Spectrophotometric determination of titanium as tetraphenylarsonium or tetraphenylphosphonium thiocyanato-titanate

The spectrophotometric determination of titanium(IV) with thiocyanate by extraction of the tetraphenylarsonium and tetraphenylphosphonium ion-association complexes is described. The extracted complexes in chloroform have a maximum absorbance at 420 nm, obey Beer's law in the range 0.1–1 μg Ti ml^?1, and are stable for at least 5 hr. The molar absorptivity of the method is 7.5 × 10⁴ liters mol^?1 cm^?1. The described method is sensitive, selective, and reproducible. The composition of the extracted complexes was studied in solution and in solid state. The complexes [(C₆H₅)₄X]₂ [Ti(NCS)₆] (X = As, P) were isolated from the chloroform solution.     

Monooctyl-α-(4-carboxyanilino)benzylphosphonic acid as a new reagent for extraction and separation of lead(II) and bismuth(III)

Monooctyl--(4-carboxyanilino)benzylphosphonic acid (H₂L) was investigated as a novel reagent for the extraction and separation of lead(II) and bismuth(III) from nitrate solutions. Stoichiometric ionization constants of H₂L in ethanol — water mixtures determined by potentiometric NaOH titration had values pK_a1 2.25 and pK_a2 4.33. Ethanol and chloroform solutions of H₂L followed Beer's law at 300 nm and 296 nm, molar absorptivities being 2.94·10⁴ mol^–1·l·cm^–1 and 2.85·10⁴ mol^–1·l·cm^–1, respectively. HNO₃ and HCl were also extracted into chloroform solutions containing H₂L. Bismuth(III) was quantitatively transferred into the chloroform H₂L solution at pH 1, and lead(II) at 3.5. The value of the separation factor D_Bi/D_Pb is 160 at pH 1.     

Extraction and separation of uranium(VI) and protactinium(V) with 1-(4-tolyl)-2-methyl-3-hydroxy-4-pyridone

Summary The extraction of uranium(VI) from aqueous hydrochloric or nitric acid, and the extraction of protactinium from hydrochloric acid by 1-(4-tolyl)-2-methyl-3-hydroxy-4-pyridone (HY) dissolved in chloroform has been studied. At pH >4, uranium (VI) is quantitatively extracted while at pH < 1 practically all the uranium remains in the aqueous phase. At hydrochloric acid concentrations lower than 1M, protactinium(V) is quantitatively extracted while at hydrochloric acid concentration higher than 5M practically all the protactinium remains in the aqueous phase. This difference in extraction of uranium and protactinium was utilized for their separation. From 0.5M hydrochloric acid, protactinium is quantitatively extracted, and separated from uranium.The composition of the extracted uranium(VI) and protactinium (V) complexes was studied. A uranium complex with the formula UO₂Y₂ · HY was isolated from the chloroform solution. The solution of this complex in chloroform has a maximum absorbance at 319 nm and the molar absorptivity is 3.1×10⁴ l · mole^–1 · cm^–1. Owing to this property uranium can be determined spectro-photometrically directly in the organic phase.

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Zusammenfassung Die Extraktion von Uran(VI) aus wäßriger Salzsäure oder Salpetersäure sowie die Extraktion von Protaktinium aus Salzsäure mit 1-(4-Tolyl)-2-methyl-3-hydroxy-4-pyridon (HY) in chloroformischer Lösung wurde untersucht. Bei pH > 4 wird U(VI) quantitativ extrahiert, während bei pH < 1 praktisch alles Uran in der wäßrigen Phase bleibt. Bei Salzsäurekonzen-trationen unter 1-m wird Protaktinium (V) quantitativ extrahiert, während bei Salzsäurekonzentrationen über 5-m praktisch alles Pa in der wäßrigen Phase bleibt. Dieser Unterschied bei der Extraktion der beiden Elemente wurde für deren Trennung benützt. Pa wird aus 0,5-m Salzsäure quantitativ extrahiert und so von Uran getrennt.Die Zusammensetzung der extrahierten U (VI)- und Pa (V)-Komplexe wurde untersucht. Ein Urankomplex der Formel UO₂ · Y₂ · HY wurde aus der Chloroformlösung isoliert. Die Lösung dieses Komplexes in Chloroform hat ein Absorptionsmaximum bei 319 nm und eine molare Extinktion von 3,1 · 10⁴ l · mol^–1 · cm^–1. Auf Grund dieser Eigenschaft kann Uran spektrophotometrisch direkt in der organischen Phase bestimmt werden.

     

Radical pairs in irradiated single crystals of 1-methyl uracil

Irradiated single crystals of 1-methyl uracil exhibit the presence of several types of radical pairs. Three of them have been identified. Each pair is composed of a hydrogen-abstraction and a hydrogen-addition radical. The calculations performed show that the postulation of a very strong exchange interaction is not necessary for the existence of the triplet state, if only the sufficiently large dipole-dipole interaction is present. On the basis of the experimental findings the mechanism of the radical formation has been discussed. The relevance of that mechanism for the damaging process of DNA has also been indicated.     

Undoped amorphous SiNx: H alloy semiconductors: Dependence of electronic properties on composition

The electrical and optical properties of a-SiN_x:H thin films prepared by rf growth-discharge in SiH₄N₂H₂ without B or P doping have been measured for 0 < x ? 0.6. It is observed that the activation energy for extended-state electron conduction as well as the optical gap are unaffected by N content for x ? 0.4. The electron mobility in extended states is improved by as much as a factor of 10 by the N incorporation. There is a rapid conversion from the tetrahedral network to a Si₃N₄ network as x increases above ≈ 0.4.