Addition Of Lanthanum Research Articles

Atomic Absorption Analyses of Zinc, Lead and Cadmium in Hot Spring Waters

Amethod for the determination of zinc, 1ead and cadmium in hot spring waters by atomic absorption spectrometry has been studied The instrument used was Shimadzu Multichannel Atomic Absorption-Flame Spectrometer, Model MAF-1 The sensitivity obtained by means of the stabilization of electric power and the scale expansion of the recoder readings was sohigh that the sample s 1utions were directly at mized int the acetylene-air ameThe condition recommended for the determinatio:n of zinc, 1ead and cadmium were as follows, wavelength;2139 A, 2170 A a:nd 2288 A, ho110w cathode lamp current;6mA 8mA and 6 mA slit width; 0.05 mm, 0.10 mm and O.05 mm, acetylene pressure;0 2kg/ cm2 0 2kg/ cm2 and O 2kg/ cm2, air pressure;1.4 kg/ cm2, 1.4 kg/ cm2 and 1 4 kg/ cm2 beam p slti n;17 mm 16 mm and 20mm, respectively.The presence of aids and coexisting elements did not iRterfere, except a large amount of silicon for zin. This interference could be eliminated through an addition of calcium or lanthanum to the sample solution.The detection limits, determined by means of respective calibration curves, were Zn O.005 ppm, Pb O.Ol ppm and Cd O.OOI C. The method was applied to the determination of the three elements in various types of hot spring waters and the results were satisfactorily coincident with those obtained by other methods.

The effect of calcium ionophores on fragmented sarcoplasmic reticulum.

X-537 A and A 23187, two antibiotics which form liphophilic complexes with divalent cations, function as ionophores in vesicular fragments of sarcoplasmic reticulum (SR). Addition of either ionophore to SR preloaded with calcium in the presence of adenosine triphosphate (ATP), causes rapid release of calcium. Furthermore, net calcium accumulation by SR is prevented, when the ionophores are added to the reaction mixture before ATP. On the contrary, ATP-independent calcium binding to SR is not inhibited. This effect is specific for the two antibiotics and could not be reproduced, either by inactive derivatives, or by other known ionophores. Neither ionophore produces alterations of the electron microscopic appearance of SR membranes or inhibition of the calcium-dependent ATPase. In fact, the burst of ATP hydrolysis obtained on addition of calcium, is prolonged in the presence of the ionophores. Lanthanum inhibits ATP-independent calcium binding to SR, ATP-dependent calcium accumulation and calcium-dependent ATPase. However, addition of lanthanum to SR preloaded in the presence of ATP, does not cause calcium release. The reported experiments indicated that: (a) ATP-dependent calcium accumulation by SR results in primary formation of calcium ion gradients across the membrane. (b) Most of the accumulated calcium is not available for displacement by lanthanum on the outer surface of the membrane. (c) Calcium ionophores induce rapid equilibration of the gradients, by facilitating cation diffusion across the membrane.

Sulfidation of binary iron alloys containing cerium or lanthanum

Additions of elements of the rare-earth group to steel, mostly in the form of “mischmetal”, are generally made to improve on the deoxidation and desulfurization. Spring1 was the first to carry out experiments with the addition of mischmetal to certain types of steel as far back as 1918. A comprehensive review of the effects of lanthanum and cerium additions to steel was given by Richerd.2

Effects of calcium and lanthanum on glycerol removed rabbit atria

Continuously driven rabbit atria were equilibrated in Ringer-Locke solution, incubated in glycerol and then returned to normal Ringer's solution. Calcium was added (final concentration of 7.2 or 12.0 mM) at the beginning of glycerol removal or at the time of maximum decline in tension during the removal (10 min). There is an immediate increase in tension to a maximum followed by a slow decline to control levels after the addition of calcium. The glycerol removal effect is intensified by the addition of lanthanum (0.1–1.0 mM). Evidence would suggest that the glycerol removal effect results from a change of tissue calcium.

Cilia: activation coupled to mechanical stimulation by calcium influx.

