AND TUT. KKI-ATION OF SPECIFIC HEAT TO ATOMIC \V Kiel IT. 



by its specific heat at constant volume when in the state of a perfect gas. 

 its atomic weight, then 



251 

 If a is 



o* = 2-414 



for all elements, because it is of this amount for hydrogen. 



Thus if a = 58-55 for cobalt, and 58'24 for nickel, k = '04123 for cobalt, and 

 04145 for nickel. 



It is, perhaps, not unreasonable to assume that in no state can the substance have 

 a smaller specific heat than this atomic specific heat. 



If the specific heat of a substance at constant volume is k, and at constant 

 pressure K, it is interesting to note that K and k are very nearly equal for solid 

 metals, and, indeed, that the heat required to raise a gramme of solid metal 1 in 

 temperature is not very different under all ordinary conditions as to pressure and 

 volume. The ratio of K to k is known to l>e the ratio of the elasticity at constant 

 entropy to the elasticity at constant temj>erature, or what we sometimes call the 

 quick and the slow elasticity. The slow may lie measured with a piezometer, or 

 calculated from YOUNG'S modulus and the modulus of rigidity, the quick may be 

 obtained from sound vibration experiments. 



Thermodynamics of a Solid. 



If we say that a is the real coefficient of expansion under constant pressure, we 



mean that 



(dv/dt) = a.v. 



When we say that is the volumetric elasticity at constant temperature, we mean 



that 



(dv/dp) v/e. 



In all probability a and e are functions of the temperature, and practically of nothing 

 else. 



The thermodynamic coefficients become, all energy being measured in ergs, 



K - k = at., 

 / = aft, 

 L = art, 



where K is specific heat at constant pressure, and k is specific heat at constant 

 volume, and the significations of / and L are given by the following expressions for 

 the heat, dll given to unit mass of the stuff when its t, p, and v become t + dt, 

 p + dp, and r + dv. 



<l\l = k.dt + l.dv = K.dt + L.dp. 



Mr. TUTTON has measured what are ordinarily known as the coefficients of expan- 



2 K 2 



