Europium oxide chloride

Acid soluble rare earth salt solution after the removal of cerium may be subjected to ion exchange, fractional crystalhzation or solvent extraction processes to separate individual rare earths. Europium is obtained commercially from rare earths mixture by the McCoy process. Solution containing Eu3+ is treated with Zn in the presence of barium and sulfate ions. The triva-lent europium is reduced to divalent state whereby it coprecipitates as europium sulfate, EuS04 with isomorphous barium sulfate, BaS04. Mixed europium(ll) barium sulfate is treated with nitric acid or hydrogen peroxide to oxidize Eu(ll) to Eu(lll) salt which is soluble. This separates Eu3+ from barium. The process is repeated several times to concentrate and upgrade europium content to about 50% of the total rare earth oxides in the mixture. Treatment with concentrated hydrochloric acid precipitates europium(ll) chloride dihydrate, EuCb 2H2O with a yield over 99%. 

Europium (II) acetate, formation of, from europium amalgam, 2 68 Europium(III) acetate, 2 66 citrate solution of, 2 67 Europium amalgams, 2 65, 66, 68n. Europium (II) carbonate, 2 69, 71 Europium(II) chloride, 2 69, 71 formation of, from europium amalgam, 2 68 Europium (III) oxalate, 2 66 Europium (III) oxide, 2 66 Europium (II) salts, 2 69 Europium(II) sulfate, 2 69, 70... 

A solution is prepared which contains 5 X 10 mol of europium(III) chloride in 200 ml. of water. Since this chloride is quite hygroscopic, it is convenient to dilute a calculated volume of standardized ca. 0.5 M aqueous solution to 200 ml. Alternatively, 0.880 g. (2.5 X 10 mol) of europium (III) oxide is dissolved in a small excess of 6 M hydrochloric acid. The resultant solution is evaporated to a small volume to remove excess hydrochloric acid and ultimately diluted to 200 ml. To the solution of europium (III) chloride is added, with stirring, a solution of 4.0 g. (an excess) of benzoylacetone in 50 ml. of 95% ethanol. The resulting suspension is stirred with a magnetic stirring bar while 15 ml. of molar aqueous ammonia is added dropwise over a period of 2 hours. The mixture of product and excess benzoylacetone is filtered, washed with water, and dried in a vacuum desiccator to give approximately 4.4 g. of solid. 

Purification of Europium. An acetate solution obtained from 20 g. of europium(III) oxide (>99% pure) was treated with 260 ml. of 0.3% sodium amalgam, added in three separate equal portions. The resulting amalgam contained all but 0.09 g. of the europium. Treatment of the amalgam with 100 ml. of 10 M hydrochloric acid caused complete precipitation of europium(II) chloride 2-hydrate. Removal of the product followed by washing with ice-cold 10 M hydrochloric acid and ultimate conversion to euro-pium(III) oxide gave a recovery of spectroscopically pure europium in excess of 90%. 

Solid Europium Compounds. Solid europium oxide, chalcogenides, halides, carbonate, phosphate, etc., may be obtained by reduction of the corresponding Eu3 + compounds or, metathetically, from EuC12. The metal reacts with liquid ammonia at 50° to give the orange amide, Eu(NH2)2, which gives EuN when heated.54 The compounds are usually isostructural with the Sr2 + or Ba2+ analogs. However, definite lower fluorides and chlorides appear to exist except for La, Ce, Pr, Gd, Tb and Er.57... 

The purity of a europium preparation may also be checked iodometrically by titrating a europium(II) chloride solution prepared from a weighed portion of the oxide. 

The reduction of europium(III) to europium(II) may be accomplished simply with a Jones reductor or, more elaborately, by the action of hydrogen on the chloride at 700°. In the three procedures below the preparation of (1) europium(II) sulfate, (2) europium(II) carbonate, and (3) europium(II) chloride are described. Fortunately, these europium salts when dry are not appreciably oxidized by dry air and hence may be handled and stored conveniently. The first procedure is based on the preparation of insoluble europium(II) sulfate after reduction of europium(III) in... 

