Ott GASEOUS EXPLOSIONS. 



205 



fiiamlned the spectrum of the flame by means of a i - ock salt prism, 

 and he found that in all flames producing both C0 2 and steam 

 most of the radiation was concentrated into two bands, the wave 

 lengths of which are, respectively, 4 - 4/t and 2-8 ju . In a pure hydrogen 

 flame the 4 - 4 band disappears completely, but the other remains; and 

 in the pure CO flame the 2"8 band disappears, the other remaining. 

 These results are independent of the nature of the combustible gas, 

 the spectrum depending solely on the products of combustion. 1 



A confirmation of the statement that the radiation from these flames 

 originates in the C0 2 and H 2 molecules only was furnished in the 

 course of the work by R. von Helmholtz, to which reference has been 

 made above. He measured the amount of radiation per litre of gas 

 consumed, emitted by flames of given size burning respectively 

 hydrogen, carbon monoxide, and Certain compound gases, such as 

 methane, giving both C0 2 and steam. The supply of air was adjusted 

 in each case so that the flame was just non-luminous. His results are 

 best given in his own words, but it should be stated that he worked 

 with a small flame about 6 mm. diameter and measured the radiation 

 with a bolometer, taking the steady change of its resistance as a measure 

 of the amount of radiation falling upon it : — 



' According to the experiments of Julius described in the first 

 chapter, the quality of the radiation of flames depends only on the 

 nature of the burnt and not on that of the burning gases. It is relevant 

 to inquire whether the quantity of radiation is also dependent on the 

 mass of the products of combustion. I have calculated in the second 

 and third columns below how many litres of H,0 and C0 2 , respectively, 

 arise theoretically from each litre of combustible gas. I then assume 

 that for every litre of water produced as much radiation is sent out 

 as corresponds to the radiating power -of a hydrogen flame — for this 

 gas yields one litre of H 2 per litre of combustible — and that in a 

 corresponding way the radiation from one litre of carbonic acid would 

 be determined by the radiating power of the carbonic oxide flame, and 

 I can then calculate the radiation from the non-luminous flames of 

 methane, ethylene, and coal-gas. 



Gas 



Hydrogen . 

 Carbon Monoxide 

 Marsh gas 

 Ethylene . 

 Coal gas . 



' The correspondence between the calculated numbers with the 

 radiation from a flame which has just been rendered non-luminous 

 surprised me the more since the latter is conditioned, in some measure, 



1 Die Licht- iml W/irmeslrahlung verbrannter Case. Dr. W. H. Julius, Berlin, 1890. 

 1910. P 



