| Bunsen flame. | Luminous flame.
+-----------+-----------+-------------+----------
| Inner. | Outer. | Inner. | Outer.
+-----------+-----------+-------------+----------
Nitrogen | 75.75 | 79.17 | 77.52 | 69.41
Water vapor | 13.47 | 14.29 | 11.80 | 19.24
Carbon dioxide | 2.99 | 5.13 | 4.93 | 8.38
Carbon monoxide | 3.69 | Nil. | 2.45 | 2.58
Marsh gas | 0.51 | 0.31 | 0.95 | 0.39
Acetylene | 0.04 | Nil. | 0.27 | Nil.
Hydrogen | 3.55 | 0.47 | 2.08 | Nil.
+-----------+-----------+-------------+----------
| 100.00 | 100.00 | 100.00 | 100.00
These figures are of the greatest interest, as they show conclusively
that the extreme top of the Bunsen flame is the only portion of the
flame which can be used for heating a solid substance without
liberating deleterious gases; and this corroborates the previous
experiment on the gases in the outer zone of a flame, which showed
that the outer zone of a Bunsen flame is the only place where complete
combustion is approached.
Moreover, this sets at rest a question which has been over and over
again under discussion, and that is whether it is better to use a
luminous or a non-luminous flame for heating purposes. Using a
luminous flame, it is impossible to prevent a deposit of carbon, which
is kept by the flame at a red heat on its outer surface, and the
carbon dioxide formed by the complete combustion of the carbon already
burned up in flame is reduced by this back to carbon monoxide, so that
even in the extreme tip of a luminous flame it is impossible to heat a
cool body without giving rise to carbon monoxide, although acetylene
being absent, gas stoves, in which small flat flame burners are used,
have not that subtile and penetrating odor which marks the ordinary
atmospheric burner stove, with the combustion checked just at the
right spot for the formation of the greatest volume of noxious
products.
It is the contact of the body to be heated with the flame before
combustion is complete which gives rise to the greatest mischief; any
cooling of the flame extinguishes a portion of the flame, and the
gases present in the flame at the moment of extinction creep along the
cooled surface and escape combustion.
Dr. Blochmann has shown the composition of the gases in various parts
of the Bunsen flame to be as follows:
Height above tube. |In tube. |1 inch. |2 inch. |3 inch. |Complete
| | | | |combustion
-------------------------------------------------------------------
Air with 100 vols. | | | | |
gas | 253.9 | 284.7 | 284.5 | 484.3 | 608.8
Hydrogen | 48.6 | 36.4 | 17.7 | 16.1 | Nil.
Marsh gas | 39.0 | 40.1 | 28.0 | 5.7 | Nil.
Carbon monoxide | 2.9 | 2.2 | 19.9 | 12.7 | Nil.
Olefiant gas | 4.0 | 3.4 | 2.2 | Nil. | Nil.
Buteylene | 3.0 | 2.5 | 1.6 | Nil. | Nil.
Oxygen | 52.7 | 52.0 | 21.7 | Nil. | Nil.
Nitrogen | 199.1 | 223.8 | 225.9 | 382.4 | 482.3
Carbon dioxide | 0.8 | 3.5 | 13.0 | 41.7 | 62.4
Water vapor | 3.1 | 11.8 | 45.8 | 116.1 | 141.2
-------------------------------------------------------------------
Which results show that it would be impossible to check the flame
anywhere short of the extreme tip (where complete combustion is
approximately taking place), without liberating deleterious products.
I think I have said enough to show that no gas stove, geyser or gas
cooking stove should be used without ample and thorough means of
ventilation being provided, and no trace of the products of combustion
should be allowed to escape into the air; until this is done, the use
of improper forms of stoves will continue to inflict serious injury on
the health of the people using them, and this will gradually result in
the abandonment of gas as a fuel, instead of, as should be the case,
its coming into general use. The English householder is far too prone
to accept what is offered to him, without using his own common sense,
and will buy the article which tickles his eye the most and his pocket
the least, on the bare assurance of the shopkeeper, who is only
anxious to sell; but when he finds that health and comfort are in
jeopardy, and has discarded the gas stove, it will take years of labor
to convince him that it was the misuse of gas which caused the
trouble. Already signs are not wanting that the employers of gas
stoves are beginning to fight shy of them, and I earnestly hope that
the gas managers of the kingdom will bring pressure to bear upon the
stove manufacturers to give proper attention to this all important
question.
So strongly do I feel the importance of this question to the gas world
and the public, that I freely offer to analyze the products of
combustion given off by any gas stove or water heater sent to me at
Greenwich during the next six months, on one condition, and that is
that the results, good, bad, or indifferent, will be published in a
paper before this Society, which has always been in the front when
matters of great sanitary importance to the public had to be taken up.
And if after that the public like to buy forms of apparatus which have
not been certified, it is their own fault; but I do think that the
maker of any stove or geyser which causes a death should be put upon
his trial for manslaughter.
