34 CALORIFIC POWER OF FUELS. 



difference between this and the " actual " reading is to be 

 added to the " actual " for the " corrected " reading. 



Now, by inspection of the calibration-curve previously 

 prepared, at the point corresponding to the corrected scale- 

 reading will be found the B. T. U.'s for the quantity burnt. 

 The ash is determined by weighing the asbestos cup after the 

 combustion. 



The following shows all the calculation needed : 



Weight of crucible (asbestos cup) 1.269 grams. 



and coal 3.017 " 



" " " " ash 1.567 " 



" " combustibles I-45O " 



" " ash 0.297 " 



" " coal 1-747 " 



1.747 grams X 0.002205 = 0.003852 pounds. 



First scale-reading 3.90 inches; time 2 hrs. 55 m. 



Second" " 14.70 " " 3 " 20" 



Third " " 14.30 " " 3 " 45 " 



"Actual" scale-reading. 14.70 3.90= 10.80 inches. 



Radiation correction 14.70 14.30= .40 " 



Corrected reading 1 1.20 " 



On the calibration-sheet 11.2 corresponds to 46.25 

 B. T. U.'s, and 46.25 B. T. U. -f- 0.003852 = 12000 B. T. U. 

 per pound. 



All air must be removed from the water in the bath, 

 the apparatus must work at a constant pressure, and the 

 pressure for which it is calibrated. A pressure of 10 inches 

 of water has been found satisfactory. Complete combustion 

 is always attained in the asbestos cups. 



It will be seen that the use of thermometers is obviated, 

 and also all corrections but one. The apparatus is intended 



