III Hydroxide

Booth and H. C. Clark, Inorg. Chem., submitted for publication. 

Submitted by M. J. SPRAGUE, G. E. GLASS, and R. S. TOBIAS Checked by JOHN RIE1 and JOHN P. OLIVERf 

The only published synthesis1 of dimethylgallium(III) hydroxide, (CHs)2GaOH, which exists in the solid state as the tetra-merie molecule, [(CH3)2GaOH]4,2 involves prior preparation of 

The halide solution is then cooled to — 78°C., and the methyl-lithium solution is added slowly over a one-hour period with 

The pure hydroxide, which has an unpleasant, sweet odor, is reasonably air-stable and undergoes only very slow decomposition if stored in a stoppered vial in the freezing compartment of 

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Note that dinitrogen oxide is the other product. In alkaline solution, however, hydroxylamine oxidises iron(II) hydroxide to iron(III) hydroxide and is itself reduced to ammonia. This is an example of the effect of pH change on oxidation-reduction behaviour (p. 101). ... 

Arsenic(III) oxide is slightly soluble in water, giving a solution with a sweetish taste—but as little as 0.1 g can be a fatal dose (The antidote is freshly-precipitated iron(III) hydroxide.) The solution has an acid reaction to litmus, due to the formation of arsenic(III) acid ... 

Chromium(III) hydroxide is obtained as a light green gelatinous precipitate when an alkali or ammonia is added to a chromium(III) salt ... 

Chromium(III) hydroxide, like aluminium hydroxide, possesses adsorptive power, and the use of ehromium compounds as mordants is due to this property. 

Chromium(III) hydroxide dissolves in acids to form hydrated chromium(lll) salts in concentrated alkali, hydroxo-complexes [Cr(OH)g] are formed. 

Addition of alkali gives a green gelatinous precipitate of chromium(III) hydroxide, soluble in a large excess of strong alkali. 

If an aqueous solution of an iron(lll) salt is treated with alkali, a red-brown precipitate of iron(III) hydroxide is obtained this is probably best represented as FeO(OH). On strong heating it gives the red oxide Fe203. Iron(III) oxide, Fc20, occurs naturally as haematite, and can also be prepared by strong heating of iron(II) sulphate ... 

Hexa.cya.no Complexes. Ferrocyanide [13408-63 ] (hexakiscyanoferrate-(4—)), (Fe(CN) ) , is formed by reaction of iron(II) salts with excess aqueous cyanide. The reaction results in the release of 360 kJ/mol (86 kcal/mol) of heat. The thermodynamic stabiUty of the anion accounts for the success of the original method of synthesis, fusing nitrogenous animal residues (blood, horn, hides, etc) with iron and potassium carbonate. Chemical or electrolytic oxidation of the complex ion affords ferricyanide [13408-62-3] (hexakiscyanoferrate(3—)), [Fe(CN)g] , which has a formation constant that is larger by a factor of 10. However, hexakiscyanoferrate(3—) caimot be prepared by direct reaction of iron(III) and cyanide because significant amounts of iron(III) hydroxide also form. Hexacyanoferrate(4—) is quite inert and is nontoxic. In contrast, hexacyanoferrate(3—) is toxic because it is more labile and cyanide dissociates readily. Both complexes Hberate HCN upon addition of acids. 

Iron(III) hydroxide [1309-33-7], FeH02, is a red-brown amorphous material that forms when a strong base is added to a solution of an iron(III) salt. It is also known as hydrated iron(III) oxide. The fully hydrated Fe(OH)3 has not been isolated. The density of the material varies between 3.4-3.9 g/cm, depending on its extent of hydration. It is insoluble in water and alcohol, but redissolves in acid. Iron(III) hydroxide loses water to form Fe203. Iron(III) hydroxide is used as an absorbent in chemical processes, as a pigment, and in abrasives. Salt-free iron(III) hydroxide can be obtained by hydrolysis of iron(III) alkoxides. 

Tris(2,4-pentanedionato)iron(III) [14024-18-1], Fe(C H202)3 or Fe(acac)3, forms mby red rhombic crystals that melt at 184°C. This high spin complex is obtained by reaction of iron(III) hydroxide and excess ligand. It is only slightly soluble in water, but is soluble in alcohol, acetone, chloroform, or benzene. The stmcture has a near-octahedral arrangement of the six oxygen atoms. Related complexes can be formed with other P-diketones by either direct synthesis or exchange of the diketone into Fe(acac)3. The complex is used as a catalyst in oxidation and polymerization reactions. 

The first equation is an example of hydrolysis and is commonly referred to as chemical precipitation. The separation is effective because of the differences in solubiUty products of the copper(II) and iron(III) hydroxides. The second equation is known as reductive precipitation and is an example of an electrochemical reaction. The use of more electropositive metals to effect reductive precipitation is known as cementation. Precipitation is used to separate impurities from a metal in solution such as iron from copper (eq. 1), or it can be used to remove the primary metal, copper, from solution (eq. 2). Precipitation is commonly practiced for the separation of small quantities of metals from large volumes of water, such as from industrial waste processes. 

The possibility of preconcentration of selenium (IV) by coprecipitation with iron (III) hydroxide and lanthanum (III) hydroxide with subsequent determination by flame atomic absorption spectroscopy has been investigated also. The effect of nature and concentration of collector and interfering ions on precision accuracy and reproducibility of analytical signal A has been studied. Application of FefOH) as copreconcentrant leads to small relative error (less than 5%). S, is 0.1-0.2 for 5-100 p.g Se in the sample. Concentration factor is 6. The effect of concentration of hydrochloric acid on precision and accuracy of AAS determination of Se has been studied. The best results were obtained with HCl (1 1). 

Chromi-nydroxyd, n. chromic hydroxide, chro-mium(III) hydroxide, -oxyd, n. chromic oxide, chromium(III) oxide, -rhodanwasser-stoffsMure, /. chromithiocyanic acid, thio-cyanatochromic(III) acid, -salz, n. chromic salt, chromium(III) salt, -suifat, n. chromic sulfate, chromium(III) sulfate, -suifocyan-saure, /. chromithiocyanic acid, thiocyana-tochromic(III) acid, -verbindung,/. chromic compound, chromium(III) compound. 

Eisen-hydrozyd, n. ferric hydroxide, iron(III) hydroxide, -hydroxydul, n. ferrous hydroxide, iron(II) hydroxide. -jodid,n. iron iodide, specif, ferric iodide, iron(III) iodide, -jodiir, n. ferrous iodide, iron(II) iodide, -jodiirjo-did, n. ferrosoferric iodide, iron(II,IIl) iodide, kalium, n. potassium ferrate, -kaliumalaun,... 

Gold-hydroxyd, n. gold hydroxide, specif, auric hydroxide, gold(III) hydroxide, -jodid, n. gold iodide, specif, auric iodide, gold(III) iodide, -jodiir, n. aurous iodide, gold (I) iodide, -kafer, m. gold beetle. 

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