1886.J on Dissociation Temperatures, dc. 473 



there, free carbon is liberated and produces smoke which envelopes 

 that part and prevents the rays of heat of the other portions of the 

 flame from reaching it. 



Eadiation plays a much greater part in all heating operations 

 than has been hitherto acknowledged, consequently any cause which 

 tends to lessen the radiating power of flame, or to screen its rays, 

 reduces also the amount of heat which can be thus utilized. 



If the flame is not allowed to come into contact with bodies to be 

 heated, combustion is improved, while full advantage is also gained 

 of its heat-radiating power, which would otherwise be diminished 

 more or less, as already explained. The ordinary mode of applying 

 flame, by allowing it to impinge directly upon the surfaces to bo 

 heated, causes imperfect combustion, prevents the rays of heat from 

 reaching them, and also destroys, or tends to destroy them ; this is 

 particularly the case when hydrocarbons and carbonic oxide are used. 

 These statements are fully borne out by the results which I have ob- 

 tained in practice with the new and old form of regenerative furnace 

 respectively, and they also fully agree with the theoretical explanation 

 I have suggested ; that theory, however, is still incomplete, as it does 

 not deal with the subject of dissociation, a subject to which for various 

 reasons I have avoided referring until recently, although it has been 

 brought forward by several writers, and used as an argument against 

 my new system of furnace ; as according to these writers it would 

 appear to be impossible to produce such exceedingly high tempera- 

 tures as I claim to reach. I have long held the opinion that appear- 

 ances of dissociation not being observable in furnaces heated by 

 radiation, but occurring in furnaces in which the flame is allowed 

 to come into contact with surfaces, must be due to the action on the 

 flame of those surfaces at high temperature. I was led to this con- 

 clusion partly from my own observations, and partly from descriptions 

 of dissociation observed by others, amongst whom was my brother, 

 the late Sir William Siemens, who described a case of dissociation 

 (see lecture delivered March 3rd, 1879, at the Royal United Service 

 Institution, entitled " On the production of Steel and its application 

 to military purposes ") which occurred in a regenerative gas furnace 

 constructed according to our old views of combustion and heating. 

 The conclusion at lohich I have arrived is, that solid surfaces, besides 

 ohstructing active combustion, must cdso at high temperatures have a dis- 

 sociating influence on combustible gases and on the products of combustion. 



In order to obtain information on this subject I examined the laws 

 and theory of dissociation, and endeavoured to bring the various 

 results obtained by scientific authorities into agreement with one 

 another, and with my own experience, but failed entirely in doing so. 

 The temperatm-es of dissociation of carbonic acid and steam, the two 

 principal gases forming the products of combustion when ordinary 

 fuel is used, vary very much according to these observers, and the 

 results I have obtained in practice are different from most of them. 

 1 hope to prove that the temperature at which dissociation sots in, is, 



