Hexamethylenetetramine as a reagent for microscopic tests for gold and the platinum metals

Summary A study of the compounds formed in acid solutions by the chlorocomplexes of gold and the platinum metals with hexamethylenetetramine (urotropine), or its salts, shows that characteristic crystals are formed which can be observed under the microscope and used for confirmatory tests.Several new tests are described including those with hexamethylenetetramine anhydromethylene citrate (helmitol). The limit of identification, limiting concentration and in the case of interferences, the limiting proportions, are given for each compound.

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Zusammenfassung Eine Untersuchung der Verbindungen, die von den Chlorokomplexen von Gold und den Platinmetallen oder deren Salzen mit Hexamethylentetramin (Urotropin) erhalten werden, zeigte, daß sie Kristalle geben, die unter dem Mikroskop charakteristische Formen erkennen lassen und für den Nachweis der genannten Metalle geeignet sind.Einige neue Nachweise werden beschrieben, darunter jene, bei denen Hexamethylentetramin-anhydromethylenzitrat (Helmitol) als Reagens zur Verwendung gelangt. Die Erfassungsgrenze, die Grenzkonzentration und die Grenzverhältnisse bei allenfalls auftretenden Störungen werden für jeden Nachweis angegeben.

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With 8 figures.     

The electrolytic test for detection of arsenic alone and in the presence of other metals

A historical account is given of the development of the electrolytic generation of arsine in the Marsh test, showing how it was early realized that a step in an analytical procedure could be advantageously replaced by a more efficient one. It also shows that well-designed apparatus never really becomes outmoded.     

Heavy metals and some other elements in medicinal plants. Determined by X-ray fluorescence analysis

Determination of Mn, Fe, Cu, Zn, Hg, Pb, Br, Se, Rb, Sr and Cd in the medicinal plants by radionuclide X-ray fluorescence analysis (using²³⁸Pu,²⁴¹Am/Ag and¹²⁵I) is described.     

Photometric complex-formation titration of submicromole amounts of metal-II The presence of other metals

End-point extrapolation with the aid of a tangent to the spectrophotometric titration curve has been discussed theoretically for the metal-indicator complex MI with a ligand L in the presence of two other metals (P(1) and P(2)). It was found that a titration end-point can only be determined when the reaction of P(1) and P(2) with L takes place only negligibly during the titration of M. Two cases of practical interest can be distinguished. The metals may react either before or after the titration has been completed. For both situations titration conditions have been derived. With these titration conditions suitable experimental conditions can directly be derived from diagrams which were introduced in a previous paper. The theory developed has been applied to mixtures of manganese and magnesium but is generally applicable.     

Determination of semimicro amounts of calcium in the presence of other alkaline-earth metals

Cyclam tetraacetic acid (CTA) is used to determine semimicro quantities of calcium in the presence of other alkaline-earth metals in natural and synthetic water samples. End-point detection is achieved amperometrically with Zn(en)(2+)(3) as the indicator. Magnesium and barium do not interfere. In the presence of strontium, two distinct end-points are obtained when its concentration is comparable with that of the calcium. If the concentrations are substantially different, calcium and strontium appear to be titrated together.     

Direct heterometric microtitration of nickel with dimethylglyoxime in the presence of other metals

A new “heterometric” method was presented for a quick, direct determination of small quantities (< 1 mg) of nickel (~2%) in the presence of other metals (~98%). The error was between zero and 1.4 micrograms of nickel per ml, or between zero and 3% of nickel.     

Direct heterometric microtitration of copper with oxine in the presence of other metals

A new heterometric method is presented for a rapid micro-determination of copper with oxine. 1 mg of copper in 20 ml of solution may be determined with an accuracy of 0-I-0 microgram per ml. The solution may contain 95% Me or Al, 98% Zn, Mn, Co. Ni, Cd or Cr and 99-8% Pb. The determination is made at room temperature and takes 10–20 minutes.     

Microdetermination of ruthenium(III) in presence of other metals

Summary Ruthenium(III) reacts with thiovioluric acid in aqueous medium at p_H 4.45–6.00 to yield pinkish-violet complex with absorption maximum at 540 nm. Full colour development requires heating for about 30 minutes on a boiling water bath. The system obeys Beer's law in the range 0–5.6 ppm of ruthenium. The sensitivity of the reaction is 0.0046g/cm² (for log 10/I=0.001) at 540 nm. The composition of the complex is 12, as shown by Job's and Bent and French methods. The effect of various foreign ions in the determination of ruthenium has also been investigated.

