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.     

Anodic stripping determination of mercury in air with a glassy carbon electrode

A technique for stripping determination of mercury traces in air employing a glassy carbon electrode is described. The sample is passed at 2 liters min^?1 for 2 hr through an absorber containing 0.2 M potassium permanganate and 10% $\text{w}\text{v}$ sulfuric acid (1:1). After reduction with hydroxylamine hydrochloride, the determination is carried out in 0.12 M potassium thiocyanate at pH 2.0 ± 0.2 in the presence of 0.2 ppm of cupric ions. Calibration curves were found to be linear in the range 20 ppb-1 ppm Hg(II) in the cell. The accuracy of the method was tested over simulated samples and it was found to be better than 95%; the relative standard deviation was 5% or less. The limit of detection of mercury in air was approximately 10 μg m^?3.     

Determination of uranium in natural waters after anion-exchange separation

A method is described for the determination of uranium by fluorimetry and spectrophotometry in samples of natural non-saline waters. After acidification with hydrochloric acid, the water sample is filtered and, following the addition of ascorbic acid and potassium thiocyanate, passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (thiocyanate form). On this exchanger uranium is adsorbed as an anionic thiocyanate complex. After removal of iron and other coadsorbed elements by washing first with a mixture consisting of 50 vol.% tetrahydrofuran, 40 vol.% methyl glycol and 10 vol.% 6 M hydrochloric acid, and then with pure aqueous 6 M hydrochloric acid, the uranium is eluted with 1 M hydrochloric acid. In the eluate, uranium is determined fluorimetrically or by means of the spectrophotometric arsenazo III method. The procedure was used for the routine determination of uranium in water samples collected in Austria.     

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.     

Determination of soluble/insoluble tungsten compounds as discrete entities in industrial hygiene samples

A method was developed for the determination of soluble and insoluble tungsten compounds collected simultaneously in industrial hygiene air samples. Soluble tungsten compounds are leached from the collection filter using deionized water. The residual tungsten material is dissolved by a $\text{HNO}{}_3\text{HF}$ digestion, after the removal of potential interfering metal ions by a hydrochloric acid extraction. Atomic absorption spectrometric determination of tungsten in a nitrous oxide—acetylene flame is feasible over the range 10—500 μg ml^-1 at the 255.1-nm line; the working range may be extended to 1000 mg ml^-1 without dilution of the sample by using the 400.8-nm line.     

Dependence of polymer specific volume on molecular characteristics

Linear and branched bisphenol A polycarbonate (PC) samples were characterized by their average molecular weights, $\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ and $\text{M}{}_{\mathrm{<mtext>w</mtext>}}$, polydispersity degree $\text{q =}\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{/}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$, and branching degree g_v. The weight fraction of microgel was also determined for branched samples. The samples were amorphized and densities were measured at 23°C to obtain the values of specific volume, v_sp. The dependence of v_sp on molecular characteristics is described by the multivariable power function $\text{Δv}{}_{\mathrm{<mtext>sp</mtext>}}\text{=}\text{A}{}_{\mathrm{sp}}\text{M}{}_{\mathrm{<mtext>x</mtext>}}{}^{\mathrm{<mtext>a</mtext>}}\text{q}{}^{\mathrm{<mtext>apx</mtext>}}\text{g}{}_{\mathrm{<mtext>v</mtext>}}{}^{\mathrm{<mtext>ab</mtext>}}$, where Δv_sp = v_sp ? v_sp,∞, and A_sp, a, a_px and a_b are constants. It has been confirmed that a = ?1, a_pn = 0 and a_pw = 1. It has also been found that the branching exponent a_b significantly depends on microgel content. The relationships found for PC should, in principle, be valid for other polymers. Examples based on literature data are given for linear polyethylene and polydimethylsiloxane.     

Determination of manganese in uranium by ion exchange and square-wave polarography

Traces of manganese in uranium and its compounds can be determined by ion-exchange separation and square-wave polarography. When a 9 M hydrochloric acid solution of the sample is introduced into a column of strongly basic anion-exchange resin, manganese can be quantitatively separated from uranium by cluting with 9 M hydrochloric acid. The determination of the separated manganese by square-wave polarography is performed in 1 M potassium hydroxide-0.4 M triethanolamine solution with an excellent sensitivity. The lower limit of the method is 0.5 p.p.m. of manganese.     

