CHEMISTRY.
[Illustration: Fig. 92. Alchemists at work.]
There is hardly any kind of knowledge which has been so slowly acquired
as that of chemistry, and perhaps no other science has offered such
fascinating rewards to the labour of its votaries as the _philosopher's
stone_, which was to produce an unfailing supply of gold; or _the elixir
of life_, that was to give the discoverer of the gold-making art the
time, the prolonged life, in which he might spend and enjoy it.
Hundreds of years ago Egypt was the great depository of all learning,
art, and science, and it was to this ancient country that the most
celebrated sages of antiquity travelled.
Hermes, or Mercurius Trismegistus, the favourite minister of the
Egyptian king Osiris, has been celebrated as the inventor of the art of
alchemy, and the first treatise upon it has been attributed to Zosymus,
of Chemnis or Panopolis. The Moors who conquered Spain were remarkable
[Page 82] for their learning, and the taste and elegance with which they
designed and carried out a new style of architecture, with its lovely
Arabesque ornamentation. They were likewise great followers of the art
of alchemy, when they ceased to be conquerors, and became more
reconciled to the arts of peace. Strange that such a people, thirsting
as they did in after years for all kinds of knowledge, should have
destroyed, in the persons of their ancestors, the most numerous
collection of books that the world had ever seen: the magnificent
library of Alexandria, collected by the Ptolemies with great diligence
and at an enormous expense, was burned by the orders of Caliph Omar;
whilst it is stated that the alchemical works had been previously
destroyed by Diocletian in the fourth century, lest the Egyptians should
acquire by such means sufficient wealth to withstand the Roman power,
for gold was then, as it is now, "the sinews of war."
Eastern historians relate the trouble and expense incurred by the
succeeding Caliphs, who, resigning the Saracenic barbarism of their
ancestors, were glad to collect from all parts the books which were to
furnish forth a princely library at Bagdad. How the learned scholar
sighs when he reads of seven hundred thousand books being consigned to
the ignominious office of heating forty thousand baths in the capital of
Egypt, and of the magnificent Alexandrian Library, a mental fuel for the
lamp of learning in all ages, consumed in bath furnaces, and affording
six months' fuel for that purpose. The Arabians, however, made amends
for these barbarous deeds in succeeding centuries, and when all Europe
was laid waste under the iron rule of the Goths, they became the
protectors of philosophy and the promoters of its pursuits; and thus we
come to the seventh century, in which Geber, an Arabian prince lived,
and is stated to be the earliest of the true alchemists whose name has
reached posterity.
Without attempting to fill up the alchemical history of the intervening
centuries, we leap forward six hundred years, and now find ourselves in
imagination in England, with the learned friar, Roger Bacon, a native of
Somersetshire, who lived about the middle of the thirteenth century; and
although the continual study of alchemy had not yet produced the
"stone," it bore fruit in other discoveries, and Roger Bacon is said,
with great appearance of truth, to have discovered gunpowder, for he
says in one of his works:--"From saltpetre and _other_ ingredients we
are able to form a fire which will burn to any distance;" and again
alluding to its effects, "a small portion of matter, about the size of
the thumb, _properly disposed_, will make a tremendous sound and
coruscation, by which cities and armies might be destroyed." The
exaggerated style seems to have been a favourite one with all
philosophers, from the time of Roger Bacon to that of Muschenbroek of
the University of Leyden, who accidentally discovered the Leyden jar in
the year 1746, and receiving the first shock, from a vial containing a
little water, into which a cork and nail had been fitted, states that
"he felt himself struck in his arms, shoulders, and breast, so that he
lost his breath, and was _two days_ before he recovered from the effects
of the blow and the terror;" [Page 83] adding, that "he would not take
a _second_ shock for the kingdom of France." Disregarding the numerous
alchemical events occurring from the time of Roger Bacon, we again
advance four hundred years--viz., to the year 1662, when, on the 15th of
July, King Charles II. granted a royal charter to the Philosophical
Society of Oxford, who had removed to London, under the name of the
Royal Society of London for Promoting Natural Knowledge, and in the year
1665 was published the first number of the _Philosophical Transactions_;
this work contains the successive discoveries of Mayow, Hales, Black,
Leslie, Cavendish, Lavoisier, Priestley, Davy, Faraday; and since the
year 1762 has been regularly published at the rate of one volume per
annum. With this preface proceed we now to discuss some of the varied
phenomena of chemical attraction, or what is more correctly termed
CHEMICAL AFFINITY.
The above title refers to an endless series of changes brought about by
chemical combinations, all of which can be reduced to certain fixed
laws, and admit of a simple classification and arrangement. A mechanical
aggregation, however well arranged, can be always distinguished from a
chemical one. Thus, a grain of gunpowder consists of _nitre_, which can
be washed away with boiling water, of _sulphur_, which can be sublimed
and made to pass away as vapour, of _charcoal_, which remains behind
after the previous processes are complete; this mixture has been
perfected by a careful proportion of the respective ingredients, it has
been wetted, and ground, and pressed, granulated, and finally dried; all
these mechanical processes have been so well carried out that each
grain, if analysed, would be similar to the other; and yet it is, after
all, only a mechanical aggregation, because the sulphur, the charcoal,
and the nitre are unchanged. A grain of gunpowder moistened, crushed,
and examined by a high microscopic power, would indicate the yellow
particles of sulphur, the black parts of charcoal, whilst the water
filtered from the grain of powder and dried, would show the nitre by the
form of the crystal. On the other hand, if some nitre is fused at a dull
red heat in a little crucible, and two or three grains of sulphur are
added, they are rapidly oxidized, and combine with the potash, forming
sulphate of potash; and after this change a few grains of charcoal may
be added in a similar manner, when they burn brightly, and are oxidized
and converted into carbonic acid, which also unites in like manner with
the potash, forming carbonate of potash; so that when the fused nitre is
cooled and a few particles examined by the microscope, the charcoal and
sulphur are no longer distinguishable, they have undergone a chemical
combination with portions of the nitre, and have produced two new salts,
perfectly different in taste, gravity, and appearance from the original
substances employed to produce them. Hence chemical combination is
defined to be "_that property which is possessed by one or more
substances, of uniting together and producing a third or other body
perfectly different [Page 84] in its nature from either of the two or more
generating the new compound_".
To return to our first experiment with the gunpowder: take sulphur,
place some in an iron ladle, heat it over a gas flame till it catches
fire, then ascend a ladder, and pour it gently, from the greatest height
you can reach, into a pail of warm water: if this experiment is
performed in a darkened room a magnificent and continuous stream of fire
is obtained, of a blue colour, without a single break in its whole
length, provided the ladle is gradually inclined and emptied. The
substance that drops into the warm water is no longer yellow and hard,
but is red, soft, and plastic; it is still sulphur, though it has taken
a new form, because that element is dimorphous ([Greek: _dis_] twice,
and [Greek: _morphê_] a form), and, Proteus-like, can assume two forms.
Take another ladle, and melt some nitre in it at a dull red heat, then
add a small quantity of sulphur, which will burn as before; and now,
after waiting a few minutes, repeat the same experiment by pouring the
liquid from the steps through the air into water; observe it no longer
flames, and the substance received into the water is not red and soft
and plastic, but is white, or nearly so, and rapidly dissolves away in
the water. The sulphur has united with the oxygen of the nitre and
formed sulphuric acid, which combines with the potash and forms sulphate
of potash; here, then, oxygen, sulphur, and potassium, have united and
formed a salt in which the separate properties of the three bodies have
completely disappeared; to prove this, it is only necessary to dissolve
the sulphate of potash in water, and after filtering the solution, or
allowing it to settle, till it becomes quite clear and bright, some
solution of baryta may now be added, when a white precipitate is thrown
down, consisting of sulphate of baryta, which is insoluble in nitric or
other strong acids. The behaviour of a solution of sulphate of potash
with a nitrate of baryta may now be contrasted with that of the elements
it contains; on the addition of sulphur to a solution of nitrate of
baryta no change whatever takes place, because the sulphur is perfectly
insoluble. If a stream of oxygen gas is passed from a bladder and jet
through the same test, no effect is produced; the nitrate of baryta has
already acquired its full proportion of oxygen, and no further addition
has any power to change its nature; finally, if a bit of the metal
potassium is placed in the solution of nitrate of baryta it does not
sink, being lighter than water, and it takes fire; but this is not in
any way connected with the presence of the test, as the same thing will
happen if another bit of the metal is placed in water--it is the oxygen
of the latter which unites rapidly with the potassium, and causes it to
become so hot that the hydrogen, escaping around the little red-hot
globules, takes fire; moreover, the fact of the combustion of the
potassium under such circumstances is another striking proof of the
opposite qualities of the three elements--sulphur, oxygen, and
potassium--as compared with the three chemically combined and forming
sulphate of potash. The same kind of experiment may be repeated with
charcoal; if some powdered charcoal is made red-hot, and then puffed
into the air with a blowing machine, numbers of sparks are produced, and
the [Page 85] charcoal burns away and forms carbonic acid gas, a little
ash being left behind; but if some more nitre be heated in a ladle, and
charcoal added, a brilliant deflagration (_deflagro_, to burn) occurs,
and the charcoal, instead of passing away in the air as carbonic acid,
is now retained in the same shape, but firmly and chemically united with
the potash of the nitre, forming carbonate of potash, or pearl-ash,
which is not black and insoluble in water and acids like charcoal, but
is white, and not only soluble in water, but is most rapidly attacked by
acids with effervescence, and the carbon escapes in the form of carbonic
acid gas. Thus we have traced out the distinction between mechanical
aggregation and chemical affinity, taking for an example the difference
between gunpowder as a whole (in which the ingredients are so nicely
balanced that it is almost a chemical combination), and its
constituents, sulphur, charcoal, and nitre, when they are chemically
combined; or, in briefer language, we have noticed the difference
between the mechanical mixture, and some of the chemical combinations,
of three important elements. Our very slight and partial examination of
three simple bodies does not, however, afford us any deep insight into
the principles of chemistry; we have, as it were, only mastered the
signification of a few words in a language; we might know that _chien_
was the French for dog, or _cheval_ horse, or _homme_ man; but that
knowledge would not be the acquisition of the French language, because
we must first know the alphabet, and then the combination of these
letters into words; we must also acquire a knowledge of the proper
arrangement of these words into sentences, or grammar, both syntax and
prosody, before we can claim to be a French scholar: so it is with
chemistry--any number of isolated experiments with various chemical
substances would be comparatively useless, and therefore the "alphabet
of chemistry," or "table of simple elements," must first be acquired.
These bodies are understood to be solids, fluids, and gases, which have
hitherto defied the most elaborate means employed to reduce them into
more than one kind of matter. Even pure light is separable into seven
parts--viz., red, orange, yellow, green, blue, indigo, and violet; but
the elements we shall now enumerate are not of a compound, but, so far
as we know, of an absolutely simple or single nature; they represent the
boundaries, not the finality, of the knowledge that may be acquired
respecting them.
The elements are sixty-four in number, of which about forty are
tolerably plentiful, and therefore common; whilst the remainder,
twenty-four, are rare, and for that reason of a lesser utility: whenever
Nature employs an element on a grand scale it may certainly be called
common, but it generally works for the common good of all, and fulfils
the most important offices.
[Page 86]
CLASSIFICATION OF THE ALPHABET OF CHEMISTRY.
13 _Non-Metallic Bodies._
Name. Symbol. Combining
proportion
or atomic
weight.
