Almost every boy and girl has seen the big tank near the gas works, and
most of them have wondered what was in it and what it is for. This big
tank is a “holder” in which the gas is stored after it is manufactured.
The giant holders are reservoirs from which gas is constantly being
taken and the quantity on storage constantly replenished, as the
ordinary gas plant never ceases manufacturing its product.
There is little or no danger of an interruption of the supply by reason
of accident, as gas plants are always equipped with duplicate apparatus
for emergencies.]
When Illuminating Gas Was Discovered.
The first practical demonstration of the value of gas made from
coal for lighting was made by a Scotchman--Robert Murdock--who in
1797, after some years of experimenting, fitted up an apparatus in
the workshop of Boulton and Watt, in Birmingham, England, which
successfully lighted a portion of that establishment. The advantages
of this kind of lighting were so apparent that its use was rapidly
extended, although in many instances the people were afraid of it. For
a time this kind of lighting was confined to street lights. One of the
first great structures to be lighted by gas was Westminster Bridge in
London, and great crowds gathered to watch the burning jets nightly. It
was difficult to remove from the minds of the people the belief that
the gas-pipes were filled with fire and the jets were only openings
through which the flame in the pipes escaped. People sometimes touched
the pipes expecting to find them hot, and when the pipes were put in
buildings they made sure that they were placed several feet from the
walls lest the fire in them set fire to the buildings.
The use of illuminating gas for lighting private houses developed quite
slowly because of this fear of the fire in the gas-pipes. This was not
entirely unwarranted, however, because at first the plumbers did not
know, as they do now, how to prevent leakage of gas from the pipes.
The methods of joining the pipes were oftentimes imperfect and, not
realizing the dangers which would follow leaks, causing explosions, the
workmen were often careless in installing the pipes.
The first American house in which gas was used for lighting was the
home of David Mellville at Newport, R. I. Baltimore, Maryland, was the
first American city to use gas for lighting. It was introduced there in
1817.
How Does Gas Get Into the Gas Jet?
If you hold a cool drinking glass over a burning gas jet for a moment,
a film of moisture will form on the inside of the glass and remain
until the tumbler becomes warm, and then disappear. Now, then, you will
remember that water is a mixture of oxygen and hydrogen, and that when
hydrogen is burned in the air, water is formed. It is also true that
whenever water is formed by burning anything, hydrogen is present in
it. You see, therefore, that the gas used for lighting purposes must
contain hydrogen.
Let us now learn something more about what gas is made of. Wet a piece
of glass with a little fresh lime water and hold this over the lighted
gas jet. In a few moments a change takes place in the water. The water
turns somewhat milky. This indicates the presence of carbonic acid gas,
and the formation of carbonic acid gas, when burning is going on, means
the presence of carbon.
From these two experiments we gather that the gas in the jet contains
hydrogen and carbon. All kinds of illuminating gas contain these two
substances. Sometimes there are small quantities of other substances
present, but the value of gas for lighting depends on hydrogen and
carbon.
We have already learned about hydrogen, but it would be well to
re-learn about carbon.
Carbon is an element, and an extremely important one, for a large part
of the composition of every living thing is carbon. It is found in
more compounds than any other element. Almost pure carbon can easily
be obtained by heating a piece of wood, in a covered utensil, until it
is turned into charcoal. Charcoal, which is black, is composed almost
entirely of carbon. It is a very interesting product in all ways; in
connection with gas we are particularly interested in the fact that
carbon will burn when heated in the air or in oxygen.
Charcoal is very much like hard coal, both being formed in practically
the same way. Ages of years ago many large forests of trees were buried
under a layer of soil and rocks, during changes that occurred in the
earth’s surface, and the hot inside earth slowly heated the wood, until
almost nothing was left but the carbon.
[Illustration: WHERE THE GAS IS TAKEN FROM THE COAL