.
579. When you look through a triangular glass prism, things appear to be where they are not.
580. Lye and hot water poured down a clogged kitchen drainpipe clear out the grease.
581. You can draw on rough paper with charcoal.
582. When little children get new shoes, the soles should be scratched and made rough.
583. You can get your face very clean by rubbing cold cream into it, then wiping the cold cream off on a towel or cloth.
584. Soft paper blurs writing when you use ink.
585. Water will flow over the side of a pan through a siphon, if the outer end of the siphon is lower than the surface of the water in the pan.
586. There is a loud noise when a gun is fired.
587. Colored cloths should be matched in daylight, not in artificial light.
588. Lamp chimneys are made of thin glass.
589. When you sweep oiled floors, no dust flies around the room.
590. The ocean is salty, while lakes are usually fresh.
591. A glass gauge on the side of a water tank shows how high the Water in the tank is.
592. You burn your hand when you touch a hot stove.
593. Pounding a piece of steel held horizontally over the earth and pointing north and south will make it become a magnet.
594. When only one side of a sponge is in water, the sponge gradually gets soft all over.
595. If we breathe on a cold mirror, a fine mist collects on it.
596. Butter is kept in cool places.
597. Water will boil more quickly in a covered pan than in an open one.
598. Mucilage, glue, and paste all become hard and dry after being spread out on a surface for a while.
599. You cannot see things clearly through a dusty window.
600. In making fire grates it is necessary to have the bars free to move a little.
APPENDIX
A. The Electrical Apparatus
For giving children a practical understanding of such laws of electricity as affect everybody, the following simple apparatus is invaluable. It is the electrical apparatus referred to several times in the text. The only part of it that is at all difficult to get is the nichrome resistance wire. There is a monopoly on this and each licensee has to agree not to sell it. It can be bought direct from the manufacturer by the school board if a statement accompanies the order to the effect that it is not to be used in any commercial devices, nor to be sold, but is for laboratory experimentation only. The manufacturers are Hoskins Manufacturing Company, Detroit, Michigan.
The following diagram will make the connections and parts of the electrical apparatus clear:
Fig. 190. Electrical apparatus: At the right are the incoming wires. Dotted lines show outlines of fuse block. A, 2 cartridge fuses, 15 A; B, 2 plug fuses, 10 A; C, knife switch; D, fuse gap; E, snap switch; F, H, lamp sockets; G, flush switch; I, J, K, nichrome resistance wire, No. 24 (total length of loop, 6 feet), passing around porcelain posts at left.
The flush switch (G) should be open at the bottom for inspection,—remove the back. The snap switch (E) should have cover removed so that pupils can see exactly how it works.
The fuse gap (D) consists either of two parts of an old knife switch, the knife removed, or of two brass binding posts. Across it a piece of 4-ampere fuse wire is always kept as a protection to the more expensive plug and cartridge fuses. Between the resistance wire (I, J, K) and the wall should be either slate or sheet asbestos, double thickness. Under the fuse gap the table should be protected by galvanized iron so that the melted bits of fuse wire can set nothing on fire when the fuse wire burns out.
B. Construction of the Cigar-box Telegraph
The "cigar-box telegraph" shown on page 381 is made as follows: An iron machine bolt (A) is wound with about three layers of No. 24 insulated copper magnet wire, the two ends of the wire (B, B) projecting. The threaded end of the bolt (C) is not wound. A nut (D) is screwed on the bolt as far down as the wire wrapping. The threaded end is then pushed up through the hole in the top of the cigar box as that stands on its edge. Another nut (E) is then screwed on to the bolt, holding it in position. The bolt can now be raised or lowered and tightened firmly in position by adjusting the two nuts (D and E), one above and one below the wood.
