H2O System

K. Osseo-Asare, F. J. Arriagada, and J. H. Adair, "Solubility Relationships in the Coprecipitation Synthesis of Barium Titanate Heterogeneous Equihbria in the Ba—Ti—C2O4—H2O System," in G. L. Messing, E. R. Fuller, Jr., and Hans Hausin, eds.. Ceramic Powder Science Vol. 2,1987, pp. 47-53. 

Control of NO emissions from nitric acid and nitration operations is usually achieved by NO2 reduction to N2 and water using natural gas in a catalytic decomposer (123—126) (see Exhaust control, industrial). NO from nitric acid/nitration operations is also controlled by absorption in water to regenerate nitric acid. Modeling of such absorbers and the complexities of the NO —HNO —H2O system have been discussed (127). Other novel control methods have also been investigated (128—129). Vehicular emission control is treated elsewhere (see Exhaust control, automotive). 

Below 10°C, chlorine forms hydrates which are greenish yellow crystals and the CI2—H2O system has a quadmple poiat at 28.7°C. Solubihty data of chlorine ia various solvents are given ia Table 16. 

The phase diagram in Eigure 3 represents equiHbria in the MgO MgCl2 H2O system at room temperature (65). 

Gel preparation and crystalli2ation is represented schematically using the Na20—AI2O2—SiO2—H2O system as an example (1). 

Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

Several compounds of the CaO—P2O3—H2O system are given in Table 8. The common names for the mono-, di-, and tricalcium phosphates arise from the traditional double-oxide formulas, CaO 2i5p T2O3, 2CaO H2O +205, and 3CaO +205, respectively. These terms are routinely used in industry. With the exception of the monocalcium salt, the calcium phosphates are all sparingly soluble. 

The earliest mention of an ammonium carbonate, salt of hartshorn, appears in English manuscripts of the 14th century. As the name implies, the material was obtained by dry distillation of animal waste such as horn, leather, and hooves. Although many salts have been described in the Hterature for the ternary NH —CO2—H2O system, most, except for ammonium bicarbonate [1066-33-7], NH HCO, ammonium carbonate [506-87-6], (NH 2 02, and ammonium carbamate [1111-78-0], NH4CO2NH2, are mixtures (5,6). 

Ammonium bicarbonate, sp gr 1.586, formula wt 79.06, is the only compound in the NH —CO2—H2O system that dissolves in water without decomposition. SolubiUty in 100 g of H2O ranges from 11.9 g at 0°C to 59.2 g/100 g of H2O at 60°C (8). The heat of formation from gaseous ammonia and carbon dioxide andUquid water is 126.5 kj/mol (30.2 kcal/mol). Ammonium bicarbonate is manufactured by passing carbon dioxide gas... 

When a base is added to sulfuious acid, ie, the SO2 H2O system, first bisulfite, and then monosulfite, is formed. Using sodium hydroxide as an example. 

Oyychlorides. Hydrolysis of TiCl yields a number of products, the composition of which depends on the hydrolysis conditions. In the TiCl —HCl—H2O system, species ranging from Ti(H20) g through TiCl(H20) 3 to TiCl3(H20) , as the acid concentration increases, has been reported (141). 

The relationships between condensed phases ia the B2O3—H2O system are shown ia Figure 1 (42). There is no evidence for stable phases other than those shown. B2O3 melts and glasses containing less than 50 mol % water have mechanical and spectroscopic properties consistent with mixtures of HBO2 and vitreous B2O3. 

The solubihty—temperature curves for the Na20—B2O2—H2O system are given in Figure 5 (Table 9). The solubiUty curves of the penta- and decahydrates intersect at 60.6—60.8°C, indicating that the decahydrate, when added to a saturated solution above this temperature, dissolves with crystallisa tion of the pentahydrate and the reverse occurs below this temperature. This transition temperature may be lowered in solutions of inorganic salts, eg, 49.3°C in solutions saturated with sodium sulfate and 39.6°C with sodium chloride. Heats of solution for borax have been determined (67,73) and the manufacturer quotes a value of about 283 kJ/kg (67.6 kcal/mol) (33). 

Fig. 8. Solubihty isotherms for the K O—B2O2—H2O system at temperatures from 5 to 95°C where A, B, C, and D represent the soHd phases B(OH)2,...