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Zusammenfassung Ruthenium(III) reagiert mit Thioviolursäure in wäßriger Lösung bei p_H 4,45–6,00 unter Bildung einer rosa-violetten Komplexverbindung mit dem Absorptionsmaximum bei 540 nm. Die volle Farbentwicklung tritt beim Erwärmen auf dem siedenden Wasserbad in etwa 30 min. ein. Das Beer'sche Gesetz ist bis 5,6 ppm Ru erfüllt. Die Empfindlichkeit der Reaktion beträgt 0,0046g/cm² bei 540 nm. Die Zusammensetzung des Komplexes entspricht dem Molverhältnis 12. Der Einfluß verschiedener Fremdionen wurde untersucht.

     

Selective edta titration of gallium or aluminium in the presence of other metals

The selective determination of aluminium or gallium by EDTA titration is reported. Gallium or aluminium is titrated together with other multivalent ions with EDTA at pH 3-7 and then the pH is raised above 10.5. Aluminates or galliumates are formed with the consequent release of EDTA from the EDTA complexes. The released EDTA is titrated with lead solution using Xylenol Orange as an indicator and with copper using photometric detection of the end-point, for the determination of gallium and aluminium respectively. The theoretical basis of the procedure is discussed.     

Spectrophotometric determination of osmium with 2R-acid in the presence of other platinum metals

Osmium(VIII) produces two coloured species with lambda(max) 680 nm (green) and 530 nm (red) with excess of 2-amino-8-naphthol-3,6-disulphonic acid in aqueous solution. The green complex is stable between pH 2.5 and 8.0 and the red complex between pH 11.0 and 12.0. The effects of temperature and time, reagent concentration, optimum conditions for the spectrophotometric determination of trace amounts of osmium, and other variables, have been studied at pH 11.5. At this pH, other platinum metals do not interfere. The sensitivity of the colour reaction is 0.2 microg/cm(2) and the system conforms to Beer's law over a concentration range of 1.5-10 microg of osmium.     

Direct heterometric micro-determination of zinc with quinaldic acid in the presence of other metals

0.001–0.005M solutions of zinc salts (1–5 mg Zn in io ml) which contain more than 95% of foreign metal as Mg, Ca, Ba, Mn.(II), Fc(III), Al or Cr(III), may be titrated hctcrometrically with an error of ? 1%. The titrated zinc solution may contain an excess of Cd (85%). The analysis with Ni or Co is very limited.     

Feasibility of using INAA for biomonitoring of heavy metals and other elements in human ectoderm derivatives

For systematic checking of the feasibility of determining elements by INAA in scalp hair, pubic hair and toenails, three different regimes were employed by varying the activation time and cooling time prior to -ray spectrometric measurements. The combination of these three regimes (activation time 1 min, cooling time 10 min; activation time 5 h, cooling time 5 d; activation time 5 h, cooling time 30 d) made it possible to determine the following 20 elements in most samples: Al, As, Br, Ca, Ce, Cl, Co, Cr, Cu, Fe, Hg, I, K, La, Mn, Na, S, Sb, Se, Zn. Further 10 elements (Ba, Cd, Mo, Ni, Rb, Sc, Sm, Th, V, W) were detectable only in some samples, however, with a fairly good precision, so that they could be detected in this way in the case of elevated concentrations exceeding physiological limits.     

Chelometric titration of gallium in the presence of indium and other metals by chloride masking

Summary In solutions containing high concentrations of ammonium chloride, indium is masked as the chloro complex and gallium can be titrated in boiling solution with EDTA to a visual end-point using Xylenol Orange as the indicator. Up to a mole ratio InGa of about 300 good results are obtained. The influence of some other metal ions on the titration has been investigated.

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Zusammenfassung Indium wird in Lösungen, die hohe Konzentrationen an Ammoniumchlorid enthalten, als Chlorokomplex maskiert und Gallium kann in kochender Lösung mit ÄDTA titriert werden. Xylenolorange dient als Indicator. Gute Resultate werden noch bei In: Ga-Verhältnissen von ungefähr 300 erhalten. Der Einfluß einiger anderer Metalle wurde untersucht.

     

The influence of the microscopic structure of surfaces on the optical properties of metals

The review outlines the state-of-the-art in the field of studies on the optical properties of metal surfaces. The use of recent theory has been examined to explain the results obtained in certain individual experiments on the surface modulation spectroscopy, outer photoemission and the surface Raman effect. The dependence of the surface plasmon spectrum on the surface microscopic structure has been given special consideration. It has been shown how information about the electronic structure of a surface, and the effect of adsorption on this structure in particular, can be extracted from the optical measurement data.     