1. Oxygen O = 8
2. Hydrogen H = 1
3. Nitrogen N = 14
4. Chlorine Cl = 35.5
5. Iodine I = 127.1
6. Bromine Br = 80.
7. Fluorine F = 18.9
8. Carbon C = 6
9. Boron B = 10.9
10. Sulphur S = 16
11. Phosphorus P = 32
12. Silicon Si = 21.3
13. _Selenium_ Se = 39.5
51 _Metals._
1. Aluminum Al = 13.7
2. Antimony Sb = 129
3. Arsenic As = 75
4. Barium Ba = 68.5
5. Bismuth Bi = 213
6. Cadmium Cd = 56
7. Calcium Ca = 20
8. _Cerium_ Ce = 47
9. Chromium Cr = 26.7
10. Cobalt Co = 29.5
11. Copper Cu = 31.7
12. _Donarium_
13. _Didymium_ D
14. _Erbium_ E
15. Gold Au = 197
16. _Glucinum_ Gl
17. Iron Fe = 28
18. _Ilmenium_ Il
19. _Iridium_ Ir = 99
20. Lead Pb = 103.7
21. _Lanthanium_ La
22. _Lithium_ Li = 6.5
23. Magnesium Mg = 12.2
24. Manganese Mn = 27.6
25. Mercury Hg = 100
26. _Molybdenum_ Mo = 46
27. Nickel Ni = 29.6
28. _Norium_
29. _Niobium_ Nb
30. _Osmium_ Os = 99.6
31. Platinum Pt = 98.7
32. Potassium K = 39.2
33. Palladium Pd = 53.3
34. _Pelopium_ Pe
35. Rhodium R = 52.2
36. _Rhuthenium_ Ru = 52.2
37. Silver Ag = 108.1
38. Sodium Na = 23
39. Strontium Sr = 43.8
40. Tin Sn = 59
41. _Tantalum_ Ta = 184
42. _Tellurium_ Te = 64.2
43. _Terbium_ Tb
44. _Thorium_ Th = 59.6
45. _Titanium_ Ti = 25
46. Tungsten W[A]= 95
47. Uranium U = 60
48. _Vanadium_ V = 68.6
49. _Yttrium_ Y
50. Zinc Zn = 32.6
51. _Zirconium_ Zr = 22.4
(N.B. The elements printed in italics are at present unimportant.)
[Footnote A: From the mineral Wolfram, and now exceedingly valuable, as
when alloyed with iron it is harder than, and will bore through steel.]
A few words will suffice to explain the meaning of the terms which head
the names, letters, and numbers of the Table of Elements. [Page 87] The
names of the elements have very interesting derivations, which it is
not the object of this work to go into; the symbols are abbreviations,
ciphers of the simplest kind, to save time and trouble in the frequent
repetition of long words, just as the signs + plus, and - minus, are
used in algebraic formulæ. For instance--the constant recurrence of
water in chemical combinations must be named, and would involve the most
tedious repetition; water consists of oxygen and hydrogen, and by taking
the first letter of each word we have an instructive symbol, which not
only gives us an abbreviated term for water, but also imparts at once a
knowledge of its composition by the use of the letters, HO.
Again, to take a more complex example, such as would occur in the study
of organic chemistry--a sentence such as _the hydrated oxide of
acetule_, is written at once by C_{4}H_{4}O_{2}, the figures referring
to the number of equivalents of each element--viz., 4 equivalents of C,
the symbol for carbon, 4 of H (hydrogen), and 2 of O (oxygen).
The long word paranaphthaline, a substance contained in coal tar, is
disposed of at once with the symbols and figures C_{30}H_{12}.
The figures in the third column are, however, the most interesting to
the precise and mathematically exact chemist. They represent the united
labours of the most painstaking and learned chemists, and are the exact
quantities in which the various elements unite. To quote one example: if
8 parts by weight of oxygen--viz., the combining proportions of that
element--are united with 1 part by weight of hydrogen, also its
combining number, the result will be 9 parts by weight of water; but if
8 parts of oxygen and 2 parts of hydrogen were used, one only of the
latter could unite with the former, and the result would be the
formation again of 9 parts of water, with an overplus of 1 equivalent of
hydrogen.
It is useless to multiply examples, and it is sufficient to know that
with this table of numbers the figures of analysis are obtained.
Supposing a substance contained 27 parts of water, and the oxygen in
this had to be determined, the rule of proportion would give it at once,
9: 27:: 8: 24. 9 parts of water are to 27 parts as 8 of oxygen (the
quantity contained in 9 parts of water) are to the answer
required--viz., 24 of oxygen. The names, symbols, and combining
proportions being understood, we may now proceed with the performance of
many interesting
CHEMICAL EXPERIMENTS.
As the permanent gases head the list, they will first engage our
attention, beginning with the element oxygen--Symbol O, combining
proportion 8. There is nothing can give a better idea of the enormous
quantity of oxygen present in the animal, vegetable, and mineral
kingdoms, than the statement that it represents _one-third_ of the
weight of the whole crust of the globe. Silica, or flint, contains about
half its weight of oxygen; lime contains forty per cent.; alumina about
thirty-three per cent. In these substances the element oxygen remains
inactive and powerless, chained by the strong fetters of chemical
affinity to [Page 88] the silicium of the flint, the calcium of the
lime, and the aluminum of the alumina. If these substances are heated by
themselves they will not yield up the large quantity of oxygen they
contain.
Nature, however, is prodigal in her creation, and hence we have but to
pursue our search diligently to find a substance or mineral containing
an abundance of oxygen, and part of which it will relinquish by what
used to be called by the "old alchemists" the _torture_ of heat. Such a
mineral is the black oxide of manganese, or more correctly the binoxide
of manganese, which consists of one combining proportion of the metal
manganese--viz., 27.6, and two of oxygen--viz., 8 × 2 = 16. If three
proportions of the binoxide of manganese are heated to redness in an
iron retort, they yield one proportion (equal to 8) of oxygen, and all
that has just been explained by so many words is comprehended in the
symbols and figures below:--
3 MnO_{2} = Mn_{3}O_{4} + _O_.
Thus the 3 MnO_{2} represent the three proportions of the binoxide of
manganese before heat is applied, whilst the sign =, the sign of
equation (equal to), is intended to show that the elements or compounds
placed _before_ it produce those which _follow_ it; hence the sequel
Mn_{3}O_{4} + _O_ shows that another compound of the metal and oxygen is
produced, whilst the + _O_ indicates the liberated oxygen gas. The iron
retort employed to hold the mineral should be made of cast iron in
preference to wrought iron, as the latter is very soon worn out by
contact with oxygen at a red heat. A gun-barrel will answer the purpose
for an experiment on the small scale, to which must be adapted a cock
and piece of pewter tubing. Such a make-shift arrangement may do very
well when nothing better offers; but as a question of expense, it is
probably cheaper in the end to order of Messrs. Simpson and Maule, or of
Messrs. Griffin, or of Messrs. Bolton, a cast-iron bottle, or cast-iron
retort, as it is termed, of a size sufficient to prepare two gallons of
oxygen from the binoxide of manganese, which, with four feet of iron
conducting-pipe, and connected to the bottle with a screw, does not
[Page 89] cost more than six shillings--an enormous dip, perhaps, in
the juvenile pocket, and therefore we shall indicate presently a still
cheaper apparatus for the same purpose. (Fig. 93.)
[Illustration: Fig. 93. A. The iron bottle, containing the black oxide
of manganese, with pipe passing to the pneumatic trough, B B, in which
is fixed a shelf, C, perforated with a hole, under which the end of the
pipe is adjusted, and the gas passes into the gas-jar, D.]
[Illustration: Fig. 94. A A. Pneumatic trough, with gas jar raised to
shelf; bubbles of air are rushing in at B, as the level of the water is
below the shelf--viz., at C C. D D. Same trough and gas jar with water
kept over the shelf by the introduction of the stone pitcher E, full of
water.]
The oxygen is conveyed to a square tin box provided with a shelf at one
end, perforated with several holes at least one inch in diameter, called
the pneumatic trough; any wooden trough, butter or wash-tub, foot-pan or
bath, provided with a shelf, may be raised by the same title to the
dignity of a piece of chemical apparatus. The gas jar must be filled
with water by withdrawing the stopper and pressing it down into the
trough, and when the neck is below the level of the water, the stopper
is again inserted, and the jar with the water therein contained lifted
steadily on to the shelf, the entry of atmospheric air being prevented
by keeping the lower part of the gas jar, called the welt, under the
water. Sometimes the pneumatic trough contains so small a quantity of
water that on raising the gas jar to the shelf the liquid does not cover
the bottom, and the air rushes up in large bubbles. Under these
circumstances it is better to provide a gallon stone jug full of water,
so that when the jar is being raised to the shelf it may be thrust into
the trough (on the same principle as the crow and the pitcher in the
fable), and thus by its bulk (as the stones in the pitcher) raise the
water to the proper level. When the gas jar is about half filled with
gas the jug may be withdrawn. This arrangement saves the trouble of
constantly adding and baling out water from the pneumatic trough. (Fig.
94.)
There are other solid oxygenized bodies in which the affinities are less
powerful, and hence a lower degree of heat suffices to liberate the
oxygen gas, and one of the most useful in this respect is the salt
termed chlorate of potash. If the substance is heated by itself, the
temperature required to expel the oxygen is almost as high as that
demanded for the black oxide of manganese; but, strange to say, if the
two substances are reduced to powder, and mixed in equal quantities by
weight, then a very moderate increase of heat is sufficient to cause the
chlorate of [Page 90] potash to give up its oxygen, whilst the oxide of
manganese undergoes no change whatever. It seems to fulfil only a
mechanical office--possibly that of separating each particle of chlorate
of potash from the other, so that the heat attacks the substance in
detail, just as a solid square of infantry might repel almost any
attack, whilst the same body dispersed over a large space might be of
little use; so with the chlorate of potash, which undergoes rapid
decomposition when mixed with and divided amongst the particles of the
oxide of manganese; less so with the red oxide of iron, and still less
with sand or brick-dust. (Fig. 95.)
[Illustration: Fig. 95. Preparation of oxygen from chlorate of potash
and oxide of manganese.
KO.ClO_{5} = { O_{6}
{ KCl.
]
This curious fact is explained usually by reference to what is called
catalytic action, or _decomposition by contact_ ([Greek: _kata_],
downwards, and [Greek: _luô_], I unloosen), _being a power possessed by a
body of resolving another into a new compound without undergoing any
change itself_. To make this term still clearer, we may notice another
example in linen rags, which may be exposed for any length of time to
the action of water without fear of conversion into sugar; if, however,
oil of vitriol is first added to the linen rags, and they are
subsequently digested at a proper temperature with water, then the rags
are converted into sugar (the author has seen a specimen made of an "old
shirt"); but, curious to relate, the oil of vitriol is unchanged in the
process, and if the process be commenced with a pound of acid, the same
quantity is discoverable at the end of the chemical decomposition of the
linen rags, and their conversion into sugar.
If a mixture of equal parts of oxide of manganese and chlorate of potash
is placed in a clean Florence flask, with a cork, and pewter, or glass
tube attached, great quantities of oxygen are quickly liberated, on the
application of the heat of a spirit lamp. Such a retort would cost about
fourpence, and if the flask is broken in the operation it can be easily
replaced by another, value one penny, as the same cork and tube will
generally suit a number of these cheap glass vessels. Corks may always
[Page 91] be softened by using either a proper cork squeezer, or by
placing them under a piece of board or a flat surface, and rolling and
pressing the cork till quite elastic.
Whilst fitting the latter into the neck of a flask, it is perhaps safer
to hold the thin and fragile vessel in a cloth, so that if the flask
breaks the chemical experiment may not be arrested for many days by the
severe cutting and wounding of the fingers. After the cork is fitted, it
is to be removed from the flask and bored with a cork borer. This useful
tool is sold in complete sets to suit all sizes of glass tubes, and the
pewter or glass being inserted, the flask and tube will be ready for
use, provided the tube is bent to the proper curve. This is easy enough
to perform with the pewter, but not quite so easy with the glass tube,
which must be held over the flame of a spirit lamp till soft, and then
bent very gradually to the proper curve. If a short length of the glass
tube is heated, it bends too sharply, and the convexity of the glass is
flattened, whilst the internal diameter of the tube is lessened, so that
at least three inches in length should be warmed, and the heat must not
be continued in one place only, but should be maintained in the
direction of the bend, the whole manipulation being conducted without
any hurry. (Fig. 96.)
[Illustration: Fig. 96. A. The cork squeezer. B. The cork borers. C. The
operation of bending the glass tube over the flame of the spirit-lamp.
D. The neck of the flask, with cork and tube bent and fitted complete
for use.]
Having filled a gas jar with oxygen, it may be removed from the
pneumatic trough by sliding it into a plate under the surface of the
water, and to prevent the stopper being thrust out accidentally from the
jar by the upward pressure of the gas, whilst a little compressed,
during the act of passing it into the plate, it is advisable to hold the
stopper of the jar firmly but gently, so that it cannot slip out of its
place. A number of jars of oxygen may be prepared and arranged in
plates, all of which of course must contain a little water, and enough
to cover the welt of the jar.
[Page 92]
EXPERIMENTS WITH OXYGEN GAS.
This gas was originally discovered by Priestley, in August, 1774, and
was first obtained by heating red precipitate--_i.e._, the red oxide of
mercury.
HgO = Hg + O.
We leave these symbols and figures to be deciphered by the youthful
philosopher with the aid of the table of elements, &c., and return to
the experiments.