Ciliated epithelial cells in the oviduct of Necturus maculosus were stimulated mechanically by brief dimpling with a microstylus. This treatment produlced a transient depolarization of the membrane, and a transient increase in the frequency of ciliary beating. The increase in frequency of ciliary beating was related to the concentration of extracellular calcium ion, decreasing with reductiotn in calcium. Addition of lanthanum was followed by a decrease in spontaneous ciliary aictivity and a hyperpolarization of the membrane. In the presence of lanthanum, the transietnt depolarization in response to mechanical stimulation had a shorter timte course, and the concomitant increase in ciliary frequency was greatly reduced. It is concluded that calciuml ions enter the cell as a result of mechanical stimulationi of the membrane, and that calcium influx leads to an increase in the frequency of ciliary activity.

Recrystallization diagrams of steels Kh18N22V2T2 and 1Kh17N2 with rare earth metals

1. Recrystallization diagrams were constructed for steel Kh18N22V2T2 with additions of lanthanum, cerium, and praseodymium, and for steel 1Kh17N2 with lanthanum oxide. 2. The rare earth metal additions reduce the size of recrystallized grains.

Lanthanum-stimulated high-temperature whisker growth of α-SiC

A study has been made of the growth and morphology of α-SiC whiskers obtained by the effect of lanthanum on silicon carbide crystals growing into a cavity in a SiC mass, heated in an inert ambient of 1 atm pressure, at temperatures between 2300 and 2600 °C. The morphology and the growth rates of the ribbonlike 6H- whiskers are compared with the corresponding properties of the almost equilateral hexagon-shaped plane- parallel platelets of 6H SiC obtained in the same conditions, except for the presence of lanthanum. The addition of lanthanum causes the growth of thinner elongated crystals with an increased growth rate in the longitudinal direction and a decreased rate of growth in width. For platelets and ribbons the activation energies associated with the increase of the growth rates with increasing temperature are the same (∼ 130 kcal/mole) for the two growth directions within experimental accuracy. Platelets and ribbons are both bounded by large-area basal faces {0001} and first-order prismatic and pyramidal side faces {10 i l}; the tips of whiskers interrupted in their growth are rounded and show both first-order faces {10 i l} and second order faces {11 2 l}. The effect of lanthanum is understood as an adsorption-blocking effect on the {10 1 l} side faces favouring ao. {11 2 l} faces of rapid growth at the tip of whiskers.

Interferences and their elimination in the determination of the noble metals by atomic-absorption spectrophotometry

A number of serious interferences in the determination of the noble metals by atomic-absorption spectrophotometry have been investigated, and ways of eliminating them considered. The use of the nitrous oxide and acetylene flame reduced many of the interferences but also reduced the sensitivity. Additions of lanthanum, copper sulphate, copper + cadmium sulphate, uranium, and vanadium as releasing agents were effective in the removal of interferences for one or more of the noble metals in the air-acetylene flame. Uranium additions were found to be effective in removing mutual interferences associated with the noble metals (osmium and indium were not tested) whereas vanadium removed mutual and base-metal interferences. The precision and accuracy of methods of analysis based on the use of uranium and vanadium were acceptable, and the application of these methods to the analysis of noble metals collected by various procedures is briefly discussed.

The determination of yttrium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium in minerals by atomic-absorption spectrophotometry

A procedure is described for determining yttrium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium in zirconium and calcium rare earth silicates by atomic-absorption spectroscopy, which involves the use of a lanthanum suppressor and has potential applications to other minerals containing these interferences. Although many of the associated ingredients are found to interfere, the addition of lanthanum overcomes these problems in many instances. Sensitivities and detection limits found with the proposed procedure are given for each element.

Effect of transition metals on the grain size of titanium

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.

High Temperature Corrosion of Some Gas Turbine Alloys

Abstract Several high temperature alloys were evaluated for hot corrosion resistance at 1500 F (816 C) using a controlled atmosphere combustion furnace burning high sulfur diesel fuel. Modification of commercial alloys and binary Ni-Cr and Co-Cr alloys were also studied using this facility. An over-all analysis of corrosion data suggests that the optimum chromium content lies in the 20–30% range in binary alloys studied, and in commercial alloys somewhat lower chromium content can be tolerated. Significant improvements in corrosion resistance were achieved in the case of commercial alloy Udimet-700 by trace additions of lanthanum and yttrium. A high concentration of SO3 in the gas stream and presence of sulfate deposits were conducive to accelerated rates of attack.