Rare-earth jS-diketonate complexes can be synthesized by extraction methods. Halverson et al. (1964a, 1964b) obtained Lewis base adducts of europium(III) j8-diketonates by equih-bration of an aqueous solution of europium(lll) nitrate with a solution of the -diketone (or its ammonium salt) and of the Lewis base in diethyl ether. As the Lewis base, trioctylphosphine oxide (topo), tributylphosphate (tbp) or dihexylsulfoxide (dhso) were used. The molar ratios Eu + diketone Lewisbase were 1 3 2. The complexes are formed in the ether layer, and could be obtained as viscous oils from the ether solution. Richardson and Sievers (1971) prepared tris complexes of 1,1, l,5,5,6,6,7,7,7-decafluoro-2,4-heptanedione by extraction of an aqueous solution of the decafluoroheptanedione in diethyl ether. The rare-earth chlorides were used in 10 to 50% excess in order to prevent the formation of the corresponding tetrakis complexes. [Eu(tla)3(phen)] was prepared by extraction of an aqueous solution of europium(III) chloride, 2-thenoyltrifluoroacetone and 1,10-phenanthroline with benzene (Melent eva et al., 1966). After separation of the benzene layer from the aqueous layer, the [Eu(tta)3(phen)] complex was precipitated by addition of petroleum ether to the benzene layer. 

Similar to chemical vapor deposition, reactants or precursors for chemical vapor synthesis are volatile metal-organics, carbonyls, hydrides, chlorides, etc. delivered to the hot-wall reactor as a vapor. A typical laboratory reactor consists of a precursor delivery system, a reaction zone, a particle collector, and a pumping system. Modification of the precursor delivery system and the reaction zone allows synthesis of pure oxide, doped oxide, or multi-component nanoparticles. For example, copper nanoparticles can be prepared from copper acetylacetone complexes [70], while europium doped yttiria can be obtained from their organometallic precursors [71]. 

Solutions of alkali metals in ammonia have been the best studied, but other metals and other solvents give similar results. The alkaline earth metals except- beryllium form similar solutions readily, but upon evaporation a solid ammoniste. M(NHJ)jr, is formed. Lanthanide elements with stable +2 oxidation states (europium, ytterbium) also form solutions. Cathodic reduction of solutions of aluminum iodide, beryllium chloride, and teUraalkybmmonium halides yields blue solutions, presumably containing AP+, 3e Be2, 2e and R4N, e respectively. Other solvents such as various amines, ethers, and hexameihytphosphoramide have been investigated and show some propensity to form this type of solution. Although none does so as readily as ammonia, stabilization of the cation by complexation results in typical blue solutions... 

It can be seen that the (111) state is highly stable with respect to disproportionation in aqueous solution and is extremely difficult to oxidize or reduce. There is evidence for the existence of the (II) state since tracer amounts of amencium have been reduced by sodium amalgam and precipitated with barium chloride or europium sulfate as earner. The (IV) state is very unstable in solution the potential for americium(III)-ameridum(IV) was determined by thermal measurements involving solid Am02. Amencium can be oxidized to the (V) or (VI) state with strong oxidizing agents, and the potential for the americium(V)-americium(Vl) couple was determined potentiometrically. 

The equilibrium constant of reaction (1), K = [Cu ][Cu ]/[Cu ], is of the order of 10 thus, only vanishingly small concentrations of aquo-copper(I) species can exist at equilibrium. However, in the absence of catalysts for the disproportionation—such as glass surfaces, mercury, red copper(I) oxide (7), or alkali (311)—equilibrium is only slowly attained. Metastable solutions of aquocopper(I) complexes may be generated by reducing copper(II) salts with europium(II) (113), chromium(II), vanadium(II) (113, 274), or tin(II) chloride in acid solution (264). The employment of chromium(II) as reducing agent is best (113), since in most other cases further reduction to copper metal is competitive with the initial reduction (274). 

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