Iron Vapour in Air-Coal Gas Flame. 237 



given by burner No. 1 *. The round side of the rod faces 

 the burner, and on the flat top is fixed a strip of asbestos 

 in order to reduce loss of heat by radiation. The spectro- 

 graphic observations were made in the direction of the 

 explosion region and as near to the lower surface of the 



\^ Mantle 



s 



Graphite Rod 



Heating of air-coal gas flame. 



graphite rod as practicable. A continuous current of 

 25 amps., which passed through the graphite rod, kept it 

 at a bright red heat. A rod treated in this way will last 

 only 12 minutes at the most, so that six rods were used for 

 an exposure of one hour. 



The most notable effect of the heating is a marked in- 

 crease in the intensity of the continuous spectrum in the 

 visible part. (Light from graphite rod reflected by metal 

 vapour ?) 



As regards the iron lines, there is only a slight all-round 

 enhancement without any very definite selective action, 

 although one has the impression that Class I. and II. 

 lines are a little more affected than those of Class III. 

 There is no appreciable effect on the bands of the Swan 

 spectrum. 



Similar results were obtained by simply holding rods of 

 carbon and graphite in the flame without applying an 

 electric current. An iron rod of the same dimensions 

 showed, however, no enhancement; this may be due to the 

 heat being more rapidly conducted away by the metal. 

 Both the carbon and graphite rods were, by the action of 

 the flame alone, raised to a red heat. It may therefore be 



* Hemsalech, /. c. p. 6. 

 Phil Mag. S. 6. Vol. 34. No. 202. Oct. 1917. S 