Some properties of tungsten and tungsten-base alloys

1. A study was made of the effect of 0.25 wt.% lanthanum and hafnium additions on the initial recrystallization temperature of tungsten. It was established that hafnium raises the initial recrystallization temperature of tungsten from 1200 to 1300°C; alloying with lanthanum fails to raise the initial recrystallization temperature of tungsten. 2. A 0.25 wt.% addition of hafnium lowers the brittle transition temperature of tungsten from 200 to 100°C, while alloying with lanthanum lowers the brittle transition temperature of tungsten in the recrystallized condition by 100–150°C. 3. Compared with unalloyed tungsten, hafnium-containing tungsten alloys retain good mechanical properties to higher temperatures.

Equilibrium Oxygen Pressures Over Solid Solutions of Urania‐Yttria and Urania‐Lanthana at 1100° to 14OO°C

Using a thermobalance, the oxygen content of urania containing small amounts of yttria or lanthana was determined as a function of the oxygen partial pressure at 1100° to 1400°C. Values for the partial free enthalpy, the partial enthalpy, and partial entropy of oxygen were calculated. Equilibrium oxygen pressures over the solid solutions (U, Y, or La)O2+x were higher than for pure UO2+X. Both the partial enthalpy and partial entropy of oxygen decreased with the addition of yttrium and lanthanum, the change being larger in the latter case. The effects observed experimentally are discussed on the basis of differences in charge and size of the foreign cation relative to the uranium ion.

The effect of small additions of yttrium, lanthanum, and cerium oxides on some magnetic characteristics of magnesium-manganese ferrites and the X-ray spectra of transition metals in them

We have studied the effect of lanthanum, cerium, and yttrium oxide admixtures on the magnetic characteristics of manganese and magnesium-manganese ferrites. We have shown that this effect differs for various rare earths and depends on their content in the ferrite. We have studied the fine structure of x-ray absorption spectra of iron and manganese in ferrites with varying content of rare earth additions. On the basis of an analysis of the experimental material we have drawn preliminary conclusions on the possible mechanism of the effect of admixtures on the energy state of the atoms of the main components in the ferrites.

Effect of the addition of rare earth elements and their oxides on the properties of some stainless steels

1. The addition of 0.1% misch metal improves the ductility of Kh18N10T steel at high temperatures. The addition of 0.15–0.25% misch metal decreases the number of nitride and carbonitride inclusions. 2. The addition of 0.05% misch metal improves the ductility of Kh17N13M2T steel somewhat at 1000°C. 3. The addition of 0.15% misch metal improves the ductility of Kh17N13M2T steel at 1000°C. The number of carbonitride inclusions decreases with increasing amounts of misch metal. 4. The addition of ferrocerium (0.05–0.30%), lanthanum (0.05–0.25%), cerium dioxide (0.05–0.4%), lanthanum oxide (0.05–8.4%), or praseodymium oxide (0.05–0.3%) does not improve the ductility of steel at high temperatures. 5. Rare earth elements do not affect the size of oxide and sulfide inclusions in steel.

Elimination of phosphate interference in flame photometric determination of strontium and barium

The interference of phosphate in the flame emission of calcium, strontium and barium was studied. The emission intensity decreases proportionally to the amount of interfering anion up to a maximum depression for equimolar amounts of phosphate to metal. A thermostable phosphate is formed before the cation enters the flame. Appropriate addition of lanthanum restores the three alkaline earth lines to their intensities in absence of phosphate, the lanthanum displacing, the alkaline earths from their phosphates before the hot region of the flame is reached.

