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.
[Illustration: FIG. 186. The platinum loop used in making the borax
bead test.]
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.
[Illustration: FIG. 187. Making the test.]
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.
[Illustration: FIG. 188. The white powder that is forming is a silver
salt.]
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 (CO_2) is present.
[Illustration: FIG. 189. The limewater test shows that there is carbon
dioxid in the air.]
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:
[Illustration: 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.
[Illustration: Fig. 191. The cigar-box telegraph.]
INDEX
An asterisk (*) indicates use of one or more illustrations in
connection with reference to which appended.
Acetylene, carbon and hydrogen in, 315.
Acids, 351 ff.;
action of, on metals, 351-353*;
action of, on cloth, 354*;
action of, on nerves of taste, 354-355;
distinguished from bases by litmus test, 358-359;
neutralization of, by bases, 360-364.
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*;
height water is forced up by, in vacuum, 19;
high and low, 20, 282;
winds caused by, 20-21.
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;
action of, in cleaning cloth, 358;
litmus test of, 359;
neutralization of acid by, 363.
Ampere, defined, 246.
Analysis, chemical, 370-376.
Aneroid barometer, 285*.
Arc, the electric, 233-240*.
Atoms, description of, 196;
electrons and, 197;
everything in the world made of, 310-311;
in molecules, 311.
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;
testing with litmus paper, 359;
neutralization of sour milk by, in cooking, 362;
carbon dioxid in, 366-367.
Ball bearings, used to diminish friction, 54-55.
Balloon, expansion of, 17-18, 109*;
reason for rising of, 26;
filling of, with hydrogen, 301-304*.
Barometer, use of, 280-285*.
Bases, substances called, 355-358;
litmus test for distinguishing from acids, 358-359;
neutralization of, by acids, 360-364.
Batteries, electric, 203-205*;
different kinds of, 205*-207*;
general principle of all, 206.
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;
human eye as a small, 151*-153;
explanation of, 327-332.
Capillary attraction, 36*-40;
difference between adhesion, cohesion, and, 47.
Carbon, in electric battery, 203-206;
resistance of, to electric current, 231;
an element, 293, 299;
one of chief elements in fuel, 315-316.
Carbon dioxid, in seltzer siphon, 17;
produced by joining of carbon with oxygen, 315;
combining of water and, by plants, 332-333;
releasing of, in baking powder, 349-350;
bubbling of, in effervescence, 365-366;
in soda water, springs, and baking soda, 366-367;
limewater test for, 375-376.
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.;
burning (oxidation), 312-322;
caused by heat, 323-325;
caused by light, 326-335;
caused by electricity, 335-339;
energy released by, 340-341;
helped by solution, 349-351.
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*;
breaking and making, 220-221;
connecting in parallel, 221-223*;
grounded, 225-229*;
short, 240-245*.
Cloth, action of acids on, 354*;
action of an alkali on, 356, 357*.
Clouds, how formed, 277-278.
Coal, carbon and hydrogen in, 315.
Cohesion, 39, 44*-49.
Cold, caused by expansion, 94;
is the absence of heat, 95, 120.
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;
definition of, 308-309;
mixtures distinguished from, 309-310.
Concave mirrors, 154*, 155*, 157;
magnification by, 157;
in reflecting telescopes, 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*;
in microscope, 155-157*;
in telescope, 157.
Cooling from expansion, 94-96.
Coolness at night and in winter, 127-128.
Copper, a good conductor of electricity, 215;
an element, 299;
nickel plating of, 336-339*;
etching of, with acid, 352*-353.
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;
generally due to freeing of carbon dioxid, 367*-368;
helped by stirring or shaking, 368.
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.;
static, 196-202;
negative and positive charges of, 198*-200;
action of, in thunderstorms, 200-201;
flowing, 203 ff.;
flowing of, in dynamo, 207-210;
alternating and direct-current, 211-212;
conduction of, 213*-218;
chemical change caused by, 335-339.
Electric lamps, vacuums in, 12*, 317;
incandescent, 125;
gas-filled, 317.
Electric motors, 256*-257*.
Electrolysis apparatus, 294-295*.
Electromagnets, 247-257*.
Electrons, 193;
description of, 197;
number of, in negative and in positive charges, 198-200.
Elements, defined, 293;
chemists' abbreviations of, 297-299;
list of common, 299-300;
hiding of, in compounds, 300-301.
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.;
automobiles made to go by succession of, 344-345;
cause of, 345;
shooting of guns caused by, 345-346.
Explosives, manufacture of, 347.
Extension lights, 238.
Eye, lens of, 142;
section of, 151*;
working of, 151*-153.
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;
carbon and hydrogen in, 315;
used for filling electric lamps, 317-318;
will not burn until hot enough, 323-324;
an explosion the sudden release of a confined, 348.
Gases, diffusion of, 269-271;
as elements, 293-294.
Gas heaters, action of, 319, 321*, 322*.
Gasoline, evaporation of, 103;
boiling of, 112;
distilled from petroleum, 114;
elements of, 315;
action of, in making automobiles go, 344-345.
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*;
electric, 230, 232;
gas, 319, 321*, 322*.
