To determine the concentration of a sample solution containing a mixture of ferrocyanide Fe CN 6^4- and ferricyanide Fe CN 6^3- ions using polarography, follow these steps:1. Prepare the sample solution: Dilute the sample containing the mixture of ferrocyanide and ferricyanide ions to a suitable concentration for polarographic analysis. The optimal concentration range depends on the sensitivity of the polarographic instrument used.2. Prepare the polarographic cell: Fill the cell with a supporting electrolyte solution, which should be an inert and non-reactive solution that provides a stable background current. Common supporting electrolytes for the analysis of ferrocyanide and ferricyanide ions include potassium chloride KCl and sodium nitrate NaNO3 .3. Add the sample solution to the polarographic cell: Add a known volume of the diluted sample solution to the polarographic cell containing the supporting electrolyte. The final volume should be sufficient to cover the working and reference electrodes.4. Perform the polarographic analysis: Apply a potential sweep to the working electrode and measure the resulting current. The potential should be swept from a value more negative than the reduction potential of ferrocyanide to a value more positive than the oxidation potential of ferricyanide. The current will increase as the potential approaches the reduction and oxidation potentials of the ferrocyanide and ferricyanide ions, respectively.5. Analyze the polarogram: The polarogram will show two distinct peaks, one corresponding to the reduction of ferrocyanide ions and the other to the oxidation of ferricyanide ions. The peak current ip is proportional to the concentration of the respective ion in the sample solution. Measure the peak currents for both ferrocyanide and ferricyanide ions.6. Calibration: Prepare a series of standard solutions containing known concentrations of ferrocyanide and ferricyanide ions. Perform polarographic analysis on these standard solutions and plot the peak currents against the known concentrations to obtain calibration curves for both ions.7. Determine the concentrations: Use the calibration curves to determine the concentrations of ferrocyanide and ferricyanide ions in the sample solution based on the measured peak currents. Calculate the concentration of each ion in the original, undiluted sample by taking into account the dilution factor.By following these steps, you can accurately determine the concentration of ferrocyanide and ferricyanide ions in a sample solution using polarography.