2.2. Reagents and analytical procedures
Before each run a known weight of potassium dichromate was
dried in an oven for 30 min to remove any humidity inside it.
Then stock solution of potassium dichromate was prepared by
dissolving 2.82 g of the dried potassium dichromate analytical
reagent in distilled water and diluted to 1L. The experimental
desired concentrations were obtained by successive dilutions
with distilled water. Sodium chloride salt (Merck, 99.9% purity)
was used to adjust the initial solution conductivity. The pH
of the solution was adjusted by adding hydrochloric acid solution
or sodium hydroxide solution for each experiment. The
pH-meter (Hana, Model pH211) was used to measure the
pH of the solutions. The analytical determination of hexavalent
chromium solutions was carried out by the colorimetric
method using 1,5-diphenylcarbazide solution to give the red
violet color complex [32], which was measured at wavelength
of 540 nm using U.V. spectrophotometer (UNICO, Model
1200). At the end of each experiment, the treated solutions
were filtered by using double ring No. 102 filter paper, before
analysis.
2.2. Reagents and analytical proceduresBefore each run a known weight of potassium dichromate wasdried in an oven for 30 min to remove any humidity inside it.Then stock solution of potassium dichromate was prepared bydissolving 2.82 g of the dried potassium dichromate analyticalreagent in distilled water and diluted to 1L. The experimentaldesired concentrations were obtained by successive dilutionswith distilled water. Sodium chloride salt (Merck, 99.9% purity)was used to adjust the initial solution conductivity. The pHof the solution was adjusted by adding hydrochloric acid solutionor sodium hydroxide solution for each experiment. ThepH-meter (Hana, Model pH211) was used to measure thepH of the solutions. The analytical determination of hexavalentchromium solutions was carried out by the colorimetricmethod using 1,5-diphenylcarbazide solution to give the redviolet color complex [32], which was measured at wavelengthof 540 nm using U.V. spectrophotometer (UNICO, Model1200). At the end of each experiment, the treated solutionswere filtered by using double ring No. 102 filter paper, beforeanalysis.
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