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;
in water, 295-296;
experiments with, 301-304*;
one of chief elements in fuel, 315-316;
part taken by, in burning, 312-319.
Ice, slight friction of, 52*;
action of molecules in, on freezing and melting, 96-97;
reason for floating of, 98-99.
Incandescence, defined, 125.
Incandescent lamps, 125-126;
number of electrons in, 197;
working of, 229-232.
Inertia, 66-71;
definition of, 70.
Insulators, of heat, 118;
of electricity, 213;
substances used as, 215.
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.
Kerosene, boiling of, 112;
distilled from petroleum, 114;
carbon and hydrogen in, 315.
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;
of camera, 143, 149*, 328;
convex, 148-149;
concave, 149*;
in telescope, 157.
Levers, 57-65*.
Light, radiation of, 122, 123*-128;
reflection of, 129-135*;
refraction of, 136*-141;
focus of, 142-149*;
brought to focus by convex lens, 149;
diffusion of, 158-161*;
color a kind of, 162;
speed of, 182;
chemical change caused by, 326-335;
and manufacture of food in plants, 332-333.
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;
experiment with, 356;
soap made from, 357;
used for clearing out drainpipe, 358;
neutralization of, by acids, 363.
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*;
use of, in thermometer, 89*, 90-91;
an element, 299.
Mercury-vapor lamps, 167-168*, 172.
Metals, good conductors of heat, 118;
good conductors of electricity, 215;
as elements, 310;
plating of, 336-339*;
action of acids on, 351-353.
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;
a non-burning gas, 308;
used in electric lamps, 317.
Northern Lights, cause of, 193.
Ocean, why salt, 104-105.
Oil, reason for floating of, 26-27;
decreasing of friction by, 53-54;
softening due to, 290-292;
carbon and hydrogen in crude, 315;
why water will not put out burning, 317.
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;
an element of water, 295-296;
experiments in getting, from two solids, 305-308*;
function of, in burning, 308;
part taken by, in burning (oxidation), 312-313;
released in manufacture of plant food, 333-335;
a compound of, an essential in explosives, 347.
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*.
Quicksilver. _See_ Mercury.
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*;
a compound, 308;
elements of, 310-311;
formed by hydrochloric acid and zinc, 351;
iron, formed by lemon juice on steel, 353;
acids and bases turned to water and, by combining, 361-362.
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;
plating of, 339;
hydrochloric acid test for, 373.
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;
difference between emulsion and, 263;
a mixture and not a compound, 309;
chemical change helped by, 349.
Sound, cause of, 174;
rate of speed, 181-182;
action of, in echoes, 183-185*;
pitch of, 185-188.
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;
geysers and volcanoes caused by, 110;
real, not visible, 112 n.
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;
how made, 157;
reflecting, 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;
reason for, in electric lamp, 12*, 317;
use of, in manufacture of thermos bottles, 126-127*;
impossibility of producing sound in, 176-177.
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.
Yardstick, experiment with, to show leverage, 59*-60.
Yeast, action of, in bread making, 365.
Yellow, in flames, 318.
Yerkes Observatory, telescope of, 156*.
Zinc, in electric battery, 203-206;
an element, 300;
used for driving hydrogen out of acid, 301, 304.
* * * * *
_CONSERVATION SERIES_
[Illustration]
Conservation Reader
_By_ HAROLD W. FAIRBANKS, _Ph. D._
_Lecturer, University of California; Geography Supervisor Berkeley
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A small book bringing out in a simple and interesting manner the
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The matter is presented in an easy narrative style that is calculated
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_INDIAN LIFE AND INDIAN LORE_
INDIAN DAYS OF THE LONG AGO
IN THE LAND OF THE HEAD-HUNTERS
TWO BOOKS FOR YOUNG PEOPLE BY
EDWARD S. CURTIS
_Author of "The North American Indian"_
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act of their lives was influenced by spiritual beliefs and practices.
The book tells the story of Kukusim, an Indian lad who is eagerly
awaiting the time when he shall be a warrior. It is full of mythical
lore and thrilling adventures, culminating in the mountain vigil,
when Kukusim hears the spirit voices which mark the passing of his
childhood. _Illustrated with photographs by the author and drawings by
F. N. Wilson._
* * * * *
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_By_ J. HENRI FABRE
_Selected and Arranged for Young People by Louis Seymour Hasbrouck_
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_NEW-WORLD SCIENCE SERIES_
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TREES, STARS _and_ BIRDS
A BOOK OF OUTDOOR SCIENCE
By EDWIN LINCOLN MOSELEY
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Ohio_
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The text deals with three phases of outdoor science that have a
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The book is illustrated with 167 photographs, 69 drawings, 9 star
maps, and with 16 color plates of 58 birds, from paintings by Louis
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INDIAN LIFE AND INDIAN LORE
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By MARY E. LAING
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Transcriber's Notes:
page 238: changed "diagramed" to "diagrammed" (As there diagrammed,
the electricity passes out...)
page 253: the Morse telegraph code is as in the original; this is not
the modern International Morse code
Page 412, changed "conrcete" to "concrete" (... shall express this
ideal in a very concrete way.)
General: variable spelling of iodin/iodine in the original has been
preserved
General: spelling of dioxid and chlorid in the original has been
preserved