There are certain thin wax tapers like waxed cord, called bougies, which
can be bent to any shape, and are very convenient for experiments with
the gases. If one of these tapers is bent as in Fig. 97, then lighted
and allowed to burn for some minutes, a long snuff is gradually formed,
which remains in a state of ignition when the flame of the taper is
blown out. On plunging this into a jar of oxygen, it instantly re-lights
with a sort of report, and burns with greatly-increased brilliancy, as
described by Dr. Priestley in his first experiment with this gas, and so
elegantly repeated by Professor Brande in his refined dissertation on
the progress of chemical science.
[Illustration: Fig. 97.]
"The 1st of August, 1774, is a _red-letter day_ in the annals of
chemical philosophy, for it was then that Dr. Priestley discovered
dephlogisticated air. Some, sporting in the sunshine of rhetoric, have
called this the birthday of pneumatic chemistry; but it was even a more
marked and memorable period; it was then (to pursue the metaphor) that
this branch of science, having eked out a sickly and infirm infancy in
the ill-managed nursery of the early chemists, began to display symptoms
of an improving constitution, and to exhibit the most hopeful and
unexpected marks of future importance. The first experiment, which led
to a very satisfactory result, was concluded as follows:--A glass jar
was filled with quicksilver, and inserted in a basin of the same; some
red precipitate of quicksilver was then introduced, and floated upon the
quicksilver in the jar; heat was applied to it in this situation with a
burning-lens, and to use Priestley's own words, _I presently found that
air was expelled from it very readily. Having got about three or four
times as much as the bulk of my materials, I admitted water into it, and
found that it was not imbibed by it. But what surprised me more than I
can well express was, that a candle burned in this air with a remarkably
vigorous flame, very much like that enlarged flame with which a candle
burns in nitrous air exposed to iron or lime of sulphur_ (_i.e._,
laughing gas); _but as I had got nothing like this remarkable appearance
from any kind of air besides this peculiar [Page 93] modification of
nitrous air, and I knew no nitrous acid was used in the preparation of
mercurius calcinatus, I was utterly at a loss how to account for it._"
(Fig. 98.)
[Illustration: Fig. 98. A. Glass vessel full of mercury, containing the
red precipitate at the top, and standing in the dish B, also containing
mercury. C. The burning-glass concentrating the sun's rays on the red
precipitate, being Priestley's original experiment.]
_Second Experiment._
The term oxygen is derived from the Greek ([Greek: _ozus_], acid, and
[Greek: _gennaô_], I give rise to), and was originally given to this
element by Lavoisier, who also claimed its discovery; and if this honour
is denied him, surely he has deserved equal scientific glory in his
masterly experiments, through which he discovered that the mixture of
forty-two parts by measure of azote, with eight parts by measure of
oxygen, produced a compound precisely resembling our atmosphere. The
name given to oxygen was founded on a series of experiments, one of
which will now be mentioned.
[Illustration: Fig. 99. A. The deflagrating spoon, B. The cork. C. The
zinc, or brass, or tin plate. D D. The gas jar.]
Place some sulphur in a little copper ladle attached to a wire, and
called a deflagrating spoon, passed through a round piece of zinc or
brass plate and cork, so that the latter acts as an adjusting
arrangement to fix the wire at any point required. The combustion of the
sulphur, previously feeble, now assumes a remarkable intensity, and a
peculiar coloured light is generated, whilst the sulphur unites with the
oxygen, and forms sulphurous acid gas. It produces, in fact, the same
gas which is formed by burning an ordinary sulphur match. This compound
is valuable as a disinfectant, and is a very important bleaching agent,
being most extensively employed in the whitening of straw employed in
the manufacture of straw bonnets. It is an acid gas, as Lavoisier found,
and this property may be detected by pouring a little tincture of litmus
into the bottom of the plate in which the gas jar stands. The blue
colour of the litmus is rapidly changed to red, and it might be thought
that no further argument could possibly be required to prove that oxygen
was _the_ acidifying agent, the more particularly as the result is the
same in the next illustration.
[Page 94]
_Third Experiment._
Cut a small piece from an ordinary stick of phosphorus under water, take
care to dry it properly with a cloth, and after placing it in a
deflagrating spoon, remove the stopper from the gas-jar, as there is no
fear of the oxygen rushing away, because it is somewhat heavier than
atmospheric air; and then, after placing the spoon with the phosphorus
in the neck of the jar, apply a heated wire and pass the spoon at once
into the middle of the oxygen; in a few seconds a most brilliant light
is obtained, and the jar is filled with a white smoke; as this subsides,
being phosphoric acid, and perfectly soluble in water, the same litmus
test may be applied, when it is in like manner changed to red. The acid
obtained is one of the most important constituents of bone.
_Fourth Experiment._
A bit of bark-charcoal bound round with wire is set on fire either by
holding it in the flame of a spirit-lamp, or by attaching a small piece
of waxed cotton to the lower part, and igniting this; the charcoal may
then be inserted into a bottle of oxygen, when the most brilliant
scintillations occur. After the combustion has ceased and the whole is
cool, a little tincture of litmus may also be poured in and shaken
about, when it likewise turns red, proving for the third time the
generation of an acid body, called carbonic acid--an acid, like the
others already mentioned, of great value, and one which Nature employs
on a stupendous scale as a means of providing plants, &c., with solid
charcoal. Carbonic acid, a virulent poison to animal life, is, when
properly diluted, and as contained in atmospheric air, one of the chief
alimentary bodies required by growing and healthy plants.
In three experiments acid bodies have been obtained; can we speculate on
the result of the next?
_Fifth Experiment._
Into a deflagrating spoon place a bit of potassium, set this on fire by
holding it in the spoon in the flame of a spirit-lamp, and then rapidly
plunge the burning metal into a bottle of oxygen. A brilliant ignition
occurs in the deflagrating spoon for a few seconds, and there is little
or no smoke in the jar. The product this time is a solid, called potash,
and if this be dissolved in water and filtered, it is found to be clear
and bright, and now on the addition of a little tincture of litmus to
one half of the solution, it is wholly unaffected, and remains blue; but
if with the other half a small quantity of tincture of turmeric is
mixed, it immediately changes from a bright yellow solution to a
reddish-brown, because turmeric is one of the tests for an alkali; and
thus is ascertained by the help of this and other tests that the result
of the combustion is not an _acid_, but an _alkali_. The experiment is
made still more satisfactory by burning another bit of potassium in
oxygen and dissolving the product in water, and if any portion of [Page
95] the reddened liquid derived from the sulphurous, phosphoric, and
carbonic acids taken from the previous experiments, be added to separate
portions of the alkaline solution, they are all restored to their
original blue colour, because an acid is neutralized by an alkali; and
the experiment is made quite conclusive by the restoration of the
reddened turmeric to a bright yellow on the addition of a solution of
either of the three acids already named. Moreover, an acid need not
contain a fraction of oxygen, as there is a numerous class of
_hy_dracids, in which the acidifying principle is hydrogen instead of
oxygen, such as the hydrochloric, hydriodic, hydro-bromic, and
hydrofluoric acids.
_Sixth Experiment._
A piece of watch-spring is softened at one end, by holding it in the
flame of a spirit-lamp, and allowing it to cool. A bit of waxed cotton
is then bound round the softened end, and after being set on fire, is
plunged into a gas jar containing oxygen; the cotton first burns away,
and then the heat communicates to the steel, which gradually takes fire,
and being once well ignited, continues to burn with amazing rapidity,
forming drops of liquid dross, which fall to the bottom of the
plate--and also a reddish smoke, which condenses on the sides of the
jar; neither the dross which has dropped into the plate, nor the reddish
matter condensed on the jar, will affect either tincture of litmus or
turmeric; they are neither acid nor alkaline, but _neutral_ compounds of
iron, called the sesquioxide of iron (Fe_{2}O_{3}), and the magnetic
oxide (Fe_{3}O_{4}=FeO.Fe_{2}O_{3}).
_Seventh Experiment._
[Illustration: Fig. 100. A. Bladder containing oxygen, provided with a
stop-cock and jet leading to, B, B. Finger glass containing boiling
water. C. The cup of melted phosphorus under the water. The gas escapes
from the bladder when pressed.]
Some oxygen gas contained in a bladder provided with a proper jet may be
squeezed out, and upon, some liquid phosphorus contained in a cup at the
bottom of a finger glass full of boiling water, when a most brilliant
combustion occurs, proving that so long as the principle is complied
with--viz., that of furnishing oxygen to a combustible substance--it
will burn under water, provided it is insoluble, and possesses the
remarkable affinity for oxygen which belongs to phosphorus. The
experiment should be performed with boiling water, to keep the
phosphorus in the liquid state; and it is quite as well to hold a [Page
96] square foot of wire gauze over the finger glass whilst the
experiment is being performed. (Fig. 100.)
_Eighth Experiment._
Oxygen is available from many substances when they are mixed with
combustible substances, and hence the brilliant effects produced by
burning a mixture of nitre, meal powder, sulphur, and iron or steel
filings; the metal burns with great brilliancy, and is projected from
the case in most beautiful sparks, which are long and needle-shaped with
steel, and in the form of miniature rosettes with iron filings; it is
the oxygen from the nitre that causes the combustion of the metal, the
other ingredients only accelerate the heat and rate of ignition of the
brilliant iron, which is usually termed a gerb.
_Ninth Experiment._
A mixture of nitrate of potash, powdered charcoal, sulphur, and nitrate
of strontium, driven into a strong paper case about two inches long, and
well closed at the end with varnish, being quite waterproof, may be set
on fire, and will continue to burn under water until the whole is
consumed; the only precaution necessary being to burn the composition
from the case with the mouth downward, and if the experiment is tried in
a deep glass jar it has a very pleasing effect. (Fig. 101.)
[Illustration: Fig. 101. A. Case of red fire burning downwards, and
attached by a copper wire to a bit of leaden pipe B, to sink it. C C.
Jar containing water.]
The red-fire composition is made by mixing nitrate of strontia 40 parts
by weight, flowers of sulphur 13 parts, chlorate of potash 5 parts,
sulphuret of antimony 4 parts. These ingredients must first be well
powdered separately, and then mixed carefully on a sheet of paper with a
paper-knife. They are liable to explode if rubbed _together_ in a
mortar, on account of the presence of sulphur and chlorate of potash,
and the composition, if kept for any time, is liable to take fire
spontaneously.
_Tenth Experiment._
Some zinc is melted in an iron ladle, and made quite red hot; if a
little dry nitre is thrown upon the surface, and gently stirred into the
metal, it takes fire with the production of an intense white light,
whilst large quantities of white flakes ascend, and again descend when
cold, being the oxide of zinc, and called by the alchemists the
"Philosopher's Wool" (ZnO). In this experiment the oxygen from the nitre
effects the oxidation of the metal zinc.
[Page 97]
_Eleventh Experiment._
A mixture of four pounds of nitre with two of sulphur and one and a half
of lamp black produces a most beautiful and curious fire, continually
projected into the air as sparks having the shape of the rowel of a
spur, and one that may be burnt with perfect safety in a room, as the
sparks consume away so rapidly, in consequence of the finely divided
condition of the charcoal, that they may be received on a handkerchief
or the hand without burning them. The difficulty consists in effecting
the complete mixture of the charcoal. The other two ingredients must
first be thoroughly powdered separately, and again triturated when
mixed, and finally the charcoal must be rubbed in carefully, till the
whole is of a uniform tint of grey and very nearly black, and as the
mixture proceeds portions must be rammed into a paper case, and set on
fire; if the stars or pinks come out in clusters, and spread well
without other and duller sparks, it is a sign that the whole is well
mixed; but if the sparks are accompanied with dross, and are projected
out sluggishly, and take some time to burn, the mixture and rubbing in
the mortar must be continued; and even that must not be carried too far,
or the sparks will be too small. N.B.--If the lamp-black was heated red
hot in a close vessel, it would probably answer better when cold and
powdered.
_Twelfth Experiment._
Into a tall gas jar with a wide neck project some red-hot lamp-black
through a tin funnel, when a most brilliant flame-like fire is obtained,
showing that finely divided charcoal with pure oxygen would be
sufficient to afford light; but as the atmosphere consists of oxygen
diluted with nitrogen, compounds of charcoal with hydrogen, are the
proper bodies to burn, to produce artificial light.
