( 301 ) 
Tr /0, ; 
hence for isopentane sate < 4.174, which does not agree with 
Pk v 
the observations. Indeed Driererior wrongly supposes that his 
formulae also represent the correct isothermals for volumes smaller 
than the critical. *) 
He derives (lc. p. 74) the following formula for sn 
1 
vn vz T's = — 2.116 vp RT gh, 
where ps represents the saturated vapourpressure and vj and vz the 
volumes of saturated liquid and vapour. 
This formula gives at the critical point: 
Td 
EE 79, 
pe dT 
According to the thermo-dynamic thesis laid down in § 3 
m= (Fn), 
at the critical point. Hence the two results contradict each other. The 
explanation may be found in the circumstance that DiereRIc1 has 
assumed that 
Vg 
| toe J. Q 
if 
RT 
ptr= RER 
C— 
and if g is the internal latent heat of evaporation. This would be 
true if 7 were not a function of the temperature; as this is however 
the case with Drerrric1 the internal latent heat of evaporation must 
be found from 
refr 
Y4 
1) See DanieL BerrueLor, Arch, Néerl. d. Sc. (2) t. V. p. 441. 
