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it is based on the fact that the reactions are dependent on one 
another and that of course it is not allowed to take them in discordance. 
Now we have represented the six schematical reaction-equations 
by a schematical reaction-diagram ; when these equations were given 
quantitatively and when we would also express them quantatively, 
then a representation in space would be necessary ; then we should 
obtain fig. 3 (II). [The six equations 55 are viz. taken from this 
figure |. . 
Consequently it is apparent from the previous that we may 
draw a schematical reaction-diagram in a plane for each system of 
n-components, while a space with —1 dimensions is wanted for 
the corresponding concentration-diagram. 
Now we shall give another form to fig. 3. For this we draw the 
diameter A,A and we prolong it through A; we dot the part A, M and 
we omit the letter A,, which is not necessary now. This line, which 
we shall also call A, represents the phase A just like the point, 
situated on this line. When we do the same with the lines 5,5, 
CC ete, then fig. 4 arises. It is evident that we may find from 
fig. 4, just as from fig. 3, the six reactions schematically. 
When we compare this diagram (tig. 4) with the P,7-diagram- 
type belonging to fig. 3 (III), which is represented in fig. 4 (IT), then 
we see that both figures are perfectly in accordance with one another. 
The only difference is that in fig. 4 the hnes represent a phase and 
in fig. 4 (III) the lines represent monovariant equilibria. 
Hence it is apparent, therefore, that a schematical reaction-diagram 
and a P,7-diagramtype are represented by the same figure and that 
the only difference exists in the meaning which we give to the lines. 
It might seem strange to the reader that we have deduced in 
the way followed above a schematical reaction-diagram, which is 
a perfect representation of a P,7-diagram, withont having spoken 
anywhere in our considerations of temperatures and pressures. 
When we compare, however, the deduction of fig. 3 and 4 from 
the reaction-equations 55 with the deduction of fig. 4 (IIT) from 
fig. 3 (LI) then we see that this deduction is perfectly the same. 
From those considerations it is apparent once more that a P7- 
diagram can be considered as a schematical reaction-diagram of the 
corresponding concentration-diagram. 
The reader himself can deduce that a concentration-diagram can 
be considered as a schematical representation of the corresponding 
P,T-diagram. 
(To be continued). 
Leiden, Inorg. Chem. Lab. 
