A spectrophotometric method for the determination of trace amounts of indole in aqueous solution is described. The method is based on the coupling reaction of the determinand with diazotised sulphanilic acid to form, in an acidic medium, an intense yellow, water-soluble, stable azo dye, which shows maximum absorption at 445 nm. The graph of absorbance versus concentration in linear, indicating that Beer's law is obeyed over the range 30-90 pg of indole in a final volume of 25 ml, i.e., 1.2-3.6 p.p.m., with a molar absorptivity of 33.4 x lo3 I mol-1 cm-1, a sensitivity index of 0.0035 pg cm-2, a relative error of 0 to -1.6% and a relative standard deviation of 0.2-1.9%, depending on the determinand concentration. The optimum reaction conditions and interferences from foreign organic compounds have been investigated.
The kinetics of oxidation of diethyl ether (DE) with sodium N-chloro-p-toluenesulphonamide (CAT) in hydrochloric acid solution has been studied at (313°K).The reaction rate show a first order dependence on [CAT] and fractional order dependence on each [DE] and [H+] .The variation of ionic strength of the medium has no significant effect on the reaction rate , addition of p-toluenesulphonamide (p-TSA) affects the reaction rate marginally the rate increased with decreasing dielectric constant of the medium , the stochiometry of the reaction was found to be 1:2 and oxidation products were identified , A Michaelis – Menten type mechanism has been suggested to explain the results.The equilibrium and the decomposition constants of CAT – diethyl ether complex have been evaluated. Thermodynamic parameters were computed by studying reaction at temperatures range ( 308 – 323°K) for the rate limiting step and for the observed first order constants by the linear Arrhenius plot. The mechanism proposed and the derived rate law are consistent with observed kinetics.
A sensitive spectrophotometric method for the determination of trace amounts of pyrrole in aqueous solution is described, The method is based on the reaction of pyrrole with diazotised 4-nitroaniline to produce, in the presence of sodium acetate, an intense yellow, water-soluble, stable monoazo dye, which shows maximum absorption at 420 nm. A graph of absorbance versus concentration indicates that Beer's law is obeyed over the concentration range 5-100 pg of pyrrole in a final volume of 25 ml, i.e., 0.2-4 p.p.m., with a molar absorptivity of 2.32 x 104 I mol-1 cm-1, a Sandell sensitivity of 0.0029 pg cm-2, a relative error of +0.9 to -1.7% and a relative standard deviation of 0.6-2.0%, depending on the concentration. A study has been made to determine the optimum conditions of the colour reaction. Interferences from foreign organic compounds have been examined and the structure of the monoazo dye is suggested.
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