Kinetics and mechanism of the reaction of aquachromium(III) with l-ascorbic acid in aqueous media

The kinetics of the reaction of l-ascorbic acid (H2A) with aquachromium(III) has been studied over the range 0.04 [H2A]T 0.16 mol dm–3, 3.5 pH 6.0, 25.0 t 50.0C, 0.03 I 1.0 mol dm–3 (KNO3) and 0% [MeOH] 20% (v/v). The reaction takes place via an outer-sphere association between Cr3+/CrOH2+ and H2A, followed by transformation of the outer- into an inner-sphere complex by slow interchange. The anation rate constants for Cr3+ and CrOH2+ species (k1 and k2) at 25C and I=1.0moldm–3 (KNO3) are 1.68×10–4 and 2.14×10–4s–1, respectively. H and S for the k1 and k2 paths are 27.0±2kJmol–1, –227±5J K–1mol–1 and 57.2± 4kJmol–1, –123±14JK–1mol–1, respectively. Anation of Cr(H2O)3+6 and Cr(H2O)5OH2+ follow an Ia path.     

The kinetics and mechanism of aquation and base hydrolysis of the cis-[Co(cyclen)Cl2]+ cation (cyclen=1,4,7,10-tetraazacyclododecane)

The aquation of cis-[Co(cyclen)Cl2]+ (cyclen=1,4,7,10-tetraazacyclododecane) has been studied over a range of temperatures with 0.1 mol dm–3 HNO3 as solvent. At 25°C, kaq=4.5×10–3 s–1 with H=78 kJ mol–1 and S298=–21 J K–1 mol–1. Base hydrolysis of cis-[Co(cyclen)Cl2]+ is extremely rapid with kOH=2.1×107 dm3 mol–1 s–1 at 25°C and I=0.1 mol dm–3. This is the largest rate constant so far reported for the base hydrolysis of a cis-dichloro-complex of a saturated macrocycle. The activation parameters, H=53 kJ mol–1 and S298=73 J K–1 mol–1 are consistent with a mechanism in which deprotonation of the substrate is rate-determining. This conclusion is confirmed by the observation of general base catalysis by formate ion. The Brønsted value for the reaction is ca. 0.72 and SN1(CB) and E2 mechanisms are considered to account for the kinetic results. Base hydrolysis of cis-[Co(cyclen)(OH)Cl]+ has also been studied in the pH range 6.5 to 8.7. The value of kOH=3.8×102 dm3 mol–1 s–1 at 25°C and I=0.1 mol dm–3 with H=110 kJ mol–1 and S298=171 J K–1 mol–1 are consistent with an SN1(CB) mechanism.     

Titrimetry in a continuous flow system

Summary Sulphate in the range of 5–2000 mol · l^–1 is automatically titrated with Ba(II) in a device with an optical detection which is able to correct automatically for dilution and turbidities. The flow-through system contains 80% v/v ethanol; the indicator is dimethyl sulfonazo(III). Above a concentration level of about 20 mol · l^–1 SO ₄ ^2– the standard deviation is less than 5% rel. The titration time is negligibly small as compared to the sampling time.

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Titrimetrie im DurchflußsystemI. Apparatur und Sulfatbestimmung

Zusammenfassung Sulfat wird im Bereich von 5–2000 mol · l^–1 automatisch mit Ba(II) mit einem Gerät mit optischer Detektion titriert, das automatisch für Verdünnung und Trübung korrigieren kann. Das Durchflußsystem enthält 80% v/v Äthanol; Indicator ist Dimethylsulfonazo(III). Die Standardabweichung für Proben mit einem Sulfatgehalt höher als 20 mol · l^–1 ist niedriger als 5% rel. Die Titrationsdauer ist vernachlässigbar im Vergleich mit der Zeit für die Probennahme.

