Showing papers on "Lanthanum published in 1970"

The distribution of vacancies in lanthana‐doped lead titanate

Abstract: The incorporation of lanthanum sesquioxide in lead titanate has been investigated at constant temperature and at constant partial pressures of oxygen and of lead monoxide in respect of lanthanum contents in the range 0.5 ≦ y ≦ 50 mol%. The gravimetric method has been used to determine the amount of lead monoxide liberated by the incorporation of the lanthana and volatilized at high temperatures. In all probability the lanthanum ions occupy the lead sites in lead titanate. In the case of lanthanum contents y ≧ 5 mol% vacancies occur exclusively at lead sites, while in the case of lanthanum contents y < 5 mol% vacancies are formed also at titanium sites. Der Lanthanoxideinbau in PbTiO3 wird bei konstanter Temperatur und unter konstantem Sauerstoff- und Bleioxid-Partialdruck fur Lanthangehalte im Bereich 0,5 Mol% ≦ y ≦ 50 Mol% untersucht. Dabei wird auf gravimetrischem Wege die infolge des Lanthanoxideinbaus freiwerdende und bei hohen Temperaturen fluchtige PbO-Menge bestimmt. Die Lanthanionen besetzen im PbTiO3 mit aller Wahrscheinlichkeit Pb-Platze. Bei Lanthan-gehalten y < 5 Mol% entstehen ausschlieslich Leerstellen auf Pb-Platzen, wahrend bei La-Gehalten y ≧ 5 Mol% auch Leerstellen auf Ti-Platzen gebildet werden.

Lanthanum Inhibition of 45Ca Efflux from the Squid Giant Axon

Abstract: LETTVIN et al.1 predicted that lanthanum ions, because of their relatively small size and high charge density, should have a much greater electrostatic attraction for any negative calcium binding site than calcium ions themselves. This was borne out for the membranes of the barnacle muscle fibres2 and the lobster axon3. If negatively charged sites located in the membrane also serve to transport calcium ions across it, then lanthanum ions would be expected to displace calcium from these sites, and thereby inhibit the calcium ion flux. It has been shown that this is true for an artificial membrane with negative groups of phospholipids lining aqueous pores4. Data obtained by Weiss and Goodman5 and Van Breemen6 indicate that lanthanum ions also block the calcium transport across smooth muscle membranes. In smooth muscle physiology there is much uncertainty about the relative contribution of calcium influx to the initiation of contraction, and a calcium transport blocking agent would be very useful. In addition, information regarding the nature of the lanthanum blockade should contribute to the understanding of the cell membrane calcium transport system itself.

Removal of phosphate from waste water

Abstract: A method for chemically removing phosphates from waste waters by treating the phosphate-containing waste water with a trivalent rare earth salt, generally as a mixture of such salts, to form an insoluble rare earth phosphate precipitate, and then separating the precipitate from the waste water. The rare earth precipitant salt, such as lanthanum chloride or sulfate, may be regenerated by treating the rare earth phosphate precipitate with a strong or weak alkali as regenerant, preferably aqueous sodium hydroxide or sodium carbonate, to form a soluble alkali metal phosphate. The aqueous alkali regenerant may be recovered by treatment of the formed sodium phosphate with lime to precipitate the phosphate as a calcium phosphate complex salt. Where it is desired to precipitate phosphate but avoid regeneration of the rare earth precipitant salt, a combination treatment using aluminum-lanthanum or iron-lanthanum as precipitant salt is preferred.

Energy bands for fcc lanthanum and praseodymium.

Abstract: We have calculated the energy bands of lanthanum and praseodymium in the face-centered-cubic structure using the relativistic augmented-plane-wave method. Calculations for the density of states, the magnetic susceptibility, and the Fermi surface are also performed, and the results are correlated with some of the electronic and magnetic properties of these metals.

Process for the production of aromatic hydroxyaldehydes

Abstract: Salicylaldehyde and other hydroxybenzaldehydes are prepared by the oxidation of a hydroxybenzyl alcohol in the presence of a platinum catalyst and a cationic oxidation promoter. Among the most effective oxidation promoters are cadmium, cerium, indium, and lanthanum ions.

Some properties of zirconates and stannates with the pyrochlore structure

Abstract: The properties of the stannates and zirconates (M2Sn2O7 and M2Zr2O7) of yttrium, lanthanum, cerium and neodymium are discussed, and the materials are considered for possible application in magnetohydrodynamic (MHD) power generation. Measurements are discussed of their structural properties, thermal expansion, thermal diffusivity, electrical resistivity, resistance to oxidation, to chemical corrosion, and to electrolytic corrosion. Thermal shock resistance is also qualitatively assessed. For non-electrical applications, lanthanum stannate has shown the most promise, especially in the corrosion tests. All the materials are insulators below 1000 K, except cerium zirconate which has ample electrical conductivity (> 10 Ω−1 m−1 above 1400 K) for use as an MHD electrode. Cerium zirconate has complicated structural and electrical properties, and must be prepared in low oxygen partial pressures. However, it is easily oxidized and may disintegrate. The equimolar ceria-zirconia solid solution formed when the oxides are fired in air would be more useful as an MHD material.

