May 20, 1886} 
INGA TiC ie 
65 
are reached in the arts, as materials used in furnace-building 
would not withstand such temperatures for any length of time ; 
but still he must call attention toe the circumstance that if the 
influence of the inner surfaces of the tubes on the combustion of 
the gases therein could be removed, the dissociation temperatures 
arrived at would be found still higher. He could not admit that 
Bunsen’s explanation of the cause of the second and third ex- 
plosions was quite satisfactory, as it was not the cooling of the 
gases alone which rendered the subsequent explosions possible, 
but also the thorough re-mixture of the gases by diffusion after 
each explosion. ‘This he illu-trated by means of diagrams which 
represented— 
(1) A tube filled with an explosive gas mixture which was 
shown white. 
(2) The same tube immediately after an explosion had taken 
place, with a white margin to indicate the unexploded mixture 
close to the sides, and deep red, towards the middle of the tube, 
the exploded gases. The white was shown as merging into 
deep red by degrees, because close up to the sides the surfaces 
prevented explosion or combustion altogether; nearer the 
middle partial combustion took place, whilst only in the middle 
of the tube the gases found sufficient space for complete com- 
| bination. 
(3) The same tube after the burnt and unburnt gases had 
mixed by means of diffusion, which was coloured light red. 
(4) The same tube immediately after the second explosion, 
coloured light red at the sides, turning into deep red by degrees 
towards the middle. 
(5) The same tube after diffusion bas done its work a second 
time, coloured a deeper shade of red. 
(6) The same tube after the third explosion, coloured nearly 
_ deep red throughout, but still a lighter shade on the sides. 
In Bun en’s inode of determining dissociation at high tem- 
| peratures we had only to deal with the obstruction which sur- 
' faces offer to combustion, leaving out their dissociating influence 
‘at high temperatures, which affected most of Deyville’s results. 
For that reason Bun-en arrived at much higher dissociation 
temperatures than Deville, and his mode of experimenting 
possessed the advantage that it might lead to a proper settle- 
ment of the question of temperatures at which dissociation 
would set in when taking place in a space unencumbered by 
surfaces. 
By taking a narrow tube of about the same size as Bunsen 
used for his experiments, and a hollow sphere of the same 
| capacity, in both of which Bunsen’s experiment should be re- 
peated, the real dissociation temperature, if no surfaces were 
| present to influence the result, might be approximately cal- 
} culated. 
Bunsen’s method of experimenting, according to his view of 
the matter, should form the foundation of further research to 
determine the dissociation temperatures of products of combus- 
tion. Even if means were found for eliminating the influence 
of surfaces, no known material at our disposal could withstand 
the very high temperature to which the vessels or tubes would 
be subjected if experiments were carried out according to 
Deville’s method. 
That the surfaces of highly heated vessels or tubes either pro- 
duce, or tend to produce, dissociation, had been corroborated 
lately by two Kussian experimentalists, Menschutkin and 
Kronowalow. These gentlemen found that dissociation of car- 
bonic acid and other gases was much facilitated when the vessels 
used for the experiments were filled with material offering rough 
surfaces, such as asbestos or broken glass. 
‘The lecturer’s view of the theory of dissociation caused or 
influenced by surfaces might be given as follows. Increase of 
temperature producing expansion of gases would reduce the 
attractive tendency of the atoms towards one another, or, in 
’ other words, diminish their chemical affinity. In the same ratio 
as the temperature was increased the repelling tendency of the 
‘atoms must increase also, until at last decomposition, or what is 
called dissociation, took place. This being admitted, it would 
follow that the adhesive or condensing influence of surfaces on 
the atoms of the gas, which action would increase at high 
temperatures, would assist this decomposition by increasing the 
repelling tendency of the atoms. 
Victor Meyer, who at first disputed the accuracy of the results 
obtained by the two Russian physicists, ultimately accepted 
them, thus confirming the results he had arrived at in practical 
work with furnaces. Thus the question might be considered 
nearly settled, the more so as Meyer was himself a great au- 
thority in questions of dissociation, having carried out many 
interesting experiments. Meyer, for instance, proved dissocia- 
tion by dropping melted platinum into water, and found that 
oxygen and hydrogen were evolved from the steam produced. 
