Authors:J. Rouland, S. Makki, J. Fournival, and R. Céolin
The sulfaguanidine—water (SG-H2O) system is a binary system with non-negligible vapour pressure which presents a monohydrate. The phase diagram of this system
is drawn from DTA experimental results, using the temperature-specific volume-molar fraction (T-v-x) model which was described in part I of this work.
The melting of the monohydrate (SG, H2O) is found to be congruent. Isochoric sections are drawn; they make it possible to determine the limits of the two eutectic
invariant planes. The composition and specific volume of the vapour phase at the eutectic equilibrium of theSG-SG, H2O subsystem are given. The triple line solid-liquid-vapour of the one-component phase diagram of the monohydrate is drawn.
The experimental results are consistent with the congruent melting of the monohydrate. These results also show that the solid,
liquid and vapour phase at the triple line have not the same composition.
Authors:J. L. Fournival, J. C. Rouland, and R. Ceolin
The binary system water-phenobarbital is presented as a new example of systems with non-negligible vapour pressure. It is explained on the basis of aT- V- x diagram. Two invariant equilibria occur at very close temperatures: a peritectic equilibrium at 123 °C and a monotectic equilibrium at 125 °C.
Authors:J. Rouland, A. Thorén, J. Fournival, and R. Céolin
A theoretical temperature-specific volume-molar fraction (T-v-x) phase diagram of the binary systemA-H2O presenting a hydrateH with congruent melting is studied. The phase diagram is divided into two subsystems by the one-component phase diagram of
the hydrateH. The eutectic invariant planes which occur in both subsystems are described. The relationships between the invariants are
Isochoric and isoplethal theoretical sections are given. The one-component phase diagram of the hydrateH is described. It is pointed out that the triple line solid-liquid-vapour which relates the congruent melting is not necessarily
perpendicular to the molar fraction axis. The means that the three phases, solid, liquid and vapour, have not necessarily
the same composition.
TheT-v-x representation gives an explanation to the deviation between the maximum of the melting curve and the stoichiometric composition
of the hydrate which is often observed in theT-x binary diagramA-H2O.