Sodium partial phase diagram

Numerous studies have been made into the phase equilibria in the Na20-B203-H20 system at 0-100°C (e.g., 135, 216, 217, 308), and more recently at 150° (96). A partial phase diagram for this system covering the range of mole ratio Na20/B203 to 0.5 in solution is shown in Fig. 6. Over 25 borates of sodium in the absence of other cations have been identified (307). 

An example for a partially known ternary phase diagram is the sodium octane 1 -sulfonate/ 1-decanol/water system [61]. Figure 34 shows the isotropic areas L, and L2 for the water-rich surfactant phase with solubilized alcohol and for the solvent-rich surfactant phase with solubilized water, respectively. Furthermore, the lamellar neat phase D and the anisotropic hexagonal middle phase E are indicated (for systematics, cf. Ref. 62). For the quaternary sodium octane 1-sulfonate (A)/l-butanol (B)/n-tetradecane (0)/water (W) system, the tricritical point which characterizes the transition of three coexisting phases into one liquid phase is at 40.1°C A, 0.042 (mass parts) B, 0.958 (A + B = 56 wt %) O, 0.54 W, 0.46 [63]. For both the binary phase equilibrium dodecane... 

Ikawa et al. [136] determined the critical solution temperature (Krafft point) and the critical solution pressure (Tanaka pressure) of sodium perfluorodecanoate in water. A phase diagram of sodium perfluorodecanoate versus pressure at 55°C is shown in Fig. 6.29. The curves of solubility versus pressure (aQb) and of cmc versus pressure (dQe) intersect at point Q, representing the Tanaka pressure. The phase diagram is divided into three regions solution of monomolecular species (S), the micellar solution (M), and the hydrated solid (C). The rapid decrease of solubility with increasing pressure (curve aQ) was attributed to the transfer of surfactant from micelles to the hydrated solid phase, which is accompanied by a large decrease in partial molar volume. 

Orthophosphate salts are generally prepared by the partial or total neutralization of orthophosphoric acid. Phase equiUbrium diagrams are particularly usehil in identifying conditions for the preparation of particular phosphate salts. The solution properties of orthophosphate salts of monovalent cations are distincdy different from those of the polyvalent cations, the latter exhibiting incongment solubiUty in most cases. The commercial phosphates include alkah metal, alkaline-earth, heavy metal, mixed metal, and ammonium salts of phosphoric acid. Sodium phosphates are the most important, followed by calcium, ammonium, and potassium salts. 

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