_Thirteenth Experiment. The Bude Light._
This pretty light is obtained by passing a steady current of oxygen gas
(escaping at a very low pressure) through and up the centre pipe of an
argand oil lamp, which must be supplied with a highly carbonized oil and
a very thick wick, as the oxygen has a tendency to burn away the cotton
unless the oil is well supplied, and allowed to overflow the wick, as it
does in the lamps of the lighthouses. The best whale oil is usually
employed, though it would be worth while to test the value of Price's
"Belmontine Oil" for the same purpose. (Fig. 102.)
[Illustration: Fig. 102. A. Reservoir of oil. B. The flexible pipe
conveying oxygen to centre of the argand lamp.]
[Page 98]
_Fourteenth Experiment. A Red Light._
Clear out the oil thoroughly from the Bude light apparatus; or, what is
better, have two lamps, one for oil, and the other for spirit; fill the
apparatus with a solution of nitrate of strontia and chloride of calcium
in spirits of wine, and let it burn from the cotton in the same way as
the oil, and supply it with oxygen gas.
_Fifteenth Experiment. A Green Light._
Dissolve boracic acid and nitrate of baryta in spirits of wine, and
supply the Bude lamp with this solution.
_Sixteenth Experiment. A Yellow Light._
Dissolve common salt in spirits of wine, and burn it as already
described in the Bude light apparatus.
_Seventeenth Experiment. The Oxy-calcium Light._
[Illustration: Fig. 103.--No. 1. A. Oxygen jet. B. The ball of lime,
suspended by a wire. C. Spirit lamp.
No. 2. D. Oxygen jet. E. Gas (jet connected with the gas-pipe in the
rear by flexible pipe) projected on to ball of lime, F.]
This very convenient light is obtained in a simple manner, either by
using a jet of oxygen as a blowpipe to project the flame of a spirit
lamp on to a ball of lime; or common coal-gas is employed instead of the
spirit lamp, being likewise urged against a ball of lime. By this plan
one bag containing oxygen suffices for the production of a brilliant
light, not equal, however, to the oxy-hydrogen light, which will be
explained in the article on hydrogen. (Fig. 103.)
_Eighteenth Experiment._
To show the weight of oxygen gas, and that it is heavier than air, the
stoppers from two bottles containing it may be removed, one bottle may
be left open for some time and then tested by a lighted taper, when it
[Page 99] will still indicate the presence of the gas, whilst the other
may be suddenly inverted over a little cup in which some ether, mixed
with a few drops of turpentine, may be burning--the flame burns with
much greater brilliancy at the moment when the oxygen comes in contact
with it.
_Nineteenth Experiment._
The theory of the effect of oxygen upon the system when inhaled would be
an increase in the work of the respiratory organs; and it is stated that
after inhaling a gallon or so of this gas, the pulse is raised forty or
fifty beats per minute: the gas is easily inhaled from a large
india-rubber bag through an amber mouthpiece; it must of course be quite
pure, and if made from the mixture of chlorate of potash and oxide of
manganese, should be purified by being passed through lime and water, or
cream of lime.
_Twentieth Experiment._
There are certain colouring matters that are weakened or destroyed by
the action of light and other causes, which deprive them of oxygen gas
or deoxidize them. A weak tincture of litmus, if long kept, often
becomes colourless, but if this colourless fluid is shaken in a bottle
with oxygen gas it is gradually restored; and if either litmus,
turmeric, indigo, orchil, or madder, paper, or certain ribbons dyed with
the same colouring matters, have become faded, they may be partially
restored by damping and placing them in a bottle of oxygen gas. The
effect of the oxygen is to reverse the _de_oxidizing process, _and_ to
impart oxygen to the colouring matters. By a peculiar process indigo may
be obtained quite white, and again restored to its usual blue colour,
either by exposure to the air or by passing a stream of oxygen through
it.
_Twenty-first Experiment._
Messrs. Matheson, of Torrington-street, Russell-square, prepare in the
form of wire some of the rarest metals, such as magnesium, lithium, &c.
A wire of the metal magnesium burns magnificently in oxygen gas, and
forms the alkaline earth magnesia. The metal lithium, to which such a
very low combining proportion belongs--viz., 6.5, can also be procured
in the state of wire, and burns in oxygen gas with an intense white
light into the alkaline lithia, which dissolved in alcohol with a little
acetic acid, and burnt, affords a red flame, making a curious contrast
between the effects of colour produced by the metallic and oxidized
state of lithium.
THE ALLOTROPIC CONDITION OF OXYGEN GAS.
The term allotropy (from [Greek: _allotropos_], of a different nature)
was first used by the renowned chemist Berzelius. Dimorphism, or
diversity in crystalline form, is therefore a special case of allotropy,
and is most amusingly illustrated with the iodide of mercury (HgI),
which is made either by rubbing together equal combining proportions
[Page 100]of mercury and iodine (both of which are to be found in the
Table of Elements, page 86), or by carefully precipitating a solution of
corrosive sublimate (chloride of mercury (HgCl)) with one of iodide of
potassium, just enough and no more of the latter being added to
precipitate the metal, or else the iodide of mercury is redissolved by
the excess of the precipitant. It is first of a dirty yellow, and then
gradually changes when stirred to a scarlet; if this be collected on a
filter, and washed and drained, it is a beautiful scarlet, and when some
of this substance is rubbed across a sheet of paper, a bright scarlet is
apparent, which may be rapidly changed to a lemon-yellow by heating the
paper over the flame of a spirit lamp; and the iodide of mercury is
again brought back to a scarlet colour by rubbing down the yellow
crystals with the fingers. This experiment may be repeated over and over
again with the like results. If some of the scarlet iodide of mercury is
sublimed from one bit of glass to another, it forms crystals, derived
from the right rhombic prism; when these are scratched with a pin they
change again to the scarlet state, the latter when crystallized being in
the form of the square-based octohedron.
Other cases of dimorphism may be mentioned--viz., with sulphur,
carbonate of lime, and lead, and many others, whilst allotropy is
curiously illustrated in the various conditions of charcoal, which, in
the more numerous examples, is black and opaque, and in another instance
transparent like water. Lamp-black is soft, but the diamond is the
hardest natural substance. The allotropic state of sulphur has been
already alluded to; phosphorus, again, exists in three modifications:
1st, Common phosphorus, which shines in the dark and emits a white
smoke. 2nd, White phosphorus. 3rd, Red or amorphous phosphorus, which
does not shine or emit white smoke when exposed to the air, and is so
altered in its properties that it may be safely carried in the pocket.
Enough evidence has therefore been offered to show that the allotropic
property is not confined to one element or compound, but is discoverable
in many bodies, and in no one more so than in the allotropic state of
the element oxygen called
OZONE.
The Greek language has again been selected by the discoverer, Schönbein,
of Basle, for the title or name of this curious modification of oxygen,
and it is so termed from [Greek: _oxein_], to smell. The name at once
suggests a marked difference between ozone and oxygen, because the
latter is perfectly free from odour, whilst the former has that peculiar
smell which is called electric, and is distinguishable whenever an
electrical machine is at work, or if a Leyden jar is charged by the
powerful Rhumkoff, or Hearder coil; it is also apparent when water is
decomposed by a current of electricity and resolved into its elements,
oxygen and hydrogen. When highly concentrated it smells like chlorine;
and the author recollects seeing the first experiments by Schönbein, in
England, at Mr. Cooper's laboratory in the Blackfriars-road. Ozone is
prepared by taking a clean empty bottle, and pouring therein a very
[Page 101] little distilled water, into which a piece of clean scraped
phosphorus is introduced, so as to expose about one-half of its diameter
to the air in the bottle, whilst the other is in contact with the water.
(Fig. 104.)
For the sake of precaution, the bottle may stand in a basin or soup
plate, so that if the phosphorus should take fire, it may be instantly
extinguished by pouring cold water into the bottle, and should this
crack and break, the phosphorus is received into the plate.
[Illustration: Fig. 104. A. A quart bottle, with the stopper loosely
placed therein. B. The stick of clean phosphorus. C. The water level
just to half the thickness of the phosphorus. D D. A soup-plate.]
When the ozone is formed the phosphorus can be withdrawn, and the
phosphorous-acid smoke washed out by shaking the bottle; it is
distinguishable by its smell, and also by its action on test paper,
prepared by painting with starch containing iodide of potassium on some
Bath post paper; when this is placed in the bottle containing ozone, it
changes the test blue, or rather a purplish blue.
[Illustration: Fig. 105. V. A small voltaic battery standing on the
stool with glass legs, S S, and capable of heating a thin length of
platinum wire about two inches long, and bent to form a point between
the conducting wires, W W.--N.B. The voltaic current can be cut off at
pleasure, so as to cool the wire when necessary. A is the prime
conductor of an ordinary cylinder electrical machine. B is the wire
conveying the frictional electricity to the conducting wires of the
voltaic battery, where the point P being the sharpest point in the
arrangement, delivers the electrified and ozonized air.]
Ozone is a most energetic body, and a powerful bleaching agent; if a
point is attached to the prime conductor of an electrical machine, and
the electrified air is received into a bottle, it will be found to
smell, and has the power of bleaching a _very_ dilute solution of
indigo. Ozone [Page 102] is not a mere creation of fancy, as it can not
only be produced by certain methods, but may be destroyed by a red heat.
If a point is prepared with a loop of platinum wire, and this latter,
after being connected with a voltaic battery, made red hot, and the
whole placed on an insulating stool, and connected with the prime
conductor of an electrical machine, it is found that the electrified air
no longer smells, the ozone is destroyed; on the other hand, if the
voltaic battery is disconnected, and the electrified air again allowed
to pass from the cold platinum wire, the smell is again apparent, the
air will bleach, and if caused to impinge at once upon the iodide of
starch test, changes it in the manner already described. (Fig. 105.)
Ozone is insoluble in water, and oxidizes silver and lead leaf, finely
powdered arsenic and antimony; it is a poison when inhaled in a
concentrated state, whilst diluted, and generated by natural processes,
it is a beneficent and beautiful provision against those numerous smells
originating from the decay of animal and vegetable matter, which might
produce disease or death: ozone is therefore a powerful disinfectant.
The test for ozone is made by boiling together ten parts by weight of
starch, one of iodide of potassium, and two hundred of water; it may
either be painted on Bath post paper, and used at once, or blotting
paper may be saturated with the test and dried, and when required for
use it must be damped, either before or after testing for ozone, as it
remains colourless when _dry_, but becomes blue after being moistened
with water.
Paper prepared with sulphate of manganese is an excellent test for
ozone, and changes brown rapidly by the oxidation of the proto-salt of
manganese, and its conversion into the binoxide of the metal.
Ozone is also prepared by pouring a little sulphuric ether into a quart
bottle, and then, after heating a glass rod in the flame of the spirit
lamp, it may be plunged into the bottle, and after remaining there a few
minutes ozone may be detected by the ordinary tests.
NITROGEN, OR AZOTE.
[Greek: _Nitron_], nitre; [Greek: _gennaô_], I form; [Greek: _a_],
privative; [Greek: _zôê_], life. Symbol, N; combining proportion, 14.
Also termed by Priestley, _phlogisticated_ air.
In the year 1772, Dr. Rutherford, Professor of Botany in the University
of Edinburgh, published a thesis in Latin on fixed air, in which he
says:--"_By the respiration of animals healthy air is not merely
rendered mephitic_ (i.e., charged with carbonic acid gas), _but also
suffers another change. For after the mephitic portion is absorbed by a
caustic alkaline lixivium, the remaining portion is not rendered
salubrious; and although it occasions no precipitate in lime-water, it
nevertheless extinguishes flame and destroys life._" Such is the
doctor's account of the discovery of nitrogen, which may be separated
from the oxygen in the air in a very simple manner. The atmosphere is
the great storehouse of nitrogen, and four-fifths of its prodigious
volume consist of this element.
[Page 103]
_Composition of Atmospheric Air._
Bulk. Weight.
Oxygen 20 22.3
Nitrogen 80 77.7
--- ----
100 100.
The usual mode of procuring nitrogen gas is to abstract or remove the
oxygen from a given portion of atmospheric air, and the only point to be
attended to, is to select some substance which will continue to burn as
long as there is any oxygen left. Thus, if a lighted taper is placed in
a bottle of air, it will only burn for a certain period, and is
gradually and at last extinguished; not that the whole of the oxygen is
removed or changed, because after the taper has gone out, some burning
sulphur may be placed in the vessel, and will continue to burn for a
limited period; and even after these two combustibles have, as it were,
taken their fill of the oxygen, there is yet a little left, which is
snapped up by burning phosphorus, whose voracious appetite for oxygen is
only appeased by taking the whole. It is for this reason that phosphorus
is employed for the purpose of removing the oxygen, and also because the
product (phosphoric acid) is perfectly soluble in water, and thus the
oxygen is first combined, and then washed out of a given volume of air,
leaving the nitrogen behind.
