OT and OTA test

OT Test enables Total, free and combined chlorine in water
The reagent is ‘analytical grade Orthotolidine’, dissolved in 10% solution of HCl
When this reagent is added to the water containing chlorine , it turns yellow
The intensity of yellow colour is proportional to the concentration of chlorine
This yellow colour is produced by both free and combined chlorine residuals
However, OT reacts with free chlorine instantaneously but reacts more slowly with combined chlorine
Add 0.1 ml of reagent to I ml of water
Yellow color is produced and matched against charts within 10 sec, this gives the amount of ‘free chlorine
The yellow color appearing after a few minutes, gives the amount of ‘Total chlorine
The orthotolidine test, however, is not accurate, because the impurities such as iron, manganese, nitrate etc., are likely to cause a false yellow color, and indicating wrong and increased chlorine residual
Orthotolidine Arsenite Test (OTA test)
This is an improvement of the OT test
The levels of the free and combined chlorine residual are determined as in the OT test
Next, the water sample is dechlorinated and the test repeated
The yellow colour produced NOW is caused by the presence of other interfering substances such as nitrites, iron and manganese
This level is subtracted from the free and combined residual chlorine levels to obtain the true residual levels
Hence the error is overcome

OT and OTA test: Orthotolidine (OT) test and Orthotolidine – Arsenite (OTA) test

Membrane processes in water purification: Membrane Processes in Treatment of Drinking Water

Super Chlorination and Break Point Chlorination: Super Chlorination and Break Point Chlorination (Disinfecting Polluted Water)

Slow sand filter: Slow Sand Filter (Biological Filter)

Rapid sand filter: RAPID Sand Filter (Mechanical Filter)

Purification of water at a large scale: Water Purification at a LARGE SCALE (for water supply)

Criteria for a Chemical to be Suitable as Water Disinfectant in Water Supplies: Criteria for a Chemical to be Suitable as Water Disinfectant in Water Supplies

Water Supplies Disinfection with Chlorination: Water Supplies Disinfection with Chlorination

Principles of Chlorination: 5 Principles of Chlorination

Methods of Chlorination in Water Supplies: Methods of Chlorination in Water Supplies

Horrock's Apparatus: Horrock’s Apparatus

Disinfection of well during emergency: Disinfection of Wells during an Emergency – The Double Pot Method

Double Pot method: Disinfection of Wells during an Emergency – The Double Pot Method

Disinfection of Wells: Disinfection of Wells

OT and OTA test: OT and OTA test

Domestic or Household Purification of Water: Domestic or Household Purification of Water