122 CALORIFIC POWER OF FUELS. 



With the throttling-calorimeter the percentage of moisture 

 P, or number of degrees of superheating, are determined as 

 explained before. 



Since the invention of the throttling-calorimeter the use 

 of the original condensing, or so-ealled barrel, calorimeter is 

 no longer warranted. Accurate results should, however, be 

 obtained by condensing all the steam generated in the boiler, 

 and this plan has been followed in certain cases. It has, 

 therefore, been thought desirable to add other formulae ap- 

 plicable to condensing-calorimeters. The following additional 

 notation is required: 



W = the original weight of the water in calorimeter, or 

 weight of circulating water for a surface condenser. 



w = the weight of water added to the calorimeter by blow- 

 ing steam into the water, or of " water of condensation " with 

 a surface condenser. 



t = total heat of water corresponding to initial tempera- 

 ture of water in calorimeter. 



^ = total heat of water corresponding to final temperature 

 in calorimeter. 



Evidently, then : 



W(t^ f] = the total thermal units withdrawn from the 

 boiler and imparted to the water in calorimeter. 



W 



(/, /) = the thermal units per pound of water with- 

 drawn from the boiler and imparted to the water in calorim- 

 eter, from which should be deducted T l t l to obtain the 

 number of thermal units per pound of water withdrawn from 

 the boiler at the pressure due to the temperature T. 



Since only the latent heat L is imparted to the portion of 

 the water evaporated, the quality Q, or proportional quantity 

 evaporated, may be obtained by dividing the total thermal 

 units per pound of water abstracted at the pressure due to the 

 temperature T by the latent heat L. Hence, as given in 