_First Experiment._
To prepare nitrogen gas, it is only necessary to place a little dry
phosphorus in a Berlin porcelain cup on a wine glass, and to stand them
in a soup plate containing water. The phosphorus is set on fire with a
hot wire, and a gas jar or cylindrical jar is then carefully placed over
it, so that the welt of the jar stands in the water in the soup plate.
At first, expansion takes place in consequence of the heat, but this
effect is soon reversed, as the oxygen is converted into a solid by
union with the phosphorus, forming a white smoke, which gradually
disappears. (Fig. 106.)
[Illustration: Fig. 106. A. Cylindrical glass vessel, open at one end,
and inverted over B, the wine-glass, supporting C, the cup containing
the burning phosphorus, and the whole standing in a soup-plate, D D,
containing water.]
Supposing two grains of phosphorus had been placed in a platinum tube,
and just enough atmospheric air passed over it to convert the whole into
phosphoric acid, the weight of the phosphorus would be increased to 4½
grains by the addition of 2½ grains of oxygen; [Page 104] now one cubic
inch of oxygen weighs 0.3419, or about 1/3rd of a grain, hence 7.3 cubic
inches of oxygen disappear, which weigh as nearly as possible 2½ grains,
so that as 36.5 cubic inches of air contain 7.3 cubic inches of oxygen,
that quantity of air must have passed over the 2 grains of phosphorus to
convert it into 4½ grains of phosphoric acid.
For very delicate purposes, nitrogen is best prepared by passing air
over finely-divided metallic copper heated to redness; this metal
absorbs the whole of the oxygen and leaves the nitrogen. The
finely-divided copper is procured by passing hydrogen gas over pure
black oxide of copper.
_Second Experiment._
[Illustration: Fig. 107. A. Glass jar, with collar of leather, through
which the stamper, C, works. B B. The tube containing the finely-divided
lead, part of which falls out, and is ignited, and retained by the
little tray just below, being part of the iron stand, D D, with crutches
supporting the ends of the glass tube, and the whole stands in the dish
of water, E E.]
A very instructive experiment is performed by heating a good mass of
tartrate of lead in a glass tube which is hermetically sealed, and being
placed on an iron support, is then covered by a capped air jar with a
sliding rod and stamper, the whole being arranged in a plate containing
water. When the stamper is pushed down upon the glass the latter is
broken (Fig. 107), and the air gradually penetrates to the finely
divided lead, when ignition occurs, and the oxygen is absorbed, as
demonstrated by the rise of the water in the jar. On the same principle,
if a bottle is filled about one-third full with a liquid amalgam of lead
and mercury, and then stopped and shaken for two hours or more, the
finely divided lead absorbs the oxygen and leaves pure nitrogen. Or if a
mixture of equal weights of sulphur and iron filings, is made into a
paste with water in a thin iron cup, and then warmed and placed under a
gas jar full of air standing on the [Page 105] shelf of the pneumatic
trough, or in a dish full of water, the water gradually rises in the jar
in about forty-eight hours, in consequence of the absorption of the
oxygen gas.
_Third Experiment._
Nitrogen is devoid of colour, taste, smell, of alkaline or acid
qualities; and, as we shall have occasion to notice presently, it forms
an _acid_ when chemically united with oxygen, and an alkali in union
with hydrogen. A lighted taper plunged into this gas is immediately
extinguished, while its specific gravity, which is lighter than that of
oxygen or air, is demonstrated by the rule of proportion.
Weight of 100 cubic Weight of 100 cubic Specific
inches of air at 60° Unity. inches of nitrogen at gravity of
Fahr., bar. 29.92 in. 60° Fahr., bar. 29.92 in. nitrogen.
30.829 : 1 :: 29.952 : 971
And its levity may be shown very prettily by a simple experiment. Select
two gas jars of the same size, and after filling one with oxygen gas and
the other with nitrogen gas, slide glass plates over the bottoms of the
jars, and proceed to invert the one containing oxygen, placing the neck
in a stand formed of a box open at the top; then place the jar
containing nitrogen over the mouth of the first, withdrawing the glass
plates carefully; and if the table is steady the top gas jar will stand
nicely on the lower one. Then (having previously lighted a taper so as
to have a long snuff) remove the stopper from the nitrogen jar and
insert the lighted taper, which is immediately extinguished, and as
quickly relighted by pushing it down to the lower jar containing the
oxygen. This experiment may be repeated several times, and is a good
illustration of the relative specific gravities of the two gases, and of
the importance of the law of universal diffusion already explained at p.
6, by which these gases _mix_, not _combine_ together, and the
atmosphere remains in one uniform state of composition in spite of the
changes going on at the surface of the earth. Omitting the aqueous
vapour, or steam, ever present in variable quantities in the atmosphere,
ten thousand volumes of dry air contain, according to Graham:--
[IIlustration: Fig. 108. A. Gas jar containing nitrogen, N, standing on
B, another jar full of oxygen, O. The taper, C, is extinguished at N,
and relighted at O. D D. Stand supporting the jars.]
[Page 106]
Nitrogen 7912
Oxygen 2080
Carbonic acid 4
Carburetted hydrogen (CH_{2}) 4
Ammonia a trace
-------
10,000
_Fourth Experiment._
It was the elegant, the accomplished, but ill-fated Lavoisier who
discovered, by experimenting with quicksilver and air, the compound
nature of the atmosphere; and it was the same chemist who gave the name
of azote to nitrogen; it should, however, be borne in mind that it does
not necessarily follow because a gas extinguishes flame that it is a
_poison_. Nitrogen extinguishes flame, but we inhale enormous quantities
of air without any ill effects from the nitrogen or azote that it
contains; on the other hand, many gases that extinguish flame are
_specific poisons_, such as carbonic acid, carbonic oxide, cyanogen, &c.
Lavoisier's experiment may be repeated by passing into a measured jar,
graduated into five equal volumes, four measures of nitrogen and one
measure of oxygen; a glass plate should then be slid over the mouth of
the vessel, and it may be turned up and down gently for some little time
to mix the two gases, and when the mixture is tested with a lighted
taper, it is found neither to increase nor diminish the illuminating
power and the taper burns as it would do in atmospheric air. (Fig. 109.)
[Illustration: Fig. 109. A. Gas jar divided into five equal parts. B B.
Section of pneumatic trough, to show the decantation of gas from one
vessel to another. The gas is being passed from C to A, through the
water.]
[Page 107]
HYDROGEN.
Hydrogen ([Greek: _udôr_], water; [Greek: _gennaô_], I give rise to), so
termed by Lavoisier--called by other chemists inflammable air, and
phlogiston. Symbol, H; combining properties, 1. The lightest known form
of matter.
Every 100 parts by weight of water contain 11 parts of hydrogen gas; and
as the quantity of water on the surface of the earth represents at least
two-thirds of the whole area, the source of this gas, like that of
oxygen or nitrogen, is inexhaustible. Van Helmont, Mayow, and Hales had
shown that certain inflammable and peculiar gases could be obtained, but
it was reserved for the rigidly philosophic mind of Cavendish to
determine the nature of the elements contained in, and giving a
speciality to, the inflammable gases of the older chemists. By acting
with dilute acids upon iron, zinc, and tin, Cavendish liberated an
inflammable elastic gas; and he discovered nearly all the properties we
shall notice in the succeeding experiments, and especially demonstrated
the composition of water in his paper read before the Royal Society in
the year 1784.
_First Experiment._
Hydrogen is prepared in a very simple manner, by placing some zinc
cuttings in a bottle, to which is attached a cork and pewter or bent
glass tube, and pouring upon the metal some dilute sulphuric or
hydrochloric acid. Effervescence and ebullition take place, and the gas
escapes in large quantities, water being decomposed; the oxygen passes
to the zinc, and forms oxide of zinc, and this uniting with the
sulphuric acid forms sulphate of zinc, which may be obtained after the
escape of the hydrogen by evaporation and crystallization. (Fig. 110.)
Zn + HO.SO_{3} = ZnO.SO_{3} + H;
or,
Zn + HCl = ZnCl + H.
In nearly all the processes employed for the generation of hydrogen gas,
a metal is usually employed, and this fact has suggested the notion that
hydrogen may possibly be a metal, although it is the lightest known form
of matter; and it will be observed in all the succeeding experiments
that a metallic substance will be employed to take away the oxygen and
displace the hydrogen.
[Illustration: Fig. 110. A. Bottle containing zinc cuttings and water
and fitted with a cap and two tubes, the one marked B, containing a
funnel, conveys the sulphuric acid to the zinc and water, whilst the gas
escapes through the pipe C.]
[Page 108]
Whenever hydrogen is prepared it should be allowed to escape from the
generating vessel for a few minutes before any flame is applied, in
order that the atmospheric air may be expelled. The most serious
accidents have occurred from carelessness in this respect, as a mixture
of hydrogen and air is explosive, and the more dangerous when it takes
fire in any closed glass bottle.
_Second Experiment._
If a piece of potassium is confined in a little coarse wire gauze cage,
attached to a rod, and thrust under a small jar full of water, placed on
the shelf of the pneumatic trough, hydrogen gas is produced with great
rapidity, and is received into the gas jar. The bit of potassium being
surrounded with water, is kept cool, whilst the hydrogen escaping under
the water is not of course burnt away, as it is whenever the metal is
thrown on the _surface_ of water.
_Third Experiment._
[Illustration: Fig. 111. A. Flask containing water, and producing steam,
which passes to the iron tube, B B, containing the iron borings heated
red hot in the charcoal stove C. The hydrogen passes to the jar D,
standing on the shelf of the pneumatic trough.]
Across a small iron table-furnace is placed about eighteen inches of
1-inch gas-pipe containing iron borings, the whole being red-hot; and
attached to one end is a pipe conveying steam from a boiler, or flask,
or retort, whilst another pipe is fitted to the opposite end, and passes
to the pneumatic trough. Directly the steam passes over the red hot iron
borings it is deprived of oxygen, which remains with the iron, forming
the rust or oxide of iron, whilst the hydrogen, called in this case
_water gas_, escapes with great rapidity. When steam is passed over
red-hot charcoal, hydrogen is also produced with carbonic oxide gas, and
this in fact is the ordinary process of making _water gas_, which being
purified is afterwards saturated with some volatile hydrocarbon and
burnt. At first sight, such a mode of making gas would be thought
extremely profitable, and in spite of the numerous failures the
_discovery_ (so called) of _water gas_ is reproduced as a sort of
_chronic wonder_; but experience and practice have clearly demonstrated
that _water gas_ is a fallacy, and as long as we can get coal it is not
worth while going through the round-about processes of first burning
coal to produce steam; secondly, [Page 109] of burning coal to heat
charcoal, over which the steam is passed to be converted into gas, which
has then to be purified and saturated with a cheap hydrocarbon obtained
from coal or mineral naphtha; whilst ordinary coal gas is obtained at
once by heating coal in iron retorts. (Fig. 111.)
Thus, by the metals zinc, tin, potassium, red-hot iron (and we might add
several others), the oxygen of water is removed and hydrogen gas
liberated.
_Fourth Experiment._
If bottles of hydrogen gas are prepared by all the processes described,
they will present the same properties when tested under similar
circumstances. A lighted taper applied to the mouths of the bottles of
hydrogen, which should be inverted, causes the gas to take fire with a
slight noise, in consequence of the mixture of air and hydrogen that
invariably takes place when the stopper is removed; on thrusting the
lighted taper into the bulk of the gas it is extinguished, showing that
hydrogen possesses the opposite quality to oxygen--viz., that it takes
fire, but does not support combustion. By keeping the bottles containing
the hydrogen upright, when the stopper is removed the gas escapes with
great rapidity, and atmospheric air takes its place, so much so that by
the time a lighted taper is applied, instead of the gas burning quietly,
it frequently astonishes the operator with a loud pop. This sudden
attack on the nerves may be prevented by always experimenting with
inverted bottles. (Fig. 112.)
[Illustration: Fig. 112. A. Bottle opened upright, and hydrogen
exploding. B. Bottle opened inverted, and hydrogen burning quietly at
the mouth.]
_Fifth Experiment._
Hydrogen is 14.4 lighter than air, and for that reason may be passed
into bottles and jars without the assistance of the pneumatic trough.
