Samuel J. Lyle

Applications of the fluoride-sensitive electrode to the study of metal-fluoride ion association constants

Abstract An “Orion” fluoride-sensitive membrane electrode has been examined critically for the measurement of metal-fluoride ion association in aqueous solutions of constant ionic strength, with a calomel reference electrode and sodium chloride salt bridge. Measurements were made with magnesium, calcium, scandium, iron(III), europium(III) and gadolinium ions at 25°; yttrium and “protonation” of [F - ] were studied at 15, 25 and 35° and enthalpy and entropy changes calculated. The electrode is limited to solutions 10 -6 M or greater in free [F - ] aq , with a consequent limitation on the magnitude of the first association constant to ≦10 6 . Further limitations are imposed by the insolubility of most metal fluoride salts. The electrode is less sensitive than the iron(III)-iron(II) electrode system, but is much more convenient. Good agreement with previous results was obtained from measurements at various temperatures.

Some aspects of n-benzoylphenylhydroxylamine and cupferron reactions with tin, antimony and other selected elements

Abstract N-Benzoyl-N-phenylhydroxylamine (BPHA) and cupferron are compared in the liquid-liquid extraction of tin and antimony. As in their precipitation reactions tin(II) and tin(IV) behave similarly with BPHA and differently with cupferron. Both reagents behave similarly in extraction of antimony (III), except at high acidity when cupferron or its decomposition products prevent extraction which otherwise occurs into chloroform alone. Separations of Sn, Sb, As and Bi are discussed for extractions from hydrochloric and perchloric acid systems with BPHA. The tin product extracted with BPHA from dilute hydrochloric acid appears to be identical with that precipitated in gravimetric analysis; infrared spectral evidence shows the latter to contain tin(IV). Other precipitation reactions of BPHA in the presence of anions other than chloride and some solubility measurements are also reported.

Complexes of lanthanum and actinium with fluoride, oxalate and sulphate in aqueous solutions

Abstract Equilibrium constants for complexes formed by lanthanum and actinium ions with fluoride, oxalate and sulphate are reported for an aqueous sodium perchlorate medium of ionic strength 0·5. A partition method making use of di-2-ethylhexylphosphoric acid in toluene was employed in this work. The values obtained are discussed in relation to data available for yttrium, other lanthanides and actinides.

A study of the distribution of series of positively charged europium complexes between a cation-exchanger and an external aqueous phase

Abstract The partition of europium (III), initially in an aqueous phase containing ligand, into a cation-exchanger and separately into di-(2-ethylhexyl) phosphoric acid in toluene has been studied. A method, which does not depend on the ion-exchange data alone, was thereby developed for the determination of distribution coefficients for a series of positively charged metal ion complexes partitioning into the cation-exchanger. The complexes formed with α-hydroxy-isobutyrate, fluoride or oxalate as ligand, A n− , at an ionic strength of 0·5 were examined. In all cases the order for the distribution of europium (III) species between resin and external solution was Eu 3+ > EuA (3−n)+ > EuA 2 (3−2n)+ with differences in the ratios of successive distribution coefficients depending markedly on A n− . Equilibrium constants for the complexes formed were computed and various tests applied to the method of computation from ion-exchange distribution data.

The distribution of positively charged cerium (III) and gadolinium complexes between a cation-exchanger and an aqueous phase

Abstract Using the method reported previously the distribution of positively charged cationic complexes partitioning into a cation-exchanger has been studied and compared with distributions for the “free” metal ions. Cerium (III) partition from α-hydroxy-isobutyrate (at μ = 1), fluoride and sulphate systems and gadolinium from oxalate, fluoride and sulphate solutions (all at μ = 0·5) have been examined. The results confirm the earlier observations on the partition of monobutyrate, fluoride and oxalate complex cations with [LnF]2+ showing by far the greatest tendency to enter the exchanger. The monosulphate complex ion of cerium (III) did not appear to exchange while the corresponding gadolinium complex exchanged slightly. Equilibrium constants for step-wise complex formation in the aqueous phase are computed and compared where possible with reported values.