A screw eye (F), large enough to form a rest for the head of another machine bolt (G), is screwed into the back of the box about three fourths of an inch below the head of the suspended bolt (A). Two or three inches away, at a slightly higher level, another screw eye (H) is screwed into the back of the cigar box. This screw eye must have an opening large enough to permit an iron machine bolt (G) to pass through it easily. A nut (I) is screwed down on the threaded end of a machine bolt until about an inch of the bolt projects beyond the nut. This projecting part of the bolt is then passed through the screw eye (H) and another nut (J) screwed on to it to hold it in place. This nut must not be so tight as to prevent the free play of the bolt as its head rises and falls under the influence of the vertical bolt. The head of the horizontal bolt rests upon the screw eye which is immediately below the head of the suspended bolt. You therefore have the wrapped bolt hanging vertically from the top of the box, with its head just over the head of the horizontal bolt. There should be about one quarter inch of space between the heads of the two bolts. An electric current passing through the wires of the vertical bolt will therefore lift the head of the horizontal bolt, which will drop back on to the screw eye when the circuit is broken.
INDEX
An asterisk (*) indicates use of one or more illustrations in connection with reference to which appended.
| A | B | C | D | E | F | G | H | I | K | L | M |
| N | O | P | Q | R | S | T | U | V | W | Y | Z |
- Acetylene, carbon and hydrogen in, 315.
- Acids, 351 ff.;
- Action and reaction, law of, 77-81*.
- Adhesion, 39, 41-44;
- cohesion, capillary attraction, and, 47.
- Air, cooling of, on expanding, 95-96;
- liquid, 97;
- heat carried by, by convection, 118-119;
- absorption of light by, 169;
- sound produced by vibrations of, 174-181*;
- pitch due to rapidity of vibrations of, 186;
- water vapor in, 275-280*;
- a mixture and not a compound, 309;
- part taken by, in making automobile go, 344;
- limewater test for carbon dioxid in, 375.
- Air pressure, 10 ff., 14*;
- Air pump, 14*, 15.
- Alcohol, boiling of, 112;
- distilling, 113*-114.
- Alkali, 356;
- in soap, 357-358.
- Alloys, definition of, 310.
- Alternating current, defined, 211-212.
- Alum crystals, experiment with, 265-266*.
- Aluminum, an element, 299.
- Alum in water, testing with litmus paper, 359.
- Amber, electricity produced by rubbing with silk, 196.
- Ammonia, example of a common base, 356;
- Ampere, defined, 246.
- Analysis, chemical, 370-376.
- Aneroid barometer, 285*.
- Arc, the electric, 233-240*.
- Atoms, description of, 196;
- Aurora Borealis, cause of, 193.
- Automobile, reason for cranking, 210;
- how made to go, 344-345.
- Automobile races, overcoming of centrifugal force in, 75*.
- Automobile tires, reason for wearing of, 80;
- blow-outs of, 348.
- Baking powder, chemical change by solution shown by, 349-350;
- elements of which made, 367-368.
- Baking soda, a common base, 356;
- Ball bearings, used to diminish friction, 54-55.
- Balloon, expansion of, 17-18, 109*;
- Barometer, use of, 280-285*.
- Bases, substances called, 355-358;
- Batteries, electric, 203-205*;
- Bell, electric battery for ringing, 204-205*;
- working of electric, 255*.
- Bending of light (refraction), 136-141*.
- Black, the absence of light, 164.
- Bleaching, process of, 326-327.
- Blow-out of tire, a real explosion, 348.
- Blue-flame heaters, 319.
- Blueness of sky, reason for, 169.
- Blueprints, making of, 330-331.
- Boiling and condensing, 107-115*.
- Borax bead test, 371*-372*.
- Brass, an alloy, 310.
- Bread making, chemical action in, 365.
- Breath, cause of visibility of, on cold days, 288, 289*.
- Bronze, an alloy, 310.
- Burning, explanation of, 308, 312-313.
- Calcium chlorid, 114.
- Camera, lens of, 143, 148;
- Capillary attraction, 36*-40;
- difference between adhesion, cohesion, and, 47.
- Carbon, in electric battery, 203-206;
- Carbon dioxid, in seltzer siphon, 17;
- Carbonic acid gas, commercial name for pure carbon dioxid, 365-366.
- Cat's hairs, static electricity in, 201.
- Caustic soda, a common base, 356.
- Center of weight, 30-33*.
- Centrifugal force, 5, 72-74;
- law of, 74-75.
- Charcoal, production of, 316.
