Goal Gas 
ENGINEERING. 
ROBERT BRIGGS, C. E. 
REPRINTED PROW THE 
JOURNAL OF THE FRANKLIN INSTITUTE, 
For April, 1878. 
PHILADELPHIA: 
Wm. P. Kildare, Printer, 734 & 736 Sansom Street. 
1878. [Reprinted from the Journal of the Franklin Institute, April, 1878.] 
COAL GAS ENGINEERING. 
Robt. Briggs, C.E. 
Common Coal Gas—its Composition, and Results of Combus- 
tion.—Some forty or more distinct gaseous chemical components are 
well known to have existence in the ordinary coal gas of the gas 
works, in four several groups : the first of which are gases which burn 
in air without, or with slight, emission of light; the second, gases 
which, when burned with the first for supply of heat, evolve carbon, 
which, becoming incandescent before burning itself, emits light; the 
third, incombustible gases ; and the fourth, gases which are considered 
impurities. The first group is over four-fifths of the volume of coal 
gas, and is composed of only three substances or compounds, to wit: 
hydrogen, marsh gas and carbonic oxide; the second, which is only 
T to 9 per cent., comprises an almost endless list of hydro-carbon com- 
pounds, which are diffused, as gases or vapors, into the gases of the 
other groups ; for the purpose of this paper this group will be con- 
sidered as if composed entirely of olefiant gas (possibly most of these 
hydro-carbons are of the olefine series of compounds); the third com- 
prises the carbonic acid, aqueous vapor and air, and is always 3 to 6 
per cent, of coal gas; while the fourth, the impurities—ammonia and 
sulphur compounds ; obnoxious as they are in quality, in any tolerably 
well purified gas the percentage of them in volume is so small, that in 
a discussion of results of combustion they do not become an element. 
With this explanation to qualify the following statements and calcu- 
lations, it is proper to say that common coal gas, of 14 to 15 candles 
illuminating power, has the following constituents in volumes per 
hundred parts: Hydrogen, H, 44 to 48 ; marsh gas, CH4, 34 to 38 ; 
olefiant gas, C2H4, and other hydro-carbons, etc., 6 to 9; carbonic 
oxide, CO, 5 to 7; carbonic acid, C02, 1 to 3; air, 4N-f-0, 1 to 3 ; 
aqueous vapor, H20 (saturation at 40° to 60°), 1 to 2. The specific 
gravity of coal gas is about 0-426, which makes the volume of a pound 
of gas at 70° (barometer 29-9 in.) equal to 31-3 cubic feet (neglecting 
1 2 
fractions, too small to be of consequence in this estimate) = 0*0319 
ib. per cubic foot. Taking an average of the constituents of coal 
gas by weight, they can be reduced to 2P8 parts of hydrogen, 51*3 
parts of carbon, and 13*6 parts of carbonic oxide, which are com- 
bustible ; leaving 13*3 parts of non-combustible substances. The 
figures of the reduction of volumes to weights are as follows : 
Volumes 
Po. 
Wt. 
Constituents. 
per ct. 
average. Specific Gravity. 
n. 
C. 
per ct. 
H 
Hydrogen, 
44 @ 48 
45 
0 0692 
8 114 
3-114 
I 
II 9-260 
21-8 
CH, 
Marsh gas, 
34 (n, 38 
30 
' 0-559 = 
20-124 
5-031 
15-093 l 
c2h4 
(Uefiant gas, 
6 @ 9 
8 
0-981 = 
7*848 
1 121 
0-727 | 
C 21-820 
51 -3 
00 
Carbonic oxide, 
7 
6 
0-907 = 
6-802 
5-802 
13-0 
co2 
Carbonic acid, 
1 (« , 3 
2 
1 -524 =3 
3-048 
3-048 
7*2 
4N-|-0 Air, 
1@ 3 
2 
1-000.-= 
2-000 
2-000 
4-0 
h20 
Vapor of water, 
1@ 2 
1 
0-622 = 
0-022 
0-022 
1-5 
100 
42-558 
9-266 
21-820 
42-558 
100- 
From these data, the heat given out by complete combustion can be 
calculated—hydrogen gas will evolve in its chemical change to vapor 
of water (including the latent heat of the vapor) 62,000 units of 
heat, while carbon, in becoming carbonic acid, evolves 14,500 units, 
and carbonic oxide, in changing to the same form, evolves 4630 units— 
with the following result: 
Combustion. 
