Complex ions, spectrophotometric

D 3116 25 0.25-25 mg Pb/L PbR4 is converted to ionic organolead by IC1 and then to inorganic lead ions spectrophotometric determination of dithizone (2) complex. 

At Los Alamos National Laboratory, the silicon content of plutonium samples is determined spectrophotometrically using a silica-molybdenum blue complex ion, which has a blue color. The sample is dissolved in a mixture of hydrochloric acid and hydrofluoric acid. After the excess hydrofluoric acid is removed, the absorbance is measured at 825 nm. All operations are carried out in a silica-free apparatus. 

X 10-3 sec.-1, was found for the dissociation of water. However, when ClOr was replaced by NO3 " as the inert anion the rates were up to 30% slower and the curvature of the k0b vs. (Cl ) plot was considerably lessened. A dependence on the nature of the inert anion would not be expected for this mechanism. The curvature cannot be explained by preassociation of chloride and complex ions. This would have to be much larger than is expected for 2 1 electrolytes of this type and no spectrophotometric evidence for it was obtained. 

The hydrolysis of certain Schiff bases is catalyzed by divalent metal ions such as cupric or nickelous ion. Spectrophotometric evidence indicates the formation of a metal ion complex of the substrate with subsequent facile cleavage of the complex. 

In the case of the octahedral robust complexes of cobalt (III) and chro-mium(III), substitution in the first sphere is hindered. This type of complex ion is, therefore, especially suitable for studying association in the second sphere. The hexammine and tris(ethylenediamine) cobalt(III) ions have especially been used for this kind of study. For the association of these ions with anions, such as sulfate and thiosulfate, the ion-pair constant is of the order of magnitude of 10 at 7 = 0, somewhat smaller for Coena" than for Co(NH3)6 21)y but strongly dependent on the ionic strength. Thus Posey and Taube 37) y from spectrophotometric measurements in the ultraviolet, obtain the following expression for the association constant of the ion pair [Co(NH3)6]S04 in solutions with y/Jvarying from 0.04 to 0.3 ... 

Thallium(III), in the form of the TICU or TlBr4" complex ions, reacts in acid media (1-2 M HCl) with the basic xanthene dye, Rhodamine B (formula 4.29), to form a red-violet, slightly fluorescent ion-associate complex, which is soluble in benzene, DIPE, and isoamyl alcohol. These extracts have been used for the spectrophotometric determination of thallium [8]. A mixture of CeHe and CCI4 (2+1) is a convenient extractant since it is denser than water. 

A spectrophotometric study of mixed tetracyano complexes of Mo and under various pH conditions has been carried out and the protonation constants and molar extinction coefficients for Mo(OH)2(CH)4" evaluated. Polarized absorption spectra of Mo(CN)8" and W(CN)g" over the temperature range 4.2—300K have been recorded. In the crystalline state these complex ions have a quasidodecahedral co-ordination structure with the exact symmetry D2. The deviation from the ideal dodecahedral structures is appreciably smaller at low temperatures than at room temperature. Also, in contrast to previous X-ray structure determinations, it was found that the only space group the crystals can be assigned to is... 

Vosburgh WC, Cooper GR. Complex ions. I. The identification of complex ions in solution by spectrophotometric measurements. J Am Chem Soc 1941 63 437-42. 

The carrier stream contains Hg(SCN)2 and Fe(III). The chloride of the injected sample reacts with Hg(SCN)2, liberating SCN, which in turn forms with Fe(III) the red-colored complex ion Fe(SCN)2, which is measured spectrophotometrically at 480 nm. The height of the recorded absorbance peak is then proportional to the concentration of chloride in the sample. Besides Fe(SCN)2 , other (higher) complex ions between Fe(III) and SCN might be formed, causing nonlinearity in the cahbration curve at high concentrations. 

Experiments are under way for the production of ion-selective membrane electrodes that can also be used in non-aqueous solutions, and studies are being made of the possibilities of application of liquid junction-free potentiometry in non-aqueous solutions. High-performance computer evaluation procedures permit the employment of spectrophotometric equilibrium measurements in the study of complex systems. Spectrophotometric measurements are not prone to greater errors in non-aqueous solutions than in water. 

F Spectrophotometric Kinetic Methods 381 14G Spectrophotometric Studies of Complex Ions 384 Questions and Problems 390... 

The concentration of anionic surfactants at the sub-ppm level in natural waters and industrial waters are determined spectrophotometrically. The anionic surfactants are extracted into a nonaqueous solvent following the formation of an ion association complex with a suitable cation. 

EDTA forms colored complexes with a variety of metal ions that may serve as the basis for a quantitative spectrophotometric method of analysis. The molar absorptivities of the EDTA complexes of Cu +, Co +, and Ni + at three wavelengths are summarized in the following table (all values of e are in cm )... 

Quantitative. Classically, silver concentration ia solution has been determined by titration with a standard solution of thiocyanate. Ferric ion is the iadicator. The deep red ferric thiocyanate color appears only when the silver is completely titrated. GravimetricaHy, silver is determined by precipitation with chloride, sulfide, or 1,2,3-benzotriazole. Silver can be precipitated as the metal by electro deposition or chemical reduciag agents. A colored silver diethjldithiocarbamate complex, extractable by organic solvents, is used for the spectrophotometric determination of silver complexes. 

Bromide ndIodide. The spectrophotometric determination of trace bromide concentration is based on the bromide catalysis of iodine oxidation to iodate by permanganate in acidic solution. Iodide can also be measured spectrophotometricaHy by selective oxidation to iodine by potassium peroxymonosulfate (KHSO ). The iodine reacts with colorless leucocrystal violet to produce the highly colored leucocrystal violet dye. Greater than 200 mg/L of chloride interferes with the color development. Trace concentrations of iodide are determined by its abiUty to cataly2e ceric ion reduction by arsenous acid. The reduction reaction is stopped at a specific time by the addition of ferrous ammonium sulfate. The ferrous ion is oxidi2ed to ferric ion, which then reacts with thiocyanate to produce a deep red complex. 

Concentration limits of the diphosphate-ion, admissible to determination of magnesium and cobalt, manganese and cobalt, zinc and cobalt by spectrophotometric method with application of the l-(2-pyridylazo)-resorcinol (PAR) are presented. Exceeding maintenance of the diphosphate-ion higher admissible supposes a preliminary its separation on the anionite in the H+-form. The optimum conditions of cobalt determination and amount of the PAR, necessary for its full fastening are established on foundation of dependence of optical density of the cobalt complex with PAR from concentration Co + and pH (buffer solutions citrate-ammoniac and acetate-ammoniac). 

SPECTROPHOTOMETRIC DETERMINATION OF HYDROXYUREA AS A COMPLEX WITH FERRIC CHLORIDE AFTER STABILIZATION BY FERROUS IONS... 

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