- Charging water with carbon dioxid, 366.
- Chemical analysis, 370-376.
- Chemical change, and energy, 293 ff.;
- Chemical equations, 297-299.
- Chlorine, an element, 299.
- Chlorophyll in plants, work of, 332.
- Cigar-box telegraph, construction of, 249*, 380-381*.
- Circuits, electric, 219-220*;
- Cloth, action of acids on, 354*;
- Clouds, how formed, 277-278.
- Coal, carbon and hydrogen in, 315.
- Cohesion, 39, 44*-49.
- Cold, caused by expansion, 94;
- Color, 161-172*.
- Comb, electricity produced by rubbing, 197-198.
- Compass, use of, 190-195*.
- Complete electric circuits, 219-224*.
- Compounds, how elements hide in, 300;
- Concave mirrors, 154*, 155*, 157;
- Conduction, of heat, 116-118;
- of electricity, 213-218.
- Conductors of electricity, good and poor, 213.
- Conduits for electric wires, 237.
- Conservation of energy, 57 ff.
- Convection, carrying of heat by, 118-119.
- Convex lens, 148-149*;
- Cooling from expansion, 94-96.
- Coolness at night and in winter, 127-128.
- Copper, a good conductor of electricity, 215;
- Copper nitrate, salt called, 353.
- Cream, separating from milk, by centrifugal force, 75-76.
- Crystals, formation of, 265-268.
- Cylinder of engine, 344*.
- Dead Sea, reason for salt in, 104-105*.
- Decay, a kind of oxidation, 313.
- Dew, 275;
- how formed, 287.
- Dictaphone, working of, 175, 178, 179*.
- Diffusion, 268-274;
- of light, 158-161.
- Direct-current electricity, 211-212.
- Distilling of liquids, 112-115*.
- Doorbell, electric battery for ringing, 204-205.
- "Down," meaning of word, 4.
- Drainpipe, cleaning of, with lye, 358.
- Dry-cell battery, 206*.
- Dust, reason for clinging to walls, 43-44.
- Dynamite, 343*;
- making of, 347.
- Dynamo, how electric current is made to flow by, 207*-210*.
- Earth, magnetism of, 190-195.
- Easy circuit, a short circuit an, 244-245.
- Echoes, explanation of, 183-185.
- Effervescence, process of, 365;
- Elasticity, 82-86;
- of form distinguished from elasticity of volume, 86-87.
- Electrical apparatus, 216-217*, 222-223*;
- description of, 379-380.
- Electric arc, the, 233*-240.
- Electric battery, the, 203-206*.
- Electricity, magnetism and, 190 ff.;
- Electric lamps, vacuums in, 12*, 317;
- Electric motors, 256*-257*.
- Electrolysis apparatus, 294-295*.
- Electromagnets, 247-257*.
- Electrons, 193;
- Elements, defined, 293;
- Emulsion, defined, 261;
- difference between solution and, 263.
- Energy released by chemical change, 340-341.
- Engine, working of cylinder and piston of, 344*.
- Ether, carrying of heat and light by, 124-125;
- light as waves of, 163-164.
- Ether waves, 124-125, 163-164.
- Evaporating dish, 101*.
- Evaporation, 100-106*;
- part taken by, in formation of clouds, rain, and dew, 277.
- Expansion, caused by heat, 88-93;
- cooling from, 94-96*.
- Expansion ball and ring experiment, 91*-92.
- Explosions, use of, 342* ff.;
- Explosives, manufacture of, 347.
- Extension lights, 238.
- Eye, lens of, 142;
- Fading, process of, 326-327.
- Filament of incandescent lamp, 125.
- Fire engines, need of, to force water high, 9.
- Fire extinguishers, action of, 317.
- Fires, caused by electric arcs, 236;
- putting out of, by water, 317.
- See Burning.
- Flames, formation of, 318.
- Floating, sinking and, 23-28.
- Focus of light, 142*-149*.
- Fogs, cause of, 288.
- Food, light necessary to production of, 332-333.
- Force, overcoming of extra motion by, in lever, 63-64*;
- reason for, of steam, 110.
- Forecasters, weather, 282-285.
