1153 
RT? (c—2) 
ll od 
Hence follows the rule’): 
when, on addition of a new substance the concentration of this 
substance in the vapour (viz. 2) is larger (smaller) than in the 
reduced mixture (viz. ce) then the boiling-point under constant pressure 
is lowered (raised) and the vapour-tension is raised (lowered) at 
constant temperature. : 
Applying those and the following rules and formula (11) we have 
to consider to following. 
When the vapour has an average composition, then c is positive 
when, however, the vapour has a non-average composition, then c 
may be as well positive as negative; w—c is then always positive 
when c is negative. 
When we substitute in the rule above “reduced mixture” by 
“liquid” then we refind the rule, which is true for the addition of 
a new substance to the unary equilibrium Z + G. 
When the added new substance is not volatile, then «=O; (LI) 
passes then into: 
d, GE 1 
an oe AV ZOO 
(d7)p = 
RT RTe 
ema is Le la Dye 
Ca AV 
When we keep in mind that c may be as well positive as nega- 
tive, then we find the rule: 
when the vapour has an average composition, then, on addition 
of a new substance, the boiling-point under constant pressure shall 
be raised and the vapour-tension at constant temperature shall be 
lowered ; 
when the vapour has a non-average composition, then for c >0 
this rule is true also; for c << 0 however an opposite rule is true. 
We may for some cases also represent the above results geome- 
trically. Let us firstly consider the addition of a new substance to 
the binary equilibrium H— L, + L, + G. In figs 1—4 the sides 
ZX and ZY of the ternary concentration-diagram are partly drawn: 
a,a, and a represent the two liquids and the vapour G of this 
equilibrium #. In figs 1 and 3 this vapour a has an average, in 
figs 2 and 4 a non-average composition. When, at constant 7 or 
P, we add a new substance, then the liquids Z, and ZL, trace the 
curves a, 6,c, and a,6,c,; the vapour traces curve abc. Each of the 
(dT)p = (12) 
1) This rule is deduced already formerly for a definite case, viz. the addition of 
a new substance to the binary equilibrium Zj + Lj + G. F. A. H. ScoREINEMAKERS. 
Zeitschr. f. Phys. Chem. 38 (1901) 252. 
