Chemistry. — ‘““/n-, mono- and divariant equilibria’. XXI. By 
Prof. F. A. H. SCHREINEMAKERS. 
(Communicated at the meeting of February 26, 1921). 
Equilibria of n components in n phases, in which the quantity of 
one of the components approaches to zero. The influence of a new 
substance on an invariant (P or T) equilibrium. (Continuation). 
In communication XX we have examined the influence of a new 
substance on the invariant (P or 7’) equilibrium: 
| yee OM a eer LY oe (1) 
With this we have assumed that L, Z,...are liquids and F, F,... 
solid substances of unvariable composition. The general form of this 
equilibrium / is: 
Disses Sy en oy bes Be 
in which G is a gas and M, M,... are mixed crystals, which may 
contain all components or not. 
When we know the reaction, occurring in this invariant (P or 7’) 
equilibrium, then we may deduce again with the aid of (12) and 
(15) (XX) which influence has the addition of a new substance. 
Now we shall consider some special cases of this equilibrium. 
We take the unary equilibrium G +4 Z, viz. an unary liquid in 
equilibrium with the vapour; this equilibrium is invariant (P or 7). 
As the reaction is L, = G, it follows: 
= (Aa) =a — a, = (4 H) = H — H, = (AV) = VV, 
in which w, H and V relate to the vapour G. 
Now it follows from (12) and (15) (XX): 
RT (#@—a#,) RI? (#,—2) 
(dT)p = — Beo ato. Wik (3) 
RT («—2,) 
(dP); = VZV, Er ie edt CE 
Herein AW is the heat of evaporation of a molecular quantity 
of liquid and V-—J, the increase of volume at the evaporation of 
this quantity of liquid. Consequently we refind in (3)-and (4) the 
known formula’s. We find, therefore, the rule well-known: 
When, at addition of a new substance the concentration of this 