Oxygen re- 
quired. 
Air required 
Airrequired to effect rorn- 
■ to supply pletecom- 
oxygen. bustion. 
Units of heat per 
lb. of combine Unitaof beat total 
tibia evolved. 
1 Product. 
11,0 CO, 
H 21 -8 
174-4 
785 
1570 
02000 
1351600 
196-2 
C 51-3 
136-8 
616 
1232 
14600 
743850 
1H8-1 
CO 13-6 
7-8 
35 
70 
4330 
58890 
21-4 
C02 7-2 
0* 
7-2' 
4N+0 4-6 
0- 
H,0* 1-5 
0- 
1-5 
100- 
319- 
1436 
2872 
2164350 
198- 
217- 
Deduct latent heat of 196*2 lbs. vapor of 70° (a) 1065°, 
208950 
Total units of heat from 100 lbs. 
coal gas (86-7 com- 
bustible -|- 13-3 of non-combustible) 
1945400 
Combustion of TOO Pounds of Coal Gas. 
[* This ratio of vapor of water corresponds to the condition of vapor in saturated 
air at the temperature of 43° or 41 per cent, humidity at 70°—perhaps a little dry 
for summer tests.] 
Accepting these quantities for the products of combustion of TOO 
pounds of coal gas, the absolute temperature attained may be esti- 3 
mated. Three different hypotheses present themselves: the first 
supposes the absolute heat to be that derived from the capacity of 
the product to take up the entire heat generated. The second limits 
the expenditure of heat in producing intensity, to the air needed to 
supply oxygen ; while the third supposes the ultimate maximum in- 
tensity to be that derived from the chemical combination of oxygen 
and carbon, and of oxygen and hydrogen. The last is probably the 
correct value for the intensity of the source of radiating heat from a 
gas light. The foliowing table gives the three computations in the 
order named: 
Pounds X Specific heat 
Sum of weight 
= multiplied by 
Specific heat. 
Pounds = 
sum, etc. 
Pounds = sum, etc. 
h20 
198 X 0-478 
■= 94-050 
h2o 
198; 
94-050 
11,0 198; 94-050 
N 
1117 X 0-245 
= 273-665 
N • 
1117; 
273-665 
4N+0 
143G X 0-238 
= 341-768 
co2 
217 X 0-217 
= 47-089 
C02 
217; 
47-089 
C02 217; 47-089 
Total 
29G8 X 0-255 
== 756-572 
1532; 
414-808 
415; 141-139 
If now the total number of units of heat, which resulted from the 
burning of 100 pounds of coal gas, be divided by the sum of weights 
of products of combustion, multiplied by their specific heat, the in- 
crement of heat to the products will be given by the result; which, 
added to the original or normal heat of the gas and air (here taken 
at 70°), will give the absolute temperature of the products as they are 
assumed to exist in the three suppositions. 
Supposed absolute temperature of flame of coal gas, where the 
products of combustion are taken to include the volume of air, which 
is the requisite for complete combustion : 
= 1945000 70o _ 2641°. 
756-572 
Supposed absolute temperature of flame of coal gas, where the 
products of combustion are taken to include the air needed to supply 
oxygen of chemical combination : 
= j945000 70° — 4760°. 
418-804 
Supposed absolute temperature of flame of coal gas, where only 
the oxygen of chemical combination is taken into the estimate: 
= 1945000 70o== 13885o> 
141139 T 4 
At the same time we are discussing the absolute temperatures of 
cdal gas flames, it may prove interesting to examine, separately, those 
of the three gases which compose it, as follows: 
Weight, 
pounds. 
Oxygen, 
pounds. 
Product 
of com. 
Weight, 
pounds. 
Specific 
heat. 
Units 
heat. 
Intens. 
of 
flame. 