     

Spectrofluorimetric determination of nucleic acids as 8-hydroxyquinoline/ yttrium ternary complexes

The formation of nucleic acids/8-hydroxyquinoline/yttrium(III) ternary complexes and their fluorescent properties have been studied. The nucleic acids studied include native and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 7.6–8.5, controlled by NH₃-NH₄C1 buffer, ternary complexes are formed that fluoresce at different wavelengths with different nucleic acids. Based on the fluorescence reactions, sensitive spectrofluorimetric methods for nucleic acids are proposed. In optimal conditions, the calibration curves were linear in the range 0.5–4.0 gml^–1 for calf thymus DNA, 0.5–2.5 g ml^–1 for fish sperm DNA and 0.5–4.0 g ml^–1 for yeast RNA. The limits of determination (3 ) were 0.030 g ml^–1 for calf thymus DNA, 0.020 g ml^–1 for fish sperm DNA and 0.090 g ml^–1 for yeast RNA. Corresponding to the interferences of coexisting substances, six synthetic samples were constructed and the results of determination were satisfactory.     

Spectrophotometric and derivative spectrophotometric determination of palladium(II) using pyridopyridazine dithione in the presence of non-ionic surfactant

Pyridopyridazine dithione (PPD) was synthesized as a new sensitive and selective reagent for spectrophotometric and derivative spectrophotometric determination of palladium(II). In aqueous and micellar medium, PPD forms 1:4 complexes having molar absorptivities of 4.68 × 10⁴ and 5.74 × 10⁴lmol^–1 cm^–1 at 570 and 615 nm, respectively. Beer's law was obeyed up to 2.2 and 2.5 g ml^–1 with detection limits of 0.2 and 0.1g ml^–1. The relative standard deviations for 1.23g ml^–1 were 2.6 and 1.3%, in the absence and presence of Triton X-100. In fourth-derivative mode, the regression equation, linear range, detection limit and RSD for 0.075 g ml^–1 wereD ₄ = 4.3C + 1.5 × 10^–3, 0.013 – 0.23 g ml^–1, 3.7 ng ml–1 and 0.78%, respectively. The ionization constants of the reagent and stability constants of the complexes were evaluated. The method is free from interference by most common metal ions and anions. The method was applied for determination of palladium in activated charcoal.     

Characterization and determination of benzalmalonitriles using infrared,nuclear magnetic resonance and mass spectrometry

Summary The stretching vibration of the CN groups at 2200–2240 cm^–1 and the singlet signal of the olefinic proton at 7–9 ppm in the IR and NMR spectra of benzalmalonitriles are correlated with Hammett sigma parameter of the substituents and the data obtained are used for their selective characterization. Using the base-line method and KBr technique or dimethylsulfoxide solvent and the integration method, 50–800g/250 mg KBr or 10–100 mg/ml of these compounds are quantitated by IR and NMR, respectively. The average recovery by both methods is 98.3% (st. dev. 1.6%). Fragmentation of these compounds using mass spectrometry gives common products that can be used for their characterization.

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Charakterisierung und Bestimmung von Benzalmalonitrilen mittels Infrarot-, Kernresonanz- und Massenspektrometrie

Zusammenfassung Die Valenzschwingung der CN-Gruppen bei 2200–2240 cm^–1 und das Singulettsignal des olefmischen Protons bei =7–9 ppm in den IR-bzw. NMR-Spektren von Benzalmalonitril wurden mit Hammett Sigma Parametern der Substituenten korreliert und die erhaltenen Daten zur selektiven Charakterisierung herangezogen. Unter Verwendung der Basislinien-methode und der Kaliumbromidtechnik bzw. Dimethylsulfoxid als Lösungsmittel und der Integrationsmethode wurden 50–800g/250 mg KBr bzw. 10–110 mg/ml dieser Verbindungen durch IR-bzw. NMR-Spektroskopie quantifiziert. Die durchschnittliche Wiedergewinnungsrate betrug bei beiden Methoden 98,3% (Standardabweichung 1,6%). Die Fragmentierung dieser Verbindungen mittels Massenspektrometrie ergibt Produkte, die zur weiteren Charakterisierung herangezogen werden können.

