Transcriber’s Notes:
Text enclosed by underscores is in italics (_italics_), and text
enclosed by equal signs is in bold (=bold=).
Additional Transcriber’s Notes are at the end, including some
corrections to the text.
* * * * *
[Illustration: HOW TO DO CHEMICAL TRICKS]
HOW TO DO CHEMICAL TRICKS.
Containing Over One Hundred Highly
Amusing and Instructive Tricks
With Chemicals.
By A. ANDERSON.
HANDSOMELY ILLUSTRATED.
NEW YORK:
FRANK TOUSEY, Publisher,
24 UNION SQUARE.
* * * * *
Entered according to Act of Congress, in the year 1898, by
FRANK TOUSEY,
in the Office of the Librarian of Congress at Washington, D.C.
* * * * *
HOW TO DO CHEMICAL TRICKS.
From the remotest ages chemistry has exercised the strongest
fascination on the minds of the curious, nor is it a matter of surprise
that boys should feel themselves drawn strongly by its mystery and
seeming magic. This attraction is undoubtedly caused by what the
ancients called the elements, earth, air, fire and water. There is
something so weird about the manifestation of air and fire, that it
is not difficult to understand how the alchemists believed them to be
forces able to be used at the bidding of spirits, who might be conjured
up by incantations and spells.
Now it is known that these uncanny beings existed only in the
imagination of the forerunners of modern chemists. Yet what boy can
look on the brilliantly colored fires of a Fourth of July display, or
the burnished gold of the setting sun, or the fantastic pictures in the
glowing coals in a grate, and not feel that there is still something
of magic and mystery in fire still? What the boy feels, the scientist
cannot explain. Nobody knows actually what fire is. All that can be
said is that fire is produced by certain substances, such as coals,
wood, or paper, that give out heat, while passing from one state to
another.
Now the word “element” was and is used to mean that simplest form of
matter, which, with other simplest forms goes to make up the whole
world of everything in it. The earth, animals, plants, the sea, the
atmosphere, are all made up of one or more of some seventy substances
called elements. Hence it is clear that the earth, air and water are
not, as the ancients thought, elements at all. As will be seen in this
little book, both air and water consist of mixtures of elements. In
chemistry such mixtures are called compounds. This word occurs again
and again, so its explanation should be remembered.
One great fact must be remembered, which is at the very root of
chemistry. Nothing is really lost, however much its form may be
changed, or however many changes it may pass through. For instance, it
may seem that when a block of wood be burned that a very large amount
of it is lost. If, however, the ashes, the smoke, and the carbon that
is burned by the air be all weighed, the result would be exactly the
same as the weight of the original block of wood.
Again take an instance of a different nature. A lump of sugar is placed
in a small glass of water. Gradually the solid is dissolved, and in
time disappears. It is not lost, however. By boiling the mixture until
all the water has evaporated the sugar will be found adhering as
crystals on the sides of the glass. If these be carefully collected,
they will be found to weigh precisely as much as the original lump of
sugar.
Once more, take a block of ice weighing an ounce. Having removed
it into a room, the solid will in an hour or two have disappeared
entirely, but the water that has replaced the block of ice will weigh
neither more nor less than an ounce. If again heat be applied to the
water it will all disappear, but if weighed in a jam jar, the steam,
although invisible to the eye, will still weigh one ounce exactly.
From the above-given experiments it may be seen that, however matter
may change its form it cannot really be destroyed. This truth will
appear in every experiment that can be performed, whether those given
in this little book or in the most learned treatise on chemistry.
Chemical Affinity.
This high-sounding term means that substances have a power of uniting
together that can be better explained by an experiment. Allow a few
drops of water to fall on a perfectly clean piece of iron. In a short
time a reddish-brown substance will appear on the iron that in ordinary
language is called rust. What does this mean? Water is a compound
substance composed of oxygen and hydrogen, but when brought into
contact with iron the oxygen prefers to unite with the iron and sets
the hydrogen free. Hence, would the chemist say, oxygen has a “stronger
affinity” for iron than for hydrogen. In this case the rust is composed
of rust, a combination of iron and oxygen called oxide of iron. What
has taken place may be shown by the following, which will be easily
understood:
Oxygen } Water + Iron = Oxide
Hydrogen } of Iron + Hydrogen.
So all that the chemical combination in the above means is that the
iron has taken the place of the hydrogen in the water used for the
experiment. If weighed it would be found as always, that the water
and the iron weighed precisely the same as the oxide of iron and the
hydrogen.
It is to this same principle of chemical affinity that the curious
experiments of magic writing with sympathetic inks are possible.
Sympathetic Inks.
By means of these may be carried on a correspondence which is beyond
the discovery of all not in the secret. With one class of these inks
the writing becomes visible only when moistened with a particular
solution. Thus, if we write to you with a solution of sulphate of iron
the letters are invisible. On the receipt of our letter, you rub over
the sheet a feather or sponge, wet with a solution of nut-galls, and
the letters burst forth into sensible being at once, and are permanent.
2. If we write with a solution of sugar of lead and you moisten with
a sponge or pencil dipped in water impregnated with sulphuretted
hydrogen, the letters will appear with metallic brilliancy.
