Some useful data of continuous variation method

Summary Conditions for the correct application of continuous variation are presented. The data (parameterR _mn , effective stability constant and total concentration) that enable a safe determination of the molar ratio metalligand (m/n) in the complex are computed. The possibility of the determination of true valuesm andn and effective stability constant from one continuous variation curve are discussed and demonstrated on the example of the iron(III)-chrome azurol S complex.

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Einige nützliche Daten zur Methode der kontinuierlichen Variation

Zusammenfassung Bedingungen für die korrekte Anwendung der Methode der kontinuierlichen Variation werden gegeben. Die Daten (ParameterR _mn effektive Stabilitätskonstante und Gesamtkonzentration), die eine zuverlässige Bestimmung des molaren Verhältnisses MetallLigand (m/n) im Komplex ermöglichen, werden berechnet. Die Möglichkeit zur Bestimmung der wahren Werte fürm undn sowie der effektiven Stabilitätskonstanten aus einer Kurve der kontinuierlichen Variation werden erörtert und am Beispiel des Eisen(III)-Chromazurol S-Komplexes demonstriert.

     

Photometric determination of calcium with antipyrylazo III

Antipyrylazo III or diantipyrylazo (3,6-bis(4-antipyrylazo)-4,5-dihydroxy-2, 7-napthalenedisulfonic acid) forms at PH 12.7 a complex Ca₂HL with calcium. The logarithmic overall stability constant, 10g β₂₁₁, is 23.99 ±0.03 (0.1 MNaClO₄,25°C).The effective molar absorptivity is 21,500 ±100 l mole^-1 cm^-1 at 605 nm. The complex can be used for a selective photometric determination of calcium(0.25–3.50μmole) if tri-and tetravalent ions are removed by extraction with cupferron (into chloroform) and transition divalent ions are masked with sodium cyanide. Only strontium (0.5 μmole) and EDTA (0.1 μmole) interfere seriously.     

Arsenic colorimetry with silver diethyldithiocarbamate

The effect of 22 interferences had been studied. Sulfur(II) must be oxidized by nitric acid; germanium, nitric acid, and perchloric acid must be removed by repeated evaporation with hydrochloric acid. Antimony, phosphate, selenium, tellurium, iron, tin, copper, nickel, and many other elements are eliminated by extraction of arsenic(III) chloride in concentrated hydrochloric acid with p-xylene or benzene. Metal ions forming complex or insoluble iodide can be blocked with an excess of potassium iodide. The method enables the determination of 2–30 μg of arsenic with a relative error <10%. It was tested with the materials of copper production.     

Spectrophotometric investigation of analytically important metal complexes

Summary A convenient way of estimation of composition, molar absorptivity, effective and overall stability constants of complexes M _m Y _i H _j L _n is described.

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Spektrophotometrische Untersuchung von analytisch bedeutenden Metallkomplexen

Zusammenfassung Methoden zur Berechnung der Zusammensetzung, des molaren Extinktionskoeffizienten sowie der effektiven und Brutto-Stabilitätskonstanten von Komplexen der Art M _m Y _i H _j L _n werden beschrieben.

     

Flame atomic absorption spectrometry of silver and gold in copper intermediates

The effect of hydrochloric acid and salts from the sample on the solubility of methyl isobutyl ketone (MIBK) in aqueous phase and the effect of hydrochloric acid concentration on the MIBK extraction of iron(III) and gold(III) were studied. As a result, an improved method by flame atomic absorption sepctrometry for determination of silver and gold in copper intermediates was developed, employing a more efficient removal of iron and special standards depending upon the concentration of salts introduced by different samples.     

X-ray fluorescence spectrometry of copper intermediates

Iron, magnetite, copper, copper(II) oxide, calcium carbonate, sulphur, silicon dioxide and aluminium oxide as components of copper intermediates (concentrates, slags, mattes, calcines and fluxes) in powdered (300-400 mesh) binary mixtures obey the Lachance-Traill equation, so the coefficients alpha(AX) of interelement effects can easily be determined experimentally. They show a reasonable agreement with the theoretical values calculated from mass absorption coefficients. This fact can be the basis of a convenient routine method for the determination of intermediates. Since the intermediates exhibit differences in the distribution of their atoms (microcosmic inhomogeneity) a correction factor k(dist) has to be used. Its value for the main components (concentrations > 5%) is in the range 0.92-1.24 The highest relative average deviation of the results from those of the classical "wet" methods is 2.7% for the major and 30% for the minor components.     

Limits of the molar-ratio method

The limiting factors (one constant molar-ratio of metal to ligand, constant excess of masking reagent and buffer, and high enough effective stability) of the molar ratio method are discussed. The lowest values of the effective stability constant for the true metal/ligand ratio to be determined for the complex and for a metal determination to be relatively independent of ligand concentration are calculated.     

Antimutagenic constituents from the thorns of Gleditsia sinensis

Antimutagenic activity-guided fractionation of an extract prepared from the thorns of Gleditsia sinensis LAM. led to the isolation of one triterpenoid and four steroids, which were identified as D:C-friedours-7-en-3-one (1), stigmast-4-ene-3,6-dione (2), stigmastane-3,6-dione (3), stigmasterol (4), and beta-sitosterol (5). Triterpenoid 1 was found for the first time in a natural source and the steroids 2-5 were first isolated from this plant. Stigmasterol was the most active antimutagen, showing 51.2% and 64.2% reduction of the induction factor against the mutagens MNNG and NQO, respectively, in the SOS chromotest. Some NMR data of the steroids 2 and 3 obtained have to be revised.