50 GENERAL BIOLOGY 



That is, the energy that binds together the hydro- 

 gen and carbon in the form of acetylene is nearly 

 one sixth greater than the sum total of the intrinsic 

 energy, measured by the heat evolved in combus- 

 tion, of the same amount of either element taken 

 separately. 1 



Conservation of Energy. In the above example 

 the potential energy is released as heat, but it is 

 conceivable, on the basis of other experiments, that 

 this energy, released by the breaking down of acet- 

 ylene, might be employed at once in building up 

 some other chemical compound, and thus be non- 

 evident to us except from its end-result. At any 

 rate the decomposition and recombination (analysis 

 and synthesis) of any chemical compound may be 

 repeated indefinitely, the same amount of energy 

 being released or absorbed at each change. All the 

 forms of energy known to us may be transformed one 

 into another in' this way. Gravitation acting on the 

 molecules of water in a brook may be caused to drive 

 a waterwheel. The wheel, by its motion, in addition 

 to producing heat by friction, may also run a dynamo, 



'The above figures refer to the heat of combustion of one gram each 

 of carbon, hydrogen, and acetylene. If equivalent amounts of sub- 

 stance be taken the difference is even more striking. The molecular 

 weight of acetylene is 26 and every gram of acetylene contains twenty- 

 four twenty-sixths of a gram of carbon (mol. wt. of C = 12) and two 

 twenty-sixths of a gram of hydrogen (H = 1) ; twenty-four twenty- 

 sixths of 193,960 cal. is 179,040 cal. and two twenty-sixths of 69,960 cal. 

 is 5,378 cal, ; the sum of these is 184,418 cal. or 126,182 cal. less than 

 the heat of combustion of one gram of acetylene. 