3. If we write with a weak solution of sulphate of copper, and you
apply ammonia, the letters assume a beautiful blue. When the ammonia
evaporates as it does on exposure to the sun or fire, the writing
disappears, but may be revived again as before.
4. If you write with oil of vitriol very much diluted, so as to prevent
its destroying the paper, the manuscript will be invisible except when
held to the fire, when the letters will appear black.
5. Write with cobalt dissolved in diluted muriatic acid; the letters
will be invisible when cold, but when warmed they will appear a bluish
green.
Secrets thus written will not be brought to the knowledge of a
stranger, because he does not know the solution which was used in
writing, and therefore knows not what to apply to bring out the letters.
Other forms of elective affinity produce equally novel results. Thus,
two invisible gases, when combined, form sometimes a _visible solid_.
Muriatic acid and ammonia are examples, also ammonia and carbonic acid.
On the other hand, if a solution of sulphate of soda be mixed with a
solution of muriate of lime the whole becomes solid.
* * * * *
Some gases when united form liquids, as oxygen and hydrogen, which
unite and form water. Some solids when combined form liquids.
Chemical affinity is sometimes called _elective_, or the effect of
_choice_, as if one substance exerted a kind of _preference_ for
another, and chose to be united to it rather than to that with which
it was previously combined; thus, if you pour some vinegar, which is
a weak acetic acid, upon some pearlash (a combination of potash and
carbonic acid), or some carbonate of soda (a combination of the same
acid with soda), a violent effervescence will take place, occasioned by
the escape of the carbonic acid, displaced in consequence of the potash
or soda preferring the acetic acid, and forming a compound called an
acetate.
Then, if some sulphuric acid be poured on this new compound, the acetic
acid will, in its turn, be displaced by the greater attachment of
either of the bases, as they are termed, for the sulphuric acid. Again,
if into a solution of blue vitriol (a combination of sulphuric acid
with copper), the bright blade of a knife be introduced, the knife will
speedily be covered with a coat of copper, deposited in consequence of
the acid _preferring_ the iron of which the knife is made, a quantity
of it being dissolved in exact proportion to the quantity of copper
deposited.
It is on the same principle that a very beautiful preparation called a
silver-tree, or a lead-tree, may be formed, thus: Fill a wide bottle,
capable of holding from half a pint to a pint, with a tolerably strong
solution of nitrate of silver (lunar caustic), or acetate of lead, in
pure distilled water. Then attach a small piece of zinc by a string
to the cork or stopper of the bottle, so that the zinc shall hang
about the middle of the bottle, and set it by where it may be quite
undisturbed. In a short time brilliant plates of silver or lead, as the
case may be, will be seen to collect around the piece of zinc, assuming
more or less of the crystalline form. This is a case of elective
affinity; the acid with which the silver or lead was united _prefers_
the zinc to either of those metals, and in consequence discards them
in order to attach the zinc to itself; and this process will continue
until the whole of the zinc is taken up, or the whole of the silver or
lead deposited.
Alum Baskets.
Form a small basket about the size of the hand, of iron wire or split
willow; then take some cotton, such as ladies use for running into
flounces; untwist it and wind it round every limb of the basket. Boil
eighteen ounces of alum in a quart of water, or quantities in that
proportion; stir the mixture while boiling until the alum is completely
dissolved. Pour the solution into a deep pan, or other convenient
vessel, and suspend the basket in the liquor, so that no part of the
basket shall touch the vessel, or be exposed to the air. Let the whole
remain perfectly at rest for twenty-four hours. When you then remove
the basket the alum will be found very prettily crystallized over all
the limbs of the cottoned frame.
Easy Crystallizations.
Saturate water _kept boiling_ with alum; then set the solution in a
cool place, suspending in it, by a hair, or fine silk thread, a cinder,
a sprig of a plant, or any other trifle. As the solution cools, a
beautiful crystallization of the salt takes place upon the cinders,
etc., which are made to resemble specimens of mineralogical spars.
To Make a Piece of Charcoal Appear as Though it were Coated with Gold.
Dilute a saturated solution of chloride of gold with five times its
bulk of water; place a thin strip of fresh burned charcoal into it, and
apply heat, gradually increasing it until the solution gently boils.
The heat will make the charcoal precipitate the metal on the charcoal,
in the form of brilliant spangles.
To Give a Piece of Charcoal a Rich Coat of Silver.
Lay a crystal of nitrate of silver upon a piece of burning charcoal;
the metallic salt will catch fire, and throw out the most beautiful
scintillations that can be imagined. The silver is reduced, and, in the
end, produces upon the charcoal a very brilliant appearance.
Many animal and vegetable substances, consist, for the most part, of
carbon, or charcoal, united with oxygen and hydrogen, which remember,
together combined, form water. Now oil of vitriol or strong sulphuric
acid, has so powerful an affinity or so great a thirst for water, that
it will abstract it from almost any body in which it exists. If you
pour some of this acid on a lump of sugar, or place a chip of wood in a
small quantity of it, the sugar or wood will become speedily blackened,
that is charred, in consequence of the oxygen and hydrogen being
removed by the sulphuric acid, and only the carbon or charcoal left.