The effect of Pb and other elements found in recycled polypropylene on the manufacturing of lead-acid battery cases

Polypropylene (PP) is one of the most common plastics used in the manufacturing of lead-acid battery cases, where the recycling of the material has become common practice, being both economically viable and environmentally friendly. During the recycling process, the various components of the spent battery are separated, where the crushed battery case is washed in order to remove any excess acid and lead-containing particles. The plastic components are subsequently melted and extruded into pellets that are then blended with virgin material to injection mold new battery cases and lids. This study showed that a significant amount of lead-containing particles in the form of lead dioxide and lead sulfate remain in the recycled plastic, and are evenly distributed throughout the polymer matrix. TEM studies showed that the particles are less than 1 μm in size and X-ray diffraction analysis of ashed recycled PP samples showed the presence, amongst others, of talc, calcium carbonate, rutile and iron oxide. These compounds come from a range of fillers, flame-retardants, colorants and impurities that originated from the various original battery cases that were recycled. The study showed that modern X-ray fluorescence (XRF) analysis is a quick and reliable method to quantify the amount of the elements found in the plastic and that the concentration of Pb in the plastic can be used as a type of “tracer” to determine the amount of recycled PP used in the manufacturing of a particular battery case. The study also showed that there is possible environmental contamination, in particular with Pb and Br contained in recycled PP during the injection molding process and the burning of the plastic. The Pb- and Br-containing particles are small enough to become air-borne during the burning process of the plastic, resulting in them being part of the soot and other hydrocarbon oils that are emitted. No Pb was observed in the gases emitted during simulated low-temperature injection molding conditions; however, a significant amount of Br was detected in the gases at the lower temperatures. Clear environmental waste classification of the battery case plastic should be done before its final incineration where the amount of trace metals present and its possible contamination to the environment should be considered. Care should also be taken for machine operators who work with the recycled plastic, that no excessive exposure to the halogenated compounds is experienced.     

Contributions to the basic problems of complexometry—X: Determination of nickel and cobalt in the presence of iron, copper and some other metals

A complexometric determination of nickel and cobalt in the same solution has been devised. It is based on the determination of the sum of nickel and cobalt by back-titration of added excess EDTA in a strongly alkaline medium with calcium chloride using Fluorexon (Calcein) as indicator. After oxidation of cobalt with hydrogen peroxide to form the cobalt^III- EDTA complex and screening of nickel by potassium cyanide, the liberated EDTA corresponding to the amount of nickel present is titrated with further calcium chloride. High concentrations of iron and aluminium are screened with triethanolamine. Copper and other heavy metals are screened with thioglycollic acid.     

Open wet ashing of some types of biological materials for the determination of mercury and other toxic elements

An open wet decomposition procedure for trace element analysis of biological material has been worked out. It is based on the utilization of nitric acid, hydrochloric acid and hydrogen peroxide and is well suited for the determination of As, Bi, Cd, Cr, Hg, Pb, Sb, Se and Tl. For these elements the recoveries were examined by the radiotracer technique, with lichens, pine needles, grass and human hair as representative biological samples. In addition to the conventional labelling technique, use was also made of in situ labelling. In all cases, recoveries between 93 and 100% were achieved, which are adequate for quantitative trace element analysis.     

Correlation between flame geometry and the absorbance of some elements in the presence of organic solvents

The correlation between the changes in flame geometry and the sensitivity of atomic-absorption determination of silver, copper, iron and lead in the presence of various solvents (water, ethanol, n-propanol, methyl acetate, ethyl acetate and acetone) has been investigated. The flame geometry was studied by the Schlieren technique. Organic solvents, allowing a greater rate of introduction of solution, enable a greater sensitivity to be achieved. However, owing to the expansion of the reaction zone, the increase in sensitivity is not as great as expected from the amount of sample introduced into the flame.     

The polarographic behaviour of some elements in concentrated calcium chloride solution: The determination of chromium in the presence of nickel

Further studies on the polarography of trivalent chromium in concentrated calcium chloride solution are described. Details are given of a chloride-hydroxylamine base electrolyte (7.4M with respect to chloride) in which chromium may be determined directly in the presence of nickel. This method is not applicable if the nickel-chromium ratio is large. Results are presented and certain theoretical aspects are discussed.