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.
Again, many animal and vegetable substances consist for the most part of
carbon or charcoal, united with oxygen and hydrogen in the proportion
which forms water. Now oil of vitriol (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 then pour
some of this acid on a lump of sugar, or place a chip of wood in it, the
sugar or wood will speedily become quite black, or be _charred_, as it is
called, 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
exhibiting unwittingly an instance of chemical elective affinity; the
pearl being simply carbonate of lime, which was decomposed by the greater
affinity or fondness of lime for its new acquaintance, (the acetic acid of
the vinegar,) than for the carbonic acid, with which it had been united
all its life; an example of inconstancy in strong contrast with the
conduct of its owner, who chose death rather than become the mistress of
her lover's conqueror.
EXPERIMENTS ON COMBUSTION.
Into an ordinary wine bottle put some pieces of granulated zinc, and pour
on them a mixture of sulphuric acid and water, in the proportion of about
one part of acid to four of water, then close the bottle with a cork
having a hole bored through the middle, in which a piece of glass tube is
inserted; wait some minutes that the atmospheric air in the bottle may be
expelled by the hydrogen gas set free by the decomposition of the water,
then apply a lighted taper to the end of the tube, when the gas will
inflame, giving out so little light as to be barely visible by daylight,
but producing so intense a heat that a piece of platinum wire instantly
becomes white hot when held in the flame. If you hold a glass tumbler
inverted over the flame, it becomes covered with minute drops of water,
the result of the union of the hydrogen with the oxygen of the air, and in
this case water is the only product.
If a piece of charcoal, which is pure carbon or nearly so, be ignited, and
introduced into a jar, containing oxygen or common atmospheric air, the
product will be carbonic acid gas only. As most combustible bodies contain
both carbon and hydrogen, the result of their combination is carbonic
acid and water. This is the case with the gas used for illumination; and
in order to prevent the water so produced from spoiling goods in shops,
various plans have been devised for carrying off the water when in the
state of steam. This is generally accomplished by suspending over the
burners glass bells, communicating with tubes opening into the chimney, or
passing outside the house.
To show that oxygen, or some equivalent, 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; that
is, 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°, 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.
[Illustration]
Into another glass put some cold water; introduce carefully some of the
salt called chlorate of potassa, 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 it touches the salt it decomposes it, 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 potassa, 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.
[Illustration]
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 making a coil of platinum wire by 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.
Experiments on combustion might be multiplied, almost to any amount, but
the above will be sufficient for our purpose.
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 white 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.
EXPERIMENT.
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. Corollary: 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.
Saltpeter, or niter, is a compound of this metal (or rather its oxide)
with nitric acid. It is one of the ingredients of gunpowder, and has the
property of quickening the combustion of all combustible bodies.
EXPERIMENT.
Rub together in a _warm_ mortar, three parts of powdered niter, two of dry
carbonate of potash, and one of flour of brimstone; place a small quantity
of the mixture in an iron ladle, and heat it over the fire, when it will
speedily melt, and then explode with a very loud noise; and if held under
a foul chimney, will save the expense of a chimney sweep: but avoid
cooking time.
Another salt of potash remarkable for the same property, in even a greater
degree, is the _chlorate_ of potash.
EXPERIMENTS.
1. Triturate together in a _dry_ mortar a few grains of flowers of
sulphur, with a small quantity of the chlorate of potash, and a succession
of sharp explosions, like the crack of a whip, will be produced.
2. Substitute half a grain of phosphorus for the sulphur, and the action
will be much more violent. The hand should be defended by a thick glove,
and the eyes carefully guarded, in making this experiment.
3. Mix very carefully a little of this salt, reduced to powder, with a
little lump sugar, also powdered, and drop on the mixture a little strong
sulphuric acid, and it will instantly burst into a flame. This experiment
also requires caution.
Want of space precludes us from considering the individual metals and
their compounds in detail; it must suffice to describe some experiments,
showing some of their properties.
The different affinities of the metals for oxygen, may be exhibited in
various ways. The silver or zinc tree has already been described.
EXPERIMENTS.
1. Into a solution of nitrate of silver, in distilled water, immerse a
clean plate or slip of copper. The solution, which was colorless, will
soon begin to assume a greenish tint, and the piece of copper will be
covered with a coating of a light gray color, which is the silver formerly
united to the nitric acid, which has been displaced by the greater
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_.
Place a piece of clean iron in the solution, and it will almost instantly
be coated with a film of _copper_, and this will continue until the whole
of that metal is removed, and its place filled by an equivalent quantity
of _iron_, so that nitrate of _iron_ is found in the liquid. The oxygen
and nitric acid remain unaltered in quantity or quality during these
changes, being merely transferred from one metal to another.
A piece of zinc will displace the iron in like manner, leaving a solution
of nitrate of zinc.
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, hydro-sulphuret of
ammonia, &c.; and 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.
EXPERIMENTS.
1. 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 a 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.
BEAUTIES OF CRYSTALLIZATION.
Dissolve alum in hot water until no more can be dissolved in it; place in
it a smooth glass rod and a stick of the same size; next day, the stick
will be found covered with crystals, but the glass rod will be free from
them: in this case, the crystals cling to the rough surface of the stick,
but have no hold upon the smooth surface of the glass rod. But if the rod
be roughened with a file at certain intervals, and then placed in the alum
and water, the crystals will adhere to the rough surfaces, and leave them
smooth bright and clear.
