Subject vanadates

Bismuth vanadate, BiV04, exhibits a ferroelashc-paraelastic phase transition and had been the subject of considerable investigation. This is reported in some detail in the entry on Vanadium. 

Despite the assertion over a number of years that vanadate is rapidly reduced in the presence of ligands such as p-mercaptoethanol and dithiothreitol, it is now known that this assertion is subject to qualification. Solution studies have shown that the vanadium(V) complexes of p-mercaptoethanol [36] and dithiothreitol [37] can be quite stable in solution. At pH 7.1, reduction of vanadium in the dithiothreitol complex occurs in a timescale of about 90 min, and even at pH 6.2, significant production of V(IV) is not observed for about 20 min. When the crystalline vana-dium(V) complex of p-mercaptoethanol was dissolved in water, it was shown to... 

The intracellular concentration of K+ is high in most animal cells relative to that of external fluids. The converse is true for Na+. The free energy necessary to pump these ions against their concentration gradients is derived from the hydrolysis of ATP. Hydrolysis is controlled by the K+ and Na+ stimulated ATPase which is imbedded in the cell membrane and has stimulation sites on both the intracellular and extracellular surfaces. To fully activate the pump, Mg2+, in addition to Na+ and K+, must be present. K+ activates the ATPase exterior to the cell and Na+ on the interior. An introduction to this subject can be found in Stryer72. The effect of vanadate on Na+, K+-ATPase has been reviewed19 73. ... 

The formation constants for the monoesters [x = 1 in Equation (2.11)] are small, typically around 0.1 m for alkyl alcohols, and an order of magnimde more for phenols.I ] Esters derived from divanadate, such as [HV205(0R)] , have also been noted. In analogy with the vanadates, the esters are subject to protonation-deprotonation equilibria. 

Among the alkali vanadates, only NaV03 is commercially available. However, the number of existing defined alkali vanadates is rather large. Only the system KaO-VgOg has been subjected to a systematic preparative study. It may be assumed that the other systems have similar structures. 

The critical regions in oil-fired furnaces are the evaporator tubes, steam superheater tubes, air heater, and channel. Evaporator tubes are affected by hot gas corrosion from hydrogen sulfide as the temperature exceeds 280°C. Superheater tubes suffer from sulfate/sulfite corrosion induced by molten sulfates above 620"C. Superheater tube holders undergo vanadic corrosion caused by molten vanadate species in the range of 550 C-600 C. Air heaters are subject to low-temperature corrosion from liquid sulfuric acid at 100°C-140°C. Flue gas channels suffer from acid deposits at the dew point (Balajka 1980). 

---