APPENDIX 11. 



THE EMISSION SPECTRUM OF THE HEFNER LAMP. 



Having had occasion to compare the radiation from a Hefner lamp 

 (amyl-acetate flame) with an acetylene flame of the Bunsen and the 

 cylindrical types, the results obtained seem of sufficient interest to record 

 in this paper. The large spectrometer was used, hence the atmospheric 

 absorption bands at 1.4, 1.8, and 2.6/1 are prominent. 



The products of combustion are solid carbon, water vapor, and COg. 

 In fig. 127 curve c shows the radiation from the Bunsen acetylene 

 flame, while curve a shows the radiation from the cylindrical acetylene 

 flame. Curve b gives the radiation from the Hefner lamp. 



The Hefner lamp is weak in light-giving power as compared with the 

 acetylene flame. The curves at 2 fi show that this is due to the diflPer- 

 ence in temperature of the incandescent carbon particles. It would be 

 interesting to learn whether this is due to the greater quantity of water 

 vapor present in the amyl-acetate flame or to the greater completeness 

 of the combustion ; it has twice as much water vapor as has the acety- 

 lene flame for the same amount of carbon dioxide. 



The emission bands at 4.4 fi are of about equal intensity. The curves 

 when corrected for slit width are shown in fig. 128. The maximum 

 for the acetylene flame comes at i .05 fi, as found by Stewart,^ while the 

 amyl-acetate maximum occurs at 1.50 /*. 



Now, the question of the precise relation between the temperature 

 of an ideal " black " body, computed by means of the constant A 

 (AmT = A), and the actual temperature of a flame is not settled. 

 Stewart (loc. cit.) adopted the value A = 2282, which gave values for 

 the temperature of the acetylene flame, the ordinary gas flame, and a 

 candle flame, computed from the maxima of their respective energy 

 curves, which agree with the temperatures obtained by Nichols^ by 

 direct measurement, viz, 1900° C, 1780° C, and 1670° C, respectively. 

 Using this value of the constant A, the computed temperature for the 

 amyl-acetate flame is 1250° C. Using Paschen's constant, 2940, gives 

 a value of 1690° C. Angstrom^ finds this temperature to be 1557° C, 

 while Wanner found it to be 1162°. Paschen* found the shifting of 

 the emission band of CO2 with rise of temperature, using a stream of 



^Stewart, G. W. : Phys. Rev., xv, p. 311, 1902. 

 *E. L. Nichols: Phys. Rev., x, p. 248, 1900. 

 Angstrom: Phys. Rev., xvii, p. 302, 1903. 

 ^Paschen : Ann. der Physik, 50, p. 409, 1893. 

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