- Form, elasticity of, 86-87.
- Freckles, cause of, 327.
- Freezing and melting, 96-99.
- Friction, 49-55*;
- electricity produced by, 197-198*.
- Frost, 97, 275;
- explanation of, 287.
- Fuel, chief elements in, 315-316.
- Fulcrum of lever, 59-60*.
- Fuse gap, the, 241*, 379*.
- Fuses, short circuits and, 240-245.
- Gas, cooling of, on expanding, 94-95;
- Gases, diffusion of, 269-271;
- as elements, 293-294.
- Gas heaters, action of, 319, 321*, 322*.
- Gasoline, evaporation of, 103;
- Geysers, cause of, 110.
- Glass, a poor conductor of heat, 118;
- used as insulator of electricity, 215.
- Glowworms, reason for glowing of, 341-342.
- Gold, an element, 293, 299;
- plating of, 339.
- Gravitation, defined, 3.
- Gravity, 1;
- pull of, opposed to pull of adhesion, 42-43.
- Grease, friction diminished by, 53-54;
- combined with lye to form soap, 357.
- Great Salt Lake, reason for salt in, 104-105.
- Greeks, early knowledge of electricity possessed by, 196.
- Green color of water, reason for, 169-171*.
- Grounded circuits, 225-229*.
- Gun, shooting of, caused by explosion, 345-346.
- Gunpowder, action of, in shooting of a gun, 345-346;
- how made, 347.
- Hail, explanation of, 286.
- Heat, a result of friction, 53;
- is the motion of molecules, 90;
- not caused by expansion, 94-95;
- cold is absence of, 95, 120;
- required to evaporate liquids, 102-103;
- conduction of, 116-118;
- carried by air, by convection, 118-119;
- radiation of, 122-128;
- of incandescent lamp, 125-126;
- brought to focus by convex lens, 149;
- chemical change caused by, 323-325.
- Heaters, hot-water, 120*;
- Heat waves, cause of, 141.
- Hydrochloric acid, getting hydrogen from, 301-304;
- testing for silver with, 373.
- Hydrofluoric acid, 351.
- Hydrogen, an element, 294, 299;
- Ice, slight friction of, 52*;
- Incandescence, defined, 125.
- Incandescent lamps, 125-126;
- Inertia, 66-71;
- definition of, 70.
- Insulators, of heat, 118;
- Iodine, an element, 299;
- testing with, for starch, 373-374.
- Iron, a good conductor of heat, 118;
- an element, 299.
- Irons, electric, 229*, 230, 232.
- Iron salt, formed by lemon juice on steel, 353.
- Iron ships, reason for floating, 24*-26.
- Laughing gas, 309.
- Lava in volcanoes, 110.
- Lead, an element, 299.
- Lead pencils, arc light from, 233*-234*.
- Leaning Tower of Pisa, 29*-30.
- Lemon juice, action of, on silver and on steel, 353;
- litmus test of, 359.
- Lens, of eye, 142, 151*-153;
- Levers, 57-65*.
- Light, radiation of, 122, 123*-128;
- Lightning, cause of, 200-201.
- Limewater test for carbon dioxid, 375*-376.
- Liquid air, 97, 112.
- Liquids, absorption of, 36-40;
- diffusion in, 272.
- Litmus paper, experiments with, 358-359.
- Litmus test, the, 358-359.
- Lye, a common base, 356;
- Machinery, oiling of, to decrease friction, 53-54.
- Magdeburg hemispheres, 15, 16*-17.
- Magnetism, 190 ff.
- Magneto, of automobile, 210, 211*;
- of old-fashioned telephone, 210-211.
- Magnets, 190-195*.
- Magnification, 150-157;
- by concave mirror, 157.
- Magnifying glass, convex lens in, 149;
- operation of, 150-156*.
- Manganese dioxid, an essential in explosives, 347.
- Megaphone, working of, 184.
- Melting, freezing and, 96-99.
- Membrane, diffusion through a, 272.
- Mercury, cohesion of, 47-48*;
- Mercury-vapor lamps, 167-168*, 172.
- Metals, good conductors of heat, 118;
- Microscope, 88;
- working of, 155-157*.