Equilibrium constants for aqueous fluoro complexes of scandium, yttrium, americanium(III) and curium(III) by extraction into di-2-ethylhexyl phosphoric acid

Abstract From studies of the extraction of yttrium, americium(III) and curium(III) from aqueous fluoride, [F − ], into di-2-ethylhexyl phosphoric acid, H 2 D 2 , it has been deduced that for [F − ] = (0·1 − 4·0) × 10 −3 ml −1 and pH = 3·60 substances other than M (HD 2 ) 3 contribute appreciably to the metal, M , ion distribution. From known equilibrium constants for for aqueous fluoro metal complexes of yttrium it was concluded that, under the prevailing experimental conditions, a substance of the form YF 3 . 3H x D x (where x is an unknown integer) also extracts. A method was thus evolved whereby distribution data alone were made to yield equilibrium constants for the stepwise formation of the first three complexes for americium(III) [ β 1 = 2·46 × 10 3 , β 2 = 1·28 × 10 6 , β 3 = 1·0 × 10 9 ] and curium-(III) [ β 1 = 2·21 × 10 3 , β 2 = 1·50 × 10 6 , β 3 = 1·2 × 10 9 ] at μ = 0·500 (NaClO 4 ). For [F − = (0·2 − 220) × 10 −5 ml −1 and pH 2·50 scandium extracts overwhelmingly as Sc(HD 2 ) 3 and β 1 – β 4 are obtained in good agreement with published values. Tests, which throw light on the nature and number of the principle metal species which extract, are described.

Preparation and properties of lanthanide complexes of some β-diketones

Abstract The preparation, thermal stability, volatility and spectral characteristics of lanthanide(III) complexes formed from 1,1,1-trifluoromethyl-5,5-dimethyl-2,4-hexanedione (HPTA), 1,1,1-trifluoromethyl-4-phenyl-1,3-butanedione (HBTA) and 1,3-diphenyl-1,3-propanedione (HDBM) are described. Under the conditions (aqueous or aqueous ethanol solution) employed HPTA gives rise to tetrakis chelates, HBTA to (hydrated) tris chelates and HDBM to basic polymeric products. The tetrakis chelates M[Ln(PTA) 4 ], where M + is an alkali metal cation, are all volatile. However those with M +  Ph 4 As + and M +  Et 4 N + are non-volatile, although still of high thermal stability.

A study of the direct spectrophotometric determination of uranium(VI) in trialkylamine extracts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Abstract A straightforward spectrophotometric method is described for the determination of uranium(VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to backextraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors.

Europium(III) complexes with propionate, lactate, pyruvate and α-alaninate in aqueous solution

Abstract Free-energy, enthalpy (measured calorimetrically) and entropy changes for the formation of europium(III) complexes from propionate, lactate, pyruvate and α-alaninate ions have been determined in a sodium perchlorate medium of ionic strength 2. In acid solution the only alanine species which interacts significantly, but nevertheless weakly, with the metal ion is the zwitterion. Results for the various systems are compared and discussed.

A selective spectrophotometric determination of europium in mixtures with other lanthanides,yttrium and scandium

Summary Spectrophotometric methods are presented for the determination of 0.04–5 mg of europium in rare earth mixtures, following a group separation, or in lanthanide compounds. Europium(III) is selectively reduced on a Jones reductor to europium(II) which in turn reduces molybdophosphoric acid to a molybdenum blue. The absorbance is measured at 810 nm in aqueous solution or at 790 nm after extraction into n-amyl alcohol; optimal reaction conditions and times are reported. Other rare earth elements, and chloride, bromide, perchlorate, acetate and sulphate, are without effect when present in gram amounts but nitrate and iodide must be absent. The method is applied to the determination of europium in various lanthanide oxides and bastnaesite.