646 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913, 



prepared for this purpose. When the temperature required does not 

 exceed 1,300° C, the bed of refractory material may be composed of a 

 good quality of fire brick, crushed and meshed to a suitable size. As 

 already remarked, the method is applicable to all kinds of gaseous 

 and vaporous fuels, but naturally the maximum temperature obtain- 

 able in any given case will depend upon the volume and heat capacity 

 of the products for a given heat development in the bed. Thus, 

 while with actual coal gas, water gas, or natural gas it is possible to 

 attain temperatures up to at least SjOOO'-" C., about 1,500° C. would 

 probably be the maximum temperature obtainable without regenera- 

 tion with producer gas of low calorific intensity, such as Mond gas. 

 With some degree of heat recuperation, which in such a case would 

 be quite practicable, this limit could be in all probability consider- 

 ably exceeded. 



The following are the results of a test on a muffle furnace in which 

 the muffle was heated between 815° and 1,425° C, with fully aerated 

 coal gas. 



Resiilts of test on a muffle furnace. 



[Dimensions of muffle, 9.5 by 5.25 by 3.26 in.] 



Mean net calorifie value of gas = 540 B. t. u. per cu. ft. at 15° C. 



The conditions under which the tests were carried out made pos- 

 sible the accurate determination of the rate of gas consumption requi- 

 site to maintain the muffle at any constant temperature between 815° 

 and 1,425° C. 



The temperatures given in the first two columns are those recorded 

 by a standard thermoj unction placed in the middle of the muffle. 

 The temperatures of the escaping products were also ascertained by 

 means of a standard thermoj unction. It will be observed that the 

 temperature of the products is in every case some 300° to 400° C. 

 lower than that of the muffle. Even with a muffle temperature of 

 1,424° C, there was no appearance of flame whatever at the top of 

 the furnace. The gas consumptions recorded in the middle column 

 ore extremely economical in comparison with ordinary heating by 

 flame contact. Thus, for example, in a similar test with a muffle 



