PROFESSOR H. B. DIXON ON THE RATE OF EXPLOSION IN GASES. 
I 59 
electrolytic gas at 75 mm., but not at 70 mm,, when an induction spark is passed 
through the mixture. Lothae. Meyer and Seubert* found tliat a spark from a 
Ruhmkorff’s coil caused partial ignition of electrolytic gas at 70 mm., and complete 
combustion at 72 mm., the exact pressure under which the gases unite varying with 
the strength of the spark. 
It is conceivable, on the “breaking-wave” hypothesis, that the projected jets of 
heated gas do not under reduced pressure initiate their own explosion-waves so 
rapidly as under higher pressure. 
Similarly with regard to changes of initial temperature, I do not know why a rise 
of temperature should diminish the rate of explosion. The limited range in which it 
is possible to conduct the experiments, and the small differences found within this 
range, do not permit of a curve being drawn which might indicate the general effect 
of changes of temperature upon the rate. In the case of electrolytic gas the effect of 
heating was found to lower the rate both at low and at high pressures. Experiments 
made at atmospheric pressure with ethylene, burning to carbonic oxide and steam, at 
10° and 100°, showed a lowering of the rate rather greater than that of electrolytic 
gas; while similar experiments made with cyanogen, burning to carbonic oxide and 
nitrogen, showed a smaller difference—hardly, perhaps, to be distinguished from the 
experimental error. 
§ 3. llie Rate of Explosion of Hydrocarbons ivith insufficdejit Oxygen. 
The explosion of hydrocarbons with insufficient oxygen has been studied by Dalton, 
J. Davy, Kersten, and E. yon Meyer. In the ‘New System of Chemical Philosophy,’ 
Part II., p. 442 (1810), Dalton thus describes the explosion of ecptal volumes of 
ethylene and oxygen :— 
“If 100 measures of oxygen be put to 100 of olefiant gas, and electrified, an 
explosion ensues, not very violent; but instead of a diminution, as usual, there is a 
great increase of gas; instead of 200 measures, there will be found about 360 ; some 
traces of carbonic acid are commonly observed, which disappear on passing two or 
three times through lime water; there will then remain perhaps 350 measures of a 
permanent gas, which is all combustible, yielding by an additional dose of oxygen, 
carbonic acid, and water, the same as if entirely burnt in the first instance. What, 
therefore, is this new gas in the intermediate state ? The answer is clear. It is 
carbonic oxide and hydrogen mixed together, an equal number of atoms of each.” 
Dalton found that marsh gas could not be exploded with less than its own volume 
of oxygen, in which case half the hydrogen formed water and the other half was 
liberated:— 
“If 100 measures of carburetted hydrogen be mixed with 100 measures of oxygen 
(the least that can be used with effect), and a spark passed through the mixture, 
* ‘ Chem. Soc. .Journ.,’ 1884, vol. 1 p. 587. 
