Determination of sulfate in waters

Determination of sulfate in industrial waters is performed by shaking with Dowex 50-X8 resin (removing of metal ion interferences) and titration of aqueous acetone ($\text{1}\text{1}\text{,}\text{v}\text{v}$) solution with barium perchlorate employing Dimethylsulfonazo III as indicator. Only phosphate and arsenate interfere.     

The crystal structure of strontium tetraiododiargentate octahydrate,SrAg2I4 · 8H2O

Crystals of strontium tetraiododiargentate octahydrate, SrAg₂I₄ · 8H₂O belong to the tetragonal space group I422(D⁹₄), with a = 12.86 ± 0.03, c = 5.56 ± 0.02Å, and Z = 2. The structure may be described as having, in one-to-one ratio, columns formed by [Sr(H₂O)₈]²⁺ entities centered at (0, 0) and ($\text{1}\text{2}\text{,}\text{1}\text{2}$) and chains of edge-sharing AgI₄ tetrahedra centered at ($\text{1}\text{2}$, 0) and (0, $\text{1}\text{2}$), the chains being linked to each other through water molecules by hydrogen bonding and through van der Waals forces between iodide ions. The crystals are obtained from a saturated aqueous solution of SrI₂ which is then saturated with AgI; dilution of this solution or addition of water to the crystals precipitates β-AgI. This demonstrates the ease with which the three-dimensional corner-sharing tetrahedra of the β-AgI transform to the edge-sharing chain arrangement of tetrahedra and vice versa. It is probable that the saturated solution itself contains [Sr(H₂O)₈]²⁺ and AgI₄-chain entities.Anhydrous compounds of strontium and barium halides with silver and copper halides appear to be unattainable at atmospheric pressure. It is speculated that this is associated with the particular coordination requirements of the alkaline earth ions.     

Radium-224 in natural waters measured by γ-ray spectrometry

A method based on Ge(Li) γ-ray spectrométry is applied to the determination of ²²⁴Ra (t_{$\text{1}\text{2}$}= 3.64 days) in natural waters. The ²²⁴Ra is first removed from several hundred liters of water by preconcentration onto manganese dioxide-impregnated acrylic fibers. The fibers are leached, radium is coprecipitated with barium sulfate, and the γ-ray activity is counted so that activity ratios among ²²⁴Ra, ²²⁵Ra and ²²⁶Ra can be calculated. Concentrations are determined by using the ²²⁶Ra concentration determined on a small separate sample. Results from samples collected from ground water, estuarine, and continental shelf environments are presented.     

Séparation baryum-strontium par chromatographie sur cellulose : Chromatographie sur poudre de cellulose

The systematic investigation of a good Ba⁺²- Sr⁺² separation using a. cellulose powder column has given us the choice of two eluants: (a) Methanol 1.2N en HCl (gazeux) + water ($\text{v}\text{v}$: $\text{100}\text{5}$) (b) Methanol-ether-HCl 12N ($\text{v}\text{v}$:75-25-5). The second one gave excellent separations, both in quantities of the order of 200 mg and in tracer amounts: Sr ? 0.001 μg-Ba ? 0.8 μg If we increase the eluting power of the solvent after the complete elution of Sr⁺² (suppression of ether), we considerably reduce the time and volume needed for the Ba⁺² elution. This work was done with the help of radioactive isotopes ¹⁴⁰Ba (12.8 days) and ⁹⁰Sr (25 years). At the same time, we found that the eluant used is also efficient for the separation of ¹⁴⁰Ba and ⁹⁰Sr from their respective decay products: ¹⁴⁰La and ⁹⁰Y (40h and 65h).     

Shape analysis of the velocity distribution in supersonic Ar beams: Comparison between experiment and theory

The shape parameters of the velocity distribution for beam densityF(v) = C($\text{v}\text{α}$)² exp[?($\text{v}\text{?}\text{u}\text{α}$)²]

from a supersonic expansion of Ar are determined both experimentally via time-of-light(TOF) analysis and computationally by solving the Boltzmann equation for a radial flow field via the method of moments. TOF spectra are recorded by means of the detection of metastable Ar atoms. This technique eliminates velocity discrimination in the detection process. Significance test and a sensitivity analysis for the experimental and theoretical results are included. The agreement of measured and calculated shape parameters is very good. Small-angle scattering of particles, travelling with small relative velocity along the same stream line, is still effective beyond the transition region to free molecular flow and continues to modify the distribution function. A primitive model that correlates the shape parameters c₃ and c₄ with the terminal speed ratio and describes their variation with the distance from the nozzlee is developed.     

Rotational and vibrational temperatures of naphthalene in a naphthalene-argon supersonic jet

In the $\text{A}$¹B_2u-$\text{X}$¹A_g system of naphthalene in a supersonic jet, rotational contour calculations show rotational temperatures of 2–60 K for argon carrier gas pressures of 1520-120 Torr. The b_1u vibration v₂₄ shows a high vibrational temperature which corresponds to the seeding temperature for pressures <400 Torr.     

