Charles V. Banks

SPECTROPHOTOMETRIC DETERMINATION OF RARE EARTH MIXTURES

Abstract The molar absorptivities for most of the rare earths have been determined at the wavelengths of the various analytically significant absorption bands. These molar absorptivities have been determined on the Beckman Model DU spectrophotometer with and without a photomultiplier attachment as well as on a Cary Model 14 recording spectrophotometer. The techniques and instrumentation necessary for the satisfactory analysis of rare earth mixtures are discussed. A general procedure is presented which has been found most useful for the routine analysis of a wide variety of rare earth mixtures.

BIS-(DISUBSTITUTEDPHOSPHINYL)-ALKANES. IV. EXTRACTION OF MINERAL ACIDS, URANIUM(VI), AND SOME LANTHANIDES

Abstract Comparative partition data are presented for the solvent extraction of mineral acids, uranium (VI), and some lanthanide elements by dis-(di-n-hexylphosphinyl)-alkanes, [( C 6 H 13 ) 2 P(O)(CH 2 ) n P(O)(C 6 H 13 ) 2 , n=1,2,3,4] , as a function of the aqueous concentration of nitric, hydrochloric, and perchloric acids. Extractions from nitric and hydrochloric acids followed quite similar patterns when comparing partition data from the same acid media among the four compounds. However, large increases were noted in the distribution ratios obtained for extractions from perchloric acid with bidentate ligands having methylene carbon bridge lengths, n ≤ 2. Loading studies, differences in extraction, and visible spectra of the uranium (VI) perchlorate adducts of HDPM ( n = 1) and HDPE ( n = 2) were interpreted as possibly indicating the formation of disolvated complexes containing two chelate rings.

GEM-BIS(DISUBSTITUTEDPHOSPHINYL)ALKANES. II. EXTRACTION OF URANIUM(VI) WITH BIS(DI-N-HEXYLPHOSPHINYL)METHANE

Abstract The solvent extraction properties of bis(di- n -hexylphosphinyl)methane, HDPM, [(C 6 H 13 ) 2 P(O)] 2 CH 2 , for uranium (VI) have been studied and compared with those of tri- n -octylphosphine oxide, TOPO, (C 8 H 17 ) 3 P(O). In contrast to TOPO, HDPM forms a polymeric-like complex with uranyl compounds in non-polar solvents. Polymer formation is prevented by the use of a polar solvent such as 1,2-dichlorobenzene. The partition equilibria of nitric acid and uranyl nitrate into 1,2-dichlorobenzene solutions of HDPM and TOPO are discussed. The partition data for various mineral acids and the effect of concentration of these acids on the extraction of uranium (VI) are presented.

COMPOSITION AND STABILITY OF SOME METAL-5-SULPHOSALICYLATE COMPLEXES

Abstract The 5-sulphosalicylate complexes of Al(III), Cr(III), U(VI), Ni(II), Co(II) and Mn(II) have been investigated by the potentiometric method. The Al(III)- and U(VI)-5-sulphosalicylate systems were also investigated spectrophotometrically. It was found that Al(III) forms 1 : 1, 1 : 2 and 1 : 3 complexes at pH values of 3·8, 5·5 and 8·6, respectively and that U(VI) forms 1 : 1 and 1 : 2 complexes at pH values of 4·5 and 7·5, respectively. The stability constants for Be(II)- and Cu(II)-5-sulphosalicylate complexes have been recalculated. The log κ values found by the potentiometric method for the step-wise stability constants are as follows: Al, 13·20, 9·63, 6·06; Cr, 9·56; U, 11·14, 8·06; Ni, 6·42, 3·82; Co, 6·13, 3·69; Mn, 5·24, 3·00; Be, 11·71, 9·10; Cu, 9·52, 6·93.

Synergic solvent extraction of lanthanides with mixtures of aliphatic fluorinated β-diketones and organophosphorus donors

The extraction of lanthanides from an aqueous acetatechloride medium into cyclohexane solutions of trifluoroacetylacetone, hexafluoroacetylacctone, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and tri-n-butyl phosphate was studied. The extraction properties of other fluorinated aliphatic beta-diketones and fluoroorganophosphates were also investigated. The efficiency of the extraction of the lanthanides, the composition of the complexes transferred to the organic phase and the extraction and stability constants for the synergic reactions were determined. Synergic extraction, as a technique for the preparation of lanthanide species, was evaluated for compatibility with subsequent gas chromatography. The lanthanides were found to be rapidly and quantitatively transferred into organic phases containing mixtures of fluorinated aliphatic beta-diketones and TBP. The resulting mixed complexes that contained fully fluorinated beta-diketones had a distinct stoichiometry and were thermodynamically more stable dan similar mixed complexes of partially fluorinated beta-diketones. These properties of the synergic systems allow precise control of the formation of anhydrous complexes in the organic phase and are compatible with the use of these systems for gas chromatography.