Method for making ceramic titanate elements and materials therefor

Abstract: A method for making ceramic titanate elements and materials therefor, particularly semiconducting lanthanide-doped barium titanate elements having positive temperature coefficients of resistance for use as solid-state sensors or the like, is shown to comprise the steps of dissolving the titanium chelate of triethanolamine with selected alkaline earth salts such as barium acetate and with selected lanthanide salts such as lanthanum acetate in a solvent to form a common solution. Alternatively, tetraisopropyl titanate mixed with lactic acid is combined with selected alkaline earth salts such as barium acetate and with selected lanthanide salts such as lanthanum acetate in a solvent to form a common solution. The solution is then heated, initially to form a semisolid material and thereafter-in an oxidizing or neutral atmosphere-to calcine the semisolid material to form the desired titanate material. The resulting titanate material is then combined with a binder, is pressed into a desired shape, and is fired at high temperature to form the desired ceramic titanate elements.

Stabilized nickel oxide-nickel chromite reforming catalyst

Abstract: A NICKEL OXIDE-NICKEL CHROMITE CATALYST STABILIZED WITH THE OXIDES OF LANTHANUM OR URANIUM IS USEFURL IN THE STEAM REFORMING OF HYDROCARBONS. THE CATALYST CAN OPTIONALLY CONTAIN OTHER OXIDES AS PROMOTERS, E.G. MANGANESE OXIDE, MAGNESIUM OXIDE, CERIUM OXIDE AND RARE EARTH OXIDES.

The Solvent Extraction of Metal Ions from Sulfuric Acid Solutions with a Mixed Extractant—Long-chain Primary Amine and Di-2-ethylhexylphosphoric Acid

Abstract: The distribution of metal ions between phases of dilute sulfuric acid and carbon tetrachloride containing long-chain primary amine (Primene JM) and di-2-ethylhexylphosphoric acid (D2EHPA) has been investigated. The degree of the extraction of bi- and tervalent metal ions, such as zinc, iron (III), indium, lanthanum, and cerium(III), is found to be the lowest when the organic phase contains 5 g/l of Primene JM and 7–8 g/l of D2EHPA, while a minimum extraction of thorium occurs at a different composition of the organic phase. Thus, thorium can be quantitatively separated from most other metals by extraction from a 0.1N sulfuric acid medium with carbon tetrachloride containing 5 g/l of Primene JM and 7–8 g/l of D2EHPA. Under these extraction conditions, a single extraction is sufficient for the quantitative separation of thorium from high concentrations of lanthanide metals. Contrary to the usual method of extraction using long-chain amines, which involves a tedious multiple extraction, the mixed-extractant ...

Studies on the Phosphate Complexes of Actinium and Lanthanum

Abstract: since no value for its cationie radii is reported. From this graph, a linear relation for the transplutonium elements complexes with tartaric, malic and citric acids is shown which suggests that the electrostatic interaction is the main factor determining the complex formation in these cases. On the other hand, for complexes with 2-methyllactic acid, a deviation from inearity is observed. This may be explained on the steric effect from the complexing ligand. This was proposed by F L E I S C H E R and P O W E L L [ 1 5 ] as a result of introduction of the methyl group to the lactic acid structure.

Neutron activation analysis of rare earth impurities in europium oxide.

Abstract: A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10−5 to 10−7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.

Studies on the Separation of Rare Earths. Determination of the Optimum Concentration of Ligand Ion Used in Electromigration

Abstract: An attempt to determine the optimum concentration of ligand ion for the separation of adjacent pairs of rare earth elements by electromigration was made using the method employed for the determination of the stability constant of complex. To examine the theory, separation of lanthanum and cerium, and cerium and praseodymium was carried out using α-hydroxyisobutyric acid as a complexing agent. From the results, factors necessary for the separation of all kinds of rare earth elements were discussed.

Radiochemical study of the separation of cerium(III) from lanthanum by solvent extraction using N-benzoyl-N-phenylhydroxylamine

Abstract: The extraction of cerium(III) and lanthanum(III) by N-benzoyl-N-phenylhydroxylamine (N-BPHA) in chloroform has been studied in order to determine the composition and extraction constants of the extracted chelates. From the results obtained, the best conditions for the separation of cerium from lanthanum (separation factor about 200) have been predicted and experimentally verified.

Microdetermination of fluorine in organic compounds containing phosphorus and in hexafluorophosphates

Abstract: A method for the microdetermination of fluorine in organic compounds containing phosphorus is described. After combustion in a Vycor flask, the species containing phosphorus are oxidized to orthophosphate with alkaline hypobromite. Phosphate is adsorbed on zinc oxide which need not be removed prior to titration of the fluoride. Fluoride is titrated potentiometrically with 0.02M lanthanum(III) in 50% ethanol solution at pH 5–7. A fluoride ion-specific indicator electrode and a calomel reference electrode are used in conjunction with an expanded-scale pH meter to monitor the emf. This method can also be used for the determination of total fluorine in inorganic hexafluorophosphates. For the more stable compounds such as potassium hexafluorophosphate, a combustion aid (paraffin) must be added to promote combustion.

Microdetermination of Fluoride in the Presence of Phosphate by Potentiometric Titration

Abstract: A method for the microdetermination of fluoride in the presence of phosphate is described. Up to a 10-fold excess of phosphorus (as phosphate) can be tolerated. Phosphate is adsorbed on zinc oxide which is added in excess and need not be removed prior to titration of fluoride. Fluoride is determined potentiometrically with 0.02M lanthanum(III) at pH 5 to 7. A fluoride ion specific electrode is used with an expanded-scale pH meter to monitor the emf.

Effect of transition metals on the grain size of titanium

Abstract: Additions of lanthanum, yttrium, nickel, palladium, and platinum are the most effective in refining the grains of cast titanium as compared with other transition metals investigated.