410 Mr. R. E. Baynes on Saturation, Specific Heats, fyc, 



We further find, by somewhat laborious work, for the case 

 of saturation 



dir 

 dv 



= BFH/Av 4 , 



dv> 



dv 



-EF//*AB, 





dr 

 dv ~ 



DEF/8v 4 ; 





and consequen 

 dir 

 dr = 



tly 



= 8BH/ADE, 



dv' _ 

 dr ~" 



-8v 4 />ABD 



The saturation specific heats 



^-K + Ldp/dt, $ ' == K' + Ii'dp/dt, 

 are thus given by 



(a-fe)/K = (DE-BH)/FG = 3v/F 



(ft-sO/ft = (H-AD)//*G = Sv/fi, 

 whence also 



(5-s')/R= ZvGJuF. 



Furthermore, the latent heat of vaporization X is given by 



X/PVEE {v'-v)rdirjdT = GH/r ; 



the work of vaporization to by 



w/PV=ir(i/-io = CG/* 2 ; 



and the real latent heat V by 



X7PV^X/PV-tt(v'-v) = 3G/V. 



We may hence tabulate the values (p. 411) of, and plot 

 curves for, all the above magnitudes with either v, "», or r for 

 abscissaB (PI. VI.) , and we at once see that : 



(i.) £— & is always positive, increasing from R toco as t 

 increases from to 1 : 



(ii.) £' — fc is always negative and has a maximum value 

 — 1*95824 R when yu = '288953, to which correspond 

 v =-477565, v'= 6*64469, tt ='238098, r ='724335; it is 

 — oo when t is either or 1 : 



(iii.) inversion in the sio-n of $' (which is negative for the 

 highest and lowest temperatures) will therefore take place if 

 fe/R>4'95824, or, on the assumption that fc/R = N + i for an 

 N-atomic gas, if N>4*45824, so that inversion will occur if 

 the gas has at least five atoms in its molecule : 



In van der Waals' lately published Lehrbuch der Thermo- 

 d/jnamik, edited by Kohnstamm, it is found by an approxi- 

 mate calculation that for $' to be positive k — 1 + R/fe must 