The elaborate treatment for the H2O system is only possible beeause of its small size. For larger systems, less rigorous methods must be employed. Let us as a more realistic example consider a determination of the relative stability of the C4H6 isomers shown in Figure 11.15. There are experimental values for the first eight structures, which allows an evaluation of the performance of different methods. This in turn enables an estimate of how much trust should be put on the predicted values for 9, 10 and 11. 

Selenophene and tellurophene were obtained in 15-20% yield by the reaction of selenium and tellurium with diacetylene in the KOH/DMSO/N2H4-H2O/H2O system at 0-20°C (90MI1). 

There are now many diagrams available for metals and alloys which have been calculated not only for metal—H2O systems, but also for metal-HiO-anion equilibria (Sections 1.4 and 7.6). 

Based on a comprehensive investigation of solubility isotherms and of conductometric and potentiometric titration in the NbF5 - HF - H2O system, Nicolaev and Buslaev [288] concluded that H2NbOF5 is the predominant niobium-containing form present in such solutions. 

The first comprehensive investigation of the TaF5 - HF - H2O system was performed by Buslaev and Nikolaev [292]. Based on the analysis of solubility isotherms, and on conductometric and potentiometric titrations, the authors concluded that in this solution, tantalum forms oxyfluorotantalic acid, H2TaOF5, similar to the formation of H NbOFs in solutions containing NbF5. 

Fig. 50. Predominant presence fields of TaF72 and TaF[ complexes in a TafJs - HF - H2O system.

Figure 7. Two-dimensional (2D) H2O system in the laser field, (a)excited and (b) ground adiabatic potentials. Filled circles nonadiabatic tunneling-type region. Open circles LZ-type region. Taken from Ref. [19].

Fig. 3.10 Pourbaix diagram for the Cu + In + Se + H2O system at 25 °C. The stability fields were drawn for activities of Cu(II), Se(IV), and In(III) reactive species equal to 10 M. The diagram was assembled by using the candidate reactions included in Table 3.2. (Kois et al.

Voloshchuk AG, Tsipishchuk NI (2002) Equilibrium potential-pH diagram of the CdTe-H2O system. Inorg Mater 38 1114-1116... 

Equilibria between Peroxo and Hydroperoxo species in the TS-I/H2O2/H2O System In Situ UV-Vis DRS... 

Concerning peroxo complexes, it is worth noticing that they can be formed in TS-1 by evolution of both or rf- hydroperoxo complexes upon a further deprotonation in presence ofwater with formation of H30 /H20. Very recently Bonino et al. [49] have shown, by titration in aqueous medium with NaOH, that the acidity of the TS-1/H2O system is remarkably increased by addition of H2O2 (compare full squares with full circles in Fig. 8), a feature not observed for the Ti-free silicalite-1 system (open circles and squares in Fig. 8). 

From the data reported in Fig. 8, it clearly emerges that the acidity of the silicalite-l/H20 and of the TS-I/H2O systems are remarkably different (compare open and full circles in Fig. 8). This difference can be explained as follows TS-1 has two main acidic sites, Ti(IV) Lewis sites and silanols, mainly located in the internal defective nests (see Sect. 3.8), while only the latter are present in silicalite-1. Addition of H2O2 to siUcaUte-l does not modify the titration curve (compare open circles with open squares in Fig. 8). This means that no additional acidic sites appear in the siUcaUte-l system upon adding H2O2, i.e., that hydrogen peroxide molecules coordinated to internal silanol do not modify their acidity. Conversely, addition of H2O2 to TS-1 moves the whole titration curve toward lower pH values, (compare full circles with full... 

For the delicate transesterification of a p-Lactam intermediate (for carbacephalosphorin skeleton), where originally hydrolysis of methyl ester was done homogeneously and then formation of the benzyl (or substituted benzyl) ester was done separately, Doecke et al. (1991) have devised a mild and efficient methodology using PTC. A dual use of a PT catalyst, Bu4NBr, in one pot was made in a CH2CI2 - H2O system. In the first step 5N NaOH was used, then the pH was adjusted to 7.2 to 7.8 and subsequently benzyl (or substituted benzyl) bromide was added. 

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