One of the most amusing proofs of its levity is that of filling paper
bags or balloons with this gas; and we read, in the accounts of the
fêtes at [Page 110] Paris, of the use of balloons ingeniously
constructed to represent animals, so that a regular aerial hunt was
exhibited, with this drawback only, that nearly all the animals
preferred ascending with their legs upwards, a circumstance which
provoked intense mirth amongst the volatile Frenchmen. The lightness of
hydrogen may be shown in two ways--first, by filling a little
gold-beater's skin balloon with _pure_ hydrogen (prepared by passing the
gas made from zinc and dilute pure sulphuric acid through a strong
solution of potash, and afterwards through one of nitrate of silver),
and allowing the balloon to ascend; and then afterwards, having of
course secured the balloon by a thin twine or strong thread, it may be
pulled down and the gas inhaled, when a most curious effect is produced
on the voice, which is suddenly changed from a manly bass to a ludicrous
nasal squeaking sound. The only precautions necessary are to make the
gas quite pure, and to avoid flame whilst inhaling the gas. It is
related by Chaptal that the intrepid (quære, foolish) but unfortunate
aeronaut, Mons. Pilate de Rosio, having on one occasion inhaled hydrogen
gas, was rash enough to approach a lighted candle, when an explosion
took place in his mouth, which he says "_was so violent that he fancied
all his teeth were driven out._" Of course, if it were possible to
change by some extraordinary power the condition of the atmosphere in a
concert-room or theatre, all the bass voices would become extremely
nasal and highly comic, whilst the sopranos would emulate railway
whistles and screech fearfully; and supposing the specific gravity of
the air was continually and materially changing, our voices would never
be the same, but alter day by day, according to the state of the air, so
that the "familiar voice" would be an impossibility.
A bell rung in a gas jar containing air emits a very different sound
from that which is produced in one full of hydrogen--a simple experiment
is easily performed by passing a jar containing hydrogen over a
self-acting bell, such as is used for telegraphic purposes. (Fig. 113.)
[Illustration: Fig. 113. A. Stand and bell. B B. Tin cylinder full of
hydrogen, which may be raised or depressed at pleasure, by lifting it
with the knob at the top, when the curious changes in the sound of the
bell are audible.]
_Sixth Experiment._
Some of the small pipes from an organ may be made to emit the most
curious sounds by passing heavy and light gases through them; in these
experiments bags containing the gases should be employed, which may
drive air, oxygen, carbonic acid, or hydrogen, through the organ pipes
at precisely the same pressure.
[Page 111]
_Seventh Experiment._
One of those toys called "The Squeaking Toy" affords another and
ridiculous example of the effect of hydrogen on sound, when it is used
in a jar containing this gas. (Fig. 114.)
[Illustration: Fig. 114. The squeaking toy, used in a jar of hydrogen.]
_Eighth Experiment._
An accordion played in a large receptacle containing hydrogen gas
demonstrates still more clearly what would be the effect of an orchestra
shut up in a room containing a mixture of a considerable portion of
hydrogen with air, as the former, like nitrogen, is not a poison, and
only kills in the absence of oxygen gas.
_Ninth Experiment._
Some very amusing experiments with balloons have been devised by Mr.
Darby, the eminent firework manufacturer, by which they are made to
carry signals of three kinds, and thus the motive or ascending power may
be utilized to a certain extent.
Mr. Darby's attention was first directed to the manufacture of a good,
serviceable, and cheap balloon, which he made of paper, cut with
mathematical precision; the gores or divisions being made equal, and
when pasted together, strengthened by the insertion of a string at the
juncture; so that the skeleton of the balloon was made of string, the
whole terminating in the neck, which was further stiffened with calico,
and completed when required by a good coating of boiled oil. These
balloons are about nine feet high and five feet in diameter in the
widest part, exactly like a pear, and tapering to the neck in the most
graceful and elegant manner. They retain the hydrogen gas remarkably
well for many hours, and do not leak, in consequence of the paper of
which they are made being well selected and all holes stopped, and also
from the circumstance of the pressure being so well distributed over the
interior by the almost mathematical precision with which they are cut,
and the careful preparation of the paper with proper varnish. One of
their greatest recommendations is cheapness; for whilst a gold-beater's
skin balloon of the same size would cost about 5_l._, these can be
furnished at 5_s._ each in large quantities.
A balloon required to carry one or more persons must be constructed of
the best materials, and cannot be too carefully made; it is therefore a
somewhat costly affair, and as much as 200_l._, 500_l._, and even
1000_l._ have been expended in the construction of these aerial
chariots.
The chief points requiring attention are:--first, the quality of the
silk; secondly, the precision and scrupulous nicety required in cutting
[Page 112] out and joining the gores; thirdly, the application of a good
varnish to fill up the pores of the silk, which must be insoluble in
water, and sufficiently elastic not to crack.
The usual material is Indian silk (termed Corah silk), at from 2_s._ to
2_s._ 6_d._ per yard.
The _gores_ or parts with which the balloon is constructed require, as
before stated, great attention; it being a common saying amongst
aeronauts, "_that a cobweb will hold the gas if properly shaped_" the
object being to diffuse the pressure equally over the whole bag or
balloon.
The varnish with which the silk is rendered air-tight can be made
according to the private recipe of Mr. Graham, an aeronaut, who states
that he uses for this purpose two gallons of linseed oil (boiled), two
ditto (raw), and four ounces of beeswax; the whole being simmered
together for one hour, answers remarkably well, and the varnish is tough
and not liable to crack.
For repairing holes in a balloon, Mr. Graham recommends a cement
composed of two pounds of black resin and one pound of tallow, melted
together, and applied on pieces of varnished silk to the apertures.
The actual cost of a balloon will be understood from information also
derived from Mr. Graham. His celebrated "Victoria Balloon," which has
passed through so many hairbreadth escapes, was sixty-five feet high,
and thirty-eight feet in diameter in the broadest part; and the
following articles were used in its construction:--
£ _s._ _d._
1400 yards of Corah silk, at 2_s._ 6_d._ per yard 175 0 0
The netting weighed 70 lbs. 20 0 0
Extra ropes weighed 20 lbs. at 2_s._ per lb. 2 0 0
The car weighed 25 lbs. 7 0 0
Varnish, wages, &c. 16 0 0
-------------
£220 0 0
Thirty-eight thousand cubic feet of coal gas were required to fill this
balloon, charged by one company 20_l._, by others from 9_l._ to 10_l._;
and eight men were required to hold the inflated baggy monster.
Such a balloon as described above is a mere soap bubble when compared
with the "New Aerial Ship" now building in the vicinity of New York; the
details are so practical and interesting, that we quote nearly the whole
account of this mammoth or Great Eastern amongst balloons, as given in
the _New York Times_.
"An experiment in scientific ballooning, greater than has yet been
undertaken, is about to be tried in this city. The project of
crossing the Atlantic Ocean with an air-ship, long talked of, but
never accomplished, has taken a shape so definite that the apparatus
is already prepared and the aeronaut ready to undertake his task.
"The work has been conducted quietly, in the immediate vicinity of
New York, since the opening of spring. The new air-ship, which has
[Page 113] been christened the City of New York, is so nearly
completed, that but few essentials of detail are wanting to enable
the projectors to bring it visibly before the public.
"The aeronaut in charge is Mr. T. S. C. Lowe, a New Hampshire man,
who has made thirty-six balloon ascensions.
"The dimensions of the City of New York so far exceed those of any
balloon previously constructed, that the bare fact of its existence
is notable. Briefly, for so large a subject, the following are the
dimensions:--Greatest diameter, 130 feet; transverse diameter, 104
feet; height, from valve to boat, 350 feet; weight, with outfit,
3½ tons; lifting power (aggregate), 22½ tons; capacity of gas
envelope, 725,000 cubic feet.
"The City of New York, therefore, is nearly five times larger than
the largest balloon ever before built. Its form is that of the usual
perpendicular gas-receiver, with basket and lifeboat attached.
"Six thousand yards of twilled cloth have been used in the
construction of the envelope. Reduced to feet, the actual
measurement of this material is 54,000 feet--or nearly 11 miles.
Seventeen of Wheeler and Wilson's sewing machines have been employed
to connect the pieces, and the upper extremity of the envelope,
intended to receive the gas-valve, is of triple thickness,
strengthened with heavy brown linen, and sewed in triple seams. The
pressure being greatest at this point, extraordinary power of
resistance is requisite. It is asserted that 100 women, sewing
constantly for two years, could not have accomplished this work,
which measures by miles. The material is stout and the stitching
stouter.
"The varnish applied to this envelope is a composition the secret of
which rests with Mr. Lowe. Three or four coatings are applied, in
order to prevent leakage of the gas.
"The netting which surrounds the envelope is a stout cord,
manufactured from flax expressly for the purpose. Its aggregate
strength is equal to a resistance of 160 tons, each cord being
capable of sustaining a weight of 400 lbs. or 500 lbs.
"The basket which is to be suspended immediately below the balloon
is made of rattan, is 20 feet in circumference and 4 feet deep. Its
form is circular, and it is surrounded by canvas. This car will
carry the aeronauts. It is warmed by a lime-stove, an invention of
Mr. O. A. Gager, by whom it was presented to Mr. Lowe. A lime-stove
is a new feature in air voyages. It is claimed that it will furnish
heat without fire, and is intended for a warming apparatus only. The
stove is 1½ feet high, and 2 feet square. Mr. Lowe states that he
is so well convinced of the utility of this contrivance, that he
conceives it to be possible to ascend to a region where water will
freeze, and yet keep himself from freezing. This is to be tested.
"Dropping below the basket is a metallic lifeboat, in which is
placed an Ericsson engine. Captain Ericsson's invention is therefore
to be tried in mid-air. Its particular purpose is the control of a
propeller, rigged upon the principle of the screw, by which it is
proposed to obtain [Page114] a regulating power. The application of
the mechanical power is ingeniously devised. The propeller is fixed
in the bow of the lifeboat, projecting at an angle of about
forty-five degrees. From a wheel at the extremity twenty fans
radiate. Each of these fans is 5 feet in length, widening gradually
from the point of contact with the screw to the extremity, where the
width of each is 1½ feet. Mr. Lowe claims that by the application of
these mechanical contrivances his air-ship can be readily raised or
lowered, to seek different currents of air; that they will give him
ample steerage way, and that they will prevent the rotatory motion
of the machine. In applying the principle of the fan, he does not
claim any new discovery, but simply a practical development of the
theory advanced by other aeronauts, and partially reduced to
practice by Charles Green, the celebrated English aeronaut.
"Mr. Lowe contends that the application of machinery to aerial
navigation has been long enough a mere theory. He proposes to reduce
the theory to practice, and see what will come of it. It is
estimated that the raising and lowering power of the machinery will
be equal to a weight of 300 lbs., the fans being so adjusted as to
admit of very rapid motion upward or downward. As the loss of three
or four pounds only is sufficient to enable a balloon to rise
rapidly, and as the escape of a very small portion of the gas
suffices to reduce its altitude, Mr. Lowe regards this systematic
regulator as quite sufficient to enable him to control his movements
and to keep at any altitude he desires. It is his intention to
ascend to a height of three or four miles at the start, but this
altitude will not be permanently sustained. He prefers, he says, to
keep within a respectable distance of mundane things, where 'he can
see folks.' It is to be hoped his machinery will perform all that he
anticipates from it. It is a novel affair throughout, and a variety
of new applications remain to be tested. Mr. Lowe, expressing the
utmost confidence in all the appointments of his apparatus, assured
us that he would certainly go, and, as certainly, would go into the
ocean, or deliver a copy of Monday's _Times_ in London on the
following Wednesday. He proposes to effect a landing in England or
France, and will take a course north of east. A due easterly course
would land him in Spain, but to that course he objects. He hopes to
make the trip from this city to London in forty-eight hours,
certainly in sixty-four hours. He scouts the idea of danger, goes
about his preparations deliberately, and promises himself a good
time. As the upper currents, setting due east, will not permit his
return by the same route, he proposes to pack up the City of New
York, and take the first steamer for home.
"The air-ship will carry weight. Its cubical contents of 725,000
feet of gas suffice to lift a weight of 22½ tons. With outfit
complete its own weight will be 3½ tons. With this weight 19 tons of
lifting power remain, and there is accordingly room for as many
passengers as will care to take the venture. We understand, however,
that the company is limited to eight or ten. Mr. Lowe provides sand
for ballast, regards his chances of salvation as exceedingly
favourable, [Page 115] places implicit faith in the strength of his
netting, the power of his machinery, and the buoyancy of his
lifeboat, and altogether considers himself secure from the hazard of
disaster. If he accomplish his voyage in safety, he will have done
more than any air navigator has yet ventured to undertake. If he
fail, the enterprise sinks the snug sum of 20,000 dollars. Wealthy
men who are his backers, sharing his own enthusiasm, declare failure
impossible, and invite a patient public to wait and see."
