Chemical Oxygen Demand (COD)

Apparatus -COD test tube, COD oil Bath, Beaker,Burette, condenser, Pipette

Chemical – Mercury sulfate (0.4g) ,Potassium Bicarbonate (0.2g), Sulfuric Acid (H2SO4), Ferron Indicator, Distill Water.

Sample – Stone Four Sample (Grey, Poly, Drink Water).

COD – chemical oxygen demand.

COD is a measured of the capacity of to consume oxygen during decomposition of organic matter & Oxidation of inorganic chemical such as Ammonia & nitrite.

COD test is used to amount of organic compound in a water sample.

Procedure –

  • Firstly washed COD four test tube
  • Add into the 2 to 3 piece of stone.
  • Add Mercury sulfate (4g) ineach tube.
  • Then add (40ml) distill water in only blank tube and other three tube in (20ml) distill water.
  • Add three tube (Grey,KHP,PABAL WATER) in (20ml)distill water.
  • Then again add the (30ml) sulfuric acid.
  • Then this four tube put in the COD oil Bath for (2hours).
  • After heating take out tube in the oil Bath and put the cool tube for (30min).
  • After cooling add 150ml distill water and add one drop of ferron indicator in each tube.
  • Then do the titration until come to the brown colour of the sample.

formula =

COD = (Blank-sample)*0.255*8000/20

BLANK -7.8

PABAL WATER – (7.8- 6.8)*0.255*8000/20 = 102

GREY -(7.8- 6.8)*0.255*8000/20 = 367.

KHP – (7.8-6.8)*0.255*8000/20 = 499