Lanthanum Nitrate Solution Research Articles

Potentiometric behaviour of lanthanum polyalkoxylate complexes in PVC membrane electrodes: effect of plasticizers and applications

Tetraphenylborate salts of lanthanum complexes of nonylphenoxypolyethyleneoxyethanol (Antarox CO-880) and polypropylene glycol-425 (PPG-425) have been prepared and examined for their applicability as sensing species for lanthanum ions by incorporating them in a poly (vinyl chloride) membrane system in the presence of 2-nitrophenyl phenyl ether (NPPE), dioctylphenyl phosphonate or a mixture of both as plasticizers. Almost all of the systems studied showed an excellent response for lanthanum ions in pure solutions with a near Nernstian response of 18–20 mV per decade between 10 −5 and 10 −1 M lanthanum and a static response time of less than 1 min. Among the systems studied, lanthanum(Antarox CO-880)TPB/100% NPPE (TPB=tetraphenylborate) was the best in terms of tolerance to interfering ions. K +, Ba 2+, Pb 2+ and Al 3+ were serious interferents, but most other interferents investigated were tolerable at [La 3+] > 10 −4 M. Plasticizers were found to be decisive in determining the sensor selectivity towards the different metal ions. A lanthanum(Antarox CO-880)TPB/100% NPPE PVC membrane electrode was utilized for the potentiometric titration of fluoride, in sodium fluoride, against lanthanum nitrate solutions. It proved to be successful for fluoride concentrations of ⩾ 10 −3 M.

Principal processes in graphite atomisers modified by high-melting carbides

Some properties of graphite atomisers, modified with an aqueous solution of sodium tungstate or lanthanum nitrate, were studied. The free oxygen concentration in the gas phase of the tungsten carbide modified atomiser is lower than that for a standard atomiser. The most probable reason for this change is that the tungsten carbide catalyses the oxidation of graphite by the free oxygen entrained in the argon. The decreased concentration of free oxygen is one of the reasons for the improved sensitivity obtained with the modified graphite atomisers for elements with thermostable oxides (Ge and possibly B and Si). The maximum ashing temperature for Mo was increased for graphite atomisers modified with lanthanum carbides due to the formation of the refractory La2O3.3MoO3. The maximum ashing temperatures for some Mo- and Sn-containing organic extracts were increased due to the decomposition of volatile chelates and on the active sites of the modified graphite atomiser surface. From a consideration of the information in the literature and the data presented here it was concluded that the processes that occur in a graphite atomiser with a pyrolytic graphite coating and a carbide coating are very different.

Semi-micro determination of fluorine in organic compounds by oxygen silica-flask combustion and gran-type potentiometric titration of fluoride with lanthanum nitrate

A sufficient amount of organofluorine compound to yield about 7 mg of fluoride was burned in a 2-l silica flask filled with oxygen. After absorption of the combustion gases in water the solution was adjusted to pH 4.6 and titrated in a polythene beaker with 0.02 M lanthanum nitrate solution using a fluoride ion-selective electrode as an indicator and a calomel electrode as a reference. Use of a calibration graph based on sodium fluoride and Gran-type evaluation of the potentiometric data gave accurate results with a coefficient of variation of 0.17%.

Gravimetric standard additions in ion-selective electrode potentiometry with application to fluoride measurements

Gravimetric single standard addition and double standard addition ion-selective electrode measurements are described and used for the determination of fluoride in dilute sodium hydroxide solutions. Fluoride concentrations below 5 μg g −1 were determined accurately when the electrode was regularly conditioned with 0.06 M lanthanum nitrate solution at pH 2.0–2.3. The only significant errors in the technique described arise from the millivolt and response slope measurements; the latter require careful measurement of blanks. It is shown that the relative error in concentration measurement by single standard addition will not exceed ± 0.8% if the error in the response slope of the electrode does not exceed ± 0.1 mV/decade, and if the potential difference after standard addition is at least 20 mV with an error not exceeding ± 0.1 mV. Single standard addition is as satisfactory as double standard addition for accurate measurements of fluoride in simple solutions.