The spectrophotometric determination of iron(III) in a flow-injection system with a mixed solvent

A fast and sensitive flow-injection procedure is described for the determination of iron(III). The complexing agent is ammonium diisopropyldithiophosphate in a 1:1 (v/v) isopropanol/water carrier stream. The linear range is 0.05–15 mg 1^?1 iron(III) with a detection limit of 0.01 mg 1^?1 and the injection rate is about 400 h^?1.     

Spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone)

A simple method is described for the rapid spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone). The yellow color is measured at 460 nm (? = 22,800 liters mol^?1 cm^?1) against a reagent blank at pH 2.5 in a solution containing 60% ($\text{v}\text{v}$) dimethylformamide. Beer's law is obeyed over the range 0.2–2 ppm of nickel.     

Constant-current coulometric determination of uranium in the pure metal

A new method is proposed for the highly precise and accurate constant-current coulometry of uranium in high-purity uranium. Precisely weighed amounts of uranium and pure iron are dissolved in 7 M sulfuric acid containing some hydrogen peroxide (40% $\text{v}\text{v}$). The solution is quantitatively transferred to the coulometric cell by rinsing with 1 M H₂SO₄, saturated with cerium(III) sulfate. The first step is the quantitative electro-chemical reduction to U(IV), Fe(II) and Ce(III) on a gold gauze electrode at constant current (100 mA) until evolution of hydrogen is observed. The hydrogen is then removed by flushing the solution with very pure nitrogen until the potential of a platinum gauze electrode reaches a constant value. Oxidation on the gold gauze electrode is carried out under precisely controlled constant current; after the quantitative oxidation of U(IV) to U(VI) and Fe(II) to Fe(III), and crossing the end-point, this end-point is determined very precisely potentiometrically through back-titration by successive current injections of 10 mA during 1 s. The method was tested on a NBS reference material, uranium (NBS 960).     

Ab initio calculation of the effective valence shell hamiltonian of carbon: Simultaneous treatment of neutral and ion states

The n = 2 effective valence shell hamiltonian, $\text{H}$^v, of carbon is evaluated through second order using ³P Hartree—Fock orbitals (5s4p) with added d functions to provide results within a few percent of the spd convergence limits. The calculated $\text{H}$^v is employed to evaluate the n = 2 valence states of C, C^?, C⁺, C²⁺ and C³⁺ with an average deviation of the 21 excitation energies, ionization potentials and electron affinity from experimental values of 0.32 eV. Three-electron parts of $\text{H}$^v contribute substantially to a number of these excitation energies.     

Solvent extraction of molybdophosphate with cationic dyes and spectrophotometric determination of micro amounts of phosphate in waters

A very sensitive spectrophotometric method for phosphate is reported. Of the several cationic dyes and extracting solvents examined, ethyl violet and a mixed cyclohexane-4-methyl-pentan-2-one solvent (1:3 $\text{v}\text{v}$) are most satisfactory. When the absorbance of ethyl violet is measured in the organic phase at 602 nm, the calibration graph is linear in the range 0–0.6 μg of phosphorus; the molar absorptivity is 2.7 × 10⁵ l mol^-1 cm^-1. The method is applied to the determination of phosphorus as orthophosphate and condensed phosphate in natural waters. The standard deviation and relative standard deviation for the determination of several ppb of phosphorus in tap water were 0.11 and 1.3%, respectively, and recoveries were good.     

Determination of cadmium, copper and lead in natural waters after anion-exchange separtion.

A method is described for the determination of cadmium, copper and lead in samples of natural non-saline waters. After acidification with hydrobromic acid, the water sample is filtered and, following the addition of ascorbic acid, passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (bromide form). On this exchanger cadmium(II). copper(I) and lead(II) are adsorbed as anionic bromide complexes. After elution of these elements with 1 M nitric acid, the determinations by atomic absorption spectrometry are carried out in a medium consisting of 90% ($\text{v}\text{v}$) methanol and 10% ($\text{v}\text{v}$) 1.5 M hydrobromic acid. The procedure was used for the routine determination of cadmium, copper and lead in water samples collected in Austria.     

Note on a theoretical interpretation of the isotopic ratio vOH/vOD versus vOH in isotopically diluted HDO molecules in solid hydrates

A simple intra- and inter-molecular potential for water molecules engaged in hydrogen bonding has been used in a one-dimensional approximation for a theoretical interpretation of the experimental correlation $\text{v}$_OH/$\text{v}$_OD versus $\text{v}$_OH in solid hydrates. The variation in the equilibrium OH(D) distance has also been considered.     

