railway DFCCIL Executive 2025 Mock Test Environmental Engineering Quality and Characteristics of Sewage
A sample of domestic sewage is digested with silver sulphate, sulphuric acid, potassium dichromate and mercuric sulphate in chemical oxygen demand (COD) test. The digested sample is then titrated with standard ferrous ammonium sulphate (FAS) to determine an unreacted amount of:
1
mercuric sulphate
2
potassium dichromate
3
silver sulphate
4
sulphuric acid