Graphical representation of ternary phase diagrams

The most correct and complete representations of fourdimensional ternary phase diagrams would be the isothermal or isobaric triangle prisms with vertical axis as either pressure or temperature and triangle base as the ternary 

The two-dimensional p-T projection or triangle prism of T-x and p-x projections can be used for correct representations of mono- and nonvariant equilibria over the wide ranges of temperature and pressme. Sometimes the three-dimensional T-x or p-x projection can be drawn as a triangle of ternary concentrations with a set of isotherms or isobars, which describe the phase behavior in a range of temperature or pressme. Usually such triangles are used to show only one surface. For instance, a critical smface or a surface of liquid phase composition in equilibrium with other phases in a wide range of ternary composition, or the borders between several adjacent surfaces - the eutonic curves (L-G-Sb-Sc) between the two solubility smfaces of several nonvolatile components. 

Points G, Tb, Tq and iG, Kb, Kq are the triple and critical points of pure components points Eab. Eac, L, M, N are the compositions of liquid and critical phases in binary nonvariant equilibria L-G-Sa-Sb, L-G-Sa-Sc, Li-I -G-Sb and Li-Lj-G-Sb. Solid lines are the compositions of liquid and critical phases in binary monovariant equilibria L-G-S, L1-L2-G and L1-L2-S. Thin lines are the composition of liquid and critical phases at constant B/C ratio in ternary equilibria L-G-S, L1-L2-G, L1-L2-S and L = G. Dashed tines are the composition of critical phase in binary (Li = L2) and ternary (Li = L2-G) monovariant equilibria. Dot-dashed tine is the composition of critical phase in ternary monovariant equilibrium Li = L2-S. Dotted lines are the metastable parts of binary (L1-L2-G and Li = L2) and ternary (L, = L2-G) monovariant curves. Heavy lines are the compositions of liquid and critical phases in ternary monovariant equilibria L1-L2-G-S, L-G-Sa-Sbc, Li = L2-G and ternary Lj = L2-S. 

Nonvariant points of pure components can be omitted on the T-X projection because they do not take part in a formation of ternary monovariant curves. Various points on the ordinates of T-X diagram show temperature of all nonvariant equilibria (stable and metastable) in binary subsystems A-B and A-C, and are the starting points for ternary monovariant curves, corresponding to the equihbria spreading from the binary subsystems into three-component region of composition. The type of binary subsystems is uniquely determined by a combination of these binary non-variant points on the ordinate of T-X diagram. For instance, the set of nonvariant points N L M N corresponds to type lb, V A - type lb. A L M - type lb . A A A i -type Ic, A Z, M A A - type Ic, A ZJ - type Id, A L M R- type Id, A L p R - type Id , A p R Q - type 2d, A L M p R Q - type 2d (where A and are the metastable nonvariant points A and R, respectively) etc. 

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