232 Mr. G. A. Hemsalech on the Line Spectrum of 



that the temperature in the cone of this flame, on passing 

 upwards, soon reaches the critical value beyond which the 

 formation of nitrides will cease. With cobalt and nickel, 

 however j the effect of the reaction in these same conditions 

 is considerably more conspicuous and is observed to extend 

 to a much greater height from the base of the cone. It 

 seems, indeed, as if the limiting value of the temperature 

 up to which the formation of nitrides of these two metals 

 will take place were greater than for iron. 



§ 7. Effect of adding Ammonia to Oxy-coal Gas and 

 Air-coal Gas Flames. 



Without entering into details, it is sufficient to state that 

 the experiment was arranged so that a greater or smaller 

 amount of ammonia could be fed into the Hame by passing 

 the whole or only a portion of the coal gas through a flask 

 containing strong ammonia solution. With a certain amount 

 of ammonia the cone of the oxy-coal gas flame becomes bril- 

 liantly coloured yellow. Spectroscopic examination of the 

 mantle and cone shows that the iron spectrum given by the 

 former is the same as when no ammonia is present, namely, 

 all the lines reach their maximum intensity in the region 

 just above the cone. The cone spectrum, on the other hand, 

 and contrary to expectation, shows no trace of Class III. 

 lines, nor is there the least sign of a strengthening of 

 Class II. lines. Thus the addition of ammonia suppresses 

 the slight reaction which exists at the base of the cone when 

 this gas is absent. With regard to the Swan spectrum, its 

 bands appear nearly as well developed as usual. But in 

 addition to this spectrum there stand out very prominently 

 the bands of cyanogen at 3884 and the group in the violet 

 at 4216. This most interesting result seems to indicate that 

 ammonia is broken up in the explosion region and that the 

 nitrogen combines with the carbon to form cyanogen. Some 

 experiments by Grotrian and Bunge appear, however, to 

 show that these bands are not due to cyanogen but to 

 nitrogen. In that case their emission in the flame would 

 probably be caused by the decomposition of the ammonia 

 and should be independent of the presence of carbon. 



When ammonia is fed into the air-coal gas flame the 

 cyanogen bands again show in the cone, though they appear 

 much less pronounced. Also the bands of the Swan spec- 

 trum are in this case appreciably weakened. The influence 

 on the various types of iron lines is very marked, the cone 

 lines especially being affected. Thus, Class III. group at 



