Phosphoric acid, solution table

Extensive hydrogen bonding takes place in phosphoric acid solutions. In concentrated (86% H PO solutions, as well as in the crystal stmctures of the anhydrous acid and the hemihydrate, the tetrahedral H PO groups are linked by hydrogen bonding. At lower (75% H PO concentrations, the tetrahedra are hydrogen-bonded to the water lattice. Physical properties of phosphoric acid solutions of various concentrations are Hsted in Table 2 the vapor pressure of aqueous H PO solutions at various temperatures is given in Table 3. 

Table 3. Vapor Pressure of Phosphoric Acid Solutions., kPa ...

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

Fig. 3.66 Limits of use of silicon iron for handling nitric acid solutions Table 3.58 Corrosion of high-silicon irons by ortho-phosphoric solutions...

Various processes have been used for uranium extraction from phosphoric acid solution their main features are listed in Table 12.4. The HDEHP-TOPO process is increasingly preferred over others because of the stability of the extractant and the well-understood chemistry of the process. 

Potentials of berkelium redox couples are summarized in Table V. Replicate values for the Bk(IV)-Bk(III) couple are in reasonable agreement with one another. The effect of anions that strongly complex Bk(IV) is clearly reflected in the values of the formal potential for the Bk(IV)-Bk(III) couple and can be seen in the Nemst equation plots for the couple in various media given in Fig. 9 (227). Values of 1.36 (220, 223) and 1.12 V (227) have been reported for the couple in sulfuric and phosphoric acid solutions, respectively. Carbonate ions, apparently... 

Thermal ionization has been used to determine isotopic abundance of virtually all the elements We have recently extnded our own capability in this direction by adapting the silica gel/phosphoric acid filament coating technique (5) to our system Five 1 of a fine silica gel suspension is placed on a filament Five l of the analyte ion solution is coated, dried then coated with 2 pi of a 0 7N phosphoric acid solution and heated until dry again The analysis is performed in a similar manner as before, except that the signal is more transient and somewhat less intense than the calcium analysis With this approach, however, we have made natural abundance isotope ratio measurements on zinc, copper, and magnesium Table II shows our measurements compared to the accepted values, shown in parenthesis, for these elements The isotope used as reference... 

Internal (carrier) driving force coefficients, and K, <, or distribution coefficients, Ep and E, are determined by membrane-based extraction experiments. Membrane-based forward and backward extraction is carried out in two-compartment modules using the F and R compartments, separated by the same membranes as in the BAHLM tests. The experiments lasted up to equilibrium conditions, when the concentration of solutes in every compartment does not change with time. Examples of membrane-based extraction of copper, cadmium, and zinc from the concentrated phosphoric acid solution by PVSH and backward extraction by 2 M HCl are presented in Table 6.2 [7]. 

Phosphoric acid solutions are used for pickling of metals, especially aluminium alloys. The dissolution rate can be controlled by adding chromates, which slow down the attack, depending on the acid concentration [23] (Table E.5.12). 

Table 2. Physical Properties of Aqueous Solutions of Phosphoric Acid...

Vitreous siUca is relatively inert to attack from most acids for temperatures up to 100°C. The weight loss data in acid solutions are summarized in Table 3. The main exceptions are phosphoric acid, which causes some corrosion above approximately 150°C, and hydrofluoric acid, which reacts readily at room temperature (91). This latter dissolution proceeds as follows ... 

For most environments quantitative studies have been reported describing the corrosion rate of various materials including a number of corrosion-resistant alloys (30). For example. Table 4 gives weight losses suffered by corrosion-resistant alloys in a solution of 28% phosphoric acid [7664-38-2] 20—22% sulfuric acid [7664-93-9] and 1—15% duoride (36). 

C17-0031. Determine the concentrations of the ionic species present in a 1.0 M solution of phosphoric acid, H3 PO4 (see Table 17-2 for values, and ignore the third value). 

The liquid is an aqueous solution of phosphoric acid, always containing 1 to 3 % of aluminium, which is essential to the cement-forming reaction (Table 6.2). Zinc is often found in amounts that range from 0 to 10% to moderate the reaction. Whereas zinc is present as simple ions, aluminium forms a series of complexes with phosphoric acid (Section 6.1.1). This has important consequences, as we shall see, in the cement-forming reaction. 

In the fertilizer manufacturing scheme, the wet process phosphoric acid most commonly ensues from dissolution of sedimentary phosphate rock in sulfuric acid. Such acid solution contains around 1 g 1 1 uranium which is recovered as the byproduct. This task is accomplished by three well-proven extraction processes, some salient details of which are presented in Table 5.10. 

Compound 98 reacts with carbon disulfide in the presence of an alkali solution to give 3 -mercapto-l,2,4-triazolo[4, 5 l,5][l,2,4]triazolo[3,4-A]benzothiazole 247. Treatment of product 98 with urea at 200°C for 4h affords 3 -hydroxy-l,2,4-triazolo[4, 5 l,5]-l,2,4-triazolo[3,4-A benzothiazole 99 (Scheme 20). Finally, the addition of concentrated phosphoric acid in the presence of sodium nitrite to compound 98 produces 1,2,3,4-tetra-zolo[l, 5 l,5]-l,2,4-triazolo[3,4- ]benzothiazole 248, and refluxing substituted benzaldehydes in acetic acid provides an easy access to 3 -aryl-l,2,4-triazolo[4, 5 l,5]-l,2,4-triazolo[3,4-A benzothiazoles 249 (Scheme 20) (Table 50) <2005IJC(B)625>. 

Table 1. Effect of Concentration of Phosphoric Acid Used as Additive on the Casting Solution Properties...

Consulting the table of the dissociation constants K s for phosphoric acid shows that the first dissociation is much greater than the second, about 100,000 times greater. This means nearly all the W(aq) in the solution comes from the first step of dissociation. The second and third steps add very little Y (aq) to the solution. So a solution of phosphoric acid will contain H3PO4 molecules in highest concentration with smaller, and nearly equal, concentrations of H and H2PO4. The HPO4 and PO4 ions are present in very small concentrations. 

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