Showing papers on "Lanthanum published in 1979"

MERGING ZONES IN FLOW INJECTION ANALYSIS Part 2_ Determination of Calcium, Magnesium and Potassium in Plant Material by Continuous Flow Injection Atomic Absorption and Flame

Abstract: SUMMARY A flow-injection analysis system is described for the automatic determination of calcium, magnesium and potassium in plant material by atomic absorption and flame emission spectrometry. Flow rates and damping factors were studied; the sample undergoes a dispersion of ca. 40-fold with automatic incorporation of lanthanum when necessary_ The proposed method allows 300 determinations per hour with a typical relative standard deviation of 0.5% and a reagent consumption of only 500 ug of lanthanum per determination, which is about 1% the usual amount_ The results for plant digests agree with those obtained by the standard a-as. procedure_

Production of Conducting Oxide Powders by Amorphous Citrate Process

Abstract: The amorphous citrate process has been used to produce Co3O4, CoO, Cr2O3, LaCoO3, LaCrO3, SrCoO3, and strontium-doped LaCoO3, and LaCrO3. The citrate-nitrate gels were produced at room temperature and dehydrated at 70°C to yield solid precursor materials. The decomposition of the precursors was studied at temperatures of 220, 310, 500,710, 880, and 1060°C. The yield of the process for strontium-doped lanthanum cobaltite is of the order of 90% which compares extremely well with the yield of 60% obtained by the conventional powder technique. Thermogravimetry, X-ray diffraction analysis, scanning electron microscopy, and analytical electron microscopy have been used to characterize the precursors and oxide materials produced by the citrate process.

Separation of strontium-89 and -90 from calcium in milk with a macrocyclic ether

Abstract: A small amount of strontium ion (20 mg) was simply separated from a large amount of calcium ion (0.5 to 13.6 g) by liquid--liquid extraction using dicyclohexyl 18-crown-6 chloroform solution. The extraction was applied to a part of the procedure for determining radiostrontium in ash of milk. The overall recovery of strontium was 75% on the average for 5 to 10 g of milk ash. Decontamination factors for Mg, Ca, Ru, I, Cs, Ba, and La in the final fraction were 1 x 10/sup 5/, 1 x 10/sup 4/, > 1 x 10/sup 6/, > 1 x 10/sup 6/, > 2 x 10/sup 6/, 2 x 10/sup 5/, and 3 x 10/sup 4/, respectively. The chemical procedure for three samples took about 2 days. 1 figure, 3 tables.

Class of cracking catalysts acidic forms of cross-linked smectities

Abstract: Novel types of molecular sieve cracking catalysts and method of preparation, the catalysts consisting of acidic forms of partially cross-linked smectites and including ions of hydrogen and rare-earth elements such as cerium, gadolinium, lanthanum, neodymium, praseodymium and samarium. In the catalyst preparation, the unit layer structure of the smectite is retained and the effective pore size obtained (8 A-30 A) is sufficiently large to accommodate molecules with a kinetic diameter greater than about 8 A.

Conditions of the formation of rare earth phosphates and the colors of their powders.

Abstract: Rare earth oxides, such as La2O3, Pr6O11, Nd2O3, and Sm2O3, can react with phosphoric acid to give four kinds of rare earth phosphates (orthophosphates LnPO4·0.5H2O and LnPO4, catena-polyphosphates Ln(PO3)3 and ultraphosphates LnP5O14), while in the reaction of CeO2 with phosphoric acid there are formed five kinds of phosphates (orthophosphate CePO4, pyrophosphate CeP2O7, two types of catena-polyphosphate Ce(PO3)3 and Ce(PO3)4, and ultraphosphate CeP5O14). The formation of these products in the CeO2–H3PO4 system are notably different from these in other systems, showing that cerium(III) phosphates as well as cerium(IV) phosphates can exist stably. It can be seen from the X-ray diffraction patterns that each corresponding phosphate (ortho, catena-Qoly, and ultraphosphates) of lanthanum, cerium(III), praseodymium, neodymium, and samarium is isomorphous. This may be caused by the facts that the valencies of all these metals are +3 and that their ionic radii are almost equal to one another (La(III) 1.06 A–Sm(...

