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the P,7-diagram; it defines viz. also which curves go in the same 
direction of pressure, starting from the invariant point. 
When in (23) all values of « are positive, then all phases in 
(21) and (22) have the same sign; when wi...u,—1 are positive 
and Up... tte negative, then in (22) F,...F, have the same sign, 
but PF... Erpe the opposite sign as in (21). 
Now we shall examine which changes occur in a P,7-diagram, 
according to the position of /, in the series of signs. In both 
reaction-equations (21) and (22) going from left to right, /, may 
be the second or the third or tbe fourth phase, ete. and at last the 
(n + 2%) phase, consequently. the last. When in (23) all values 
of u are positive, then this phase /, is missing. 
Let us assume, for fixing the ideas, that the series of signs of 
reaction (21) is represented by series a of table 1 or 2. Then the 
P,T-diagram consists of the bundles of curves 4 + 7, R, B, Sand 
C. [Confer e.g. figs 1, 2 and 3}. 
When in (23) all values of u are positive, so that the phase #, 
is missing, then series 6 in table 2 represents the series of signs of 
the isovolumetrical reaction. When F, is the (m+ 2) phase, there- 
fore the last phase of the subgroup 7’, then in series 6 of table 2 
the last phase obtains the opposite sign; when /’, is the ((m + 1)" 
phase, then in series 6 of table 2 the two last phases obtain the 
opposite sign, ete. 
When Ff, is e.g. the first phase of group S, then in series 4 of 
table 1 all phases of groups S, C, and 7’ get the opposite sign. When 
Fy) is situated within the group B so that this group is divided into 
two sub-groups B, and 45, then the series of signs is represented 
by series 6 of table 1. When 4, is the phase A,, then in series 5 
of table 2, all phases, except the first one, get the opposite sign. 
It is evident. that this change of signs in series 6 has no influence 
on the series, which indicate the signs of AP; the series which 
define the signs of 47 undergo however similar changes. 
Let us now take for the isentropical reaction AV <0 and for 
the isovolumetrical reaction Ax > 0. When the phase #/, is missing, 
then we find, as we have seen above, for the signs. of APand AT’ 
the series ¢ and & of table 2 and for the P,7-diagram fig. 3. 
We divide this diagram into four quadrants by two lines which 
go through the invariant point. We imagine the one-line parallel to 
the P-axis, the other parallel to the 7-axis. Those four quadrants 
are indicated in fig. 3 by the encircled figures 1, 2, 3 and 4. Con- 
sequently in fig. 3 all curves are situated within the quadrants 1 and 3. 