Observations of the pattern of secondary wall development in the hypodermis of onion (Allium cepa) roots

This brief communication reports the appearance, under certain circumstances, of root hypodermal cells with transfer cell labyrinths. These cells lie at regular intervals around the hypodermis at the bases of onion bulb roots. They are narrower (smaller tangential dimension) than unmodified cells but have the same radial dimension. These “narrow cells” contain small vacuoles, their main volume being composed of a cytoplasm rich in organelles, especially mitochondria. When treated with a low concentration of lanthanum nitrate solution, the tracer accumulates in the outer tangential wall and in small vacuoles and vesicles.

Investigations of the Determination of Phosphorus in Organic Media by Atomic Absorption Heated Graphite Atomizer

The analysis of phosphorus in organic compounds used as product additives has been investigated. It has been found necessary to change the organic phosphorus to inorganic phosphorus before measuring it by atomic absorption spectrophotometry. In the determination of tricresyl phosphate in gasoline the gasoline is ashed on magnesium sulfonate. The tricresyl phosphate is converted to Mg2P2O7 and subsequently dissolved in nitric acid, diluted to desired concentration, and then injected into the heated graphite furnace. A calibration curve is made from gasoline containing a known phosphorus content to give a range of 1 to 10 ppm. Twenty-five microliters of the knowns and unknown are injected on 10 µl of a 1% solution of lanthanum nitrate on the graphite tube. An alkyl phenyl phosphite additive is diluted in dimethylformamide to bring it into solution in the range of 1 to 10 ppm phosphorus. A portion is ashed on magnesium oxide with the addition of 1 ml of 30% hydrogen peroxide. The Mg2P2O7 is dissolved in nitric acid, then diluted to the calibration curve range. It is injected into the heated graphite furnace in the presence of 10 µl of a 1% lanthanum nitrate solution.

Some aspects of the infrastructure of the ‘Stäbchendrüscnzellen’, a peculiar cell associated with the endothelium of the bulbus arteriosus and with other fish tissues*

The fine structure of an unusual cell, the ‘Stäbchendriisenzellen’ (the so‐called foliaceous or rodlet cells of several authors), associated with the endothelium of the vascular system of marine and freshwater fishes was studied in the goldfish Carassius auratus (L.). The bulbus arteriosus was fixed with either a 6 % solution of buffered glutaraldehyde or with one part of a 3 % solution of lanthanum nitrate plus two parts of a 3 % solution of buffered glutaraldehyde and then post‐fixed in a 1.2% solution of osmium tetroxide. Electron micrographs of the vascular tissue show four cell forms which appear to be phases in the life cycle of the endothelium‐associated cell. Two of the phases are not encased and are characterized by their inclusions: in one cell these are crystalline, while in the second, they are amorphous and granular. In the other phases the cell is encased partially or completely within an apparently contractile fibrous wall surrounded by the plasmalemma. In the encased phases, the arrangement and condition of the cell organelles appears to have been changed, and in the fully‐encased phase mitochondrial activity seems to have decreased. This apparent change in the mitochondrial activity is accompanied by a thickening of the mitochondrial membrane from 48 to 109 Å. The micrographs seem to indicate that this cell in question behaves as a foreign body and, in some way, may be interacting with the epithelial tissue of the bulbus arteriosus.

Neutralized lanthanum solution: a largely noncolloidal ultrastructural tracer.

Lanthanum nitrate solution adjusted to pH 7.4 and pH 7.7 was subjected to column chromatography, ultrafiltration and conductivity measurements. Lanthanum concentration was measured by a colorimetric method employing eriochrome cyanine RC. Under these conditions, lanthanum was not excluded from the column by a packing with an exclusion limit of 1800 daltons. Ultrafiltration through a membrane with a filter limit of 500 daltons allowed approximately 75% of the lanthanum to pass. Conductivity measurements showed a decrease of charge of about 20% on adding sodium hydroxide to a solution of lanthanum nitrate up to a pH of 7.7. It is concluded that approximately 80% of the lanthanum exists as a charged particle of less than 500 daltons at pH 7.7; the other 20% consists of larger, possibly colloidal particles. Nonfiltered and ultrafiltered lanthanum have equally good staining and tracer properties in the electron microscope, suggesting that staining depends largely on the ultrafiltrable noncolloidal lanthanum ion.

