Sulfate-phosphate, condensed anions

The condensed compounds of this type so far investigated are mainly phosphate-silicate, sulfate-phosphate, vanadate-phosphate, and arsenate-phosphate. All the component 0x0 acids or the anions of these condensed compounds can form isopoly acids or their anions. As can be seen in silicate minerals, there are several structural types of isopoly silicates which are polymers of interconnected Si04 tetrahedra. For example, pyroxene has a chain structure 1 (13). In the structure of... 

Shaver and Stites have found that combined sulfate can be separated from ionic sulfate by ion-exchange chromatography. The anion-exchange method employed by Peters and Pieman (50) for the separation of polyphosphates is adapted for this purpose. Ionic sulfate present in the form of sodium sulfate in a sample is readily eluted in a manner similar to orthophosphate. Combined sulfate present as condensed sulfate-phosphate, however, is strongly held on the resin and can only be eluted after hydrolyzing the sulfate-phosphate on the resin column with warm hydrochloric acid. 

Figure 3 Ion chromatogram of a condensate discharge water sample. Peak identification 1 =fluoride, 2 = acetate, 3=formate, 4 = chloride, 5 = nitrite, 6 = carbonate, 7 = sulfate, 8 = unknown, 9 = nitrate, 10 = unknown, 11 = phosphate. (Reprinted with permission from Lu Z, Liu Y, Barreto V, etal. (2002) Determination of anions at trace levels in power plant water samples by ion chromatography with electrolytic eluent generation and suppression. Journal of Chromatography A 956. 129-138 Elsevier.)...

Fig. 3-117. Gradient elution of standard inorganic anions and condensed phosphates utilizing suppressed conductivity detection. - Separator column lonPac ASH eluant (A) water, (B) 0.1 mol/L NaOH gradient 20% B linearly to 80% B in 10 min flow rate 2 mL/min detection suppressed conductivity injection volume 25 pL solute concentrations 3 mg/L chloride (1), carbonate (2), 5 mg/L sulfate (3), 10 mg/L each of orthophosphate (4), pyrophosphate (5), trimetaphosphate (6), tripolyphosphate (7), tetrapolyphosphate (8), and tetrametaphosphate (9).

Some mono or polydentate anions can affect permanently only part of the coordination sphere of the cation if they do not prevent hydrolysis and condensation. Phosphates, chromates, sulfates, carbonates and sometimes chlorides and nitrates are good examples. They form basic salts in which the complexed anions are an integral part of the structure of the solid. 

A few strong complexing ions are able to remain coordinated to the cation throughout hydrolysis and condensation. They are therefore included in the structures of the solid. Since these structures include ions other than 0x0 or hydroxo ions, they are called basic salts . In a way, these anions play a role in the formation of the network since, under similar acid conditions, no solid is formed in their absence. Most metallic elements form basic salts in nature, such as carbonates, sulfates and phosphates, which play an important role in mineralogy. A few structurally interesting zirconium(IV) compounds are discussed belosv. 

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