November 18,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
407 
Rut at any heat which does not thus alter the constitu¬ 
tion of the gas, the only result of raising the temperature 
must he to increase its volume by expansion; and the 
effect would be that, if the gas were heated after it has 
passed through the meter, and the meter were made to 
pass a fixed quantity, then the heated gas, being en¬ 
larged in volume, would have to pass more quickly through 
the burner than if it were of the same temperature as it 
had when passing through the meter. 
The question is one of considerable importance as re¬ 
gards the construction of burners; and two opposite 
views have been held on the subject,—the Leslie burner 
having been devised on the theory that the gas should 
be heated as much as possible before being ignited; 
while Mr. Sugg and others, more recently, adopt the 
•opposite opinion, and make their burners, in whole or in 
part, of non-mctallic substances, in order (inter alia ) that 
the gas may be heated as little as possible. In order to 
test the accuracy of the results obtained at Munich, and, 
..generally, to ascertain correctly what effect (if any) tem¬ 
perature has upon the illuminating power ot gas, the re¬ 
ferees made the following series of experiments (the 
temperature of the room being about 65°):— 
A 12-ft. coil of half-inch metal pipe was placed in a 
w r ater-bath ; a metal pipe 18 inches long led from the top 
of the coil to the burner; and midway between the coil 
nnd the burner a thermometer was inserted in the pipe, 
in such a manner that the gas passed over the bulb. The 
water was then raised to the boiling-point ( 212 ° F.), but 
4he thermometer only rose one or two degrees and re¬ 
mained stationary. Oil was then used instead of water, 
and the coil was lengthened from 12 to 56 feet; never¬ 
theless, when the oil was raised to its boiling-point (about 
400° F.), the thermometer in the gas only rose to about 
79° F. Inferring (as will appear, too hastily) from this 
that the gas, in passing through the coil, failed to absorb 
the heat from the surrounding oil, large shot were intro¬ 
duced into the coil of pipe, in order to conduct the heat 
inwards, and bring the gas at all points in contact with 
heated metal. Even then the thermometer hardly showed 
■any further rise of temperature ; but it was incidentally 
observed that the quicker the gas was sent through the 
pipe, the greater was the rise of the thermometer,— 
although, of course, the gas was then for a shorter time 
in contact with the heated metal. 
This fact at once showed that the stationary position 
of the thermometer was not so much owing to a difficulty 
in heating the gas in the coil, as to the rapidity with 
which the gas lost the heat so acquired, after leaving the 
•coil. Accordingly, in tho subsequent experiments, the 
pipe leading from the coil was surrounded by a jacket 
filled with boiling oil, and extending to within 2 inches 
of the point of ignition,—the thermometer being again 
placed between the coil and the burner. The effect of 
this change in the apparatus was that the thermometer 
at once rose to 296° F., tho temperature.at which, ac¬ 
cording to tho experiments made at Munich, produced 
an increase of illuminating power to the extent of 18 per 
cent. An apparatus was then so constructed that tho 
I)urner could be supplied instantaneously with cool and 
heated gas alternately, and any change of illuminating 
power, produced by a high or low temperature of the 
gas, could be readily noticed. But the heated and the 
cool gas gave exactly the same amount of illuminating power . 
Indeed the heat acquired by gas immediately upon 
ignition is so great—the heat of a Bunsen-flame being 
•estimated at about 1800° C. (3272° F.)—that the highest 
temperature at which it is practicable to supply gas to a 
burner is quite insufficient to make any appreciable dif¬ 
ference in the temperature of the gas-flame. As a de¬ 
duction from these experiments, the referees express an 
opinion that the advantages claimed for various mate¬ 
rials used in the manufacture of burners are wholly 
imaginary, except that non-metallic substances are likely 
to be more enduring, inasmuch as they are not so liable 
lo oxidation as metal. 
As to the effects of cold upon the illuminating power 
of gas, it is reported that in the experiments made at 
Munich, when the U-tube was immersed in snow, so as 
to bring the temperature of the gas down to 32°, the 
illuminating power fell from 100 down to a point varying 
from 75 to 86 ; in other words, the light was reduced 
on the average to the extent of 20 per cent. And when 
the temperature of the gas was still further lowered, 
by using a mixture of salt and snow (temperature 4 be¬ 
low zero), the illuminating power was reduced by nearly 
one-third, ranging from 33 to 40, as against its full illu¬ 
minating power of 100 . 
The latter temperature (— 4° F.) is one to which, in 
this country at least, gas as supplied to the public is 
never subjected; but as regards gas at the freezing- 
point (32° F.) and a little below it, the referees’ experi¬ 
ments showed that this reduction of temperature made 
no difference in the illuminating power, gas at the freez¬ 
ing-point, and at a temperature of 296° F., being sup¬ 
plied alternately to the burner without making any dif¬ 
ference in the readings of the photometer. At the same 
time it must be said that when gas is subjected to a 
freezing temperature for some time, a considerable de¬ 
crease of its illuminating power will certainly occur; for 
in such a case a change will be produced in the constitu¬ 
tion of the gas. Just as a very high heat alters the 
composition of gas, greatly diminishing its illuminating 
power; so will extreme cold from a kindred cause pro¬ 
duce a similar result. In the former case, there is a dis¬ 
integrating chemical effect produced by excessive heat, 
occasioning, inter alia , a deposit of carbon; in the latter 
there is the effect of freezing, by which the water con¬ 
tained in gas, in the form of aqueous vapour, is separated 
from the gas in tho form of ice, and a portion of the 
illuminating hydro-carbons are condensed along with 
it. 
It may be observed, as a matter of fact, that in street 
lamps (where the gas is fully exposed to the effects of 
temperature) there certainly is a marked diminution in 
the illuminating power during a severe frost. The ex¬ 
periments, however, were specially directed to determine 
whether a mere cooling of the gas (apart from the altera¬ 
tion of its constitution by the freezing of its aqueous 
vapour) produced any loss of light-giving power ; and it 
was found that it did not,—the result of the experiments 
made by the referees entirely conflicting with that ob¬ 
tained in the laboratory at Munich. 
Advantage was taken of the recent opening of the 
Chartered Gas Company’s works at Beckton, to attempt 
to ascertain whether the distance of the point of manu¬ 
facture from that of consumption had any effect upon 
the illuminating power, the gas produced at the Beckton 
works having to travel nearly nine miles to the Brick 
Lane station of the above company. This point is not 
yet definitively settled, but the present evidence tends to 
show that no appreciable injury occurs to the gas in its 
long passage. This is a very important question, and 
the answer given to it by further investigation will de¬ 
termine whether the existing legislation as to the position 
of the official testing-stations (namely, at 1000 yards 
from the gas-works) is adequate security for the interests 
of the public. . 
The last subject treated upon by the referees in this 
report, viz. the transparency of gas-flames to light, is one 
of considerable importance, bearing as it does upon the 
effective and economical arrangement.of burners. It a 
gas-flame offers no obstruction to the light of other gas- 
flames or to a part of itself, then it matters not how the 
burners are placed or arranged; but if it does impede 
the transmission of light, then burners should not be 
arranged in such a manner that the light from one ot 
them has to pass through that of the others,—or even 
through a part of itself, as happens when a bat wing or 
fishtail burner is placed edgeways to the point ot sight. 
To determine this point,—namely, the transparency ot 
gas-flames to the light of other such flames, the to - 
