2 CALORIFIC POWER OF FUELS. 



Liquid fuels petroleum, shale oils, vegetable and animal 

 oils. 



Gaseous fuels coal gas, producer gas, water gas, mixed 

 gas, natural gas. 



CALORIFIC POWER OR HEAT VALUE. 



The quantity of heat generated by the combustion of 

 a definite quantity of fuel in oxygen is called the calorific 

 power, heat value, or heat of combustion. 



The expression calorific power or heat value has a wider 

 signification than heat of combustion. In the popular sense 

 the former ones apply to the measure of an industrial yield as 

 well as to the heat given off by the fuel during its complete 

 combustion. The expression heat of combustion, more nearly 

 correct from a scientific point of view, is applied, on the con- 

 trary, only to that quantity of heat generated by the substance 

 when completely burnt; that is to say, when the carbon and 

 hydrogen are completely changed to carbonic acid and water. 

 The unit adopted for these quantities of heat is the Calorie 

 and the British Thermal Unit. 



The Calorie is the quantity of heat absorbed by the unit of 

 weight of pure water when its temperature is increased one 

 degree Centigrade. This unit is usually one gram or one 

 kilogram. When it represents the atomic or molecular 

 weight, it is called the atomic or molecular calorie, the gram 

 being taken as the atomic unity. 



The British Thermal Unit (B. T. U.) is the quantity of 

 heat absorbed by one unit (usually one pound) when its tem- 

 perature is increased one degree Fahrenheit. It is -^ of a 

 calorie. 



A kilogram in burning generates n calories with a kilogram 

 as unit and the Centigrade scale; a pound generates n calories 

 with a pound as unit and the Centigrade scale (W. Kent's 

 pound-calorie); or, whatever the weight taken, there will be 

 generated the same number of calories, using the same unit of 