Tie some threads of lamp-cotton irregularly around a copper wire or glass
rod; place it in a hot solution of blue vitriol, strong as above, and the
threads will be covered with beautiful blue crystals, while the glass rod
will be bare.
Bore a hole through a piece of coke, and suspend it by a string from a
stick, placed across a hot solution of alum; it will float; but, as it
becomes loaded with crystals, it will sink in the solution according to
the length of the string. Gas-coke has mostly a smooth, shining, and
almost metallic surface, which the crystals will avoid, while they will
cling only to the most irregular and porous parts.
If powdered turmeric be added to the hot solution of alum, the crystals
will be of a bright yellow; litmus will cause them to be of a bright red;
logwood will yield purple; and common writing ink, black; and the more
muddy the solution, the finer will be the crystals.
To keep colored alum crystals from breaking or losing their color, place
them under a glass shade with a saucer of water; this will preserve the
atmosphere moist, and prevent the crystals getting too dry.
If crystals be formed on wire, they will be liable to break off, from the
expansion and contraction of the wire by changes of temperature.
TO CRYSTALLIZE CAMPHOR.
Dissolve camphor in spirit of wine, moderately heated, until the spirit
will not dissolve any more; pour some of the solution into a cold glass,
and the camphor will instantly crystallize in beautiful tree-like forms,
such as we see in the show-glasses of camphor in druggists' windows.
CRYSTALLIZED TIN.
Mix half an ounce of nitric acid, six drams of muriatic acid, and two
ounces of water; pour the mixture upon a piece of tin plate previously
made hot, and after washing it in the mixture it will bear a beautiful
crystalline surface, in feathery forms. This is the celebrated _moirée
métallique_, and, when varnished, is made into ornamental boxes, &c. The
figures will vary according to the degree of heat previously given to the
metal.
CRYSTALS IN HARD WATER.
Hold in a wine-glass of hard water a crystal of oxalic acid, and white
threads, _i. e._ oxalate of lime, will instantly descend through the
liquid suspended from the crystal.
VARIETIES OF CRYSTALS.
Make distinct solutions of common salt, niter, and alum; set them in
three saucers in any warm place, and let part of the water dry away or
evaporate; then remove them to a warm room. The particles of the salts
in each saucer will begin to attract each other, and form crystals, but
not all of the same figure: the common salt will yield crystals with six
square and equal faces, or sides; the niter six-sided crystals; and the
alum, eight-sided crystals; and if these crystals be dissolved over and
over again, they will always appear in the same forms.
A LIQUID CHANGED TO A SOLID, AND HEAT FROM CRYSTALLIZATION.
A strong saline solution excluded from the _air_ will frequently
crystallize the instant that air is admitted. For this purpose make a
solution of Glauber's salt (sulphate of soda) in boiling water (3 lbs.
of the salt to 2 lbs. of water); bottle and cork quickly; also tie over
the neck a piece of wet bladder. When perfectly cold, or even a few days
afterwards, remove the cork, and the salt will immediately crystallize,
shooting out the most beautiful crystals, at last becoming nearly solid:
at the same time the whole becomes warm, in consequence of the latent
heat generated by the change of the liquid to the solid state. If the
liquid will not crystallize quickly on removing the cork, tie a crystal of
Glauber's salt to a bit of wire, touch the surface of the liquid, and the
crystallization will then generally occur.
ANOTHER EXPERIMENT.
Heat some blue vitriol (sulphate of copper) in an iron ladle till all the
water contained in the crystals is driven off, and the color changes to
a gray. Take the lumps out without breaking them, and lay the dried blue
vitriol on a plate; if this be moistened with water, steam is produced;
and if a slice of phosphorus is then laid on the sulphate of copper, it
ignites, demonstrating again that the condensation of a liquid produces
heat. The addition of the water restores the blue color, thus proving that
water was necessary to the composition of blue vitriol.
A SOLID CHANGED TO A LIQUID, AND INTENSE COLD FROM THE LIQUEFACTION.
Mix five parts by weight of powdered muriate of ammonia, commonly termed
sal ammoniac, five parts of niter in powder, and sixteen parts of water.
A temperature of twenty-two degrees below the freezing point of water is
produced; and if a phial of water, or any convenient metallic cylinder
containing water, be surrounded with a sufficient quantity of the freezing
mixture, ice is obtained. The ice clings to the interior of the tube, but
may easily be removed by dipping it in tepid water.
This experiment is the reverse of the last, and proves that a sudden
reduction of a solid to the liquid condition always affords cold.
An amusing combination of two experiments may be made by putting some
fresh-burned lime into one tea-pot and this freezing mixture into another.
When water is poured on the one containing lime, it gives out steam from
the spout; while the addition of water to the other produces so much cold,
that it can hardly be kept in the hand. Thus heat and cold are afforded by
the same medium, water.
MAGIC OF HEAT.
Melt a small quantity of the sulphate of potassa and copper in a spoon
over a spirit lamp; it will be fused at a heat just below redness, and
produce a liquid of a dark green color. Remove the spoon from the flame,
when the liquid will become a solid of a brilliant emerald green color,
and so remain till its heat sinks nearly to that of boiling water; when
suddenly a commotion will take place throughout the mass, beginning from
the surface, and each atom, as if animated, will start up and separate
itself from the rest, till, in a few moments, the whole will become a heap
of powder.
SUBLIMATION BY HEAT.