When Cleopatra dissolved pearls of wondrous value in vinegar, she was
unwittingly giving an example of chemical affinity. The pearl is simply
carbonate of lime stored up by the oyster in layers. Consequently the
precious jewels were decomposed by the greater affinity or fondness
of lime for the acetic acid in the vinegar, than for the carbonic
acid with which it had been before united. This was an example of
inconstancy in strong contrast with the conduct of their owner, who
chose death rather than become the wife of her lover’s conqueror.
Combustion.
It is necessary to distinguish between burning and the mere appearance
of it. A gas flame is gas in a state of combustion, whereas the
electric light is no example of it, although the wire within the
glassen cylinder is red hot, and to all appearance burning. Combustion
generally takes place through the strong affinity of some element, such
as carbon in a substance for the oxygen in the atmosphere. In coal gas,
for instance, the carbon contained in it unites with the oxygen in the
air to form a colorless substance called carbonic acid gas. The latter
is unable to support life, and may be called, therefore, poisonous. It
is the presence of this gas which makes it unhealthy to burn many jets
without proper ventilation.
Also, carbonic acid gas is given off by the lungs. It may seem
curious, but it is none the less true, that breathing is a process of
combustion. The blood brings to the surface of the lungs the carbon,
which has resulted from the waste of the internal organs of the body.
When drawing in a breath the oxygen present in the atmosphere meets the
impure blood at the surface of the lungs, and purifies it by uniting
with the carbon in it. Then, though oxygen has been breathed in,
carbonic acid gas has been breathed out.
To prove this will be interesting: Obtain from a chemist a little lime
water--two cents worth will do. It looks like ordinary water, being
perfectly transparent and colorless. Pour some into a clean glass, and
through a glass tube blow steadily into the water. In half a minute the
hitherto colorless liquid will become milky and opaque. If allowed to
stand there will fall down at the bottom of the glass a white powder.
What has happened in this case? The carbonic acid gas from the lungs
has formed with the lime in the lime water a substance called carbonate
of lime, which, being insoluble in water, falls to the bottom of the
glass as a white powder.
If carbonic acid gas were not present in the air blown from the lungs,
this milkiness would not appear, for no other gas, except this, would
alter the lime water’s clearness.
Chemistry of The Air.
Before proceeding further, it will be well to perform one or two
experiments, to prove that the air we breathe is by no means the simple
substance it is generally supposed to be. Although it is invisible, it
must be remembered that it presses with a force of over fifteen pounds
to the square inch, over the whole surface of the earth. It extends,
too, to a height of some forty miles above the earth, and though it
cannot be seen, it can be felt in the rush of the hurricane, and heard
in the roar of the tempest. It is chiefly composed of a mixture of two
gases, oxygen and nitrogen.
Did the air consist entirely of the former, people would breathe too
quickly, and die in a very short time in a high fever, burned up, in
fact. If only consisting of nitrogen, the human race would also die,
because this element is incapable of supporting life; people would be
suffocated, in fact.
Therefore, a judicious mixture of the two is essential to the life
of animals. Generally, in a hundred parts of air by weight there are
seventy-six parts of nitrogen to twenty-three of oxygen.
Besides these two gases, there is also a quantity of carbonic acid gas
in the air, given off by all the fires and animals in the world. Of
course, its amount is much greater in the great towns and manufacturing
centers than in country districts.
Now herein must be recorded one of these charming arrangements which
Nature has designed for the benefit of her children. Carbonic acid gas
is much heavier than the air, and, therefore, sinks towards the ground,
where, if allowed to accumulate, would cause the death of every animal.
Fortunately, however, plants breathe in through their leaves carbonic
acid gas during sunshine, and break it up into carbon and oxygen. The
former, they use for building up their trunks, leaves, and flowers,
while during the night they give off oxygen into the air.
This is the reason why plants and trees planted in the streets so
largely help to sweeten and purify the foul air of a great city.
* * * * *
An experiment to prove that the atmosphere does consist of nitrogen
and oxygen, may be prettily proved in the following simple manner: A
glass marmalade jar, or a soup-plate filled with water, and a piece of
phosphorus as large as a pea, are the only things necessary. Take very
great care not to touch the phosphorus, for the heat of the hand is
sufficient to set it on fire, and a terrible wound would be caused.
Place the phosphorus in a match-box on the surface of the water, touch
it with a lighted match, and put the jar-mouth downwards over it to the
bottom of the plate. The phosphorus burns with a dazzling brilliancy,
and gives off dense white fumes. At the same time the water rises a
third of the way up the jar, but not to the top, thus showing that all
the invisible matter has not been consumed. The white soon settles into
the water and is dissolved. The phosphorus has combined with the oxygen
in the jar and forms phosphoric oxide, which dissolves in water. There
is then only the nitrogen left. The disappearance of the oxygen allows
the water to fill up the space it formerly occupied.
This may be followed by another experiment.
To show that oxygen is necessary for the support of combustion, fix
two or three pieces of wax taper on flat pieces of cork, and set them
floating on water in a soup-plate, light them, and invert over them a
glass jar.
As they burn, the heat produced may perhaps at first expand the air, so
as to force a small quantity out of the jar, but the water will soon
rise in the jar, and continue to do so until the tapers expire, when
you will find that a considerable portion of the air has disappeared,
and what remains will no longer support flame.
