Sulfate anion characteristics

Another class of framework aluminosilicates is the ultramarines. They are characterized by an open framework and intense colors. They diller from the previous examples by having free anions and no water in the cavities. Ultramarine blue, which is the synthetic equivalent of the mineral lapis lazuli, contains radical anions. SjT and ST. The dominant Sj gives rise to its blue color. Ultramarine green also contains the.se two anions but in comparable amounts. Although these two anions are also found in ultramarine violet and pink, the characteristic color is due to a third species, perhaps or S - - Structurally related, but colorless, minerals such as sodalite (containing chloride unions) and noselite (containing sulfate anions) are sometimes included in the broad category of ultramarines. 

Sulfate sol- fat [F, fr. L sulfur] (1790) n. SO4. (1) A salt or ester of sulfuric acid. (2) A bivalent group or anion characteristic of sulfuric acid and the sulfates. 

Stimming and his coworkers found by in situ STM that adsorbed sulfate ions on Pt(lll) form the same adlayer structure as that found on Au(lll) [34]. Ordered domains with X V7) symmetry appeared in the potential range between 0.5 and 0.7 V versus a reversible hydrogen electrode (RHE) in 0.05 M H2SO4. As shown in Fig. 3, only the (111) surface shows the characteristic butterfly peaks at potentials slightly negative than 0.5 V. Their STM observations confirmed that the butterfly peaks are formed because of the adsorption and desorption of sulfate ions as indicated by the CO replacement technique used by Clavilier as described above [14]. STM images obtained on Pt(lll) were interpreted in terms of the coadsorption of sulfate anions and water. 

The adsorption isotherm of sodium dodecyl sulfate (SDS) on alumina at pH = 6.5 in 0.1 M NaCI (Fig. 4.11a) is characteristic of anionic surfactant adsorption onto a positively charged oxide. As shown by Somasundaran and Fuerstenau (1966) and by Chandar et al. (1987), the isotherm can be divided into four regions. These authors give the following explanation for the adsorption mechanism ... 

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