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X. Radiation in Explosions of Coal-Gas and Air. 

 By W. T. DAVID, E.A., B.Sc., Trinity College, Cambridge. 



Communicated by Prof. B. HOPKINSON, F.R.S. 

 Received May 24, Read June 29, 1911. 



IN the first part of this paper results of experiments are given on the radiation 

 emitted during the explosion and subsequent cooling of mixtures of various strengths 

 and densities of Cambridge coal-gas and air. Bolometric measurements were made 

 of that part of the radiation from the hot gaseous mixtures which was transmitted 

 through clear plates of fluorite, quartz, plate glass, and water (contained between two 

 plates of glass). The fluorite (6 mm. thick) transmits very approximately 95 per 

 cent, of the total radiation emitted by the gas ; the quartz (also 6 mm. thick) 

 transmits about 70 per cent, of the radiation from water vapour and cuts off a very 

 large proportion of that from CO a ; the water cell transmits practically only luminous 

 radiation. It has been therefore possible to estimate fairly accurately the total 

 radiation emitted by the gas, and, roughly, the proportions emitted by water vapour 

 and by COj, and also the amount of energy in the luminous radiation. The radiation 

 emitted in the explosion of a 25-per-cent. mixture of hydrogen and air has also been 

 measured. 



The second part of the paper consists of an investigation into the diathermancy 

 and emissive power of the hot gaseous mixture after explosion. The conclusions 

 drawn from these experiments offer an explanation of many of the peculiar results 

 given in the first part. 



Prof. HOPKINSON has already shown that the heat lost by radiation in explosions 

 of coal-gas and air is a considerable fraction of the total heat of combustion of the 

 gas. Recently he has made a very complete investigation of this radiation loss in 

 15-per-cent. mixtures.* He exploded mixtures of the same strength in a vessel of 

 bout f cub. ft. capacity whose walls were silver-plated, first, when the walls were 

 highly polished, and then when these same walls were coated with a thin layer of 

 dull black paint. In the first case the maximum pressure developed was about 3 per 

 cent, greater and the subsequent rate of cooling much slower than in the second 



* 'Roy. Soc. Proc.,' A, voL 84, p. 155. 

 VOL. ccxi. A 480. 20.10.11 



