Gallium hydroxides

Porphyrin, octaethyl-, gallium hydroxide complex cyclic voltammetry, 4, 399 <73JA5140)... 

Figure 51 Structures of the water-gallane adduct 762 and two gallium hydroxides 828 and 836.

By dissolving gallium hydroxide in caustic potash, and electrolyzing the solution with a current from five or six Bunsen cells, Boisbaudran prepared more than a gram of gallium metal. This was first prepared in November, 1875. On December 6th he presented 3.4 milligrams of solid gallium (14) to the Academy of Sciences, and three months later he... 

Gallium hydroxide is amphoteric, and is a much stronger acid than aluminum hydroxide. For Ga(OH)3 the first acid dissociation constant is 1.4 x 10-7 [for Al(OH)3 the value is 2 x 10-11].1 Polymerization occurs in aqueous Ga3+ solutions to which OH- is added,533 but this tendency is less than in the case of aluminum solutions (Section 25.1.5.1). The formation constants of mononuclear hydroxo complexes of Ga, including Ga(OH)4, and the hydrolysis constants of gallium ions have been measured by a competing ligand technique.534... 

The dark brown, diamagnetic powder is stable in dry air and may be purified by vacuum sublimation at 500 °C, but undergoes surface oxidation at higher temperatures. Above 800 °C it disproportionates according to the reverse of equation (3). The hydrous oxides Ga(0)OH and Ga(OH)3 are similar to their aluminum analogs. Thus gallium hydroxide... 

In August 1875, Boisbaudran observed a pair of violet lines in the spark spectrum of some material he had separated from zinc blende from the Pierrefitte mine, from which he concluded the presence of a new element. This he named gallium in honour of his native country. Later in the year he obtained a small quantity of the free metal by electrolysis of a solution of gallium hydroxide in caustic potash. It was Mendel eff himself who, in November 1875, suggested the identity of this element with eka- aluminium, and further study of its properties and those of its compounds confirmed this view. 

As the group is descended, atomic radii increase and ionization energies are all lower than for boron. There is an increase in polar interactions and the formation of distinct M ions. This increase in metaUic character is clearly Ulustrated by the increasing basic character of the hydroxides boron hydroxide is acidic, aluminium and gallium hydroxides are amphoteric, indium hydroxide is basic, and thaUium forms only the oxide. As the elements of group 13 have a vacant p-orbital they display many electron-acceptor properties. For example, many boron compounds form adducts with donors such as... 

Pb(OH)2, lead(II) hydroxide Mg(OH)2, magnesium hydroxide Ga(OH)3, gallium hydroxide... 

A sample placed behind a 25 jum copper beam intensity monitor is irradiated for 15-20 min with a 2 mA beam of 25 MeV He. By chemical etching in 6 M nitric acid a 25-50 Asurface layer is removed. The sample is dissolved in 14 M nitric acid to which some sodium fluoride, zinc nitrate and gallium oxide carrier are added. After addition of phosphoric acid, the temperature is raised to 125° and 150 ml of distillate are collected. Gallium oxide is added to the distillate and gallium hydroxide is precipitated and filtered off. Finally, fluorine is precipitated as lead chlorofluoride The precipitate is repeatedly measured with a Ge(Li) detector during a 10 h period to allow the control of the half-life. Afterwards the yield of the chemical separation is determined by activation with an Ac-Be isotopic neutron source using the F(n,a) N reaction. 

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