     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Photometrische Bestimmung von Bor in hochreinen Chemikalien

Zusammenfassung Bor reagiert in Form des Tetrafluoroboratkomplexes mit dem basischen Farbstoff Methylenblau unter Bildung eines mit 1,2-Dichlorethan extrahierbaren Ionenassoziatkomplexes. Die optimalen Bedingungen für die photometrische Bestimmung von Mikromengen Bor werden ermittelt und das vorgestellte Verfahren hinsichtlich Empfindlichkeit, Genauigkeit und kleinster bestimmbarer Menge charakterisiert.Die Borbestimmung ist im Bereich von 0,25–2,5 g Bor mit einer relativen Standardabweichung von 3,8% für 1,0 g Bor möglich. Der molare Extinktionskoeffizient beträgt ₆₆₅=8,2·10⁴1·mol^–1·cm^–1, die Nachweisgrenze nach Kaiser 0,125 g Bor.Das Verfahren wurde zur Bestimmung von 10^–6 bis 10^–5% Bor in folgenden hochreinen Chemikalien eingesetzt: Methanol, Ethanol, Isopropanol, Aceton, Mineralsäuren, Essigsäure, Ammoniak und Wasserstoffperoxid.

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Photometric determination of boron in high-purity chemicals

Summary Boron reacts with fluoride to form borofluoride which itself reacts with the basic dye methylene blue forming a complex which can be extracted into 1,2-dichloroethane. Optimum conditions were established for the determination of microamounts of boron by an extraction-photometric method. The procedure presented has been characterized with regard to sensitivity, precision and detection limit.Boron can be determined within a range from 0.25 to 2.5 g with a relative standard deviation s _rel=3.8% for 1 g B. The absorptivity is ₆₆₅=8.2·10⁴1·mol^–1·cm^–1, the detection limit according to Kaiser was found to be 0.125 g B.The procedure was used to analyse high-purity chemicals (10^–6–10^–5% B) such as organic solvents, mineral acids, acetic acid, ammonia, hydrogen peroxide etc.

     

Spectrophotometric determination of nitrite in environmental waters using column preconcentration on biphenyl

Column preconcentration methods have been established for the spectrophotometric determination of trace nitrite with sulfanilic acid (SA) orp-aminoacetophenone (AAP) as the diazotizable aromatic amine andN, N-dimethylaniline (DMA) or 1-aminonaphthalene (AN) as the coupling agent, using differention-pairs co-precipitated with biphenyl. Nitrite ion reacts with SA in the pH range 2.0–3.0 and AAP in the pH range 1.7–3.0 in HCl medium to form water-soluble colourless diazonium cations. These cations are subsequently coupled with DMA in the pH range 3.7–6.1 for the SA-DMA system and AN in the pH range 1.7–2.3 for the AAP-AN system to be retained on microcrystalline biphenyl packed in a column. The solid mass is dissolved out from the column with 5 ml of DMF and the absorbance is measured by a spectrophotometer at 420 nm for the SA-DMA system and at 517 nm for the AAP-AN system. The calibration was linear over the concentration ranges 0.3–6.0 g of nitrite in 5 ml of DMF solution (i.e., 0.02–0.40 g/ml in the sample solution) for the SA-DMA system and 0.5–7.0 g of nitrite in 5 ml of DMF solution (i.e., 0.03–0.47 g/ml in the sample solution) for the AAP-AN system. The molar absorptivity and Sandell's sensitivity were respectively 2.63 × 10⁴lmol^–1cm^–1 and 1.75 × 10^–3 g cm^–2 for SA-DMA and 3.28 × 10⁴lmol^–1 cm^–1 and 1.40 × 10^–3 g cm^–2 for AAP-AN. The concentration factors were 4 and 16 for SA-DMA and AAP-AN, respectively. The detection limits were 0.0138 and 0.0175 g/ml NO₂ ^– for SA-DMA and AAP-AN, respectively. Seven replicate determinations of a solution containing 3.5 g of nitrite gave mean absorbances of 0.410 and 0.500 with relative standard deviations of 0.51 and 0.55% for SA-DMA and AAP-AN, respectively. Interference from various foreign ions has been studied and the methods have been applied to the determination of nitrite in environmental samples.     