Effects of lanthanum on the heart sarcolemmal ATPase and calcium binding activities.

Abstract: Effects of lanthanum on Ca2+-ATPase, Mg2+-ATPase, Na+–K+-ATPase, and calcium binding activities were studied in rat heart sarcolemma. Ten to 100 μM lanthanum depressed significantly the Ca2+-ATPase activity and 50–200 μM lanthanum inhibited the calcium binding activity. Lineweaver–Burk plots of the Ca2+-ATPase activity showed that the inhibition by lanthanum was competitive with calcium concentration. Neither Mg2+-ATPase nor Na+–K+-ATPase activities were affected by lanthanum when the assay medium contained 1 mM EDTA; however, in the absence of EDTA, these enzyme activities were significantly decreased by 10–100 μM lanthanum. Rat hearts perfused with HEPES buffer containing 0.5 mM lanthanum showed electron-dense deposits restricted to the outer cell surface and the sarcolemma obtained from these hearts also had the deposits, indicating that the membrane fraction isolated by the hypotonic shock – LiBr treatment method is of sarcolemmal origin. The Ca2+-ATPase activity of the sarcolemma isolated from lantha...

Cobalt-containing alloys

Abstract: A wear-resistant alloy, which excluding impurities, has the following composition: (a) about 50 to 70% of cobalt, nickel and iron; (b) 27 to 35% of chromium; (c) 5 to 15% of molybdenum and/or tungsten; (d) 0.3 to 2.25% of carbon and/or boron; (e) 0 to 3% of silicon and/or manganese; (f) 0 to 5% of one or more of titanium, hafnium, zirconium, vanadium, niobium, and tantalum; (g) 0 to 5% of copper, and (h) 0 to 5% of one or more of the following rare earths: lanthanum, cerium, yttrium, and thorium. The cobalt is the range 25 to 40%, and the nickel in the range 4 to 12%. There is from 0 to 7.5% of constituents (f), (g) and (h). The iron is present in a quantity not exceeding 25%. If there is 2% or more of carbon and/or boron, there is more than 30% chromium. (All percentages by weight). A welding or surfacing consumable which (ignoring the effect of dilution by substrate) is capable of depositing such an alloy may also be made.

Superconductivity in the hexaborides

Abstract: Powder samples of the mixed hexaborides (Y, La)B6 were prepared by borothermal reduction. The superconducting transition temperatures, as measured by static Faraday susceptibility and by Meissner flux expulsion, were observed to range from 6.0 ± 0.1 K for YB6 to 1.6 ± 0.1 K for Y0.5La0.5.5B6. The influence of the impurities ytterbium, cerium, neodymium, iron, barium and calcium was systematically examined. It appears that the very low critical temperature (0.1 K) of LaB6 is due to a small magnetic moment from the lanthanum itself. The change of lattice parameter only exerts a minor influence on the superconductivity.

Precipitation and micellization of silver, copper and lanthanum dodecyl sulphates in aqueous media

Abstract: The precipitation and micellization of silver, copper and lanthanum dodecyl sulphates was followed through determination of precipitation-solubility concentration limit. The experiments were performed at 21 °C.

Hydrogen and electricity from water and light - A lanthanum chromite-titanium dioxide anode

Abstract: Abstract A photo-active anode involving lanthanum chromite has been studied. The electrodes were made by firing lanthanum and chromium oxides, or salts which are converted upon heating to the oxide, in a paste of citric acid on a titanium oxide base. The anodic photo currents obtained were around four times greater than on an TiO2 single crystal in the same potential region on a conventional scale. The photoelectrochemical spectrum showed a pronounced and characteristic peak which differed markedly in wave length region from that on TiO2. The efficiency of conversion of solar light at a LaCrO3-TiO2 electrode is at least one order of magnitude greater than on TiO2. Hence, the situation for photo-assisted electrolysis is improved. In self-generating photo-electrolysis cells in solar light, the expected efficiency of conversion is calculated to be about one order of magnitude more than the hitherto most efficient couple, GaP-TiO2. The efficiency of hydrogen production from solar light is expected to be about 1.8% (up from 0.2175%), but the implication for the use of transition metal oxides for photo anodes is encouraging.

