( 867 ) 
senting an expansion which is characterised by equal values of 
enthalpy in the initial and final states may by the usual methods *) 
be transformed into 
PE 
end “(cee Op 
C,(T,—T, =| i | alia dv + pyv.— piv, - « » (4) 
vy 
or 
Pa 4 
no RN iil ce. 
Atje | is OT —v|dp . A 2 
P 
Pi 
where 
1 
Di id Vdd. 
TS 
Since 7 and 7, never differ much in value, and since, in any 
case, C varies very slowly with temperature, the difference between 
C and C must be extremely small. 
For the present calenlation equation (4) seems at first sight more 
directly applicable than (5), but the evaluation of v, would necessitate 
the use of successive approximations; it is, therefore, better to use 
equation (5). For this purpose, the following transformation, valid. 
as long as excessive densities are not reached, may be applied to 
equation (2); this equation maybe written in terms of reduced 
pressure as 
Apy = Uw) 4+ Bop + Cop? 4 Dop? + EC)pt + ete. . (6) 
if 
TG Sees | Meth dE AE AE et AL 
B 
BY) =a a 4 . . e . . e . e . . . (8) 
CUB? 
Gop) = ae (9) 
23° —3 ABE 
Aere (10) 
ue 
DU? 5 BH _2 EEL LOMB 
| C00) = r | (11) 
etc. mT 
Equation (5) in reduced magnitudes becomes 
i dv 
C, (7,—T,) = — Tr af | & — | EP! eres HB 
11 
1) See: J. P. Kuenen Die Zustandsgleichung, pp. 106—9 Vieweg 1907. 