The oxygen has been converted partly into water, and partly into
carbonic acid gas, by uniting with the carbon and hydrogen of which
the taper consists, and the remaining air is principally nitrogen,
with some carbonic acid. The presence of the latter may be proved by
decanting some of the remaining air into a bottle, and then shaking
some lime water with it, which will absorb the carbonic acid and form
chalk.
Into an ale glass, two thirds full of water at about 140 degrees,
drop one or two pieces of phosphorus about the size of peas, and they
will remain unaltered. Then take a bladder containing oxygen gas, to
which is attached a stop cock and a long fine tube. Pass the end of
the tube to the bottom of the water, turn the stop cock, and press the
bladder gently. As the gas reaches the phosphorus it will take fire,
and burn under the water with a brilliant flame, filling the glass with
brilliant flashes of light dashing through the water.
Into another glass put some cold water; introduce carefully some of the
salt called chlorate of potash; upon that drop a piece of phosphorus;
then let some strong sulphuric acid (oil of vitriol) trickle slowly
down the side of the glass, or introduce it by means of a dropping
bottle.
As soon as the acid touches the salt the latter is decomposed, and
liberates a gas which ignites the phosphorus, producing much the same
appearance as in the last experiment.
Into the half of a broken phial put some chlorate of potash, and pour
in some oil of vitriol. The phial will soon be filled with a heavy gas
of a deep yellow color. Tie a small test tube at right angles to the
end of a stick not less than a yard long, put a little ether into the
tube, and pour it gently into the phial of gas, when an instantaneous
explosion will take place, and the ether will be set on fire. This
experiment should be performed in a place where there are no articles
of furniture to be damaged, as the ingredients are often scattered by
the explosion, and the oil of vitriol destroys all animal and vegetable
substances.
Into a jar containing oxygen gas introduce a coil of soft iron wire,
suspended to a cork that fits the neck of the jar and having attached
a small piece of charcoal to the lower part of the wire, ignite the
charcoal. The iron will take fire and burn with a brilliant light,
throwing out bright scintillations, which are oxide of iron, formed by
the union of the gas with the iron; and they are so intensely hot that
some of them will probably _melt_ their way into the sides of the jar,
if not through them.
But by far the most intense heat, and most brilliant light, may be
produced by introducing a piece of phosphorus into a jar of oxygen.
The phosphorus may be placed in a small copper cup, with a long handle
of thick wire passing through a hole in a cork that fits the jar. The
phosphorus must first be ignited; and as soon as it is introduced into
the oxygen, it gives out a light so brilliant that no eye can bear it,
and the whole jar appears filled with an intensely luminous atmosphere.
It is well to dilute the oxygen with about one-fourth part of common
air, to moderate the intense heat, which is nearly certain to break the
jar if pure oxygen is used.
The following experiment shows the production of heat by chemical
action alone: Bruise some fresh-prepared crystals of nitrate of copper,
spread them over a piece of tin foil, sprinkle them with a little
water; then fold up the foil tightly, as rapidly as possible, and in a
minute or two it will become red hot, the tin apparently burning away.
This heat is produced by the energetic action of the tin on the nitrate
of copper, taking away its oxygen in order to unite with the nitric
acid, for which, as well as for the oxygen the tin has a much greater
affinity than the copper has.
[Illustration]
Combustion without flame may be shown in a very elegant and agreeable
manner, by taking a coil of platinum wire and twisting it round the
stem of a tobacco pipe, or any cylindrical body for a dozen times or
so, leaving about an inch straight, which should be inserted into the
wick of a spirit lamp. Light the lamp, and after it has burned for a
minute or two, extinguish the flame quickly; the wire will soon become
red hot, and, if kept from draughts of air, will continue to burn
until all the spirit is consumed.
Spongy platinum, as it is called, answers rather better than wire, and
has been employed in the formation of fumigators for the drawing-room,
in which, instead of pure spirit, some perfume, such as lavender water,
is used; by its combustion an agreeable odor is diffused through the
apartment. These little lamps were much in vogue a few years ago, but
are now nearly out of fashion. Finally, all the readers of this little
book should be very careful in performing all experiments. If possible,
he should use a room with a stone floor and no curtains, while an
outhouse with an earthen floor is still less dangerous.
Amateur Air Pump.
A most interesting class of experiments can be made with an air pump, a
piece of apparatus unfortunately beyond the pocket-money supply of the
average boy. Nevertheless, if the following instructions are exactly
followed and carefully carried out, a very excellent air pump can be
made at a comparatively small cost. Some pretty, as well as interesting
results will amply repay you for the trouble you take to make the pump.
Although the air seems so light in comparison with water or a heavy
metal like iron, you must remember that it really presses upon every
square inch of the earth’s surface, aye, on every square inch of your
own bodies, with a force of fourteen and a half pounds. In other words,
the weight of the air at the sea level resting on each square inch of
surface weighs fourteen and a half pounds.
Don’t be frightened, boys, at the explanation of one word that must
be used in connection with air experiments. The word is vacuum.