Production of Strontium-Doped Lanthanum Cobaltite Conducting Oxide Powder by Freeze-Drying Technique

Abstract: The freeze-drying of mixed nitrate solutions has been used to produce lanthanum cobaltite and strontium-doped lanthanum cobaltite. The freeze-dried nitrates were decomposed in vacuum at 500°C and the residue heat-treated for one hour at 1060°C. The yield of the freeze-drying process is shown to be the same as that of a commercial process involving the repeated sintering and milling of a carbonate/oxides mixture. X-ray diffraction analysis, scanning electron microscopy, and analytical electron microscopy have been used to characterize both the freeze-dried material and the commercial material.

Crystal data for the trimetaphosphates of lanthanum, cerium and praseodymium

Abstract: LaP3O9, CeP3O9 and PrP3O9 are orthorhombic, space group C2221 and isomorphous with NdP3O9; lattice parameters and powder diffraction data are given.

Method for obtaining iron-based alloys allowing in particular their mechanical properties to be improved by the use of lanthanum, and iron-based alloys obtained by the said method

Abstract: This invention relates to the use of lanthanum in the production of iron-based alloys. Accordingly, is provided a method comprising adding at least 0.0001 to about 0.5 to 2 weight percent of lanthanum to said iron-based alloy during its production. Thus the solidification curve is modified, as shown in FIG. 2, thereby reducing or preventing certain defects of said alloys, such as pinholes and cavities in spheroidal graphite cast-irons, carbides in flaky graphite grey-iron; the castability, rollability and anisotropy of steels are improved.

Method of producing fluorescent material

Abstract: PURPOSE: On the production of fluorescent substances of rare earth metal silicate activated with rare earth metal, ammonium fluoride or acid ammonium fluoride is added as a flux and they are calcined to increase the emission efficiency and brightness of rare earth metal-activated rare earth silicate under excitation with ultraviolet rays, which is used as a fluorescent film for cathod ray tubes or discharge lamps. CONSTITUTION: On the production of fluorescent substance of rare earth activated rare earth silicate of the formula (L n is yttrium, lanthanum, gadolinium, lutetium; Ln' is cerium, europium or terbium; x, y satisfy following relations; 1×10 -4 ≤x≤ 3×10 -1 , 0.8≤y≤2.2), at least one of ammonium fluoride and acid ammonium fluoride and, when necessary, additional barium compound are added to the starting materials for fluorescent substance as a flux by 1W7.5wt% and 0.5W3wt% respectively; they are calcined to give the objective fluorescent substance. The starting materials are provided by weighing, for example, Ln 2 O 3 , SiO 2 and Ln' 2 O 3 stoichiometrically and mixing them. The flux is mixed by a dry or wet method. COPYRIGHT: (C)1981,JPO&Japio

Catalyst for oxidation of sulfur dioxide

Abstract: A catalytic material for oxidation of sulfur dioxide to sulfur trioxide at any temperature above 300° C., comprising a catalyst which at reaction conditions is a melt including sulfatized vanadium ions as the active catalytic component and two different promoters and which is dispersed in an inert porous carrier. The first promoter comprises cesium ions, optionally in combination with ions of another alkali metal such as sodium, potassium or rubidium, known to promote vanadium catalysts. The second promoter comprises ions of a metal such as aluminum, magnesium, yttrium or lanthanum, which does not promote formation of inactive V 4 species and the oxide of which has a heat of formation greater than 100 kcal per oxygen atom and is at least partly soluble in the heavily sulfatized environment of the melt.

Organometallic Chemistry of the Lanthanides under Reductive Conditions

Abstract: Although the lanthanide metals comprise nearly 20% of the stable metallic elements in the periodic system, relatively little use has been made of these elements in catalytic reactions (1). Homogeneous catalyses involving the lanthanide metals are particularly rare (2). This situation does not arise because the lanthanides are rare elements, for lanthanum, cerium, praseodymium, and neodymium, are as common as lead, and even the rarest lanthanide, thulium, is more common than mercury (3). It is more likely that the limited use of the lanthanide metals in catalytic sequences is a reflection of the limited chemistry which has been developed for these elements. Indeed, the chemistry of this series of metals is sufficiently narrow that it can be summarized in a single paragraph.