Oho-toluidine test measures the levels of:-
1. OHOTOLUIDINE (OT) TEST Gives value of free and total (combined + free) chlorine levels. Combined chlorine can be easily calculated by subtracting free chlorine from total chlorine. Reagent: Ohotoluidine dissolved in 10% solution of hydrochloric acid. Yellow color produced on reacting with chlorine. Reading within 10 seconds of addition of chlorine --> Free chlorine. Reading after a lapse of 15-20 mins --> Total chlorine. 2. OHOTOLUIDINE-ARSENITE (OTA) TEST Modification of OT test. Gives value of free and combined chlorine separately. Not affected by presence of nitrates/iron/manganese (Thus, superior to OT test).
Combined chlorine
Both free and combined chlorine
Nitrates in water
Hardness of water
Water