# What is the equation for potassium dichromate react with potassium iodide?

Cr2O72- + 6 I- + 14 H+ → 2 Cr3+ + 3 I2 + 7 H2O

### What is principle of potassium dichromate in COD estimation?

The titer volume of the sample gives the volume of Ferrous Ammonium Sulphate required to react with the excess potassium dichromate in the solution. Similarly, the titer volume for the blank (distilled water) gives the volume of Ferrous Ammonium Sulphate required to react with the excess potassium dichromate in the blank. The equation for the titration can be expressed as: Cr2O72 -- + FeSO4 (NH4)2SO4 = Cr+ + NH4+ + Fe 3+ From above equation…