Which of the following is/are estimated by titrating polluted water with potassium dichromate solution in…
Which of the following is/are estimated by titrating polluted water with potassium dichromate solution in acidic medium? \begin{array}{|c|c|c|}\hline COD & BOD & DO \\\hline I & II & III \\\hline\end{array}
I only
II only
II & III only
I,II,III
Solution
The COD (chemical oxygen demand) test is widely used as an alternative to BOD test 10 estimate the strength of domestic and industrial waste as COD test can give result in few hours as compared to BOD (Biological Oxygen Demand) test which takes normally 5 days.
It use potassium dichromate $\left(\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7\right)$ in pressure of concentrated sulphuric acid $\left(\mathrm{H}_2 \mathrm{SO}_4\right)$ solution and that oxidizes both organic and inorganic substance in a waste water sample.