June 14, 1873.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
1003 
SOCIETY OF ARTS. 
Recent Processes for the Manufacture of Gas 
for Illuminating Purposes.* 
by t. wills' f.c.s. 
During the last two years various causes have com¬ 
bined to make the time a very favourable one for the 
introduction of new schemes for the manufacture of gas. 
Amongst these causes the following may he mentioned:— 
First, the fear (although to a great extent perhaps ground¬ 
less, yet, nevertheless, frequently expressed) that our supply 
of coal will be gradually lessening, and that, at no very 
distant date, it will become so curtailed as to increase its 
value to a formidable extent; second, the tendency of 
the coal market to push the price of coal up, to an extent 
out of all proportion to the necessity, has also created 
uneasiness ; and third, partly in consequence of this, 
although it must also be said, partly on account of a wide¬ 
spread suspicion of mismanagement, gas companies have 
avowedly been occupying lately an exceedingly difficult 
position (a position immediately recognised and very soon 
taken advantage of by their employes), with no great 
prospect which could inspire hope for the future. Again, 
the great prosperity of the country, and the free circula¬ 
tion of money, coupled with a comparatively small number 
of safe and lucrative investments, have to a great degree 
been the motive power of many schemes, which, without 
their aid, would have had considerable difficulty in fighting 
their way into public notice. There is one other cause 
lending its tendency in this direction, which, though 
perhaps only entertained by a few, is yet. continually 
growing in importance, and that is the belief that the 
present mode of gas manufacture is wasteful and unscien¬ 
tific, and only at the best a poor method of obtaining the 
desired result. To those who have not realized this fact, 
it is only necessary to point to the very small amount of 
the hydrogen and carbon contained in the coal which find 
their way into the gas ; to the large number of bye- 
products obtained in the process—bye-products which, it 
must be remembered, although themselves valuable, and 
daily increasing in value, are produced and disposed of 
only because at present it is impossible to prevent their 
formation, and which should consequently occupy quite a 
secondary position ; and to the existing imperfections 
in the apparatus used in the purification, storage, and 
distribution of the principal product. 
The present paper takes into consideration two or three 
of the most important of these new processes. . It is in¬ 
tended to examine them by the light of scientific .facts, 
and to say very little about the commercial merits or 
demerits of any particular scheme or schemes, although it 
cannot be overlooked that the one has a very important 
bearing upon the other. To do even this satisfactorily, 
it will be necessary to review briefly the chemical and 
physical laws which are called into operation in the manu¬ 
facture of gas, and also to give a short description of the 
apparatus at present employed for this purpose. 
The organic origin of coal is, at this time, an undisputed 
fact ; and we recognize, in the black carbonaceous mineral, 
the decayed and partially decomposed remains of a luxuri¬ 
ous tropical vegetation, a vegetation as far excelling, in 
extent and rapidity of growth, the present growth of the 
tropics, as that does the more moderate growth, of the 
temperate regions. This being so, in order to. anive at a 
correct knowledge of the nature and constitution of coal, 
we must go back to the stems, tissues, and foliage of . the 
plants and trees, the growth and death of which has given 
us our coal measures. 
The number of elements entering into the constitution 
of such vegetation is exceedingly limited—at the most 
four_yet the arrangement of these four is so complex 
that it is at times impossible to perceive in what manner 
they are united. This complexity of arrangement is 
* Read Wednesday, May 21, 1873. 
peculiar to organic compounds, and as a rule stamps them 
as being the product of some vital energy or force. 
Woody fibre, viz., that part of the plant or tree which 
gives to it its form and shape, we know contains the ele¬ 
ments carbon, hydrogen, and oxygen, and we also know 
the amount of each which enters into its constitution, but 
the exact manner in which the three are united to each 
other is unknown. Now, when any complex organic body 
is left to itself to decay, in other words, to become oxidized, 
the tendency is for it to resolve itself into simpler com- ’ 
pounds ; and if the decomposition goes on to completion, 
the carbon and hydrogen will each unite with oxygen, to 
form the most stable compound which they possibly can 
with that body, viz., in the case of carbon, carbonic acid 
(C 0. 2 ), and of hydrogen, water (H 2 0). If the fermenta¬ 
tion or decay be arrested at some intermediate stage, then 
compounds will be formed less complicated than the 
original woody fibre, but still more or less removed from 
the final result, according to the stage at which the action 
was stopped. The decomposition of this woody fibre has 
proceeded to a considerable extent in coal, a portion of the 
carbon and a large portion of the hydrogen having gone 
off in the form of marsh gas (fire-damp), and a further 
portion of carbon, together with the oxygen, as carbonic 
acid, while a third portion of carbon has been separated in 
its elementary state. We are able to trace this action 
through several stages, which will be more distinctly seen 
from the following table, in which the amount of carbon 
is kept up to 100 in the several carbonaceous materials:— 
Carbon. 
Hydrogen. 
Oxygen. 
Wood .... 
100 
12-18 
83 07 
Peat. 
100 
9-85 
55-67 
Lignite .... 
100 
8-37 
42-42 
Bituminous coal . 
100 
6-12 
21-23 
1 Anthracite. . . 
1 
100 
2-84 
1-74 
Here, not only are we able clearly to trace, by the analy¬ 
sis of’ these substances, the changes through which they 
have passed and are passing, but their physical appearance 
and structure fully confirms this evidence. Thus, in peat, 
the structure of woody fibre is recognisable at a glance ; 
in lignite and bituminous coals this structure is not so 
clear° but still unmistakable ; while in anthracite or stone 
coal nearly all trace of it is gone. This slow decomposition 
or fermentation may be regarded as a slow burning or 
combustion, viz., a union of the matter of the wood or coal 
with oxygen, and it is attended with the same result. 
If, instead of slow fermentation and decay of the wood 
into coal taking place, the wood had been burned at once, 
practically the same result would have been obtained ; the 
elements of the wood would seek to place themselves in a 
much simpler relationship to each other ; the. various 
changes would have been gone through more rapidly, but 
the final result would be identical with that of the previous 
case, viz., the production of water and carbonic acid. 
Here also there are many intermediate stages. Com¬ 
bustible gases are formed in abundance, together with 
tarry and oily matters, composed of carbon and hydrogen, 
and it is only by the further burning of these that the- 
complete decomposition is obtained. What is true here 
of wood is also true of coal itself, if it be taken as the 
starting point, more particularly, however, of those coals 
which still contain a fair proportion of hydrogen and 
oxygen. , . „ 
In each case the more intense the heat, the more rapidly 
does the decomposition proceed, or, in other words, the 
quicker does the combustion take place. Further, the 
more complicated the structure of any particular substance, 
the more readily will it be split up by the action of heat, 
provided that its constituents can exist in a number ot 
simpler states, which in carbon compounds and organic 
substances is invariably the case. In the above instances 