- Mirrors, concave, 154*, 155*, 157.
- Mixtures, distinguished from compounds, 309-310.
- Molecular attraction, 36 ff.
- Molecules, pull of, on each other, 46-47;
- explanation of, 88-89;
- heat defined as the motion of, 90;
- action of, in evaporation, 102-103*;
- action of, in boiling water, 107;
- action of, in conduction of heat, 117;
- action of, in radiation of heat and light, 125;
- action of, in magnetizing, 194*-195;
- made up of atoms, 196, 310;
- mingling of, 259 ff.;
- action of, in formation of clouds, rain, and dew, 277.
- Moon, cause of ring around, 131.
- Morse telegraph code, 253.
- Motion-picture machines, lenses of, 143, 148.
- Motor, the electric, 255-257*.
- Mountains, rainfall on, 286-287.
- Musical instruments, pitch of, 185-187*, 188;
- vibrating devices of, 188.
- Nail plug, the, 241*, 379*.
- Needle, magnetizing of, 192*, 193*-195.
- Negative charges of electricity, 198-200.
- Neutralization of acids and bases, 360-364.
- Niagara Falls, electricity generated by, 210.
- Nickel, an element, 299.
- Nickel-plating copper, process of, 336-339*.
- Night, reason for coolness at, 127-128.
- Nitric-acid, etching copper with, 352*-353;
- action of, on cloth, 354*.
- Nitrogen, an element, 299;
- Northern Lights, cause of, 193.
- Ocean, why salt, 104-105.
- Oil, reason for floating of, 26-27;
- Oil heaters, action of, 319.
- Orange, litmus test of, 359.
- Osmosis, process called, 272-274.
- Osmotic pressure, 272-273*.
- Oxidation, 312-322.
- Oxygen, an element, 293, 299;
- Pancakes, made from sour milk, 362.
- Paper, carbon and hydrogen in, 315.
- Paraffine, production of, 114.
- Parallel circuits, 221-223*.
- Peat, carbon and hydrogen in, 315.
- Pencils, making arc light with, 233*-234*.
- Periscope experiment, 134-135*.
- Petroleum, gasoline and kerosene distilled from, 114.
- Phonograph, working of, 177-178*.
- Phosphorescence, cause of, 341-342.
- Phosphorus, an element, 300;
- meaning of name, 341.
- Photographs, process of making, 327-332*.
- Pitch of sound, explanation of, 185-188*.
- Plants, light and the manufacture of food in, 332-333;
- how oxygen is supplied by, 333-335.
- Plating of metals, 336-339*.
- Platinum, an element, 300.
- Poles, positive and negative, 206-207.
- Porcelain, used as insulator, 215.
- Positive charges of electricity, 198-200.
- Potassium, experiment with, 304.
- Potassium chlorate, an essential in explosives, 347.
- Precious stones, formation of, 263-264.
- Prism, refraction of light by, 136-140*;
- separation of light into rainbow colors by, 162-163*.
- Radiation of heat and light, 122*-128.
- Radium, an element, 300.
- Rain, 275;
- cause of, 278-280.
- Rainbow, making a, on wall, 162*-163;
- how formed, 170-171.
- Reading glasses, 144*;
- convex lens in, 150.
- Red color of sky at sunset, reason for, 170.
- Reflecting telescopes, 157.
- Reflection of light, 129-135*.
- Refraction of light, 136-141*.
- Resistance, electrical, 229-232.
- Retina of eye, 151*, 153.
- Reverberation of sound, 183-185.
- Ring around moon, cause of, 131.
- Rock candy, how made, 267.
- Rubber, used as insulator, 215.
- Rusting of iron, 349.
- Safety valves on steam boilers, 347.
- Salt, reason for, in sea, 104-105*;
- Salt water, litmus test of, 359.
- Samson cells, 204.
- Scattering of light (diffusion), 158-161*.
- Seesaw, example of a lever, 57-58*.
- Seltzer siphon, working of, 17.
- Ships, reason for floating, 24*-26.
- Shock, electrical, 214-215.
- Short circuits and fuses, 240-245.
