THE CAUSE OF THE LUMINOSITY OF FLAME. 
127 
Exp. 10.—A thick iron-wii-e put into soda-water caused a copious disengagement of 
gas. The wire was wiped with a clean duster, it still produced the same effect; it was 
carefully polished with sand-paper, and still the same effect; it was dipped into spirit 
and washed in water, and when placed in soda-water not a bubble appeared on its sur¬ 
face ; it was then wiped with what is usually called a clean duster, and, on putting it 
into soda-water, it immediately disengaged bubbles. 
Exp. 11.—A large fragment of flint disengaged gas from every part of its surface. 
It was broken into two pieces, and again put into the soda-water. Not a bubble of gas 
was liberated from the two fresh surfaces. 
It may be objected to this experiment that the new surfaces had not had time to be¬ 
come active by exposure to the air. I say that they were active, as active as Nature’s 
chemically clean surfaces are ; more active, in fact, than if they had been exposed to the 
air. It is true they did not disengage gas ; the adhesion of the liquid was too perfect 
for that; and it was necessary to tame down the adhesive force, in order to apply to 
them any one of what I cannot help thinking are the mistaken terms active , catalytic , 
and dynamic , as used with reference to this class of phenomena. 
The ingenious experiment on which M. Gernez chiefly relies for the success of his 
theory seems to me to require quite another explanation. A narrow tube, closed at one 
end and rendered “ inactive ” on the outside, was lowered full of air into the gaseous solu¬ 
tion. “ Gas adhered to the column of air which the tube contained, forming quickly a 
large bubble, which was disengaged ; then another was produced, and so on. The gas 
formed then only at the point where the liquid touched the column of air.” “ From 
this experiment,” says M. Gernez, “which I have varied in several ways, it may be con¬ 
cluded that air sets up the disengagement of carbonic acid.” Had M. Gernez made the 
inside of his tube as “inactive ” as the outside, I think he would have found that the 
column of air had nothing to do with the liberation of the gas. 
Exp. 12.—A narrow tube 11 inches long was kept for an hour in a quantity of spirits 
of wine 5 inches deep It was then washed in water, and closed at the top with the 
finger, and so just dipped into a fresh quantity of soda-water. There was no disengage¬ 
ment of gas. The tube was lowered to various depths with the same result; the finger 
was then removed, so that the solution could enter the tube. There was no liberation 
of gas until the immersion of the tube just exceeded 5 inches ; and then, at and about 
the boundary line marked by the spirit, there was a liberation of gas both on the inside 
and the outside of the tube. The solution was 6 inches deep ; the tube was chemically 
clean for 5 inches of its length both inside and out. Above this there was 1 inch of the 
tube that was not chemically clean, which liberated gas. The tube was taken out, 
wiped with a duster, drawn through the hand, and again inserted into the solution. 
The whole length of 6 inches was now covered with gas-bubbles, while a length of 5 
inches on the outside was free from them as before. 
I cannot resist the conclusion to which these experiments lead me, that the so-called 
“ active ” condition of solids in liberating gas from solutions is a lowering of the ad¬ 
hesive force of such solids for liquids, in consequence of want of chemical purity. Make the 
solids chemically clean, and the solution adheres to them without any disengagement of 
gas ; make them unclean, and then the adhesive force of the solid becomes more euer- 
getic for the gas than for the liquid, and there is a consequent separation of gas from 
the solution.— Fhilosophical Magazine and Journal of Science. 
THE CAUSE OF THE LUMINOSITY OF FLAME. 
Dr. Frankland, in lecturing on coal-gas, at the Royal Institution, entered at some 
length into the consideration of the came of the luminosity of flame, and propounded a 
theory which differs materially from that which has been generally received on the 
subject. 
He said:—“We have here a gas-flame burning in the usual way—what is the source 
of its luminosity? The explanation usually given is something like this:—Coal-gas 
is a mixture of certain compounds called hydrocarbons or carbo-hydrogens, and these, 
on being decomposed, throw off little particles of carbon which remain suspended for a 
short time in the flame, and become incandescent or white-hot. These solid particles 
