Properties of Gases and Vapour*, &c. 

 Table II. Specific Heats of Steam. 



279 



Variation of the Total Heat and Latent Heat. 



The Total Heat, H, of a vapour, defined in the usual manner, is 

 related to the Latent Heat, L, by the simple equation 



H = L + A (29), 



if the Heat of the Liquid h is reckoned from the same zero as the total 

 heat of the vapour. In the case of water both H and h are reckoned 

 from the state of water at C. The specific heat of water is so nearly 

 constant that h may often be taken as equal to t. More generally we 

 may write 



h = t + dh (30), 



where dh is the small difference of the heat h from the value t, which 

 it would have if the specific heat were constant and equal to unity. 

 According to the observations of Barnes, the variation of the specific 

 heat is very nearly linear between 60 and 100 C. The value of h at 

 temperatures above 60 C. may be taken as 



h = t + dh = * + 0-0001 10(*-60) 2 (31). 



