1886.] Mt\ F. Siemens on Dissociation Temj>eratures^ dc. 471 



WEEKLY EVENING MEETING, 



Friday, May 7, 1886. 



William Huggins, Esq. D.C.L. LL.D. F.R.S. Vicc-Prcsidout, 

 in the Chair. 



Frederick Siemens, Esq. 



On Dissociation Temperatures with special reference to Pyrotechnical 



questions. 



In bringing the subject of dissociation before the Royal Institution of 

 Great Britain, I wish it to be understood that I propose to confine 

 myself to its influence on combustion and heating, that is to say, to 

 its effects on combustible gases and the products of combustion, and 

 on furnace work generally. My researches have been made for the 

 most part in connection with large gas furnaces constructed according 

 to my new system of working with radiated heat, or what may be 

 otherwise called free development of flame. In perfecting this system 

 of furnace the principle of which is in many respects the reverse of 

 that generally accepted, both as regards construction and working, 

 I had to examine into the accuracy of certain scientific theories which 

 could not be brought into harmony with the actual results I obtained. 



In order that I may be clearly understood it is necessary to 

 describe shortly my system of furnaces before entering upon the 

 theory which alone appears to explain satisfactorily the practical re- 

 sults obtained by its means. These furnaces have of late been largely 

 introduced and are now extensively applied. I first described them 

 in a paper read at tlie Meeting of the Iron and Steel Institute held 

 at Chester in September 1884; their main peculiarity consists in the 

 arrangements by which the heat is abstracted in two different ways, 

 and at two different periods. In the first, or active, stage of com- 

 bustion the flame passes through a large combustion chamber (all 

 contact with its surfaces being avoided), and parts with its heat by 

 radiation only ; while in its second stage the products of combustion 

 are brought into direct contact with the surfaces and materials to be 

 heated, by which means the remainder of its heat is abstracted. This, 

 in a few words, is a description of the method of heating with free 

 development of flame, and it now only remains to explain how to 

 construct fireplaces and furnaces on this principle. 



As regards its principal application hitherto, namely, to regene- 

 rative gas furnaces, the two successive stages of heating are, by 

 radiation in the furnace chamber, and by contact in the regenerators. 

 The flame during active combustion heats the furnace chamber and 

 material placed therein by radiation only, and as soon as this stage is 

 completed the fully burnt gases enter the regenerative chambers and 

 deposit their remaining heat by coming into contact with the loose 