Hydrogen, II 1 8 II20 9 X O’4-5 = 4-275)52447(12268° + 70° = 12:588° 
Carbon, C 1 2 2-3 C02 3 2-3 X 0-217 = 0-796)145(X)( 18223° -f 70° = 18293° 
Carb. ox., CO 1 4-7 C02 1 4-7 X 0-217 = 0-341) 4329(12694° + 70° = 12764° 
The value for the heat effect of one pound of hydrogen is derived 
in the same way as was used in the estimate for coal gas, as follows: 
Total heat effect of 1 lb. of hydrogen, = 62,032 units. 
Deduct latent heat of 9 lbs. vapor of 
70°, 1065°, . = 9,585 “ 
Heat effect of 1 lb. of hydrogen, with- 
out condensation of vapor, . = 52,447 “ 
These estimates of the heat of the flame of gases have taken for 
granted the constancy of the relative values of specific heats at high 
temperatures, and the results may therefore be considered as only 
approximations of the truth; still they give, probably, the most 
nearly correct estimate of the values of intensity possible. 
The heat evolved by the burning of coal gas is dispersed in two 
ways—as radiant, and as convected or imparted heat. With the 
open burner, it is fair to assume that a large portion of the heat is 
dispersed as radiant heat. According to Peclet, 50 per cent, of the 
heat of a flame of burning wood or coal is dispersed as radiant heat, 
and it does not seem to be an improper assumption, that one-half the 
heat of burning of coal gas will be dispersed as radiant heat, and the 
other will be communicated to the gases of combustion, and dissemi- 
nated by convection and intermixture with the surrounding air. The 
limited base from which the flame of a gas burner emerges, as com- 
pared to the magnitude of the flame or burning surface, prevents the 
loss or expenditure of radiant heat upon the fuel (which would again 
impart its heat to air in contact before burning), and thus reduces 
the convected heat to its least quantity. The supposition appears 
the more reasonable when we consider the enormous intensity of the 
heat of chemical combination; nearly 14000°, as above indicated, when 
unmixed with other gases to absorb its heat. If we proceed on this 
supposition, it follows that the convected heat of 100 pounds of coal 
gas becomes one-half of 1045400 = 972700 units; and this heat 5 
imparted to the products of combustion, when they are taken to 
include the volume of air necessary to effect complete combustion, 
gives the temperature of these products: 
= 972500 • + 70° = 1356°. 
756-572 
The relations of volumes of the products of combustion of coal gas 
to the weights as ascertained, can be seen by the following table— 
estimated at 70°: 
Product. 
Spec. 
grav. 
Wt. per 
cu. ft. 
Cubic ft. per 
pound. 
Wt. of 
product. 
Cu. It. of 
product. 
Cu. ft. per ft. 
of gas. 
Vol. per ct. 
of product. 
h2o 
0-622 
0-0466 
21-45 
X 
198 = 
4247 
1-355 
10-45 
N 
0 972 
0-0729 
13 73 
X 
1117 =.-■ 
15332 
4-891 
37-73 
4N+0 
1-000 
0-0750 
13-34 
X 
1436 = 
19158 
6-111 
47-15 
C02 
1-524 
0-1142 
8-754 X 
217 = 
1900 
0-606 
4-67 
2968 = 
40637 
12-963 
100-00 
Gas 
0-426 
0-0319 
31-35 
X 
100 = 
3135 
1 
7-71 
Oxygen* 
1-106 
0-0829 
12-07 
X 
319 = 
3849 
1-228 
9-47 
Air 
1-000 
0 0750 
13-34 
X 
1432 = 
19103 
6-094 
47-01 
Dbl. Air 
1-000 
0-0750 
13-34 
X 
2868 =■ 
38259 
12-204 
94-15 
Heat total, units 
1945400 
622 
Heat convected, units 
9 
72700 
311 
[* The oxygen taken is that of actual combination, and represents the quantity 
needed, with coal gas, when used for the lime light or Bunsen burner.] 
The preceding computation can be verified by another arrange- 
ment of data, in which volumes alone appear, taking the second 
column from the table of reduction of volumes to weight: 
100 vols. X 
spec. grav. 
If. 
C. 
0. 
N. 
