CATALYSIS AND CATALYSTS 209 



To these publications readers interested in the matter must be 

 referred for details. 



The following abbreviated version contains the most prominent 

 and important facts : 



Mr. Thomas Fletcher in 1887 showed that when a mixture 

 of ignited gas and air is directed on to a large ball of iron wire 

 so as to heat it to the necessary temperature, and the current 

 of gas is then momentarily interrupted, the ball will continue to 

 glow with great increase of temperature, but without any sign 

 of flame. 



Bone began investigations in 1902 as to the influence of various 

 hot surfaces on the combustion of hydrogen and carbon monoxide, 

 and has arrived at the following general conclusions. (1) The 

 power of accelerating gaseous combustion is possessed by all 

 surfaces at temperatures below the igniting point in varying 

 degrees, depending on their chemical characters and physical 

 texture. (2) Such an acceleration of surface combustion is 

 dependent on an absorption of the combustible gas and probably 

 also of the oxygen by the surface, whereby it becomes activated 

 (probably ionised) by association with the surface ; and (3) the 

 surface itself becomes electrically charged during the process. 



It also appears that while hot surfaces possess the power of 

 accelerating gaseous combustion at temperatures below or near 

 to the igniting point, the same power is manifested in an in- 

 creasing degree as the temperature rises. And there is experi- 

 mental evidence that the differences manifested by different 

 surfaces at low temperatures practically disappear when the 

 temperature of the surface reaches bright incandescence. 



Incandescent surface combustion has been applied to a 

 number of practical purposes, such as heating rooms and pro- 

 viding a hot surface suitable for many cooking operations such 

 as grilling or roasting. It has also been applied on a large scale 

 to raising steam, melting metals and alloys, and other practical 

 purposes. 



In the former case a diaphragm is prepared of granulated fire 

 brick or other material bound together into a block and fitted 

 into a suitable frame, which provides a space at the back into 

 which the gas and air mixture can be fed (Fig. 56, p. 210). 

 The gas being first turned on and lighted, air is then gradually 

 added till a fully aerated mixture is obtained. 



The flame soon becomes non-luminous and diminishes in size ; 



