CHAPTER V. 



CHEMICAL ENERGIES. 



WE have seen * that the quantity of energy given out in 

 the fall of a weight is proportionate to the weight 

 multiplied into the height through which it falls ; and 

 that this energy is exactly sufficient to raise it again to 

 the height from which it has fallen. This last is a result 

 of the law of the conservation of energy. 



It is equally true that the quantity of energy that is Energy 

 given out, in the form of heat or electricity, by the com- ^ combi- 

 bination of any two elements, is proportionate to the nation, a 



constant 



quantity of the compound formed, being constant for the quantity, 

 formation of equal quantities of the same compound. 

 One pound of hydrogen, for instance, in uniting with 

 oxygen to form water, gives out as much heat as would 

 raise the temperature of 34,462 pounds of water by one 

 degree centigrade.^ And it is a result of the law of the and suffi- 

 conservation of energy, and is amply proved by experiment, je^cMnpose 

 that the energy given out in the formation of a given the com- 

 quantity of water or any other compound is exactly suffi- 

 cient, if it were applied in the form of a current of 

 electricity, to decompose the compound back into its 

 constituent elements. 



Of course it is not possible actually to decompose a 

 pound of water by the energy given out in the formation 

 of another pound of water. In chemical experiments 

 there is always great loss of energy by what may be com- 



' P. 19. 



- All the numerical data referred to in this chapter are given in the 

 Appendix to Miller's Chemistiy, on the authority of Fabre and Silbermann. 



