We concluded a previous notice of some of the uses to which water is
subservient in nature, by mentioning that modern science had fully proved
the incorrectness of the ancient idea of the elementary nature of water;
and that by the processes which chemistry places at our disposal, we are
now able to resolve water into its elements, or, having obtained these
elements from other sources, to cause them to unite, and to produce water
in combining. In the present article we shall point out the manner in
which this may be accomplished, and describe some properties and uses of
water which the space at our disposal did not allow us to notice before.
Water consists in great part of the substance to which is due the power
the atmosphere possesses of supporting life and combustion, and of which
we have formerly spoken under the name of oxygen. Every nine ounces of
water contain eight ounces of oxygen, the remainder being made up of
another and very peculiar substance, termed hydrogen. Hydrogen is a gas,
invisible, colourless, and transparent, and consequently in all external
characters precisely like the air we breathe. But it differs from it very
much in other respects. If a lighted candle be placed in hydrogen gas,
the candle is extinguished, for hydrogen does not support combustion, but
the gas itself takes fire, where it mixes with the air, and burns with a
pale yellowish flame, scarcely visible in broad day-light. Hence hydrogen
is in its properties the very reverse of oxygen: it burns, which oxygen
does not; oxygen supports combustion, which hydrogen cannot do. When
hydrogen burns with oxygen, water is always formed.
Now, to decompose water it is only necessary to act upon the principle of
hydrogen being a combustible substance. All substances are not equally
combustible; that is to say, they do not burn or combine with oxygen with
equal facility or quickness. Thus charcoal is more combustible than iron,
iron is more combustible than copper, and copper than gold or silver,
whilst phosphorus is still more combustible than charcoal. Now, oxygen
will combine with any of these combustible substances; but if it have a
choice, it will take that which is most combustible--that which it likes
best. And even if the oxygen be already united with one body, and that
another more combustible be brought into action on it, it will leave
the former, and attach itself altogether to the latter substance. The
combustibility of hydrogen is about equal to that of iron. It is inferior
to carbon and to many other bodies; but it is superior to that of copper,
silver, gold, and others. If, therefore, we take water in the state of
steam, and bring it into contact with red-hot charcoal or coke, the
oxygen of the water goes to the most combustible body, and the hydrogen
is set free. In this way charcoal may be made to burn brilliantly without
air, but not without oxygen. A red-hot bit of charcoal burns in steam,
because it decomposes the water; it takes the oxygen, and turns the
hydrogen out, which assuming the form of gas, may be collected by means
of peculiar chemical apparatus.
Iron and hydrogen are, as mentioned above, about equally combustible: in
fact it depends upon the degree of heat, which is the more combustible.
If the iron be bright red, it decomposes water, taking away the oxygen;
but if it be only dull red, then hydrogen is the more combustible; and
if there be a compound of oxygen and iron ready formed (oxide of iron,
rust), the hydrogen will decompose it, and water being formed, the iron
will be set free. If, therefore, a gun barrel be laid across a fire, and
heated to bright redness, and a little water be poured into it at one end
by means of a tun-dish with a stop-cock soldered to it, hydrogen gas will
issue from the other end, and may be burned, or collected for various
purposes.
Hydrogen gas may be prepared more easily by other processes, which do
not show, however, so clearly the fact of its being derived from the
decomposition of the water. The property which iron acquires at a bright
red heat may be given to it without any heat, by means of some oil of
vitriol (called in the language of chemists, sulphuric acid). Iron quite
cold will decompose water, if the water be previously mixed with some
sulphuric acid. The oxygen goes to the iron, which dissolves, and the
liquor contains green copperas. The metal zinc, which is now so very much
used in the arts, may also be employed with sulphuric acid and water to
decompose water, and it gives a purer hydrogen gas than iron, the latter
metal containing always a little charcoal, which mixes with the hydrogen
and contaminates it.
In all of these processes, although the water is decomposed, yet we
obtain only one of its elements; the other, the oxygen, remaining
combined with the iron, the charcoal, or the zinc. We may, however,
produce the separation of water into its elements, so as to exhibit both.
This is done by passing a current of electricity from the apparatus
termed the galvanic battery, through the water. One of the grandest and
most fruitful discoveries ever made in chemistry was that by Sir Humphry
Davy, who proved that electricity possesses the power of separating
compound substances into their elements; and by that means he succeeded
in decomposing numerous bodies which had resisted all processes known
before that time, and obtained new substances of a simple nature, and of
most curious and important properties. To decompose water by means of
electricity, the wires from the galvanic battery are made to dip into
a little cup of water, and over each wire there is hung a bell-shaped
vessel, inverted, full of water. When the current passes, pure oxygen gas
is disengaged from one wire, and pure hydrogen gas is liberated at the
other, and being received as the bubbles rise in the bell-glasses, the
gases are collected for use.
So much for the separation of water into its elements; the production of
water by the union of its elements is still easier. The simplest way to
show this is to take a little bottle, and put into it the zinc, water,
and sulphuric acid, by which the hydrogen is to be obtained, to fit to
the mouth of the bottle a cork, through which passes a little glass or
metal tube, ending in a fine jet. The gas may be set on fire as it issues
from the jet, and by holding a cold plate or a tumbler over the flame,
and at a little distance, a copious dew of water will be deposited upon
it, which after a few moments will increase so much as to run into large
drops. This water is formed by the hydrogen gas combining as it burns
with the oxygen of the air.
Hydrogen gas in burning produces very little light: one cause of this
is, that the product of combustion-formed water being in a state of
steam, there is no solid substance in the flame; and it appears to be
always true that no bright light can exist without a solid material.
