Radiation emitted in Gaseous Explosions. 91 



cent, mixture, which develops a maximum temperature of 

 2400° C. abs., loses by radiation 16*1 per cent. of its heat 

 of combustion ; the 15 per cent, mixture, which develops a 

 maximum temperature of 1500° 0. abs., loses 10 per cent. ; 

 and the 10 per cent, mixture, with a maximum temperature 

 of 1230° C. abs., loses 82 per cent. 



11. The loss of heat by radiation expressed as a per- 

 centage of the heat of combustion in coal-gas and air 

 mixtures within the limits of mixture strength 9*8 per cent, 

 to 15 per cent, does not vary nearly so much*. A 15 per 

 cent, mixture developing a maximum temperature of 

 2410° C. abs. loses by radiation 26*1 per cent, of its heat 

 of combustion ; a 13 per cent, mixture with a maximum 

 temperature of 2170° C. abs. loses 25 per cent. ; and a 

 9*8 per cent, mixture with a maximum temperature of 

 1700 6 C. abs. loses 23'6 per cent. 



12. The explanation of this is pretty clear in the light of 

 the experiments on the analysis of radiation emitted in the 

 hydrogen and the coal-gas mixtures. The exploded weak 

 hydrogen mixtures spend only a comparatively short period 

 of their history at temperatures at which they emit the 

 2 '8 /jl band (in which is concentrated the bulk of the 

 radiation energy in hydrogen mixtures). The coal-gas 

 and air mixtures, on the other hand (e\en the weakest 

 mixture experimented on), spend a great deal of their 

 history at radiating temperatures, both on account of their 

 much slower cooling and also because they emit the strong 

 44 ij, band which has considerable energy at temperatures 

 at which the 2'8 yu band ceases to be emitted. 



when the bolometer is placed close up to the plate of fiuorite (as was the 

 case in the other measurements). The figures may not compare as 

 regards accuracy with the figures for the other mixture strengths, 

 both for this reason and also because one record only is available 

 for this mixture strength. They are, however, substantially correct ; 

 the radiation figure of (H2 agrees fairly closely with that calculated on 

 the assumption "that the linear law connecting total radiation emitted 

 witli maximum temperature developed holds for hydrogen and air 

 mixtures in tho experimental vessel (see page 81, supra). The equation 

 calculated from the figures measured for the 2-/4 per cent, and the 15 per 

 cent, mixtures is R T =0'00042(^ m as.— 950), which gives for the 10 per 

 cent, mixture a value for R T =0'U. 

 * Phil. Trans. A. vol. ccxi. pp. 384-5. 



