Rare earth salts

We found that completely soluble compounds can be obtained in two ways. The first method, which is widely applicable, is to react a rare earth carboxylate with a small amount of an aluminum alkyl (11). Neodymium octoate can be converted into a product which is completely soluble in cyclohexane by reacting one mole of it with 1 to 5 moles of triethylaluminum. We also found that the rare earth salts of certain tertiary carboxylic acids are very readily soluble in non-polar solvents (12). In conjunction with a Lewis acid and aluminum alkyls, these compounds form highly active catalysts for the polymerization of butadiene. The neodymium Lewis acid aluminum alkyl molar ratio is within the range 1 (0.4-2.0) (10-40). 

A. Bianco, M. Brufani, C. Melchioni, and P. Romagnoli, A new method of regioselective protection of primary alcoholic function with rare earths salts,... 

Anhydrous permanganic acid, 15 596-597 Anhydrous phosphoric acid, 18 817-818 Anhydrous rare-earth salts, 14 634 Anhydrous silica... 

For enthalpies of solution of rare-earth salts in a really wide range of solvents, one has to look outside the halide family to nitrates. Enthalpies of solution of lanthanum(III) nitrate have been measured in 15 solvents, under comparable conditions. Unfortunately, it was the hexa-hydrate rather than the anhydrous nitrate that was used (227). 

Electrowinning Generally this method is limited to La, Ce, Pr and Nd because of their low-melting points. The rare earth salt (fluoride, chloride, etc.) mixed with an alkali or alkaline-earth salt is heated to 700-1100°C and then an electric dc current passed through the cell. If the bath temperature is above the melting point of the R, drops of the molten metal drip off of the cathode and are collected at the bottom of the cell. Generally, the electrowon metal is not as pure as that obtained by metallothermic reduction. 

Kamboj MP, Kar AB. 1964. Antitesticular effect of metallic and rare earth salts. J Repro Fert 7 21-28. 

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%. 

Ammino-derivatives of Rare Earth Salts—Derivatives of Neodymium Chloride and Samarium Chloride—Pyridine Derivatives of Rare Earth Chlorides. 

Cerous iodates and the iodates of the other rare earths form crystalline salts sparingly soluble in water, but readily soluble in cone, nitric acid, and in this respect differ from the ceric, zirconium, and thorium iodates, which are almost insoluble in nitric acid when an excess of a soluble iodate is present. It may also be noted that cerium alone of all the rare earth elements is oxidized to a higher valence by potassium bromate in nitric acid soln. The iodates of the rare earths are precipitated by adding an alkali iodate to the rare earth salts, and the fact that the rare earth iodates are soluble in nitric acid, and the solubility increases as the electro-positive character of the element increases, while thorium iodate is insoluble in nitric acid, allows the method to be used for the separation of these elements. Trihydrated erbium iodate, Er(I03)3.3H20, and trihydrated yttrium iodate, Yt(I03)3.3H20,... 

Dieke and Hall (88) measured the fluorescent lifetimes of some rare-earth salts. Their data were collected by an electronic-switch technique. Their results of the 5D4 state of terbium at 77°K and 293°K are ... 

S. Hosono, W.-S. Kim, H. Sasai, and M. Shibasaki, A new glycosidation procedure utilizing rare earth salts and giycosyi fluorides, with or without the requirement of Lewis acids, J. Am. Chem. Soc. (in press). 

In dilute solution the rare earth salts behave as 1 3 electrolytes and obey the Onsager equation in a modified form up to a concentration of 0.01 N. The behaviour of various rare earth salts, such as chlorides, bromides, nitrates and perchlorates has been examined [209—212]. The equivalent conductivity data for the rare earths is compiled in Table 11. Extensive ion-pair formation has been observed for rare earth sulphate solutions. 

Figure 10 shows the schematic illustration of the sintered layer-type sensor chip. The catalyst powder is ground using an auto-grinder and only fine particles are selected using a mesh filter. When the rare-earth ion is doped into the catalyst, an aqueous solution of rare-earth salt (e.g., (Dy(N03)3) is mixed in and then the catalyst is calcined. The rare-earth-activated phosphors used for thermoluminescence (TL) measurements, e.g., BaSO Eu, CaSO Eu, and SrSO Eu, also act as CTL catalysts. 

The first systematic studies of polyoxometalate—rare-earth complexes were published in 1971 (Peacock and Weakley, 1971a, 1971b). Two classes of polytungstate complexes were described and these can now be seen to have common structural features. The complexes of Y, La, Ce(III and IV), Pr, Nd, Sm, Ho, Er, and Yb in which R W = 1 10 were readily formed by reaction of WO - with the appropriate rare-earth salt, but are stable only within the pH range 5.5-8.5. More recent 183W-NMR studies (Inoue et al., 2003) indicate that in solution the anions containing the heaviest R (Tm, Yb and Lu) are partially decomposed. 

Ion-exchange (or ion) chromatography uses vertical columns loaded with ionic resins with either mobile anions or mobile cations (typically acidic cations and aminium anions) to separate ionic salts dissolved in water. These resins can separate even rare earth salts from each other and would have been a godsend to Marie Curie The charge, polarizability, and size of the solvated ion and the properties of the anionic or cationic resins are factors that influence the separability. 

A reference standard compound is traditionally used [tetramethylsilane (TMS) Si(CH3)4 for both H1 and C13, 85% H3PO4 for P31], and the chemical shift 8, relatable to cr, is usually a down-shift of the resonance from the reference compound, a small amount of which is added to each sample as an internal standard Table 11.11 lists some typical H1 NMR chemical shifts <5. Table 11.12 shows some C13 chemical shifts. Sometimes rare-earth salts are added to the solution, to deliberately shift resonances by a Coulomb interaction these are called lanthanide shift reagents. 

The most popular method for determining crystal-field levels of rare earth salts is spectroscopy [17,18]. The maximum number of energy levels (stark sublevels) generated in the various point groups are given in Table 8.4. 

Methods for obtaining high-purity rare earth salts combined with the availability of high resolution spectrophotometers led to comprehensive studies of the absorption spectra of lanthanides [136-141]. The experimental work on the spectra of single crystals of rare earth salts by Dieke was of immense value in the theoretical interpretation of the energy level structures of the lanthanide ions [142]. 

A synthetic method for preparing polyisoprene having a cis-, A linkage of 99.0% or greater using diethylaluminium chloride with the rare earth salt neodymium tris(bis (2-ethylhexyl)phosphate) is described. Reproducible Mooney viscosities of 85 and higher were also observed. 

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