Separation and spectrophotometric determination of rare earths

Abstract At the present time arsenazo appears to be widely used for the spectrophotometric determination of rare earths. Unfortunately, the method is not selective. The separation of rare earths and yttrium from interfering elements has been studied, and the following method is proposed. Rare earths are precipitated as fluorides using calcium fluoride as the carrier. Thorium and zirconium are removed by extraction with thenoyltrifluoroacetone (TTA) in xylene at pH 1·3. Small amounts of residual aluminium, iron, etc., are removed by extraction with 8-quinolinol-chloroform at pH 4·5. Rare earths are separated from calcium by TTA extraction at the same pH, then they are back-extracted into 1M nitric acid. After evaporation of the solution, the rare earths are determined spectrophotometrically with arsenazo.

Volatile complexes of some lanthanides and related elements with fluorinated β-diketones and organophosphorus adducts

Abstract The behavior of lanthanide trifluoroacetylacetonates and hexaf luoroacetyl-acetonates of mixed complexes with tri- n -butylphosphate as the adduct has been studied by thermogravimetric methods. Thermal properties of mixed ligand-adduct complexes containing new fluoroorganophosphorus donors have also been examined. Substantial improvements in volatility and thermal stability of chelates of the lan-thanides with either HTFA or HHFA were obtained by displacing the hydrated water with an organophosphorus donor. The thermal stability and volatility of chelates of uranium(IV), uranium(VI) and thorium(IV) were also determined.

Bis-(disubstitutedphosphinyl)-alkanes—V: Solvation of uranyl nitrate by bis-(di-n-hexylphosphinyl) -methane, -ethane, -propane, -butane, and by tri-n-octylphosphine oxide

Abstract The nature of the complexes existing in solutions of uranyl nitrate and various bifunctional phosphine oxides in several organic diluents (1,2-dichlorobenzene, 1,2-dichloroethane, nitrobenzene, and acetonitrile) was investigated. The bifunctional phosphine oxides studies have the general structure, R2-P(O)-(CH2)n-P(O)-R2, where R = n-hexyl group and n = 1, 2, 3, 4 for HDPM, HDPE, HDPP and HDPB, respectively. These compounds, like tri-n-octylphosphine oxide (TOPO), are all powerful extractants for many cations. Infra-red spectroscopic, partition, conductivity and viscosity data are given. These data show that the bifunctional compounds all form monosolvates with uranyl nitrate which appear to be similar to the disolvate formed by TOPO. In both cases the nitrate groups are strongly coordinated to uranium. Higher solvates are readily formed by the bifunctional compounds with the displacement of one or both nitrate groups from the coordination sphere of uranium. In the case of HDPM and HDPE it appears that disolvates are formed in which all four phosphoryl groups are symmetrically bonded to the uranyl ion. The appearance of ionic nitrate in solutions containing TOPO in excess of a 2:1 ligand to uranium ratio and of HDPP or HDPB in excess of a 1:1 ratio also indicates higher solvates in these cases. HDPB appears to form a 3:2 species. Loading capacity data indicate that if the organic phase is equilibrated with an aqueous phase containing a large excess of uranium, the lowest solvates are a disolvate for TOPO and a monosolvate for the bifunctional compounds. If solid uranyl nitrate dihydrate is added to the dry organic phase, the loading capacity indicates that a monosolvate is formed with TOPO and a hemisolvate with the bifunctional compounds. Hemisolvate formation is most extensive with HDPP and HDPB (n = 3, 4).

Spectrophotometric determination of scandium with arsenazo

Abstract Arsenazo is used for the spectrophotometric determination of scandium in the range 10 to 50 μg. The absorbance is measured at 570 mμ and pH 6.1. A method is proposed for the successive determination of scandium and thorium. Scandium is separated from magnesium, calcium, rare earths, zirconium, fluoride, phosphate, and some other metals by extraction with TTA in xylene. Copper, aluminum, and iron(III) are removed by 8-quinolinol-chloroform extraction. Uranium(VI) is removed by anion exchange using hydrochloric acid. Thorium is separated from scandium by anion exchange using nitric acid.

The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysls. Lutetium, ytterbium, cerium (III), scandium. gadolinium, terbium, dysprosium, holmium, erbium, and thulium auorides can be hydrolyzed in 30 min or less. Yttrium. lanthanum, praseodymium. neodymlum, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U/sub 3/C/sub 8/), chromium(UI) oxide. and a mixture of these oxides have been used successfully to reduce the time required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium, and neodymium. (auth)