Sorption kinetics of tributyltin on Elbe river biofilms

For the first time detailed sorption kinetics of tributyltin on native Elbe river biofilms are presented. For this purpose a modified annular rotating continuous flow reactor has been used to develop a reproducible biofilm. Important parameters, such as flow rates, sheer forces, and nutrient concentrations could be varied independently and adjusted to natural conditions. Time-resolved sorption kinetics have been carried out with tributyltin, the most toxic compound in many antifouling paints. The highest sorption rates of tributyltin were observed during the first 0–10 min (0.60±0.05 g Sn m^–2min^–1) than they decreased to a value of 0.10±0.10 g Sn m^–2min^–1 (10–90 min) and increased to a value of 0.20±0.05 g Sn m^–2min^–1 (90–120 min).     

Reaction of trans-tetracyanodioxomolybdate(IV) with salicylaldehyde as an important stage in the Schiff base ligand formation. Kinetics and mechanism

The kinetics of the reaction between the protonated species of trans-[Mo(CN)4O2]4– and salicylaldehyde (Hsal) was studied in the 7.8–12.0 pH range in H2O-MeOH mixtures. Spectroscopic characterization of the product indicates that the aqua and cyano ligands are substituted by sal– with formation of the [Mo(CN)3O (sal- 2O,O)]2– ion. The formation quotient, Kf for the overall reaction=31 (±1) at 25°C. In the presence ofan excess of ligand, the rate law is of the formd[Mo(CN)3O(sal- 2O,O)2–]/dt =kobs[Mo(CN)4O (H2O)2–]. The kobs value is equal to 2.9 (±8)×10–3 at 25°C. The activation parameters H (kobs) and S (kobs) are 103 (±9)kJmol–1 and 45 (±8)JK–1mol–1, respectively. The amount of the product formed decreases with increasing pH but the rate of the product formation increases. The reaction mechanism and the possible formation of Schiff base ligands in the presence of amines are discussed.     

Application of standard materials and standard reference materials in the analysis of lead in blood

Summary Valuable information can be obtained at little expenses from quality control samples prepared in-house to monitor the determination of blood lead by atomic absorption spectrophotometry. Commercially manufactured control materials can also be used for this purpose. These materials are compared to standard reference materials which at present are available.The relative standard deviations for analysis of NBS standard reference materials were 15.4–2.8% (range 60–754 g/l) and in agreement with the relative standard deviation estimated for the analytical method. The corresponding figures for BCR control reference materials were lower: 1.1–1.4% (range 134–795 g/l).The average analytical bias demonstrated by analysis of NBS standard reference material and BCR control reference material were 3–6% (range 795–60 g/l) and in agreement with bias estimated by analysis of commercially manufactured and in-house prepared control materials.     

Kinetics and mechanism of osmium(VIII) mediated cerium(IV) oxidation of dimethylsulfoxide in aqueous sulfuric acid

Under the experimental conditions [DMSO]T [CeIV]T [Os]T the kinetics of oxidation of dimethylsulfoxide (DMSO) to dimethylsulfone (DMSO2) have been followed at different temperatures (40–55°C) in 1.0 mol dm–3 sulfuric acid media. The rate of disappearance of [CeIV] shows a first-order dependence on both [Os]T and [DMSO]T and zeroth-order kinetics with respect to [CeIV]. The suggested mechanism involves oxidation of DMSO by OsVIII in a rate-determining step through an outer-sphere mechanism, followed by rapid regeneration of OsVIII by CeIV from OsVI. The rate law conforms to: –d[CeIV]/dt=k0=k[Os]T[DMSO]T. The values of k and the activation parameters are: 102k=(4.9 ± 0.10) mol–1 dm3 s–1 at 40°C, [H2SO4] =1.0 mol dm–3;H=58±3kJmol–1, S= –88 ±5JK–1mol–1.     

Semi-automatic catalytic titration of some aminopoly-carboxylic acids,copper(II), and cobalt(II)

Summary A semi-automatic potentiometric method is described for the catalytic titrimetric determination ofg amounts of some aminopolycarboxylic acids. The method is based on their inhibitory effect on the copper(II)-catalyzed periodate-thiosulfate reaction. Amounts of EDTA in the 0.7–600g range (10^–6–8×10^–5 M), of DCTA in the 7–7000g range (10^–6–10^–3 M), of EGTA in the 0.8–800g range (10^–7–10^–4 M), and of DTPA in the 4–800g range (5×10^–7–10^–4 M) were determined with average relative errors and coefficient of variation of about 0.4–1%. The method has also been used for the indirect catalytic titrimetric determination ofg amounts of Cu²⁺ and Co²⁺ ions with about the before mentioned accuracy and precision.