Anwendung von ionenaustauschverfahren zur bestimmung von spurenelementen in natürlichen wässern—IV: Uran,kobalt und kadmium

A method is described for separating and determining. by spectrofluorimetric or spectrophotometric measurement, traces of uranium. cobalt and cadmium at ppM levels in natural waters. The sample is acidified with HCl. filtered. and after addition of ascorbic acid and potassium thiocyanate, passed through a column of Dowex 1.- × 8 anion-exchange resin in the thiocyanate form. The three ions are concentrated on the resin as thiocyanate complexes, being at the same time separated from most of the other ions present in the sample. Elution with a tetrahydrofuranmethylglycol-HCl mixture removes other interfering ions. then 6M HCl strips the cobalt. 1M HCl the uranium, and 2M HNO₃ the cadmium. Data are presented for concentrations of uranium (0·01–5 ppM) cobalt (0·04–1·9 ppM) and cadmium (0·04–0·6 ppM) in a large number of water sources in Austria.     

Analytical applications of azoisoxazoles. III. Complexes of cobalt,copper, and cadmium with 2-(5′-methyl-2′-isoxazolylazo)-4-methoxyphenol

2-(5′-methyl-2′-isoxazolylazo)-4-Methoxyphenol has been synthesized and its ionization constant (pK_a = 7.98 ± 0.08) spectrophotometrically determined in a 4% ($\text{v}\text{v}$) ethanol-water medium at μ = 0.25 M (NaClO₄). The reagent originates water soluble complexes with cobalt (log β₂ = 11.45 ± 0.16), copper (log β₁ = 7.15 ± 0.10), and cadmium (log β₁ = 3.96 ± 0.12), and can be used for the spectrophotometric determination of cobalt and copper as well as metallochromic indicator for copper.     

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.     

Bestimmung von blei und zink in stäuben durch atomabsorption

The contents of lead and zinc in particles of ambient air, in particulate samples of waste gases and in particles of automobile exhaust gases are determined by atomic absorption spectrometry. The samples are dissolved by constantly boiling hydrochloric acid; commonly some nitric acid is added. Unsolvable components are separated by filtration. The concentrations of lead and zinc in the hydrochloric solutions are estimated by use of the acetylene-air-flame.The measuring ranges are between 1 and 10 mg $\text{Pb}\text{l}$, 5 and 50 mg $\text{Pb}\text{l}$ and 50 to 250 mg $\text{Pb}\text{l}$, and between 0,05 and 1,0 mg $\text{Zn}\text{l}$ and 0,5 and 5,0 mg $\text{Zn}\text{l}$. In the hydrochloric solutions of particles sampled in exhaust gases of automobiles the concentrations of lead were determined between 1 and 250 mg $\text{Pb}\text{l}$. The percentage of different particulate samples was found between 0,1 and 1,2 % for Pb and between 0,1 and 74% for Zn.     

Application of gel permeation chromatography and viscometry for characterization of branched polydisperse polycarbonate

Gel permeation chromatography (GPC) and viscometry (V) methods have been combined for determination of long-chain branching in bisphenol-A polycarbonate (PC) by means of a branching factor $\text{g}{}_{\mathrm{v}}\text{=}\text{M}{}_{\mathrm{vg}}{}^1\text{/}\text{M}{}_{\mathrm{v}}{}^1$, where $\text{M}{}_{\mathrm{vg}}{}^1$ and $\text{M}{}_{\mathrm{v}}{}^1$ are the apparent viscosity-average molecular weights calculated from GPC data and from intrinsic viscosities [η] of the samples respectively. A linear dependence of g_v on molar % of branching agent has been obtained. The GPC data on PC samples have also been applied for verification of an earlier [η]?M relationship for branched polydisperse polymers.     

Simple conditions for the use of ferroin indicator in cerimetric titrations of antimony(III) alone and in mixtures with arsenic(III)

The titration of antimony(III) with cerium(V) sulphate in the presence of ferroin indicator at room temperature is entirely satisfactory in media consisting of 50% ($\text{v}\text{v}$) acetic acid and 1–3 M hydrochloric acid. In the absence of acetic acid, ferroin reacts with the antimony(V) formed in the very early stages, to give a sparingly soluble red complex, which remains in suspension and resists oxidation by cerium(IV). This titration provides a rational method for sequential visual titrations of antimony(III) and arsenic(III). The composition of the ferroin-antimony(V) complex is discussed. Titrations of antimony(III) in 0.5–1 M sulphuric acid medium do not require acetic acid but need iodine monochloride catalyst.     

A thallium(I)-selective electrode based on a liquid ion-exchanger containing 0,0'-didecyldithiophosphoric acid

A liquid ion-exchange electrode containing thallium(I) 0,0'-didecyldithiophosphate in chlorocyclohexane is described. Nernstian behaviour is obtained in the pTI range 1–5.5, the slope of the calibration graph being 57.6 mV/decade change in activity at ionic strength 0.1, Alkali and alkaline earth metal cations do not interfere (K_{$\text{TI}\text{M}$} < 10^?5). Potentials are established rapidly, and are unaffected by pH in the range 5–12. In analytical applications direct potentiometry and potentiometric precipitation titrations with iodide or tetraphenylborate solutions are satisfactory. Various interfering ions can be masked with EDTA.     

