CHEMISTRY 245 



upon oxidation they yield it all back again, 

 just as water vapor on condensing yields 

 back the latent heat which it has taken up 

 during evaporation. In this manner, every 

 gram of glucose or other monosaccharide is 

 necessarily a temporary depository of solar 

 energy amounting to about 3.74 calories, 

 taking up just that amount of energy when 

 synthesized by chlorophyll, yielding it back 

 when burned in the muscle. 



Compounds of carbon and hydrogen are 

 especially well qualified to be reservoirs of 

 energy which may be liberated by oxidation, 

 as the following table shows: — 



HEATS OF COMBUSTION OF ELEMENTS PER GRAM 



Hydrogen, it will be seen, far exceeds any 

 other element in the amount of heat that it 