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Halbautomatische katalytische Titration einiger Aminopolycarbonsäuren sowie von Cu(II) und Co(II)

Zusammenfassung Eine halbautomatische potentiometrische Methode zur katalytischen Maßanalyse von Mikrogrammengen einiger Aminopolycarbonsäuren wurde angegeben. Sie beruht auf dem Hinderungseffekt gegenüber der Cu(II)katalysierten Perjodat-Thiosulfatreaktion. EDTA in Mengen von 0,7–600g, DCTA in Mengen von 7–7000g, EGTA in Mengen von 0,8–800g und DTPA in Mengen von 4–800g wurden mit einem mittleren relativen Fehler von etwa 0,4–1% bestimmt. Das Verfahren wurde auch zur Bestimmung von Cu(II) und Co(II) mit der angeführten Genauigkeit verwendet.

     

Röntgenstrahlenbeugung bei hohen Temperaturen zur Untersuchung der thermischen Ausdehnung von MnSe und MnSe2

Zusammenfassung Durch Röntgenstrahlenbeugung mit Hilfe einer 190 mm Unicam-Hochtemperaturkamera wurde die thermische Ausdehnung von MnSe und MnSe₂ von Zimmertemperatur bis 710° bzw. 522° C untersucht. Der thermische Ausdehnungskoeffizient wurde aus den Meßdaten nach der Methode der kleinsten Fehlerquadrate erhalten und beträgt für MnSe: =24,5·10^–6°C^–1 (94–450° C) und =14,3·10^–6°C^–1 (450–710° C). Die Ausdehnung von MnSe₂ verläuft bis zum Bereich, in dem Zersetzung eintritt, linear. Die Methode der kleinsten Fehlerquadrate ergibt den Wert =20,0·10^–6°C^–1 (73–522° C).

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High temperature X-ray studies of the thermal expansion ofMnSe andMnSe ₂

The thermal expansion of MnSe and MnSe₂ has been studied above room temperature up to 710° and 522° C, resp., by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The thermal expansion coefficients, , obtained from a linear least-squares analysis of the data are for MnSe: =24.5·10^–6°C^–1 (94–450° C) and =14.3·10^–6°C^–1 (450–710° C). The expansion of MnSe₂ is linear up to the temperature range of decomposition. A least-squares analysis yields a value for of 20.0·10^–6°C^–1 (73–522° C).

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Mit 2 Abbildungen

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Herrn Prof.H. Nowotny gewidmet.     

Synthesis and magnetism of binuclear cobalt(II) complexes with the tetraacetylethene dianion as a bridging ligand

Three novel binuclear CoIIcomplexes, [Co2(TAE)-(phen)4](ClO4)2·3H2O(1),[Co2(TAE)(Nphen)4](ClO4)2 ·4H2O(2) and [CO2(TAE)(bipy)4](ClO4)2·H2O(3) (TAE=tetraacetylethene dianion, phen=1,10–phenanthroline, Nphen=5–nitro·1,10–phenanthroline, bipy =2,2-bipyridy1), have been synthesized and characterized by elemental analysis, i.r., molar conductance and electronic reflection spectra. The complexes are proposed to contain tetraacetylethene dianion bridged structures and two CoII ions. The variable-temperature magnetic susceptibility of complex (1) was measured in the 4–300 K range. The magnetic coupling parameter is consistent with antiferromagnetic exchange between the two CoII centres and the data fit a binuclear magnetic exchange model based on the Hamiltonian operator ( = –2 J12, S1=S2=3/2), giving the antiferromagnetic coupling parameter of 2J=–1.55cm–1.     

