Iron Vapour in Air-Coal Gas Flame. 233 



4957, which in ordinary circumstances is plainly visible and 

 more intense than Class I. group y, shows only traces with 

 ammonia and is relatively feebler than group <y. 



The Class II. triplets at 4046 and 4384 are considerably 

 reduced in intensity, the latter relatively much more so than 

 the adjacent group <y. Class I. lines, although appreciably 

 weakened, are so much less than those of Classes II. and III. 



Hence the addition of ammonia to the air- coal gas mixture 

 reduces to a considerable extent the particular reaction 

 between nitrogen and iron, and farther, it affects also the 

 temperature of the flame, as is evidenced by the weakening 

 of the temperature (Class I.) lines of iron. 



It is not possible in this case to account for the weakening 

 of the cone emission by lack of nitrogen alone, for, in ad- 

 dition to the nitrogen set free from the ammonia, there is the 

 usual amount available from the air which is mixed with 

 the coal gas. But we must remember that, in addition to 

 nitrogen, a considerable amount, about three times as much, 

 of hydrogen is set free by the decomposition of ammonia. 

 This, added to the hydrogen derived from the coal gas, repre- 

 sents a large quantity, and it may be safely assumed that, 

 even after a great portion of it has been burned to water, 

 an appreciable amount will remain over. It may be this 

 excess of hydrogen which restrains the reaction between the 

 nitrogen and iron, such as may be expected to happen in 

 accordance with the hypothesis suggested. This same cause 

 may also account for the suppression of the cone emission in 

 the oxy-coal gas flame. 



It would have been interesting to know if the so-called 

 water-vapour spectrum is in any way influenced by the 

 presence of ammonia. The characteristic bands of this 

 spectrum are, however, situated in the ultra-violet and were 

 therefore not within reach of my spectrograph. 



§ 8. Spectrum of Iron given by an Air Flame burning 

 in an Atmosphere of Coal Gas. 



The burner used consists of one row of six holes each 

 having a diameter of 2 millimetres. Its construction is other- 

 wise similar to that of burner No. 2, previously described * 

 The flame is inverted in the well-known manner by sur- 

 rounding the burner with an ordinary paraffin-lamp chimney. 

 The air, before entering the burner, flows through a sprayer 

 in which it can be charged with the spray from a perchloride 

 of iron solution. A continuous stream of coal gas is passed 



* Hemsalecli, /. c. p. 6. 



