( 664 ) 
R= 1.00706 X 0.0036625 = 0.003688: ) 
hence — = 3.98. 
: z 
HARTMAN finds at zz = 0.020: zj — 0.090, therefore: 
Ee 
A) 
I find for methyl chloride, with earbon dioxide as admixture, from : 
f= 0.276, Ky, = 3.314, by, = 0.001193, big = 0.009893: 
= —0.221, 6=0.281. 
From Youna’s observations on normal pentane ?) I derive at 
282.5 
= — = 0.679: 
ae TTT Pagal 
d 7 1 m 1 —= 
EEA abd VSN 
Tim dr C4 T 
With this I find: 
2e = 10.79, 
of | 
x 
while HARTMAN finds at #j=0.021 : 2.=0.242, therefore 2115. 
ab | 
The agreement between observation and calculation may be consi- 
dered as satisfactory. 
S 4. Now that we have a relation between z, and zj we may 
derive from the equation 
v d 
Vy — VU — (#3 — 2) (=) ae = (22 — ose) - + (6) 
how the pressure of saturated liquid and vapour varies by adding 
a small quantity of a second substance. For small 7; and 2. we 
may put for this: 
(vy — 1) (py — p) = MRT lek 1), 2 | 
if we are not too near the critical temperature of the pure substance 
dv, 
for then (5) becomes very large. 
£y/ pT 
Here vg and vj represent the molecular volumes of saturated vapour 
and liquid, p the saturated vapour pressure of the pure substance, 
p, the pressure above the liquid with the composition «, while 
Seca eem 4 eee aps oe P (% — vj) 
MET Np ae MRT 
1) Comp. KAMERLINGH ONNEs, Comm. no. 71. Proceedings June 1901, p. 130. 
2) S. Youne, Trans. Chem. Soc. 1897, p. 452. 
5) VAN DER Waats, Continuität II, p. 108. 
