757a. An analysis of an aqueous solution of a mixture of cobalt (II) and nickel (II) without preliminary separation of the components of the mixture was carried out by an extraction-photometric method based on the difference in the absorption spectra of diethyldithiocarbamate complexes CoL2 and NiL2 (L is a ligand) in chloroform.
First, under the experimental conditions, we found the specific extinction coefficients E of these complexes in chloroform at two wavelengths λ (in terms of cobalt cations Co2 and Ni2 ).
λ, nm Specific extinction coefficients E of complexes in chloroform
λ1=328 E1(CoL2)=3700 E1(NiL2)=6000
λ2=367 E2(CoL2)=2430 E2(NiL2)=670

Then, the analyzed V(x)H2O aqueous solution of the mixture was placed in a separating funnel, and after appropriate treatment with a solution of sodium diethyldithiocarbamate, the formed complexes V(x)CHCl3 were extracted with ml of chloroform. The resulting chloroform extract of the mixture was transferred into a quartz cuvette with an absorbing layer thickness of 1.00 cm, and the optical density A1 and A2 of the extract was measured on a spectrophotometer at 328 and 367 nm. Pure chloroform was used as a reference solution.
Using the optical density additivity law, use the data below to calculate the concentration (mcg/ml) of C(Co), C(Ni) of cobalt (II) and nickel (II) in the analyzed solution.
V(x)H2O V(x)CHCl3 optical density A of the mixture extract
A1 at 328 nm A2 at 367 nm
50 10 0.461 0.213

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