Vacuum really means an empty space, devoid of all matter, even of
air. Although it seems easy to think of an empty space, it is quite
impossible to exhaust a space of all matter, even of air. For this
reason, the alchemists of the middle ages used to say: “Nature abhors
a vacuum.” This was only their way of saying how impossible it was to
make a space, such as the inside of a vessel, quite empty. Yet it is
possible to reduce the amount of air in a vessel almost to nothing.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
Now for the pump. In the first place obtain three pieces of
gutta-percha tubing of the following lengths:
No. 1.--A tube twelve and a half inches long, measuring outside two and
a half, inside one and a half inches in circumference.
No. 2.--This must be seven and a half inches long, one and a half
inches outside, and an inch inside.
No. 3.--This is a length of tubing about sixty inches long, two and a
half inches in outside circumference, and at least an inch thick. If an
inch and a half thick all the better, as it will be more air-tight.
Divide tube No. 2 into two equal parts, cutting from right to left at
an angle of 45 degrees. Into one of the parts fit a plug of hard wood
pierced lengthwise by a red hot wire (fig. 1); the figure shows the
shape of it sufficiently. In the hollow side cut a small opening, and
over this tie very tightly a band of flexible india-rubber (fig. 3).
This band will serve as the valve of the piston of the pump. Figs. 3
and 4 give a side and front view of this valve. Great care must be
taken neither to split the plug in boring the hole nor to cut the tube.
[Illustration: FIG. 3.]
[Illustration: FIG. 4.]
This valve must now be inserted in the large tube No. 1, as seen in
fig. 2.
At the other end of the large tube, which will serve as the body of
the pump, at B fig. 2, fix a similar valve to the above, but the
india-rubber band must be fixed on the other side of the valve as at B
fig. 2. The fitting A will serve for escape, the second for withdrawing
the air from the space to be exhausted. Finally fix tube No. 3 on
valves A or B, fig. 2, according to your wish to produce a vacuum or to
compress the air.
[Illustration: FIG. 5.]
By means of a pedal made simply with two boards put together on hinges
(fig. 5), one pressed with the foot, the air contained in the body of
the pump (fig. 2) tends to escape. It therefore lifts the valve of the
fitting fixed at A, and escapes through the flexible elastic band tied
over the hole in the hollow side of tube No. 2. If the pressure ceases
the big tube, on account of its own elasticity, takes its former form
and sucks in the air. This time it is the valve at B which is lifted
and lets pass the air which fills the body of the pump. If one has
fixed on to the fitting at B, the long india-rubber tube No. 3, which
is plunged in a receiver--a receiver is any vessel in which the air is
exhausted, or into which it is forced--it is easily understood that
after a few moves of the pedal, the air is drawn out, and a vacuum is
obtained.
[Illustration: FIG. 6.]
If one wishes to have a force-pump one has only to modify slightly the
construction of the valve. Instead of a band of india-rubber fixed as
shown in fig. 3, it is altered as in fig. 4, that is to say the valve
is formed by a band of supple india-rubber fastened by two tacks only
on one side of the opening in the side of the plug. For this object it
is also necessary to take stronger tubes.
Let us now review the few experiments that can be made with this
machine.
In order to conduct experiments a receiver must be obtained. The best
vessel for your purpose is a large bell-jar with a ground glass stopper
and neck to insure absolute tightness. Such a jar may be cheaply
obtained at a scientific instrument maker’s for about seventy-five
cents. If you cannot get a bell-jar procure a 4-lb. jam pot and a
tightly-fitting bung. In the middle of the latter bore a hole to admit
a glass tube, some six inches long and an inch in diameter, and then
sealing-wax the whole of the upper surface of the bung so that air
cannot enter. Over the projecting end of the glass tube, bind very
tightly the free end of the long tubing affixed to the pump. To ensure
tight binding, waxed thread should be used.
Asphyxia.
Put a mouse--it is necessary to catch him first--into the receiver, and
work the pump. Soon the animal will show all the signs of being choked,
and eventually will die. This is proof sufficient that animals cannot
live without air.
[Illustration]
Balloon in Vacuum.
Place in the receiver a small bladder, such as are sold in the streets
for a few cents. Wet it a little to make it more supple. Now, in the
ordinary way the air inside the bladder exerts the same pressure on
the skin of the bladder as does the air on the outside. Now work the
pedal so that the air in the receiver is gradually exhausted. The
bladder will be seen to gradually swell and finally burst. It bursts
because as the air in the receiver is exhausted by the pump, the air
outside the bladder exerts a less force than the air inside. But the
air inside is confined by the bladder skin, a not very strong material,
as you know, so as soon as the difference between the inside and
outside pressures is greater than the strength of the bladder, the
latter bursts. This experiment also shows the expansible power of air.
[Illustration]
Boiling Cold Water.
Place in the receiver a tumbler of cold water and work the pump as
before. In a few minutes, as soon as the air is sufficiently exhausted,
the water will apparently boil. Yet you know the water does not boil
in a kettle unless heated to 212 degrees. This phenomenon is thus
explained: The vacuum causes the air-bubbles contained in the water to
escape. They easily do so, because there is scarcely any reserve on the
surface of the liquid (see fig.).
[Illustration]
A Sucking Tube.
This force, the pressure of the air which you have just ascertained,
supplies various experiments in its illustration.
