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



§ 3. Effect of adding Traces of Nitrogen and Air to 



the Gases feeding an Oxy-coal Gas Flame. 

 The observations on the appearance of the cone lines given 

 in the preceding paragraph have rendered it very probable 

 that nitrogen is one o£ the essential factors in the emission 

 of the cone lines. It was therefore natural to expect the 

 reappearance or enhancement of these lines in the explosion 

 region of the oxy-coal gas flame on adding traces of nitrogen 

 to the gas mixture. In one experiment the nitrogen, which 

 was produced in the usual way by passing air over red-hot 

 copper, was added to the oxygen and, in another experiment, 

 to the coal gas. In either case there resulted an enhance- 

 ment of Class II. lines in the cone, not merely near its base 

 but along its entire height ; also the stronger lines of 

 Class III. became perceptible. On the other hand, Class I. 

 lines were not affected and remained, as before, brightest in 

 the region just above the cone. Similar results were obtained 

 by adding traces of air to the oxy-coal gas mixture. 



§ 4. Effect of adding Oxygen to the Gases feeding 

 an Air-coal Gas Flame. 



As was to be anticipated, an increase in the proportion of 

 oxygen in the air-coal gas mixture causes a strengthening 

 of the flame lines due to a rise in the flame temperature. 

 Also, if, as had been concluded from the results of previous 

 observations, nitrogen is one of the determining factors in 

 the emission of the cone lines, the further dilution of it with 

 oxygen should result in a diminution of the cone emission. 

 This is, indeed, what has been observed (PL II. No. 3 ; to 

 be compared with No. 1). The principal facts derived from 

 this experiment may be summarized as follows : — 



a. Class I. lines are all more or less enhanced, especially 



the triplets at 3720 and 3860. They show no effect 

 due to any special actions in the cone, but gain their 

 maximum strength just above the cone ; in this respect 

 they behave similarly to those of the oxy-coal gas flame. 



b. Class II. lines are affected in a most striking manner. 



In the cone they are relatively much weakened, 

 whereas in the flame above the cone they are con- 

 siderably strengthened. This is well shown by the 

 triplets at 4046 and 4384. 



c. Class III. lines are considerably reduced, only traces of 



the brighter ones remaining visible. 



d. The continuous spectrum in the cone is greatly 



diminished, but the carbon bands, on the other hand, 

 are markedly enhanced and more fully developed. 