A night ascent witnessed at any of the public gardens is certainly a
stirring scene, particularly if the wind is rather high. On approaching
the balloon, swayed to and fro by the breeze, it seems almost capable of
crushing the bold individual who would venture beneath it; seen as a
large dark mass in the yet dimly-lighted square, it appears to be
incapable of control; when the inflation is completed, the aeronaut, all
importance, seats himself in the car, and blue lights, with other
fireworks, display the victim who is to make a "last ascent," or perhaps
_descent_. Finally the word is given, the ropes are cast off, and the
bulky chariot rises majestically to the sound of the National Anthem.
The crowd see no more, but the next day's _Times_ reports the end of the
aerial journey.
Balloons can never be of any permanent value as means of locomotion
until they can be steered; and this is a problem, the solution of which
is something like _perpetual motion_. In the first place, a balloon of
any size exposes an enormous surface to the pressure and force of the
winds; and when we consider that they move at the rate of from three to
eighty miles per hour, it will be understood that the fabric of the
balloon itself must give way in any attempt to tear, work, or pull it
against such a force. Secondly and lastly, the power has not yet been
created which will do all this without the inconvenience of being so
_heavy_ that the steering engine fixes the balloon steadily to the earth
by its obstinate gravity. When engines of power are constructed without
the aeronaut's obstacle of weight--when balloons are made of thin copper
or sheet-iron, then we may possibly hear of the voyage of the good ship
_Aerial_, bound for any place, and quite independent of dock, port, and
the host of dues (_quere_), which the sea-going ships have to disburse.
It is, however, gratifying to the zeal and perseverance of those who
dream of aerial navigation, to know that a balloon is not quite useless;
and here we may return to the consideration of Mr. Darby's signals,
which are of various kinds, and intended to appeal to the senses by
night as well as by day; and first, by _audible sounds_. Such means have
long been recognised, from the ancient float and bell of the "Inchcape
Rock," to the painful minute-gun at sea, or the shrill railway whistle
and detonating signals employed to prevent the horrors of a collision
between two trains. The signal sounds are produced by the explosion of
shells capable of yielding a report equal to that of a six-pounder
cannon, and they are constructed in a very simple manner. A ball,
composed of wood or copper, and made up by screwing together the two
hemispheres, is attached to a shaft or tail of cane or lance-wood,
properly feathered like an arrow; at the side opposite to that of the
arrow--viz., at its antipodes, is placed a slight protuberance
[Page 116]containing a minute bulb of glass filled with oil of vitriol, and
surrounded with a mixture of chlorate of potash and sugar, the whole
being protected with gutta-percha, and communicating by a touch-hole
with the interior, which is of course filled with gunpowder. These
shells are attached to a circular framework by a strong whipcord, which
passes to a central fuse, and are detached one after the other as the
slow fuse (made hollow on the principle of the argand lamp) burns
steadily away. Directly a shell falls to the ground, the little bulb
containing the oil of vitriol breaks, and the acid coming in contact
with the chlorate of potash and sugar, causes the mixture to take fire,
when the gunpowder explodes. During the siege of Sebastopol many similar
mines were prepared by the Russians in the earth, so that when an
unfortunate soldier trod upon the spot, the concealed mine blew up and
seriously injured him; such petty warfare is as bad as shooting
sentries, and a cruel application of science, that unnecessarily
increases the miseries of war without producing those grand results for
which the truly great captains, Wellington and Napoleon, only warred.
(Fig. 115.)
[Illustration: Fig. 115. A. Ring attached to balloon, carrying an
hexagonal framework with six shells. B. Hollow fuse, which burns slowly
up to the strings, and detaches each shell in succession. C. Section of
shell. The shaded portion represents the gunpowder.]
[Illustration: Fig. 116. The bill distributor, consisting of three
hollow fuses, with bills attached in packets.]
The bill distributor consists of a long piece of wood, to which are
[Page 117] attached a number of hollow fuses, with packets of bills,
protected from being burned or singed by a thin tin plate; 10,000 or
20,000 bills can thus be delivered, and the wind assists in scattering
them, whilst the balloon travels over a distance of many miles. It must
be recollected that in each case the shells and the bills are detached
by the string burning away as the fire creeps up from the fuse. (Fig.
116.)
Another most ingenious arrangement, also prepared by Mr. Darby, is
termed by the inventor, the "Land and Water Signal," and may be thus
described:--A short hollow ball of gutta-percha, or other convenient
material, five or six inches in diameter, and filled with printed bills,
or the information, whatever it may be, that is required to be sent, is
attached to a cap to which a red flag, having the words "_Open the
shell_" and four cross sticks, canes, or whalebones with bits of cork at
equal distances, are fitted. The whole is connected by a string to the
fuse as before described. These signals are adapted for land and water:
in either case they fall upright, and in consequence of the sticks
projecting out they float well in the water, and can be seen by a
telescope at a distance of three miles. (Fig. 117.) Many of these
signals were sent away by Mr. Darby from Vauxhall; one was picked up at
Harwich, another at Brighton, a third at Croydon; in the latter case it
was found by a cottager, who, fearing gunpowder and combustibles, did
not examine the shell, but having mentioned the circumstance to a
gentleman living near him, they agreed to cut it open; and intelligence
of their arrival, in this and the other cases, was politely forwarded to
Mr. Darby at Vauxhall Gardens.
[Illustration: Fig. 117. The land and water signal, which remains
upright on land, or floats on the surface of water. A. The water-tight
gutta-percha shell, containing the message or information. B B B. Sticks
of cane to keep the flag in an upright position; at the ends are
attached cork bungs.]
Balloons, like a great many other clever inventions, have been despised
by military men as new-fangled expedients, toys, which may do very well
to please the gaping public, but are and must be useless in the field.
Over and over again it has been suggested that a balloon corps for
observation should be attached to the British army, but the scheme
has [Page 118] been rejected, although the expense of a few yards of silk
and the generation of hydrogen gas would be a mere bagatelle as compared
with the transport and use of a single 32-pounder cannon. The antiquated
notions of octogenarian generals have, however, received a great shock
in the fact that the Emperor Napoleon III. was enabled, by the
assistance of a captive balloon, to watch the movements and dispositions
of the Austrian troops; and with the aid of the information so obtained,
he made his preparations, and was rewarded by the victory of Solferino;
and as soon as the battle was over Napoleon III. occupied at Cavriana
the very room and ate the dinner prepared for his adversary, the Emperor
Francis Joseph.
Over and over again the most excellent histories have
been written of aerostation, but they all tend to one truth, and that
is, the great danger and risk of such excursions; and to enable our
readers to form their own judgment, a chronological list of some of the
most celebrated aeronauts, &c., is appended.
1675. Bernair attempted to fly--_killed_.
1678. Besnier attempted to fly.
1772. L'Abbé Desforges announced an aerial chariot.
1783. Montgolfier constructed the first air balloon.
" Roberts _frères_, first gas balloon, destroyed by the peasantry
of Geneva, who imagined it to be an evil spirit or the moon.
1784. Madame Thiblé, the first lady who was ever up in the clouds;
she ascended 13,500 feet.
" Duke de Chartres, afterwards _Egalité_ Orleans, travelled 135
miles in five hours in a balloon.
" Testu de Brissy, equestrian ascent.
" D'Achille, Desgranges, and Chalfour--Montgolfier balloon.
" Bacqueville attempted a flight with wings.
" Lunardi--gas balloon.
" Rambaud--Montgolfier balloon, which was burnt.
" Andreani--Montgolfier balloon.
1785. General Money--gas balloon, fell into the water, and not rescued
for six hours.
" Thompson, in crossing the Irish Channel, was run into with the
bowsprit of a ship whilst going at the rate of twenty miles
per hour.
" Brioschi--gas balloon ascended too high and burst the balloon;
the hurt he received ultimately caused his _death_.
" A Venetian nobleman and his wife--gas balloon--_killed_.
" Pilatre de Rozier and M. Romain--gas balloon took fire--both
_killed_.
1806. Mosment--gas balloon--_killed_.
" Olivari--Montgolfier balloon--_killed_.
1808. Degher attempted a flight with wings.
1812. Bittorf--Montgolfier balloon--_killed_.
1819. Blanchard, Madame--gas balloon--_killed_. [Page 119]
1819. Gay Lussac--gas balloon, ascended 23,040 feet above the level of
the sea. Barometer 12.95 inches; thermometer 14.9 Fah.
" Gay Lussac and Biot--gas balloon for the benefit of science.
Both philosophers returned safely to the earth.
1824. Sadler--gas balloon--_killed_.
" Sheldon--gas balloon.
" Harris--gas balloon--_killed_.
1836. Cocking--parachute from gas balloon--_killed_.
1847. Godard--Montgolfier balloon fell into and extricated from the
Seine.
1850. Poitevin, a successful French aeronaut.
" Gale, Lieut.--gas balloon--_killed_.
" Bixio and Barral--gas balloon.
" Graham, Mr. and Mrs.--gas balloon.--Serious accident ascending
near the Great Exhibition in Hyde Park.
" Green, the most successful living aeronaut of the present time.
Of the 41 persons enumerated, 14 were killed, and nearly all the
aeronauts met with accidents which might have proved fatal.
[Illustration: Fig. 118. Flying machine (_theoretical_).]
[Page 120]
_Tenth Experiment._
Soap bubbles blown with hydrogen gas ascend with great rapidity, and
break against the ceiling; if interrupted in their course with a lighted
taper they burn with a slight yellow colour and dull report.
_Eleventh Experiment._
By constructing a pewter mould in two halves, of the shape of a
tolerably large flask, a balloon of collodion may be made by pouring the
collodion _inside_ the pewter vessel, and taking care that every part is
properly covered; the pewter mould may be warmed by the external
application of hot water, so as to drive off the ether of the collodion,
and when quite dry the mould is opened and the balloon taken out. Such
balloons may be made and inflated with hydrogen by attaching to them a
strip of paper, dipped in a solution of wax and phosphorus, and
sulphuret of carbon; as the latter evaporates, the phosphorus takes fire
and spreads to the balloon; which burns with a slight report. The pewter
mould must be very perfectly made, and should be bright inside; and if
the balloons are filled with oxygen and hydrogen, allowing a sufficient
excess of the latter to give an ascending power, they explode with a
loud noise directly the fire reaches the mixed gases.
_Twelfth Experiment._
In a soup-plate place some strong soap and water; then blow out a number
of bubbles with a mixture of oxygen and hydrogen; a loud report occurs
on the application of flame, and if the room is small the window should
be placed open, as the concussion of the air is likely to break the
glass.
_Thirteenth Experiment._
Any noise repeated at least thirty-two times in a second produces a
musical sound, and by producing a number of small explosions of hydrogen
gas inside glass tubes of various sizes, the most peculiar sounds are
obtained. The hydrogen flame should be extremely small, and the glass
tubes held over it may be of all lengths and diameters; a trial only
will determine whether they are fit for the purpose or not.
_Fourteenth Experiment._
Flowers, figures, or other designs, may be drawn upon silk with a
solution of nitrate of silver, and the whole being moistened with water,
is exposed to the action of hydrogen gas, which removes the oxygen from
the silver, and reduces it to the metallic state.
In like manner designs drawn with a solution of chloride of gold are
produced in the metallic state by exposure to the action of hydrogen
gas. Chloride of tin, usually termed muriate of tin, may also be reduced
in a similar manner, care being taken in these experiments that [Page
121] the fabric upon which the letters, figures, or designs are painted
with the metallic solution be kept quite damp whilst exposed to the
hydrogen gas.
_Fifteenth Experiment._
A mixture of two volumes of hydrogen with one volume of oxygen explodes
with great violence, and produces two volumes of steam, which condense
against the sides of the strong glass vessel, in which the experiment
may be made, in the form of water. As the apparatus called the Cavendish
bottle, by which this experiment only may be safely performed, is
somewhat expensive, and requires the use of an air-pump, gas jars with
stop-cocks, and an electrical machine and Leyden jar, other and more
simple means may be adopted to show the combination of oxygen and
hydrogen, and formation of water.
If a little alcohol is placed in a cup and set on fire, whilst an empty
cold gas jar is held over the flame, an abundant deposition of moisture
takes place from the combustion of the hydrogen of the spirits of wine.
