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tation, temperature concentration diagrams for a complex of a definite 
composition ; I will, however, not go into this any further. 
2. The complex F+ #” has an incongruent sublimation line, four- 
phase line, and melting point line. 
We will assume that both liquid and vapour have such a com- 
position that on the sublimation curve a'D (fig. 1) occurs the reaction 
F'ZF+HG, on the four-phase curve DS the reaction /”2F+L+G 
and on the melting point curve Sd" the reaction ” S F+ L. Hence 
if J” is placed in an evacuated space and if gas is generated, then 
according to the capacity of this space /+ /” + G or + G is 
formed or merely a vapour G of the composition /” ; if liquid and 
vapour are generated “+ HF’ + 1+ G is formed, or F4 LG, 
or L+G; if liquid is generated + /#” + L is formed or 1+ L 
or merely a liquid of the composition #7. 
From #” according to the conditions chosen, one of the complexes 
FAr+G, F+G4G, G, F+G, F+Ph4L4+6, F+L+4+4, 
L+G, F4 +L, F+ L or L will form or else the compound 
I’ may remain unchanged. If only LZ or G is formed these will, 
of course have the same composition as the compound /”. Hence, 
we can never obtain from the compound F' one of the complexes 
FAG, f’’+L+G or Ff’ + L unless these appear in a meta- 
stable condition. 
In fig. 1 all curves relating only to the compound J” (a’K’ , K/ PY, 
Fl’ Fe’ and K’f’) and the regions encompassed by them, therefore 
represent only metastable conditions of the compound +” ; hence, 
they cannot be realised in the stable condition. If, therefore, the 
compound #” is introduced into an evacuated space it will not 
occur in the conditions which correspond with the P, 7-diagram of 
F’, but with those corresponding with the P, 7-diagram of the 
complex 4 + #7. 
The terminal point D of the sublimation curve a’ D is here not 
only the highest sublimation point of the complex /’ + +”, but it 
also represents the highest pressure at which the conversion of 4” 
into / takes place. by the side of gas; the initial point S of the 
melting point curvé Sd" is here not only the lowest melting point 
of the complex /-+ F”, but represents also the lowest pressure 
at which the conversion of /” into # takes place in presence of 
liquid. 
From a consideration of what happens with the complex /’ + /” 
on supply or withdrawal of heat or on a change in volume we 
deduce : 