Hydrogen, H 3-114 
3-114 
Marsh gas, CH2 20-124 
5-031 
15-093 
Olefines, C2H4 7-848 
1-121 
6-727 
Carbonic oxide, CO 5-802 
2-487 
3-315 
Carbonic acid, C02 3-048 
0-831 
2-217 
Air, 4N+0 2-000 
0-444 
1-550 
bustion of hydro- 
Aqueous vapor, IT20 0-622 
0-009 
0-530 
gen and carbon 
with definite pro- 
portion of oxyg. 
100 vols. X spec, grav , totals 42-558 
9-335 
25-138 
6-529 
1-556 
II20 co2 
Per cu. ft. gas, weights, lbs. 0-0319 
0-0070 
0-0188 
0-0049 
0-0012 
0-063 0 069 
“ “ volumes, cu. ft. 1-000 
1-349 
0-059 
0-017 
1-351 0-605 
In general, the combustion of all substances, oils, fat acids, or 
gases used for illuminating purposes, is unquestionably perfect com- 
bustion of the carbon and hydrogen elements into carbonic acid and 
aqueous vapor. Neither smoke nor carbonic oxide, nor hydrogen in 
free or combined state, other than water, can be found in the air of 6 
any room where the lighting is at all satisfactory to the occupants, 
and the production of heat, as has been estimated, becomes one of the 
positive facts in physics beyond question as to existence and quan- 
tity. With the case of the open gas burner, it is possible that one- 
half the heat of the flame is dispersed as radiant heat, but this 
dispersal does not, however, get rid of the heat in a room; it merely 
transfers it to solid bodies of less temperature, more or less remote 
from the flame, which again are cooled in great measure by contact 
of the air of room, which takes up their excess of warmth, so that the 
heat emanating from a burner really is nearly all expended in the 
air. But when the burners are shaded by glass or other shades, and 
particularly for argand burners with chimneys, the larger part of 
the radiant heat is cut off by the shade or chimney, or both together, 
and imparted to an unknown volume of air which accompanies the air 
for or of combustion. As a practical application, it may be well to 
consider what volumes of air are requisite to disperse the heat of gas 
lights if the air in any part of a room is limited to some definite tem- 
perature. 
The following table exhibits the effect of gas burning from a single 
burner of the usual sizes : 
(All figures refer to quantities per hour—air of room and gas 
at 70°.) 
Gas burned, cu. ft., 
1 
3 
3} 
4 
4-] 
5 
6 
8 
Carbonic acid evolved, cu. ft., 
0-606 
1-82 
2-12 
2-42 
2-73 
8-03 
4 24 
4-84 
Aqueous vapor “ “ “ 
1 -355 
4-07 
4-74 
5-42 
7-10 
7-78 
8-13 
10-84 
“ “ “ lbs., 
0 068 
0-19 
0-221 
0-263 
0-285 
0-317 
0-38 
0-506 
Oxygen removed, cu. ft., 
1-228 
3-68 
4-30 
4-91 
2 
6-14 
7-37 
8-60 
Heat produced, units, 
622 
1866 
2177 
2488 
2799 
3110 
3732 
4976 
Coal to produce equal heat, lbs. 0-062 
0-19 
0-22 
0-26 
0-28 
0*81 
0-37 
0-50 
Air supply = 10 cu. ft. j cu 
per min. per cu. ft. gas j 
, 600 
1800 
2100 
2400 
2700 
3000 
3600 
4800 
With the supply of air to each gas burner given by the preceding 
table, the temperature of the current ascending from open burners, 
where one-half the heat is supposed to be radiated away, becomes 
99°; while the temperature of the same current arising from an 
argand burner, where the glass chimney will have intercepted the ra- 
diant heat, becomes 128°. 
The figures for this temperature are thus obtained : The weight of 
air at 70° is 0*075 pound per cubic foot, which, multiplied by 0*238. 
the specific heat of air, gives 001785 unit as the capacity of one 
cubic foot of air for each degree Fahr.; with 000 feet of air supply 7 
per hour to 1 foot of gas, the capacity of the 600 feet becomes 10*71 
units for each degree of elevation of temperature ; and to absorb 622 
units by the 600 cubic feet of air, the latter will become heated 
622 
10-71 = 58 °’ 
which, added to the 70° of primary temperature, give 128° as the 
final one when all the heat is taken up by the air. When but half 
the heat is assumed to be given to the air, wTe have 29° -f- 70° = 99°. 