Take a tin tube, for example, the tin holder of a penny pen, which you
may procure at any stationer’s. Put a little water in it and make it
boil so that the steam takes the place of the air.
When steaming furiously stop the mouth of the tube with a small cork,
sealing the opening hermetically. Oil it a little, so it may glide with
ease. If you cool the tube by plunging it in a basin of cold water,
for example, the steam is condensed, forming a vacuum in the interior,
and under the atmospheric pressure the cork will glide down. Fasten
a string to the cork and you can withdraw it and begin the operation
again. As the water gets hot, steam is reformed; you will see the cork
come up again.
A capital way of making this cork is to stick the tube in a piece of
potato, cutting out of the latter a perfectly-fitting cork.
[Illustration]
Cupping.
Instead of a jar-receiver, take a long-necked bottle open at both ends.
If you place the hand on one of the open ends and exhaust the air, by
attaching the long tube of the pump to the other you cannot remove the
hand easily. Do not try to pump the air out entirely, as the suction
may be too strong and draw blood. It is by the rarefaction of the air
that the cupping-glass is applied to people who require bleeding. In
the antiquated surgical operation of cupping, the doctor burned a few
pieces of paper in small glass cups, which are then applied to the
skin; the air, in getting cold, contracted and produced a partial
vacuum, thus acting as the bottle did in the above experiment.
[Illustration]
The Barometer.
Now you shall learn something about the pressure exercised by the
atmospheric layer which surrounds the earth to the height of about
forty miles. This is done with the aid of a very well-known instrument
called the barometer.
You may construct one yourselves. Procure a glass tube closed at one
end, about a yard long and one tenth of an inch in diameter. Fill it
with mercury, then turn it upside down into a bowl filled with the same
metal, taking care that the air does not enter the tube. The column
will stop at a height between 29 and 30 inches.
This, therefore is the measure of the force of the air’s pressure, for
in the upper part of the tube there is an absolute vacuum and nothing
would prevent the mercury from going higher up. The weight of the
air layer corresponds, therefore, to a height of nearly 30 inches of
mercury.
[Illustration]
This weight has been before stated, viz., fourteen and a half pounds,
such a weight being supported by every single square inch of the
globe’s surface. A marvelous pressure is thus exerted on the whole
earth. In other words, the weight of the air that surrounds the
earth on all sides is no less than the following enormous number of
5,184,740,000,000,000 tons.
A man of average height, himself supports the enormous pressure of
34,171 pounds, or over 15 tons, and yet does not feel the least
inconvenience in his movements. It is because this pressure is
exercised in all directions, and a human body carries within it elastic
fluids that counterbalance that tremendous weight.
So accustomed do people become to this weight that when the weather is
stormy, a feeling of heaviness comes on.
However, it is just the contrary which takes place when the barometer
is lower; that is to say, the atmospheric pressure has diminished.
Consequently there is less weight to be carried.
You would experience the same sensation when going up in a balloon. As
you rise higher and higher the weight of the air is less felt, and this
makes people so uncomfortable that at a height of about 9,000 or 10,000
yards the liquids in our body--the blood, the water, the bile--tend to
escape outwards. Why? Because they are no longer balanced by an outside
pressure equal in force to them. In fact, if you continued to ascend,
your fate would be that of the bladder in the first experiment--you
would burst. Thus are you and all creatures attached to the face of the
earth, and it seems as if great heights were forbidden to our curiosity.
A Novel Barometer.
Construct a toy house of cardboard, painted, and let there be two
open doorways in the front, and let it stand on a wooden platform to
represent the ground. The two sides and back may come right down to the
ground, but there must be a slight space between the front of the house
and the ground upon which it stands.
Next make a flat wheel or disc of wood about the thickness of a penny,
its diameter or measurement across the center to measure the same as
the distance between the two doorways of the house. The wheel disc or
turn-table must have a shaft or spindle in the middle, so that it will
revolve easily in a hole made for it in the floor or ground which your
cardboard house stands on; this pivot-hole should be just within the
house and exactly half way between the two doors.
In the next place get two small dolls of such size that they will pass
easily through the doorways, or you may cut them out of cork or some
light substance. Dress one to represent an old man and the other as his
wife, and fix them opposite each other at the edge of the disc or wheel
in such a manner, that when it turns on its axle, the figures move in
and out of the two doorways provided for their accommodation, for it
appears that, although residing in the same house, they are not on very
good terms. When the husband goes out the wife remains at home, and as
she only ventures abroad in fine weather, her spouse is obliged to look
out when rain may be expected.
The motive power has now to be provided and this takes the form of
a piece of catgut, such as violin strings are made of; this is a
substance very susceptible of atmospheric influences, for dry weather
contracts or tightens it, while a damp atmosphere causes it to relax.
Double your catgut and twist it, fasten one end of the rope so formed
near the back of the house inside and fasten the other to the pivot
or axle, with two or three turns round it. As the weather changes the
tightening or relaxing of the rope will cause the figures to move in
and out of the house. Of course, the figures must be arranged so that
the lady comes out when the rope is tightened by the dryness of the
atmosphere.
Compressed Air.