Infrared chemiluminescence in the reactions of 0.45 eV hydrogen atoms with Cl2, SCl2 and PCl3

Infrared chemiluminescence from HCl has been observed in “arrested relaxation” experiments to yield vibrational and rotational distributions from the reactions $\text{H}$+Cl₂, SCl₂ and PCl₃, where $\text{H}$ denotes hydrogen atoms with translational energy of 0.45 eV. The following relative populations were determined: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.89:1.00:0.84:0.47:0.26:0.11 for $\text{H}$+Cl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.80:1.00:0.72:0.48:0.24:0.10 for $\text{H}$+SCl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5 = 0.79:1.00:0.88:0.36:0.14 for H+PCl₃. In all three reaction systems the chemiluminescence was attributed to the primary chlorine abstraction. Comparison with the results of the thermal processes (0.04 eV hydrogen atoms) led to the following conclusions: for H+Cl₂ the excess of translational energy is transformed into translational product energy and rotational energy of the molecule HCl; for H+SCl₂ the excess of translational energy is transformed mainly into translational energy of the products and perhaps internal energy of SCl; for H+PCl₃ the excess of translational energy allows the observation of the primary abstraction reaction, which could in earlier experiments at 300 K not be separated from secondary chemiluminescent processes. Bimodal rotational distributions were confirmed for several vibrational states of HCl formed in the systems $\text{H}$+Cl₂, and $\text{H}$+SCl₂. Bimodal rotational distributions were also detected in the chemiluminescent reaction H(0.04 eV)+CH₃SCl → HCl(v ? 5)+CH₃S.     

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).     

Dilute solutions of nylon 12—II. Relationship between intrinsic viscosity and molecular weight

Samples of poly(12-dodecanelactam) (polylaurolactam, nylon 12) with $\text{M}$_n 1 × 10³?33 × 10³ were prepared. Polymerizations initiated with water or with lauric acid proceeded under conditions for minimum changes in end-group concentration. Values of $\text{M}$_n were calculated from the end-group content and $\text{M}$_n from light scattering in the mixture m-cresol/60 vol% of 2.2,3,3-tetrafluoropropanol. From measurements of intrinsic viscosity in m-cresol, the relationship [n] ? $\text{M}$_n was established in the given range of $\text{M}$_n. The relationship [n] ? $\text{M}$_w for $\text{M}$_w from 3.3 × 10³ to 125 × 10³ has been established.     

Photometric titrations with indicators

Various types of photometric titration curves are discussed. If a metal M is titrated conipleximetrically using a metal indicator and the absorbance is plotted vs. the titrant consumed, the inflection point appears at a pM value defined by the equation 3 pM_infl = pM_trans + 2 pM_eqThis expression is valid when M combines in a 1 : 1 ratio with the complexing agent and the indicator and when the indicator concentration is small compared to the total metal concentration.The difference between the pM values at the inflection and equivalence points can be calculated from the equation ΔpM = pM_infl — pM_eq = $\text{1}\text{3}$(pM_trans — pM_eq) = $\text{1}\text{6}$log(C_MK²_MI/K_MY)If the inflection point is taken as the equivalence point, the error arising can be calculated from ΔpM, or more simply, read from a diagram.If transmittance, instead of absorbancc, is plotted as a function of the titrant volume, the inflection point depends on the added amount of indicator. However, at high transmittance values, i.e., at low indicator concentrations, the inflection point of a transmittance curve occurs practically at the same volume of added titrant as the inflection point of an absorbance curve. Rules are given for applying an indicator correction for the amount of metal bound to the indicator at the end-point.The derived equations and discussions can also be applied to acid-base titrations.     

Determination of sulfate in river water by flow injection analysis

Sulfate ion in river water is determined by flow injection analysis at a rate of 30 samples per hour; the sulfate contents are typically less than 30 ppm. The reagent solution contains dimethylsulfonazo-III, barium chloride, potassium nitrate and chloroacetate buffer in 70% ($\text{v}\text{v}$) ethanol, and is saturated with barium sulfate. The aqueous carrier stream is also saturated with barium sulfate. The sample is filtered and treated with Amberlite IR120-B cation-exchanger before injection into the carrier stream, and the decoloration of the barium—dimethylsulfonazo-III complex by sulfate is measured at 662 nm. The calibration graph is linear over the range 0–30 μg ml^-1 for sulfate in water.     

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,