Chelate formation of ammonium aurintricarboxylate with bivalent copper : Micro-determination of copper by the colorimetric method

The formation of a coloured copper II chelate by ammonium aurintricarboxylate with λmax at 540 mμ may be utilised in the colorimetric determination of cupric ions on a micro-scale. It has been found that, for satisfactory results, at least a twentyfold molar excess of the reagent should be added. The colour intensity can be measured by using a spectrophotometer or a photoelectric colorimeter with a suitable filter.The colour is stable at room temperature for sufficiently long periods, but the intensity decreases above 30°C. For the formation of a colour suitable for measurement, the pH should be within 5.3–6.7. The smallest amount of copper that can be detected by the reagent is 1.7 p.p m. Details have been worked out for the use of this reagent, and the interference by various foreign ions has been noted and tolerance limits determined spectrophotometrically.     

Sodium alizarin-3-sulphonate as a chromophoric reagent

Summary A method has been recommended for the determination of thorium and molybdenum when present in micro-quantities, based on the formation of a red coloured water soluble chelate ( _max=520 nm for thorium and _max=470 nm for molybdenum) of the composition MRe=12, with sodium-alizarin-3-sulphonate. A large number of ions, however, interfere and should be removed before measurements are made. The solution of thorium chloride or ammonium molybdate may then be treated with a freshly prepared solution of Alizarin Red S. The p_H should be kept within the range 3.2 to 8.0 for thorium, 3.5 to 5.6 (preferably at 5.0) for molybdenum and the colour intensity may be measured with a photoelectric colorimeter or with a spectrophotometer. Temperature has no influence on the colour intensity. Determinations are possible between 0.23 and 16.70 ppm of thorium and 0.19 to 6.9 ppm of molybdenum.

---

Zusammenfassung Zur Bestimmung von Mikromengen Thorium und Molybdän wird ein Verfahren vorgeschlagen, das auf der Bildung einer rotgefärbten, wasserlöslichen Komplexverbindung mit Natriumalizarin-3-sulfonat beruht. Die Zusammensetzung des Komplexes beträgt in beiden Fällen MeReagens=12. Die Absorptionsmaxima liegen bei 520 nm (Th) bzw. bei 470 nm (Mo). Viele Fremdionen verursachen Störungen und müssen vor der Messung entfernt werden. Die Lösung von Thoriumchlorid bzw. Ammoniummolybdat werden mit frisch bereiteter Alizarinrot S-Lösung behandelt; der p_H-Wert soll im Bereich 3,2–8,0 für Thorium bzw. 3,5–5,6 (am besten 5,0) für Molybdän liegen. Die Farbintensität wird mit einem photoelektrischen Colorimeter oder einem Spektrophotometer gemessen; sie wird von der Temperatur nicht beeinflußt. Die Bestimmung läßt sich im Bereich 0,23–16,70 ppm Thorium bzw. 0,19–6,9 ppm Molybdän durchführen.

---

---

Part. II: Sinha, S. N., and A. K. Dey: Z. analyt. Chem. 183, 182 (1963).     

Kinetics and mechanism of the oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine

Oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine proceeds by a mechanism involving transfer of a hydride ion from the aldehyde to the oxidantvia an intermediate complex.     

Studies on mixed ligand complexes,part 4. Cobalt(III) heterochelates containing trimethylenediamine and some bidentate NN,NO and OO donor ligands

Summary A series of new diamagnetic cobalt(Ill) mixed ligand complexes having general formula [Co(AA)(tn)₂]ⁿ⁺ (where AA = biguanide, picolinic acid, acetoacetanilide, benzoylacetanilide,m-nitrobenzoylacetanilide, acetylacetone,N-benzoylphenylhydroxylamine and malonic acid, tn = trimethylenediamine and n = 1–3) have been synthesized and characterized by elemental analysis, conductance measurements, electronic spectra, i.r. spectra, equivalent weight and magnetic measurements. The electronic spectra are typical of octahedral cobalt(III) complexes. The effect of cationic charge and the nature of the ligands on the R_f values of the complexes have been determined by paper chromatography.Author to whom all correspondence should be directed.     

Near-infrared fluorescent probes: synthesis and spectroscopic investigations of a few amphiphilic squaraine dyes

With the objective of developing near-infrared fluorescence probes for biological applications, a few squaraine dyes 3a-d, containing amphiphilic substituents, were synthesized and their photophysical properties have been investigated in the presence and absence of the organized media. These dyes exhibited absorption in the range 630-650 nm, with significant absorption coefficients (epsilon = 1-3 x 10(5) M(-1) cm(-1)) in the aqueous medium. The fluorescence spectra of these dyes showed emission maximum from 660 to 675 nm, depending on the nature of substituents. The fluorescence quantum yields were in the range from 0.15 to 0.21 in ethanol, but 10 times lower values were observed (phi(f) = 0.01-0.02) in the aqueous medium. In the presence of micelles such as cetyltrimethylammonium bromide, sodium dodecyl sulfate, and Triton X-100, these dyes showed negligible changes in their absorption properties, whereas a significant enhancement (5-10-folds) in their fluorescence yields was observed. Picosecond time-resolved studies indicated that these dyes show single-exponential decay in ethanol and ethanol-water mixtures; however, they exhibit biexponential decay with longer lifetimes in the presence of the micellar media. The results indicate that these novel amphiphilic squaraine dyes 3a-d, which exhibit favorable photophysical properties, good solubility in the aqueous medium, and interact efficiently with micelles, can have potential biological applications as near-infrared fluorescence sensors.     

Starch-mediated shape-selective synthesis of Au nanoparticles with tunable longitudinal plasmon resonance

We report the synthesis ofAu nanoparticles, with tunable longitudinal plasmon band and shape selectivity, mediated by starch in the presence of ultrasonic waves. The synthesis was carried out by reduction of HAuCl4, at various concentrations, using H2O2 as the reducing agent. When the reactions were carried out in the absence of ultrasonic waves, there was no occurrence of the longitudinal resonance band, while the transverse plasmon resonance band shifted toward a higher wavelength. Transmission electron microscopic measurements revealed an increase in particle sizes with increasing higher initial HAuCl4 concentration. On the other hand, in the presence of ultrasonic waves, as the initial concentration of HAuCl4 was increased, while the transverse plasmon resonance band remained the same, the longitudinal plasmon resonance band increasingly shifted toward a higher wavelength. Transmission electron microscopic measurements revealed the change in shape from spherical to triangular to hexagonal particles with increasing initial HAuC14 concentration. We also report that the starch-stabilized nanoparticles could be precipitated from the solution by a starch digesting enzyme which also binds with the particles resulting in its precipitation.     

FBG Sensor technology to interfacial strain measurement in cfrp-strengthened concrete beam

Experimental Techniques - Fiber-reinforced polymer (FRP) composite materials are very attractive for use in strengthening of civil engineering structures because of their high strength to weight...