To make experiments with compressed air, you must put your wits
together to make a reservoir. Air, you know, is a gas consisting of
particles called atoms. These atoms are at a certain distance from one
another. They can be pushed further from one another as when you heat
them, or closer together by cold and compression. So compressed air
only means air whose atoms are pressed more closely together than as
the case with the air around us.
Now you have heard that a column of air on a square inch weighs
fourteen and a half pounds. Also, you know that air in a receiver or
any other vessel presses on the vessel inside and out with a force (or
weight) of fourteen and a half pounds.
If now into the vessel you push another quantity of air, equal to the
vessel’s capacity, you simply push the atoms of air closer together.
In fact, they are now only half as far apart as the atoms of an open
vessel. But the pressure is doubled and the compressed air, therefore,
will press on the inside of the vessel with a force of twenty-nine
pounds.
[Illustration]
Now to make the reservoir. Get a tin tube about 40 inches long and
four in diameter, closed at both ends. Take care that the soldering
is well done. Two openings must be made, and a small tube inserted in
each. To each of these attach an indiarubber tube, one four feet long,
and the other six. (See fig.).
To fill this reservoir with compressed air, apply the air-pump fitted
with the valve shown in fig. 4, in the description of an air-pump.
Squeeze tightly the upper tube of the reservoir before beginning to
pump, and then it will be easy to judge the amount of compression of
the air. For the first experiment place a light ball or sheet of paper
over the mouth of the tube, and loosen your hold on it. The object will
immediately be blown away with considerable force.
Noiseless Bell.
We know that sound is a succession of vibrations which must be
transmitted in a medium with weight, as air or water; in other words,
in a vacuum there can be no sound at all. To prove this, introduce
into the receiver a small bell, and as the air is extracted the sounds
become weaker and weaker, and cease altogether when the air is
completely rarified.
[Illustration]
The Bursting Bladder.
Tie a thin piece of light indiarubber round the top of the bottle, and
you will notice that as the air is withdrawn, the indiarubber will
stretch, and at length form a round small balloon in the interior of
the bottle. (Fig. 1).
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
If a piece of bladder is tightly stretched and tied round the vessel
(fig. 2.) it will burst under the force of the atmospheric pressure
which acts upon it, through a vacuum having been made underneath. This
is another case of the first experiment with the air pump described
above.
Weight of the Air.
Another experiment will still better make you appreciate the value of
this factor: the weight of the air.
Put a piece of supple leather in which a ring is attached under the
bottle; pump the air out of the latter and you will be astonished at
the weight you may hang on this leather without dragging it off.
[Illustration]
Should you not have at hand a glass receiver, a wooden reel may serve
instead (see fig.). On one of its faces place a piece of strong
cardboard, in the middle of which a hook has been fastened; when the
rarefaction is made, rather heavy weights must be hooked on before the
cardboard is detached from the face of the rest.
Spoons which will Melt in Hot Water.
Fuse together in a crucible, eight parts of bismuth, five of lead and
three of tin; these metals will combine and form an alloy, of which
spoons may be made, possessed of the remarkable property of melting in
boiled water.
Effect of Compression.
Take a wooden reel and hollow out either the top or bottom, beginning
at the hole in the center and working towards the edge. In the hollow
place a ball. Apply to the other end the indiarubber tube which
conducts the forced air, and the ball will be lifted up (see fig.).
[Illustration]
To Cover Iron with Copper.
If you are about to perform a conjuring trick, you will, of course take
great care that your apparatus is ready. Therefore, clean your piece
of iron or steel from dirt. Dip a piece of polished iron--the blade
of your knife, for instance--into a solution, either of nitrate or
sulphate of copper, when it will assume the appearance of a piece of
pure copper.
The Elements.
Before entering into the next series of experiments the young chemist
must know that all the substances of which the world and everything in
it are made up--_i.e._, the elements are arranged in two classes, the
metals and the non-metals. The former are by far the more numerous,
altogether numbering more than fifty. Among the better known are
such well known substances as iron, mercury, copper, tin, potassium,
antimony, strontium, and nickel. The non-metals are more widely
distributed and together made up of the bulk of the universe.
They comprise the gases--oxygen, hydrogen, nitrogen, and chlorine,
and such substances as sulphur, carbon, phosphorus and iodine. To the
latter class also belongs a peculiar element called fluorine, which,
when combined with hydrogen, destroys glass. It is the only liquid
known which cannot be contained in a glassen or earthenware vessel, and
when used for experimental purposes must be kept in a leaden bottle.
Of course it will be understood that the above is not a complete
list by any means, but is sufficient to give a clear idea of the
difference between the two classes. The metals generally speaking are
of a more or less sparkling, lustrous appearance. The metals, too, are
good conductors of heat and electricity, and generally heavy. These
characteristics are almost entirely wanting in the non-metals. We shall
now give some tricks with the metals.
Potassium.
Potassium was discovered by Sir H. Davy, in the beginning of the
present century, while acting upon potash with the enormous galvanic
battery of the Royal Institution, consisting of two thousand pairs of
four inch plates. It is a brilliant metal, so soft as to be easily cut
with a penknife, and so light as to swim upon water, on which it acts
with great energy, uniting with the oxygen and liberating the hydrogen,
which takes fire as it escapes.