There could be no doubt on this point, but the question arose 
whether heat was the sole agent that brought about the dissocia- 
tion of steam in this case. In the first place the dissociating 
influence of the highly heated surfaces of platinum on steam had 
to be taken into consideration, and, secondly, the chemi al 
affinity which platinum had for oxygen, and still more for hydro- 
gen. The same remarks applied to Meyer’s experiment of 
passing steam or carbonic acid through heated platinum tubes, 
in which case he obtained only traces of dissociation, the 
temperature being much lower. Other experiments might be 
mentioned, but none led to a different conception of the 
question. 
There is one other circumstance connected with dissociation, 
proved by experiment, which, however, required explanation. It 
was considered asa sure sign that dissociation was going on when 
a flame whose temperature was raised became longer ; this it 
was said could only be accounted for by dissociation having 
commenced, He agreed with this conclusion, but the experi- 
ments by which it had been proved had been made, like others 
referred to, in narrow tubes or passages in which the dissociating 
action of the heated surfaces must come into play. It was not 
alone the heat to which the gases were raised that in these cases 
caused dissociation and increased the length of the flame, but 
also the influence of the heated surfaces in contact with the 
combustible gases, more e pecially if these gases contained 
hydrocarbons. The extension of the flame was also partly due 
to the obstruction which the surfaces offered to the recombusti »n 
of the dissociated gases through want of space. If the same 
flame were allowed free developmen’ in a spice unencu nbered 
by surfaces, as in the lecturer’s radiation furnace, no such exten- 
sion of its length would be observed ; but, on the contrary, it 
would get shorter with increase of temperature. This action 
could be best observed in the regenerative gas-burner exhibited, 
whose flame became shorter the greater the intensity of the 
temperature, and therefore of the light, produced. On the other 
hand, flame might be extended almost to any length if conducted 
through narrow passayes ; this might be seen in regenerative 
furnaces, which would send the flame to the top of the chimney 
if the reversing valves were so arranged that the flame, instead 
of passing through the furnace chamber, was made to burn 
directly down into the regenerators. No proper combustion 
could then take place in the brick checkerwork of the regenera- 
tive chambers, and the flame would consequently continue to 
extend until co led down below a red heat, being ultimately 
converted into dark smoke ; thus in this case the extensive sur- 
faces offered by regenerators would act both ways, by preventing 
combustion, and by assisting dissociation. 
It would be understood that regenerative furnaces them- 
selves offered special opportunities for making experiments, most 
questions, indeed, being best settled by the results obtained in 
actual work. If dissociation set in the consequences were seen 
in want of heat, reduced output, and in destruction of furnace 
and material. If the causes of dissociation were removed, a rise 
in temperature, increased output, longer furnace life, and saving 
of material ensued. Similar results might be obtained with 
other furnaces, but the beneficial action would not be so great as 
in the case of the regenerative furnace, because the intensity ot 
heat obtainable in them was much lower. 
After describing a new regenerative gas stove he had lately 
introduced, the lecturer referred to the better distribution of the 
radiated heat by its use; he found that a room warmed by 
means of a stove or open fire, such as described, was of a more 
uniform temperature than when warmed by an ordinary fire or 
by a gas and coke fire, such as his brother was engaged im intro- 
ducing into this country shortly before his death. 
This, in his opinion, was mainly due to the fact that a source 
of radiant heat of low intensity but of large surface, sending out 
its rays at various angles, heated an object in its vicinity very 
much more than was the case with a smaller source of radiant 
heat of greater intensity, whose rays struck the object from one 
direction only, notwithstanding that both sources radiated the 
same quantity of heat. This action was illustrated by means of 
two diagrams exhibited, which represented two rooms, the one 
heated by asmall flame of high intensity, and the other by a 
large flame of low intensity, both radiating the same quantity of 
heat. In each room two objects, globes or spheres, were repre- 
