302 Dr. Woods on the Heat of Chemical Combination. 



If L, the latent heat, were always equal to the expansion, the 

 numbers in the last column should be equal, or multiples of each 

 other : but I do not say it is equal to the expansion, it only ap- 

 proximates. In the case of ice, the table shows the expansion 

 from the solid to the liquid state is only half what is represented 

 by the latent heat. And this is evidently what is to be expected ; 

 for the contraction between masses, so to speak, whereby water 

 is rendered heavier than ice, is opposed to the atomic expansion. 

 In the case of lead, on the contrary, the expansion is somewhat 

 greater. But generally the numbers show that the substitution 

 of the atomic expansion for the latent heat would be correct if 

 we knew exactly the amount. And therefore it is proved, that 

 as in the expansion of liquids into vapours, so in the expansion of 

 solids into liquids, the amount of that expansion is, when taken in 

 connexion with the fusing-point, inversely as the atomic volume or 

 a multiple of it ; from which I deduce, that as the less the atom 

 is the greater is the space, so the greater the expansion existing 

 between the particles of matter, the greater the subsequent ex- 

 pansion in all cases for a given contraction in another body. 



But in the formula (160 + ^) - = -= -, the less either factor 



s L — 1 



in the left-hand side of the equation, the greater is L ; and as 



the greater the expansion of a body is the less number of degrees 



of heat we must suppose it would require to be raised to its 



fusing-point, so the smaller t is, the greater we may take the 



expansion among its particles in the solid state to be ; therefore 



from whatever other cause, as well as the smallness of the atomic 



volume, a greater expansion in the solid state exists, the greater 



will be the expansion of the body from that condition to the 



liquid. 



