11. — Steam Boiler Tests as a means of Determining the 

 Calorific Value of Fuels. — By D. W. Robb. 



(Received Dec. 6th, 1890.) 



It will be recognized by those who use large quantities of fuel, 

 especially of bituminous coals, that they differ very greatly in 

 value, even coals which are taken from adjoining areas give very 

 different results, so that it is sometimes puzzling to the con- 

 sumer and difficult to decide upon the merits and proportionate 

 values of the various fuels within his reach. It is likewise diffi- 

 cult to determine when the greatest practicable amount of 

 work is being obtained from the fuel, and consumers are 

 frequently subjected to great loss from the want of this know- 

 ledge. There are three recognized methods of determining the 

 calorific value of coal, viz : by chemical analysis, by the use of a 

 calorimeter, and by actual measurement of the water evaporated 

 by a definite amount of fuel in a steam generator. 



By the first method it is possible to ascertain the constituents 

 of the fuel in their various proportions and to determine the theo- 

 retical heat value when combined with a definite proportion of 

 pure oxygen, and approximately to compute the amount of heat 

 which would be converted into work when combined with ordin- 

 ary air, and consumed under usual conditions. But this becomes 

 a complicated problem, as will be seen when it is considered that 

 the heat absorbed and wasted in heating the non-combustible 

 constituents of both the air and fuel must be taken into account 

 and that these wastes vary with the amount of superfluous air 

 admitted through the grate, and with the proportion of noncom- 

 bustible matter in the fuel; therefore, any estimate of the prac- 

 tical value of a fuel deduced from chemical analysis can only be 

 approximate. 



In testing fuels by a calorimeter a sample of the fuel mixed 

 with chlorate of potassium is placed in an open-mouthed copper 

 vessel, which is submerged open mouth downward, like a diving 

 bell, in a vessel containing a measured quantity of water, com- 



