198 Flame Spectra at High Temperatures. [June I4 r 



We cannot, however, conclude from this that the flame is not 

 hot enough to produce these lines, for though the temperature may 

 be high enough the quantity of material present is not sufficient to 

 cause their appearance. Moreover, there are two intensely brilliant 

 bands of manganese closely adjacent, one of which certainly overlies 

 these lines. Lastly, they are not to be seen in the photographed 

 spectrum obtained from slag heated in the oxyhydrogen flame, which 

 melts platinum easily and slowly volatilises iridium wire. 



From thermo-chemical data the heat evolved during the " blow " 

 has been calculated, bat the specific heats of cast iron, slag, carbon 

 monoxide, and nitrogen are unknown at temperatures between 

 1200 C. and 2000 C. If we allow for 50 per cent, of the heat 

 developed at high temperatures being lost by radiation or absorbed, 

 then the estimated temperature of the metal in the converter is mora 

 than 1900 C. 



Le Chatelier (' Comptes Bendus,' vol. 114, p. 670) found the steel 

 in the ladle of a Robert converter to be at 1640 C. Reasons are 

 adduced for believing that it must certainly have been hotter than 

 this at the highest temperature of the " blow." 



The Technical Aspect of this Investigation. 



The spectrum obtained from Bessemer- slag by the oxyhydrogen 

 flame is composed of precisely the most characteristic features of the 

 flame spectrum, as seen issuing from the converter at Crewe. Hence 

 at this temperature iron and manganese are freely volatilised, as 

 they are in the oxyhydrogen flame. As a matter of course the 

 continuous spectrum of carbon monoxide, the bands and lines of that 

 compound and of elementary carbon are absent from the slag 

 spectrum. The flame spectrum at Dowlais differs from this, and 

 resembles the spectrum of metallic manganese or more closely that 

 of ferro-manganese. For reasons given, I conclude that the spectrum 

 at Crewe results from materials in the slag ; but that at Dowlais from 

 constituents vaporised from the bath of metal. 



The complete termination of the " fining stage " is clearly indicated,, 

 but there is no indication by the flame of the composition of the 

 metal within the converter at any previous stage. As the progress of 

 the " blow" is governed by the composition of the metal and its tem- 

 perature in the converter, and as these cannot be controlled with 

 perfect exactitude during each " blow," it follows that the practice of 

 complete decarburization* is the best course to pursue, the required 



* The words " carburizing " and " decarburizing " are to be preferred to 

 " carbonising " and " decarbonising " when applied to metals, because these expres- 

 sions were those originally used in the older worts on metallurgy, and they avoid 

 confusion with the other signification of the word " carbonising." 



