4 OXYGEN 



Grammes of water raised 

 1 C. in temperature by the 



Substance. combustion of 1 gramme 



of the substance. 



Charcoal 8080 



Hydrogen 34460 



Air-dried wood 2800 



Charred wood 3600 



Average coal 7500 



Good coke 7050 



Albumin (serum) . . . . . , 5918 



Casein 5860 



Albumin (egg) 5735 



Muscle 5660 



Peptone . . . ... . . . 5300 



Asparagine ....... 3514 



Urea . 2542 



Fat of pig 9477 



,, ox 9486 



,, ,, sheep 9494 



,, ,, butter 9216 



Olive oil 9400 



Eape-seed oil 9500 



Arabinose ........ 3730 



Glucose 3740 



Galactose 3720 



Fructose 3755 



Cane sugar 3955 



Milk sugar (cryst.) 3736 



,, (anhyd.) 3952 



Maltose (cryst.) 3722 



(anhyd.) 3949 



Cellulose 4185 



Starch 4182 



As has been stated, the heat of combustion of a substance is con- 

 stant, whatever be the manner in which union with oxygen occurs, 

 provided only that the same final products be obtained. The tempera- 

 ture attained, however, varies greatly with the conditions under which 

 combination takes place. For example, the temperatures reached when 

 substances are burnt in pure oxygen are much higher than when they 

 burn in air, though the same products are formed and, as is seen from 

 the above statements, the same quantities of heat are evolved in both 

 cases. It will be easily seen why such different temperatures are 

 produced, the combustion in pure oxygen takes place more rapidly, 

 in a smaller space (generally with a smaller flame) and the process is 

 carried on without a large amount of cool, indifferent gas (nitrogen) 

 which would abstract heat and keep the temperature down, while in 

 air, the conditions are just the opposite. 



A still more extreme case is furnished by the many processes of 

 slow oxidation or combustion which occur so frequently in nature. 

 Under ordinary circumstances, these processes generate heat only at 

 about the same rate as it is carried away by contact with surrounding 

 objects, consequently little or no elevation of temperature occurs, but 

 occasionally, the rate of loss of heat may be greatly diminished, when 

 a decided and, in some cases, a destructive rise of temperature ensues. 



