Scandium hydroxide Sc

Like the hydroxides of the Rare earth, scandium hydroxide, Sc(OH)3, is precipitated by addition of alkalies to solutions of scandium salts however, the latter is precipitated at pH 4.9, while the former require pH 6.3 or more, a property which is utilized in one method of separation. Upon heating the hydroxide (or certain oxyatid salts), scandium oxide. Sc>C>3 is produced. Scandium hydroxide is less acidic than aluminum hydroxide, requiring boiling KOH solution to form the complex potassium compound, K2[Sc(OH)5 H 0] 3H 0. 

Scandium (Sc, at. mass 44.96) occurs in its compounds exclusively in the III oxidation state. Some of its chemical properties resemble those of the lanthanides and yttrium. Scandium hydroxide Sc(OH>3 precipitates at a pH as low as 4.8 and dissolves in alkaline medium in this respect scandium resembles aluminium. 

Scandium hydroxide Sc(OH), 17674-34-9 96.978 col amorp solid I EIjO s dil acid... 

The hydroxide and oxide phases that exist for scandium(III) include scandium hydroxide, Sc(OH)3(s), which likely has both amorphous and crystalline forms, ScOOH(s), and scandium oxide. It would be expected that the amorphous hydroxide is the most soluble and Sc203(s) the least. There have been few studies that have examined the solubility of these phases. None of the hydroxide or oxide phases of scandium are known to form naturally, with scandium present, as a major component, in eight mineral phases only (Wood and Samson, 2006). Moreover, there is much conjecture over which phases have actually been studied as well as their crystallinity (Baes and Mesmer, 1976 Wood and Samson, 2006). This review has selected data for both the hydroxide and oxide phases, based largely on the similarity in the stabilities obtained for the phases studied. Baes and Mesmer (1976) provided a stability constant for ScOOH(s) on the basis of data provided by Schindler (1963), but it is believed that the phase actually studied was Sc(OH)3(s) given the similar solubility found in the studies of Feitknecht and Schindler (1963) and Shkolnikov (2009). 

Scandium forms all its compounds in 3+ oxidation state. This is the only valence known for the metal. These compounds include the oxide, SC2O3 hydroxide, Sc(OH)3 chloride, ScCls fluoride, ScFs sulfate, Sc2(S04)3, and the nitrate salt, Sc(N03)s. 

Addition of scandium hydroxide to aqueous trifluoroacetic acid gives Sc(0H)(02C CF3)a,2H20 in high yield at 230—330 °C the anhydrous material decomposes according to the equation ... 

Scandium oxide is a refractory white solid (mp 3100 °C) formed on ignition of either the metal or appropriate compounds such as the nitrate, sulfate, and hydroxide. It has amphoteric tendencies denoted by its solubihty in excess alkali from which compounds like K3[Sc(OH)6], containing octahedrally coordinated scandium, have been isolated. In the solid state it has six-coordinate scandium in the Mu203 structure. 

These [(H20)5Sc(/j,-0H)2Sc(H20)5p ions are significant in that they are believed to be formed in the first stage of the hydrolysis of the scandium aqua ion, and the coordination geometry involving scandium bound to seven water molecules and hydroxide ions can clearly derive from a [Sc(OH2)7] ion, in the way that [(H20)4Fe(//-0H)2Fe(H20)4]" is believed to relate to the [Fe(OH2)e] ion. 

A novel scandium complex formed from scandium triflate in the presence of 18-crown-6 and p-sulfonatocalix[4]arene has been investigated.224 The crown ether resides in cavities created by two calixarenes from adjacent polymeric sheets. There are two types of scandium ions in the complex, one type is bound to the phenolic oxygen of the calixarene and the second exists as the hydroxide bound dimer ion [Sc(OH)2(H2O)10]4+. A similar complex may also be prepared without the crown ether. 

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