Lattice spacing relationships in the system thorium-cerium-lanthanum

Lattice spacings measured at 25° C are reported for the systems cerium-lanthanum, thorium-cerium and thorium-cerium-lanthanum. In the cerium-lanthanum system, the spacings show a small positive deviation from a straight line drawn between the lattice spacings of the pure components. For thorium-cerium alloys, previous work in the authors' laboratory which showed that cerium decreases the lattice spacing of thorium in spite of its larger atomic diameter is confirmed, in contrast to the conclusion of van Vucht that cerium scarcely affects the spacing of thorium. The addition of lanthanum to thorium-cerium alloys progressively diminishes the initially large deviation of the lattice spacings from the straight line joining the lattice spacings of thorium and γ-cerium; at 39 at % lanthanum, the graph of lattice spacing against cerium content shows only a small deviation from additivity. The results are critically discussed, and provide support for the view that the chief reason for the adoption of a contracted form of cerium in the thorium-rich alloys, by the promotion of a 4f electron to the conduction band, lies in the substantial compressive forces which would be exerted by the thorium matrix on substitutionally dissolved cerium atoms corresponding to the normal 3-valent form.

Effect of rare earth metals on the properties of heat-resistant nickel-chrome alloy

1. Separate additions of cerium, lanthanum, neodymium, and praseodymium to alloy EI437 produce a substantial increase in the strength and plasticity of metal in long- and short-time tensile tests at 700°, and also reduce the total contents of gases in the metal. 2. The maximum effect of rare-earth metals is observable when the residual amount of the injected addition does not exceed 0.02%. 3. By the effectiveness of their influence on the rupture strength of alloy EI43V the investigated elements range in the order corresponding to their progressively increasing melting points.

THE LANTHANUM—BORON SYSTEM1

From thermal metallographic x-ray, and electrical resistance data a phase diagram is proposed for the lanthanum--boron system. Two compounds are formed, LaB/sub 4/ and LaB/sub 6/. The former has a very narrow range of homogeneity and decomposes peritectically at 1800 plus or minus 15 deg . The crystal system is tetragonal, and the compound is a metallic type conductor. LaB/ sub 6/ exists in the range 85.8 to 88% boron, melts above 2500 deg , and has a simple cubic lattice. The coibr of the compound changes with composition, going from purple to a bright blue with increasing boron content. The addition of boron to lanthanum has no measurable effect on the melting point or transition points of the metal. The addition of lanthanum to boron appears to have very little effect on the melting point of boron. There is metallographic evidence for an allotropic transformation in boron above 2100 deg . Evidence also is given for a new compound CaB/sub 4/, which appears to be isomorphous with LaB/sub 4/. (auth)

The determination of americium in Plutonium Alloy fuels for fast reactors

Summary For the determination of americium in fast-reactor plutonium fuels, a method is required which is quantitative and which gives a product free of either alpha or gamma contaminants, since either alpha or gamma counting may be used for the detection of Am241. In the present method, americium, plutonium, and the rare-earth fission products are precipitated as hydroxides from an HCl solution of the fuel sample, after the addition of lanthanum as a carrier. Ceric sulfate is added to the acidified hydroxide precipitate to oxidize plutonium to the hexavalent state. The hexavalent plutonium remains in solution when americium and the rare-earth fluorides are precipitated. After the fluoride precipitate is dissolved in HNO3 and H3BO3, a second hydroxide precipitation is performed to remove fluoride. This precipitate is dissolved in a small quantity of HNO3 and transferred to an ion-exchange column packed with Dowex 50-X4, 200- to 400-mesh resin. Americium and the rare-earth elements are eluted with 5 % NH4NO3 saturated with ethylenediaminetetra-acetic acid at a pH of 2.3. The americium is eluted after the yttrium and just prior to the elution of the europium fractions. In fresh samples (less than 2 days old), the americium may be contaminated with Eu156, but it is free of all other rare-earth elements, permitting alpha counting in a sample with low beta activity. Recovery of americium is better than 98 %, with less than 2 % plutonium alpha activity and with a gamma decontamination factor of 2 × 104. If the sample has aged sufficiently to allow the short-half-lived rare-earth elements to disappear, the americium may be determined by counting the gamma activity.