SS Major W. T. David : Analysis of the 



of course to be expected, for the quartz and glass plates 

 are transparent over more or less the same region of the 

 infra-red spectrum. 



7. A glance at these tables will show that the ratio 

 of the emission through quartz to that through fluorite 

 is largely dependent upon the temperature of the gaseous 

 mixtures, and in Table IV. these ratios have been collected 



Table IV. 



Ratio of the Hate at which Radiation is received through 

 Quartz to that through Fluorite for mixtures of 

 Coal-gas and Air of various strengths. 



Mean gas temp. 

 (° C abs.) 



2000 



1800 



1600 



1400 



1200 



1000 



for various temperatures. They show that the ratio of 

 the energy in the 2*8 fi band to the total energy (which, 

 as has been indicated, is mainly concentrated in the two 

 bands whose maxima are at 28 /jl and 4*4 //,) decreases 

 as the temperature decreases. They show, further, that the 

 2*8 fju band is rapidly disappearing in the neighbourhood 

 of 1200° C. abs., and when the gas temperature has fallen 

 to 1000° C. abs. it has almost entirely disappeared*. 



Radiation from Hydrogen and Air Mixtures. 



8. Similar experiments to those described above were 

 made on 25'4 per cent, mixtures of hydrogen and air f. 



* It is worthy of remark that the temperature (roughly 1000° C. abs.) 

 at which the 2'8ju radiation ceases to be emitted is roughly that at which 

 the energy in the 2*8/* radiation from a black body is a maximum 

 in the energy spectrum curve corresponding to this temperature. 



It may be noted that after the gas temperature has fallen to about 

 1200° C. the radiation curves recorded through quartz and glass (fig. 1) 

 become very nearly flat, while that recorded through fluorite goes on 

 increasing (slightly) even after the temperature has fallen to below 

 900° C. abs. 



f The 25*4 per cent, mixture of hydrogen after explosion consists of 

 29 per cent, of water vapour and the remainder almost entirely nitrogen 

 and a little excess oxygen. 



% mixture. 



13 % mixture. 



10 % mixture. 



0-53 



051 



— 



0-50 



0-50 



— 



0-46 



0-48 



0-40 



0-44 



0-46 



0-36 



0-29 



0-27 



0-25 



o-o 



00 



o-o 