In conclusion, let us consider for a moment what is likely to be the
future of gas during the next half century. The labor troubles, bad as
they are and have been, will not cease for many a weary year. The
victims of imperfect education (more dangerous than none at all, as,
while destroying natural instinct, it leaves nothing in its place)
will still listen and be led by the baneful influence of irresponsible
demagogues, who care for naught so long as they can read their own
inflammatory utterances in the local press, and gain a temporary
notoriety at the expense of the poor fools whose cause they profess to
serve. The natural tendency of this will be that every labor-saving
contrivance that can will be pressed into the gas manager's service;
and that, although coal (of a poorer class than at present used) will
still be employed as a source of gas, the present retort setting will
quickly give way to inclined retorts on the Coze principle; while,
instead of the present wasteful method of quenching the red hot coke,
it will be shot direct into the generator of the water gas plant, and
the water gas carbureted with the benzene hydrocarbons derived from
the smoke of the blast furnace and coke oven, or from the creosote oil
of the tar distiller, by the process foreshadowed in the concluding
sentences of my last lecture. It will then be mixed with the gas from
the retorts, and will supply a far higher illuminant than we at
present possess. In parts of the United Kingdom, such as South Wales,
where gas coal is dear, and anthracite and bastard coals are cheap,
water gas highly carbureted will entirely supplant coal gas, with a
saving of fifty per cent. on the prices now existing in those
districts. While these changes have been going on, and while improved
methods of manufacture have been tending to the cheapening of gas, it
will have been steadily growing in public favor as a fuel; and if in
years to come the generation of electricity should have been so
cheapened as to allow it to successfully compete with gas as an
illuminant, the gas works will still be found as busy as of yore, the
holder of gas shares as contented as to-day; for with a desire for a
purer atmosphere and a white mist instead of a yellow fog, gas will
have largely supplanted coal as a fuel, and gas stoves, properly
ventilated and free from the reproaches I have hurled at them
to-night, will burn a gas far higher in its heating power, far better
in its power of bearing illuminating hydrocarbons, and free from
poisonous constituents.
When the demand for it arises, hydrogen gas can be made as cheaply as
water gas itself, and when time is ripe for a fuel gas for use in the
house, it is hydrogen and not water gas which will form its basis.
With carbureted water gas and 20 per cent. of carbon monoxide we are
still below the limit of danger, but a pure water gas with over 40 per
cent. of the same insidious element of danger will never be tolerated
in our households. Already a patent has been taken by Messrs. Crookes
and Ricarde-Seaver for purifying water gas from carbon monoxide, and
converting it mainly into hydrogen by passing it at a high temperature
through a mixture of lime and soda lime, a process which is chemically
perfect, as the most expensive portion of the material used could be
recovered; but in the present state of the labor market it is not
practical, as for the making of every 100,000 cubic feet of gas,
fifteen tons of material would have to be handled, the cost of labor
alone being sufficient to prevent its being adopted; moreover,
hydrogen can be made far cheaper directly.
From the earliest days of gas making, the manufacture of hydrogen by
the passage of steam over red-hot iron has been over and over again
mooted, and attempted on a large scale, but several factors have
combined to render it futile.
In the first place, for every 478.5 cubic feet of hydrogen made under
perfect theoretical conditions never likely to be obtained in
practice, 56 lb. of iron were converted into the magnetic oxide, and
as there was no ready sale for this article, this alone would prevent
its being used as a cheap source of hydrogen; the next point was that
when steam was passed over the red-hot iron, the temperature was so
rapidly lowered that the generation of gas could only go on for a very
short period, while, finally, the swelling of the mass in the retort
and fusion of some of the magnetic oxide into the side renders the
removal of the spent material almost an impossibility. These
difficulties can, however, be got over. Take a fire clay retort, six
feet long and a foot in diameter, and cap it with a casting bearing
two outlet tubes closed by screw valves, while a similar tube leads
from the bottom of the retort. Inclose this retort by a furnace
chamber of iron lined with fire brick, leaving a space of two feet six
inches round the retort, and connect the top of the furnace chamber
with one opening at the top of the upright retort, while air blasts
lead into the bottom of the furnace chamber, below rocking fire bars,
which start at bottom of the retort, and slope upward, to leave room
for ash holes closed by gas tight covers. The retort is filled with
iron or steel borings, alone if pure hydrogen is required, or cast
into balls with pitch if a little carbon monoxide is not a drawback,
as in foundry work. The furnace chamber is now filled with coke, fed
in through manholes, or hoppers, in the top, and the fuel being
ignited, the blast is turned on, and the mixture of nitrogen and
carbon monoxide passes over the iron, heating it to a red heat, while
the fuel in contact with the retort does the same thing.
When the fuel and retort full of iron are at a cherry-red heat, the
air blast is cut off, and the pipe connecting the furnace and retort,
together with the pipe in connection with the bottom of the retort,
are closed, and steam, superheated by passing through a pipe led round
the retort or interior wall of the furnace, is injected at the bottom
of the red-hot mass of iron, which decomposes it, forming magnetic
oxide of iron and hydrogen, which escapes by the second tube at the
top of the retort, and is led away either to a carbureting chamber if
required for illumination, or direct to the gasholder if wanted as a
fuel. The mass of incandescent fuel in the furnace chamber,
surrounding the retort, keeping up the temperature of retort and iron
sufficiently long to enable the decomposition to be completed.
The hydrogen and steam valves are now closed and the air blast turned
on. The hot carbon monoxide passing over the hot magnetic oxide
quickly reduces it down to metallic iron, which, being in a spongy
condition, acts more freely on the steam during later makes than it
did at first, and being infusible at the temperature employed, may be
used for a practically unlimited period.
What more simple method than this could be desired? Here we have the
formation of the most valuable of all fuel gases at the cost of the
coke and steam used, a gas also which has double the carrying power
for hydrocarbon vapors possessed by coal gas, while its combustion
gives rise to nothing but water vapor.
In this course of lectures I have left much unsaid and undone which I
should have liked to have had time to accomplish, and if I have been
obliged to leave out of consideration many important points, it is the
time at my disposal and not my will which is to blame. And now, in
conclusion, I wish to express my thanks to my assistants, Messrs. J.A.
Foster and J.B. Warden, who have heartily co-operated with me in much
of the work embodied in these lectures.
* * * * *