The computation of the temperature to accompany any other volume 
of air supply is easy. Thus, if for each cubic foot of gas burned 
per hour—normal temperature 70°: 
Air supply per minute, cu. ft., 
5 
10 
15 
20 
25 
30 
Corresponding air supply per hour, cu. f. 
, 300 
600 
900 
1200 
1500 
1800 
Temperature of air ascending from 
open burners, 1 
128° 
99° 
89° 
841° 
81 £° 
79£° 
Temperature of air ascending from 1 
argand burners, J 
187° 
128° 
118° 
99° 93° 
89° 
The estimate of weight of coal, the consumption of which will pro- 
duce an equal effect in warming a room with gas burning, is not based 
on the theoretical value of coal as a producer of heat, but upon aver- 
age usual results from heating apparatus, as steam or hot water 
apparatus, hot air furnaces of best construction, or close stoves, in 
utilizing the heat of the fuel. That is, 10,000 units of heat have 
been assumed to be given out efficiently by the consumption of one 
pound of good anthracite coal. 
The capacity of the air requisite for dispersal of the heat of a gas 
flame, to take up the moisture generated by the process of burning, 
can be investigated. According to the best authority (Ilegnault, 
from Guyot’s tables), saturated air has the following quantities of 
moisture per cubic foot of air : 
Temperature of air, 70° 75° 80° 85° 90° 95° 100° 105° 
Weight of moisture, lbs., 0-0011 0-0013 0-0016 0-0018 0-0021 0-0024 0 0028 0 0032 
If it is assumed that the air of supply is 70°, and has 60 per cent, 
of saturation, then such air has 0-0007 pound of water to each cubic 
foot, whence the capacity of this air, to take up moisture in becoming 
saturated, is: 
0-0004 0-0006 0-0009 0-0011 0-0014 0-0017 0-0021 0 0025 
and there will be needed to carry off the 0-063 lb. of moisture which 
the burning of each cubic foot of gas per hour evolves: 
Air at gis-en tempera- 
tures, cu. ft., 
158 105 70 57 45 37 30 25 8 
Comparison of these quantities, with the volume of air supply, 
and corresponding resulting temperatures as given in the previous 
table, demonstrates that the moisture generated hy gas burning will 
be absorbed, in all cases, into the air for dispersal of heat. 
While it appears to be impossible to discern any error in the 
method and data of this inquiry, and the mathematical accuracy 
(errors of computation excepted) of the results seems to be unques- 
tionable, yet their application to practice is found to need great 
qualification. The material products of combustion, i e., aqueous vapor 
and carbonic acid, and the corresponding abstraction of oxygen from 
the air of a room, are established facts, but it is very difficult to 
account for the dispersion of the heat. Great allowance is needful 
for conductivity of the enclosing surfaces—floors, walls, ceilings, 
windows and doors—and also for fresh air currents, surreptitious or 
otherwise, before the heat imparted to the air, as derived from these 
computations, will conform to what is really found to be the heat effect 
of gas lighting. For instance, a 4 ft. gas burner would be held to he 
ample for lighting a small bed-room, and such a burner is frequently 
permitted to remain burning all night in a room of, not to exceed, 
800 cubic feet capacity. This burner, by the computation, would 
produce 2488 units of heat each hour. In moderate weather no 
considerable loss of heat from the surfaces enclosing the room is 
supposable, and the figures give 7200 cubic feet of air per hour (or 
120 feet per minute) as the indispensable necessity to keep down the 
temperature to 19° above the normal one. To be sure, the current 
of gases ascending from the burner will reach the ceiling of the room 
at a greatly elevated temperature, perhaps 140° even, and a stratum 
of hot air next the ceiling be formed (unless some arrangement of 
ventilation removes the hot air at once), and then the conductivity of 
the ceiling will be brought into action, but yet it is hard to feel satis- 
fied that this means is sufficient to account for all the loss of heat 
apparently demanded. 
It must be admitted that further inquiry and experiment are 
wanted to elucidate the subject of the dispersal of heat of gas lights, 
and perhaps to review the entire subject of the quantity of heat 
produced by them. THE JOURNAL 
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