Indirekte Bestimmung leichter Elemente durch R?ntgenfluorescenzanalyse

Zusammenfassung Es wird über eine röntgenfluorescenzanalytisehe Methode zur quantitativen Bestimmung leichter Elemente in Mikrogramm-Mengen berichtet, die durch Verwendung eines Bezugsstandards auf eine quantitative Überführung und reproduzierbare Verteilung von Niederschlägen auf Filtern verzichten kann. Das zu bestimmende leichte Element wird zusammen mit einem Bezugsstandard, der mit der Röntgenfluorescenz gut meßbar sein muß, durch ein mit der Röntgenfluorescenz ebenfalls gut meßbares Fällungsreagens ausgefällt. Das Niederschlagsgemisch wird direkt auf dem Filter vermessen. Aus den Intensitätsverhältnissen des Fällungsreagens zum Bezugsstandard werden Eichkurven erstellt und Analysenergebnisse ermittelt. Die Methode wird an Bestimmungen von Cl^– (0,7 g–4 mg), SCN^– (6 g–1mg), CN^– (10–100 g) und P0₄ ^3– (1–10 mg) demonstriert.

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Indirect determination of light elements by X-ray fluorescence analysisI. Determination of chloride, thiocyanate, cyanide and phosphate using a dependent reference standard

Because of the coprecipitation of the light element and an heavier reference element by a suitable precipitant a quantitative transfer and a reproducible distribution of the precipitate is not needed. The precipitated mixture is measured directly on the filter. From the intensity ratios of the reagent to the reference standard calibration curves are established and results are calculated. The method is demonstrated by the determination of Cl^– (0.7 g–4 mg), SCN^– (6 g–1 mg), CN^– (10–100 g) and P0₄ ^3– (1–10 mg).

     

Synthesis of pyridine bases from piperidine derivatives

The corresponding substituted pyridines are obtained in 40–90% yields when N-alkyl-substituted piperidines, gD⁴-piperideines, and secondary and tertiary -piperidols are heated at 240–270C with pyridine N-oxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 787–789, June, 1977.     

Photometrische Bestimmung von Arsen in hochreinen Chemikalien

Zusammenfassung Zur Bestimmung sehr kleiner Arsengehalte kann die Umsetzung von Arsenwasserstoff, der sich bei der Reduktion mit Zink bildet, mit einer Silberdiethyldithiocarbamatlösung in Chloroform in Gegenwart von Brucin herangezogen werden.Das auf dieser Basis ausgearbeitete photometrische Verfahren wurde hinsichtlich Empfindlichkeit, Genauigkeit, kleinster bestimmbarer Menge und Störung durch Fremdionen charakterisiert.Die Arsenbestimmung ist im Bereich von 0,5– 5,0 g As mit einer relativen Standardabweichung von 8,9% für 2,0 g As möglich. Der molare Extinktionskoeffizient beträgt ₅₀₅=8.5·10³l·mol^–1·cm^–1, die Nachweisgrenze nach Kaiser 0.30 g As. Se(IV), Te(VI), Sb(V) und Thiosulfat stören, zahlreiche andere Ionen sind ohne Einfluß.Das Verfahren wurde zur Bestimmung von 10^–5 bis 10^–6% Arsen in folgenden hochreinen Chemikalien eingesetzt: Methanol, Ethanol, Isopropanol, Aceton, Mineralsäuren, Essigsäuren, Ammoniak und Wasserstoffperoxid.

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Photometric determination of arsenic in high-purity chemicals

Summary Solutions of silver diethyldithiocarbamidate (Ag-DDTC) in chloroform containing organic bases (brucine) can be used in the photometric determination of very small contents of As after its reduction to AsH₃ with metallic zinc.The procedure presented has been characterized with regard to sensivity, precision, detection limit and interferences by other elements.Arsenic can be determined within a range from 0.5 to 5.0 g with a relative standard deviations _rel=8.9% for 2.0 g As. The absorptivity is ₅₀₅=8.5·10³l ·mol^–1·cm^–1, the detection limit according to Kaiser was found to be 0.30 g As. Se(IV), Te(VI), Sb(V) and thiosulphate interfere, many other ions are without effect.The procedure was used to analyse high-purity chemicals (10^–5–10^–6% As) such as organic solvents, mineral acids, acetic acid, ammonia and hydrogen peroxide.