Alcohol contains six combining properties of hydrogen, with four of
charcoal and two of oxygen. If a lighted candle, or an oil, camphine,
Belmontine, or gas flame, is placed under a proper condenser, large
quantities of water are obtained by the combustion of these substances.
(Fig. 119.)
[Illustration: Fig. 119. A. A burning candle, or oil or gas lamp. Copper
head and long pipe fitting into B C, the receiver from which the
condensed water drops into D. E E. Two corks fitted, between which is
folded some wet rag.]
[Page 122]
_Sixteenth Experiment._
During the combustion of a mixture of two volumes of hydrogen with one
of oxygen, an enormous amount of heat is produced, which is usefully
applied in the arrangement of the oxy-hydrogen blowpipe. The flame of
the mixed gases produces little or no light, but when directed on
various metals contained in a small hole made in a fire brick, a most
intense light is obtained from the combustion of the metals, which is
variously coloured, according to the nature of the substances employed.
With cast-iron the most vivid scintillations are obtained, particularly
if after having fused and boiled the cast-iron with the jet of the two
gases, one of them, viz., the hydrogen, is turned off, and the oxygen
only directed upon the fused ball of iron, then the carbon of the iron
burns with great rapidity, the little globule is enveloped in a shower
of sparks, and the whole affords an excellent notion of the principle of
Bessemer's patent method of converting cast-iron at once into pure
malleable iron, or by stopping short of the full combustion of carbon,
into cast-steel.
The apparatus for conducting these experiments is of various kinds, and
different jets have been from time to time recommended on account of
their alleged safety. It may be asserted that all arrangements proposed
for burning any quantity of the _mixed_ gases are extremely dangerous:
if an explosion takes place it is almost as destructive as gunpowder,
and should no particular damage be done to the room, there is still the
risk of the sudden vibration of the air producing permanent deafness. If
it is desired to burn the _mixed_ gases, perhaps the safest apparatus is
that of Gurney; in this arrangement the mixed gases bubble up through a
little reservoir of water, and thus the gas-holder--viz., a bladder, is
cut off from the jet when the combustion takes place. (Fig. 120.) This
jet is much recommended by Mr. Woodward, the highly respected President
of the Islington Literary and Scientific Institution, and may be fitted
up to show the phenomena of polarized light, the microscope, and other
interesting optical phenomena.
[Illustration: Fig. 120. Gurney's jet. A. Pipe with stop-cock leading
from the gas-holder. B. The little reservoir of water through which the
mixed gases bubble. C. The jet where the gases burn. D. Cork, which is
blown out if the flame recedes in the pipe, C.]
Mr. Woodward states, that a series of experiments, continued during many
years, has proved, that while the bladder containing the mixed gases is
under pressure, the flame cannot _be made_ to pass the safety chambers,
and consequently an explosion is impossible; and even if through extreme
carelessness or design, as by the removal of pressure or the contact of
a spark with the bladder, an explosion occurs, it can produce no other
than the momentary effect of the alarm occasioned by the report; [Page
123] whereas, when the gases are used in separate bags under a pressure
of two or three half hundredweights, if the pressure on one of the bags
be accidentally removed or suspended, the gas from the other will be
forced into it, and if not discovered in time, will occasion an
explosion of a very dangerous character; or if through carelessness one
of the partially emptied bags should be filled up with the wrong gas,
effects of an equally perilous nature would ensue.
[Illustration: Fig. 121. A. The bladder of mixed gases, pressed by the
board, B B, attached by wire supports to another board, C C, which
carries the weights, D D. E E. Pipe to which the bladder, A, is screwed,
and when A is emptied, it is re-filled from the other bladder, R. F F F.
Pipe conveying mixed gases to the lantern, G G, where they are burnt
from a Gurney's jet, H.]
In the oxy-hydrogen blowpipe usually employed, the gases are kept quite
separate, either in gasometers or gas bags, and are conveyed by distinct
pipes to a jet of very simple construction, devised by the late
Professor Daniell, where they mix in very small volumes, and are burnt
at once at the mouth of the jet. (Fig. 122.)
[Illustration: Fig. 122. Daniell's jet. O O. The stop-cock and pipe
conveying oxygen, and fitting inside the larger tube H H, to which is
attached a stop-cock, H, connected with the hydrogen receiver. A. The
orifice near which the gases mix, and where they are burnt.]
The gases are stored either in copper gasometers or in air-tight bags of
Macintosh cloth, capable of containing from four to six cubic feet of
gas, and provided with pressure boards. The boards are loaded with two
or three fifty-six pound weights to force out the gas with sufficient
[Page 4] pressure, and of course must be equally weighted; if any change
of weight is made, the stop-cocks should be turned off and the light put
out, as the most disastrous results have occurred from carelessness in
this respect. (Fig. 123.)
[Illustration: Fig. 123. Gas bag and pressure boards.]
The oxy-hydrogen jet is further varied in construction by receiving the
gases from separate reservoirs, and allowing them to mix in the upper
part of the jet, which is provided with a safety tube filled with
circular pieces of wire gauze. (Fig. 124.) With this arrangement a most
intense light is produced, called the Drummond or lime light, and coal
gas is now usually substituted for hydrogen.
[Illustration: Fig. 124. A A. Board to which B B is fixed. O. Oxygen
pipe. H. Hydrogen pipe. C C. Space filled with wire gauze. D. Lime
cylinder.]
[Page 125]
_Seventeenth Experiment._
There are many circumstances that will cause the union of oxygen and
hydrogen, which, if confined by themselves in a glass vessel, may be
preserved for any length of time without change; but if some powdered
glass, or any other finely-divided substance with sharp points, is
introduced into the mixed gases at a temperature not exceeding 660°
Fahrenheit, then the gases silently unite and form water.
This curious mode of effecting their combination is shown in a still
more interesting manner by perfectly clear platinum foil, which if
introduced into the mixed gases gradually begins to glow, and becoming
red-hot causes the gases to explode. Or still better, by the method
first devised by Dobereiner, in 1824, by which finely prepared spongy
platinum--_i.e._, platinum in a porous state, and exposing a large
metallic surface--is almost instantaneously heated red-hot by contact
with the mixed gases. When this fact became known, it was further
applied to the construction of an instantaneous light, in which hydrogen
was made to play upon a little ball of spongy platinum, and immediately
kindled. These Dobereiner lamps were possessed by a few of the curious,
and would no doubt be extensively used if the discovery of phosphorus
had not supplied a cheaper and more convenient fire-giving agent. When
the spongy platinum is mixed with some fine pipeclay, and made into
little pills, they may (after being slightly warmed) be introduced into
a mixture of the two gases, and will silently effect their union. The
theory of the combination is somewhat obscure, and perhaps the simplest
one is that which supposes the platinum sponge to act as a conductor of
electric influences between the two sets of gaseous particles; although,
again, it is difficult to reconcile this theory with the fact that
powdered glass at 660°, a bad conductor of electricity, should effect
the same object. The result appears to be due to some effects of surface
by which the gases seem to be condensed and brought into a condition
that enables them to abandon their gaseous state and assume that of
water.
When Sir H. Davy invented the safety-lamp, he was aware that, in certain
explosive conditions of the air in coal mines, the flame of the lamp was
extinguished, and in order that the miner should not be left in the
dreary darkness and intricacies of the galleries without some means of
seeing the way out, he devised an ingenious arrangement with thin
platinum wire, which was coiled round the flame of the lamp, and fixed
properly, so that it could not be moved from its proper place by any
accidental shaking. When the flame of the safety-lamp, having the
platinum wire attached, was accidentally extinguished by the explosive
atmosphere in which it was burning, the platinum commenced glowing with
an intense heat, and continued to emit light as long as it remained in
the dangerous part of the mine. Sir H. Davy warned those who might use
the platinum to take care that no portion of the thin wire passed
_outside_ the wire gauze, for the obvious reason that, if ignited
outside the wire gauze protector, it would inflame the fire-damp.
[Illustration: Fig. 125. P P. Two platinum plates connected with wires
to the cups. The wires are passed through holes in the finger-glass, B
B, and are fixed perfectly steady by pouring in cement composed of resin
and tallow to the line L L. Two glass tubes filled with water acidulated
with sulphuric acid, and placed over the platinum plates in
finger-glass, which also contains dilute sulphuric acid to improve the
conducting power of the water. The wires of the battery are placed in
the cups, and the arrows show the direction of the current of
electricity.]
[Page 126]
_Eighteenth Experiment._
Water is decomposed by passing a current of voltaic electricity through
it by means of two platinum plates, which may be connected with a
ten-cell Grove's battery. The gases are collected in separate tubes, and
the experiment offers one of the most instructive illustrations of the
composition of water. (Fig. 125.)
There is a current of electricity passing from and between two platinum
plates decomposing water, offering the converse of the Dobereiner
experiment, and highly suggestive of the probability of the theory
already advanced in explanation of the singular combination of oxygen
and hydrogen in the presence of clean platinum foil, and more especially
when we consider the operation of Grove's gas battery, in which a
current of electricity is produced by pieces of platinum foil covered
with finely-divided platinum, called platinum black; each piece is
contained in a separate glass tube filled alternately with oxygen and
hydrogen, and by connecting a great number of these tubes a current of
electricity is obtained, whilst the oxygen and hydrogen are slowly
absorbed and disappear, having combined and formed water, although
placed in separate glass tubes. (Fig. 126.)
The analysis of water is shown very perfectly on the screen by fitting
up some very small tubes and platinum wires in the same manner as shown
in fig. 125. The vessel in which the tubes and wires are contained with
the dilute sulphuric acid must be small, and arranged so as to pass
nicely into the space usually filled by the picture in an ordinary magic
lantern, or, still better, in one lighted by the oxy-hydrogen or lime
light. If the dilute acid is coloured with a little solution of indigo,
the gradual displacement of the fluid by the production of the two gases
is very perfectly developed on the screen when the small voltaic battery
is attached to the apparatus; and of course a large number of persons
may watch the experiment at the same time.
With respect to the application of the light produced from a jet of the
[Page 127] mixed gases thrown upon a ball of lime, it may be stated that
for many years the dissolving view lanterns and other optical effects
have been produced with the assistance of this light; and more lately
Major Fitzmaurice has condensed the mixed gases in the old-fashioned oil
gas receivers, and projected them on a ball of lime; and it was this
light thrown from many similar arrangements that illuminated the British
men-of-war when Napoleon III. left her Majesty's yacht at night in the
docks at Cherbourg.
[Illustration: Fig. 126. Grove's gas battery consists of tubes
containing oxygen and hydrogen alternately, and having a thin piece of
platinum foil, P, inserted by the blowpipe in each glass tube. The foil
hangs down the full length of the interior of the glass. Each pair of
tubes is contained in a little glass tumbler containing some dilute
sulphuric acid, and the hydrogen tube, H, of one pair, is connected with
the oxygen tube, O, of the next. W W. The terminal wires of the series.]
Mr. Sykes Ward, of Leeds, has also proposed a most simple and excellent
application of the oxy-hydrogen light for illumination _under_ the
[Page 128] surface of water, and for the convenience of divers, who are
frequently obliged to cease their operations in consequence of the want
of light. Mr. Ward's submarine lamp consists of a series of very strong
copper tubes, which are filled with the mixed gases by means of a
force-pump; and in order to prevent the lamp being extinguished, it
burns under _double_ glass shades, which are desirable in order to
prevent the glass immediately next to the light cracking by contact with
the cold water.
[Illustration: Fig. 127. Cherbourg.]
The author tried this lamp at Ryde, and although the coast-guards
objected to the production of a brilliant light at night, which they
stated might be mistaken for a signal and would cause some confusion
amongst the war vessels in the immediate neighbourhood, enough
experiments were made, to show that the Ward lamp would burn for a
considerable time under water, and could be kept charged with the gas by
means of a process that was easily workable in the boat. The gases were
taken out mixed in gas bags, and pumped into the reservoir when
required. With a much larger reservoir greater results could be
obtained; and if nautilus diving bells are to be used in modern warfare,
they will require a powerful light to show them their prey, so that they
may attach the explosives which are to blow great holes in the
men-of-war.
[Illustration: Fig. 128. A A. Tube reservoir to hold the mixed gases. B.
The jet and lime ball. D. The first glass shade, held down by a cap and
screw. C. The second glass shade. E E. The handle by which it is lowered
into the water.]
[Illustration: Fig. 129. Submarine lamp.]
[Page 129]