- Silver, an element, 300;
- Silver chlorid, formation of, 327.
- Sinking and floating, 23-28*.
- Siphon, 18*.
- Sky, reason why blue, 169;
- why red at sunset, 170.
- Smoke, consistency of, 318-319.
- Snow, 275;
- formation of, 285-286.
- Snowflakes, 97, 286*.
- Soap, how made, 357-358.
- Soda water, how made, 365-366.
- Sodium, experiment with, 304.
- Softening due to oil or water, 290-292.
- Soil, litmus test of, 359.
- Solution, defined, 261;
- Sound, cause of, 174;
- Sour milk, litmus test of, 359;
- neutralization of, by baking soda, 362.
- Sourness, taste of, caused by acids, 353, 354-355.
- Spectroscope, use of the, 172.
- Spectrum, the, 172.
- Spring water, carbon dioxid in, 366.
- Stability, 29-34.
- Starch, iodine test for, 373-374.
- Stars, twinkling of, 141;
- how to tell of what made, 171-172.
- Static electricity, 196-202*.
- Steam, reason for force exerted by, 110;
- Steel, generally an alloy, 310.
- Stereopticons, lenses of, 148.
- Storage battery, 206, 207*;
- action of electricity in, 339.
- Stoves, electric, 230, 232.
- Street car, electric motor of, 255-257.
- Suction pump, 19*.
- Sugar, making of, by plants, 332-333;
- litmus test of, 359.
- Sulfur, an element, 300.
- Sulfuric acid, action of, on cloth, 354;
- litmus test of, 359.
- Sun, radiation of heat and light from the, 122-128;
- how to tell of what made, 171-172.
- Sunbeams, explanation of, 131.
- Sweat glands, function of, 291.
- Tanning, process of, 327.
- Telegraph apparatus, 247-252*, 380-381*.
- Telegraph code, 253.
- Telephone, working of, 253-255.
- Telescopes, 156*, 157;
- Temperature, finding the, by reading a thermometer, 90-91.
- Thermometer, the, 89*-91*.
- Thermos bottle, how made, 126-127*.
- Thunder, cause of, 200-201.
- Tin, an element, 300.
- Tin salt, poisonous, 353.
- Toasters, electric, 230, 232.
- Tomatoes, use of soda to neutralize acid of, 362-363.
- Tungsten, in incandescent lamps, 231.
- Tuning-fork experiments, 181*, 186-187*.
- Twinkling of stars, cause of, 141.
- "Up," meaning of word, 4.
- Vacuum, defined, 11;
- Valves, safety, on boilers, 347.
- Vaseline, production of, 114.
- Vibrations, of air, 174-181*;
- pitch due to rapidity of, 186.
- Vinegar, litmus test of, 359;
- neutralization of lye by, 363.
- Violin, tuning of, 187.
- Volcanoes, cause of, 110;
- explosions and, 346*.
- Volume, elasticity of, 86-87.
- Washing soda, a common base, 356;
- litmus test of, 359.
- Water, seeks its own level, 6-10;
- gurgling of, when poured from bottle, 13;
- experiment with, to show centrifugal force, 73-74;
- used for making thermometer, 90*-92;
- expansion of, when frozen, 98;
- evaporation of, 100-106;
- action of, in geysers and volcanoes, 110;
- absorption of light by, 169-170;
- as conductor of electricity, 216;
- use of, for generating electricity, 256-257;
- softening due to, 290-292;
- elements of, 294-297;
- a compound and not a mixture, 308;
- formed by burning fuel, 316;
- why fire is put out by, but not burning oil, 317;
- combining of carbon dioxid and, by plants, 332-333;
- rusting of iron by, 349;
- acids and bases turned to salt and, by combining, 361-362.
- Wear, a result of friction, 53.
- Weather, forecasting of, 282-285.
- Weight, center of, 30-33*.
- Wet battery, 204-205*.
- White, a combination of all colors, 162.
- Winds, cause of, 20-21.
- Winter, reason for cold in, 127-128.
- Wiring for arc lamps, 236-239.
- Wood, poor conductor of heat, 118;
- carbon and hydrogen in, 315.