An electrophoretic investigation of the behavior of monodisperse polystyrene latices in solutions of lanthanum, neodymium, and thorium nitrates

The electrophoretic mobilities of monodisperse polystyrene latex particles, varying in diameter from 600 A to 4230 A, have been investigated at constant pH as a function of the concentration of lanthanum and thorium nitrate solutions. Measurements were made in lanthanum nitrate solutions at pH values of 4.5, 5.5, and 7.0 and in thorium nitrate solutions at pH 4.5. Reversal of the charge on the particles occurred at all pH values, and in the case of lanthanum nitrate the reversal of charge concentration was pH dependent. The effect of particle size was found to be small. Investigations were also made of the electrophoretic behavior of the latex particles in 10 −5 M lanthanum and neodymium nitrate solutions as a function of pH. Reversal of charge was observed at pH 4.2 and 7.6 and maxima in positive mobilities occurred at pH 5.4 and 7.1. These results have been considered in terms of the known hydrolysis behavior of the La 3+ and Nd + ions.

Polarography of hydrogen peroxide in lanthanum nitrate solutions

The reduction of hydrogen peroxide at the D.M.E. is catalyzed in lanthanum, salt solutions. In. 0.01 M La(NO 3) 3 it has been shown that a cathodic hydrogen peroxide current appears at +0.2 V vs. S.C.E., followed by a depression in the current which extends to the main hydrogen peroxide wave at −0.3 V. Experiments on suspensions of lanthanum hydroxide in lanthanum nitrate-hydrogen peroxide solutions have shown that the reduction current at potentials more oxidizing than −0.3 V increased upon contact with the solid, while the height of the normal wave decreased. Filtration of these mixtures and tests with potassium permanganate and nitric acid on the filtrate indicated that the species responsible for the reduction current was soluble, oxidizable, and unstable to acid. Mercury in contact with the lanthanum nitratehydrogen peroxide test solution led to the more rapid production of this species along with the evolution of oxygen. A soluble complex between lanthanum ion and hydrogen peroxide, formed under mildly alkaline conditions, is postulated as the species being reduced. The suppression of the catalytic current in the potential range +0.1 to −0–2 V is interpreted as the result of adsorption of insoluble lanthanum hydroxide or polymeric lanthanum hydroxy-complexes on the D.M.E. Current-time curves consistent with this explanation have been obtained.

Amperometric titration of lanthanum by ferrocyanide

Lanthanum nitrate solutions have been titrated with a standard solution of potassium ferrocyanide at the dropping mercury electrode at a potential of −1.58 V. The two solutions react in the ratio of 1 : 1 with the formation of the compound LaKFe(CN) 6. Amperometric titration of La(NO 3) 3 and K 4Fe(CN) 6 affords a sensitive method for the estimation of lanthanum.

Geochemistry and mineralogy of a uraniferous lignite [South Dakota

Detailed studies have been carried out on a uraniferous lignite from the Mendenhall strip mine, Harding County, S. Dak. By means of heavy-liquid separations, a mineral-free concentrate of the lignite was obtained that contained 13.8 percent ash and 0.31 percent uranium in the ash. The minerals (gypsum 69 percent, jarosite 10 percent, quartz 2 percent, kaolinite and clay minerals 19 percent, and calcite trace) contain only 7 percent of the uranium in the original coal, indicating an association of the uranium with the organic components of the lignite.Batch extractions show that 88.5 percent of the uranium can be extracted from the lignite by two consecutive treatments with boiling 1 N hydrochloric acid. Continuous extraction with hot 6 N hydrochloric acid removes 98.6 percent of the uranium.Columns of coal were treated with water, 1 N hydrochloric acid, 6 N hydrochloric acid, and a solution of lanthanum nitrate. The experiment with lanthanum nitrate indicated that only 1.2 percent of the uranium in the coal is held by ion exchange. The elutriation experiments showed that the uranium is held in the coal as an organo-uranium compound or complex that is soluble at a pH of less than 2.18.A geochemical mechanism by which the uranium may have been introduced into and retained by the lignite is discussed.