In order to produce a great light with the flame of hydrogen gas, it
is only necessary to place a wire or a bit of flint, or any solid
substance, in the flame. The solid immediately becomes intensely bright,
and by using lime or magnesia, which are peculiarly fitted for the
purpose, a light so intense as to be only surpassed by the noon-day
summer sun, may be obtained. This lime light has been introduced for
experiment into lighthouses, and has been particularly serviceable in the
trigonometrical surveys of those kingdoms, in consequence of which it is
generally known as the Drummond light, from the eminent philosopher whose
recent melancholy loss every Irishman must deplore. The heat produced
by the flame of hydrogen is thus most intense; substances which are
inattackable by the strongest furnaces melt like wax in the jet of oxygen
and hydrogen, and in the Drummond light the lime appears gradually to
evaporate.
A mixture of hydrogen and oxygen, or of hydrogen and air, may be thus
set fire to by a candle; and when previously mixed, a terrific explosion
is produced. Persons should therefore be very cautious how they perform
experiments with hydrogen, as even skilful chemists have occasionally
suffered severely from accidents of this kind. When a young person makes
hydrogen for the first time, he is naturally curious, and hastens to
satisfy himself by seeing that it burns: he applies the candle before
all the common air has been expelled from the apparatus, and the mixture
inside being still explosive, the flame passes back, and the whole is
shattered into pieces with the noise and violence of a bombshell. At the
same time, therefore, that we would be happy if this article induced
many of our young readers to satisfy themselves of the composition and
decomposition of water by actual experiment, yet we trust they will do so
prudently, and with the guidance of some older person who has previously
seen how chemical apparatus are employed.
If a wide tube of glass be held over the jet of burning hydrogen gas,
a very curious result is produced: a powerful musical sound is heard,
which changes according as the jet is moved up and down in the tube. The
nearer the jet is to the orifice, the graver, the higher up in the tube
it is, the more acute, is the sound heard. The cause of this is, that the
flame, which to the eye appears uniform and continuous, is in reality a
number of very small explosions of mixed air and gas. These succeed one
another so rapidly that the intervals of darkness which intervene are not
perceived, and the quantity of gas which explodes is too small to produce
any audible noise; but on bringing a tube, the air in which is capable of
vibrating with the same quickness as the little explosions are produced,
the air is thrown into vibrations which reach the ear, and produce the
peculiar musical tone. With a selection of gas jets and tubes a variety
of notes may be produced, so great that a musical instrument has been
constructed by their means.
Hydrogen gas is the lightest substance in nature, and it is consequently
used to fill balloons, by which men have been carried to a height in
the air much exceeding that of the loftiest mountains. When balloons
were first made use of, they were of the kind which are now termed
fire-balloons: the bag of the balloon was open at the bottom, and in the
car was a furnace, the chimney of which terminated at the aperture of the
balloon. The hot air and gases generated by the burning of the fuel in
the furnace ascending into the bag, expelled the heavier cold air, and a
sufficient power of rising was thus obtained, by the difference between
the weight of the heated and of the cold air, to enable the balloon to
take up a very considerable weight. Hydrogen gas being, however, at
least ten times as light as the hot air, was much more convenient, as
it required only a much smaller balloon; and the unfortunate death of
the most remarkable experimenter of the fire-balloon, Pilatre de Roxier,
contributed also very much to show their great danger, and prevent their
being used.
Although many persons had proposed from time to time to ascend by means
of balloons filled with heated or rarified air, or with hydrogen gas,
it was reserved for the brothers Montgolfier of Lyons to realize this
bold and singular idea. These brothers had originally been destined to
science, but on the death of an elder brother who had been an extensive
paper maker at Lyons, they abandoned their former pursuits to continue
the manufacture. They made large paper balloons, which, whether filled
with hydrogen gas or heated air, ascended, and one brother ascended to a
small height at Lyons. On introducing their invention to the notice of
the public and the royal family at Paris, the greatest enthusiasm was
excited, and personages of the highest rank accompanied the adventurous
brothers in their aërial voyages. Pilatre de Roxier, then director of
the king’s museum, devoted himself completely to the improvement of the
new art of the navigation of the air; and after having ascended from
Versailles frequently, and gained a considerably greater height than any
of his predecessors, he resolved to cross the British Channel, and pass
from France to England in a fire-balloon. He ascended from a village
about half way between Calais and Boulogne, on September the 16th,
1784, with a gentleman of the town as a companion; and having attained
a considerable height, was carried by the favourable wind over the sea
in his proper course. The balloon however continuing to rise, got into a
current of air in an opposite direction, and was brought again over the
land; at this moment the spectators on shore were horrified to observe
that the balloon, half lost in the clouds, was on fire, and after a
moment the car was observed to fall. The remains of the car and of the
unfortunate aëronauts, in whom scarcely a vestige of human form could
be traced, were found in a field on the road to Abbeville; and a stone
bearing the simple inscription of the fate of Pilatre de Roxier and his
companion marks to the present day the place, close by the road-side,
where the bodies were inhumed.
The substitution of hydrogen or of coal gas for the fire-balloon, has
deprived aërial navigation of its greatest dangers. No good means of
steering or tacking a balloon having been discovered, the art has not yet
fulfilled the expectations that were at first formed of it: the balloon
is at the mercy of the winds; and although the voyagers travel in ease
and safety, and often with rail-road speed, yet as it cannot be foretold
in what direction the balloon must go, voyages in the air have been as
yet only an exciting and not very dangerous amusement.