Trace some continuous lines on paper with a camel’s-hair brush dipped
in water, and place a piece of potassium about the size of a pea on one
of the lines, and it will follow the course of the pencil, taking fire
as it runs, and burning with a purplish light.
The paper will be found covered with a solution of ordinary potash. If
turmeric paper be used, the course of the potassium will be marked with
a deep brown color. Hence if you touch potassium with wet fingers you
will burn them.
If a small piece of the metal be placed on a piece of ice, it will
instantly take fire, and form a deep hole which will be found to
contain a solution of potash.
In consequence of its great affinity for oxygen, potassium must be kept
in some fluid destitute of it, such as naphtha acid, which has been
displaced by the great affinity or liking of the oxygen and acid for
the copper.
2. When the copper is no longer coated, but remains clean and bright
when immersed in the fluid, all the silver has been deposited, and the
glass now contains a solution of copper.
Nearly all the colors used in the arts are produced by metals and
their combinations; indeed, one is named chromium, from a Greek word
signifying color, on account of the beautiful tints obtained from its
various combinations with oxygen and the other metals. All the various
tints, of green, orange, yellow and red are obtained from this metal.
Solutions of most of the metallic salts give precipitates with
solutions of alkalies and their salts, as well as with many other
substances, such as what are usually called prussiate of potash,
hydrosulphret of ammonia, etc. The colors differ according to the metal
employed; and so small a quantity is required to produce the color,
that the solutions before mixing may be nearly colorless.
Metallic Colors.
To a solution of sulphate of iron add a drop or two of a solution of
prussiate of potash, and a blue color will be produced.
2. Substitute sulphate of copper for iron, and the color will be a rich
brown.
3. Another blue, of quite a different tint, may be produced by letting
a few drops of a solution of ammonia fall into one of sulphate of
copper, when a precipitate of a light blue falls down, which is
dissolved by an additional quantity of the ammonia, and forms a
transparent solution of the most splendid rich blue color.
4. Into a solution of sulphate of iron, drop a few drops of strong
infusion of galls, and the color will become a bluish black--in fact
ink. A little tea will answer as well as the infusion of galls.
This is the reason why certain stuffs formerly in general use for
dressing-gowns for gentlemen were so objectionable; for as they were
indebted to a salt of iron for their color, buff as it was called, a
drop of tea accidentally spilled produced all the effect of a drop of
ink.
5. Put into a largish test tube two or three small pieces of granulated
zinc, fill it about one-third full of water, put in a few grains of
iodine, and boil the water, which will at first acquire a dark purple
color, gradually fading as the iodine combines with the zinc. Add a
little more iodine from time to time, until the zinc is nearly all
dissolved. If a few drops of this solution be added to an equally
colorless solution of corrosive sublimate (a salt of mercury), a
precipitate will take place of a splendid scarlet color, brighter, if
possible, than vermilion, which is also a preparation of mercury.
Crystallization of Metals.
Some of the metals assume certain definite forms in return from the
fluid to the solid state. Bismuth shows this property more readily than
most others.
EXPERIMENT.
Melt a pound or two of bismuth in an iron ladle over the fire; remove
it as soon as the whole is fluid; and when the surface has become
solid break a hole in it and pour out the still fluid metal from the
interior; what remains will exhibit beautifully formed crystals of a
cubic shape.
Sulphur may be crystallized in the same manner, but its fumes, when
heated, are so very unpleasant that few would wish to encounter them.
One of the most remarkable facts in chemistry--a science abounding in
wonders--is the circumstance that the mere contact of hydrogen, the
lightest body known, with the metal platinum, the heaviest when in a
state of minute division called spongy platinum, produces an intense
heat sufficient to inflame the hydrogen; of course this experiment must
be made in the presence of atmospheric air or oxygen. If a small piece
of the metal in the state above named be introduced into a mixture
of oxygen and hydrogen, it will cause them to explode. A very small
quantity of gas should be employed and placed in a jar lightly covered
with a card, or the explosion would be dangerous.
Crystallization.
Nearly all the metals are characterized by the crystals, which
are formed as they pass from a state of intense heat to that of
comparative coldness. It is by this process they have been formed when
in the mine or vein in the rocks. The earth was once a fiery mass
of molten matter, as seen even now when a volcano is in a state of
eruption. And it was only by the cooling of the outside shell of the
earth, or crust, as it is called, that it became habitable.
When the crust was cooling down the metals crystallized among the
cooling rocks and gradually formed the crude arts. You may represent by
a very pretty experiment the manner in which this cooling off of the
earth took place. Obtain a little flour of sulphur and put it in a red
earthenware unglazed jar. Thrust it well into the fire and watch the
rust. As soon as the heat has penetrated the vessel the yellow powdery
sulphur becomes first of all brown, and then assumes the consistency
of thick birdlime. Take out a little of this on the end of a stick and
plunge it into cold water. It can then be pulled backwards and forwards
like cobblers’ wax. This well represents the state of the half-cooled
crust of the earth.
Meanwhile the sulphur on the fire begins to boil, and looks very much
like bubbling treacle. Remove it from the fire and allow it to cool.
When quite cool the surface will be a flat, yellow mass, like ordinary
roll sulphur, which, when ground, give the ordinary flour of sulphur.