Decomposition of biological materials,rocks, and soils in pure oxygen under dynamic conditions for the determination of selenium at trace levels

Selenium is evolved from organic materials and from rocks and soils, after admixture with silicic acid and with silicic acid/cellulose, respectively, by combustion in oxygen under dynamic conditions in a special combustion apparatus. While concomitant elements that form sparingly volatile oxides remain in the ash on the sample holder, seleniun dioxide volatilizes and condenses on a cold finger, whence it is dissolved off with hydrochloric acid (1 + 1) or nitric acid (65% $\text{w}\text{v}$) by boiling under reflux. The isolated selenium is determined either by hydride-generation a.a.s. or by differential pulse cathodic stripping voltammetry. Detection limits for the overall procedures lie at 3 and 30 ng g^-1 respectively.     

Spectrophotometric determination of phosphate by extraction of reduced molybdoantimonylphosphoric acid with acetophenone-chloroform

A 90% ($\text{v}\text{v}$) mixture of acetophenone-chloroform is an effective extractant for reduced molybdoantimonylphosphoric acid. The extraction is quantitative over the acidity range of 0.04 to 4.8 N sulfuric acid. The mixed solvent extractant is virtually immiscible with water and can be used at aqueous/organic volume ratios from 1:1 to 40:1 with no loss of solvent or decrease in % extraction. Phosphate is easily determined from 5 to 1000 ppb. No interference from silicate was experienced.     

1-(1,2,4-Triazolyl-3-azo)-2-naphthol as a spectrophotometric reagent for inorganic ions

The synthesis, characteristics and analytical reactions of 1-(1,2,4-triazoly 1-3-azo)-2-naphthol are described. Coloured complexes are formed with 21 metal ions. For the cadmiuin(II) complex, the molar absorptivity is 2.8 × 10⁴ 1 mol^-1 cm^-1 at 515 nm for 40% ($\text{v}\text{v}$) ethanolic solutions at pH 8.0. For the mercury(II) complex at pH 10, the molar absorptivity is 2.7 × 10⁴ mol^-1 cm^-1 at 530 nm. Complexes of the ML₂ type are formed.     

Étude du comportement polarographique de Ge(IV)

A reduction wave of Ge(IV) is observed at pH valvest greater than 7. The study of the wave has shown that the reduction is irreversible and occurs from Ge⁺⁴ to Ge° and that its height is strongly dependend on the pH. We have shown that the second wave observed by Das Gupta and Nair in the medium NH₄CI-NH₄OH cannot be ascribed to Ge. From an analytical point of view, it should be operated in the pH-regiXXXn. from 8 to 9, wliere the height of the wave can be considered as constant ; the diffusion current constant equals 6.82. In the KCl 0.05M medium, we have measured D = 0.79.1O^-5 cm²/sec and E$\text{1}\text{2}$ = —1.50 volt v/SCE; where as NH₄Cl-NH₄OH, medium. D = 0.89–10^-5 cm²/sec and E$\text{1}\text{2}$ = —1.56 volt v/SCE,     

Preferential energy transfer from N2(A) to specific energy levels of Cu atoms

Emission spectra resulting from reaction of “clean” N₂(A³ Σ_u⁺) with copper atoms were studied using a flowing afterglow apparatus. The population distribution of the Cu states was calculated from the spectrum; it indicates that Cu atoms are excited by nearly resonant energy transfer processes. N₂(A,v') + Cu(²S_{$\text{1}\text{2}$}) → N₂(X, v) + Cu^* , and that the transfer is most efficient for N₂(A,v') → N₂(X,v) transitions with large Franck-Condon factors. The preferential energy transfer results in population inversion between some of the Cu states.     

Rapid determination of nicotinic acid by immobilized lactobacillus arabinosus

A rapid determination of aicotinic acid by using immobilized Lactobacillus arabinosus and a combined glass electrode is reported. L. arabinosus is immobilized in agar gel. The optimum agar concentration is from 2–2.5% ($\text{w}\text{v}$) and the optimum bacterial concentration in the agar gel matrix is 10 mg wet cells ml^-1. The relationship between the potential difference and the logarithm of the nicotinic acid concentration is linear over the range 5 X 10^-8–5 X 10^-6 g ml^-1. The assay requires only 1 h; potentials are reproducible with an average relative error of 5%. The growth of L. arabinosus in agar gel matrix is observed in the medium containing nicotinic acid. Immobilized L. arabinosus is stable for 30 days.     

Triplet-mediated coupling of 5-bromo-1,3-dimetrhyluracil to Nb-methoxycarbonyltryptamine involving a double electron transfer

On acetone-sensitization, 5-bromo-1,3-dimethyluracil ($\text{1}$ reacts with N^b-methoxycarbonyltryptamine ($\text{4}$ under the assistance of an electron carrier such as 2-methoxynaphthalene to give a coupling product $\text{6}$. A mechanism involving a double electron transfer via the triplet state of $\text{1}$ is proposed.