92 Professors Kirchhoff and Bun sen on Chemical 



the bodies with which the metals employed were combined, the 

 variety in the nature of the chemical processes occurring in the 

 several flames, and the wide differences of temperature which 

 these flames exhibit, produce no effect upon the position of the 

 bright lines in the spectrum which are characteristic of each metal. 

 The following considerations show how much the temperature 

 of these various flames differ. An approximation to the tempe- 

 rature of a flame is obtained by help of the equation 



._Zgw 



in which t signifies the required temperature of the flame, g the 

 weight of one constituent of substance burning in oxygen, w the 

 heat of combustion of this constituent, p the weight, and s the 

 specific heat of one of the products of combustion. The heat 

 of combustion of the following bodies may be taken as — 



Sulphur 2240 C. 



Bisulphide of carbon . . 3400 



Hydrogen 34462 



Marsh-gas 13063 



Elayle 11640 



Ditetryle 11529 



Carbonic oxide .... 2403 



The specific heats under constant pressure were found by 

 Regnault to be — 



Sulphurous acid = 0*1553 

 Carbonic acid =0*2164 

 Nitrogen =0*2440 



Aqueous vapour =0*4750 



Hence the temperatures of the flames are found to be — 



The sulphur flame 1820 C. 



The bisulphide of carbon flame . . 2195 



The coal-gas flame* 2350 



The carbonic oxide flame f .... 3042 



The hydrogen flame in air % . . . 3259 



The oxyhydrogen flame § .... 8061 



It was found that the same metallic compound, placed in one 

 of these flames, gives a more intense spectrum the higher the 

 temperature of the flame. In the same flame, those of the com- 

 pounds of a metal give the brightest spectra which are most 

 volatile. 



* Ann. Chem. Pharm. vol. cxi. p. 258. 



t Bimsen's ' Gasometry,' p. 242. J Ibid. § Ibid. 



