Ortho-toluidine test measures the levels of:

Ans. b. Both free and combined chlorineTest for chlorination of waterOrtho-toluidine test (OT)Ortho-toluidine Arsenite test (OTA)* Free (residual) chlorine* Free chlorine* Free and Combined chlorine* Combined chlorineOTA test is better than OT test as:Detects both free and combine water chlorine separately.Not affected by interfering substances (Nitrites, Iron, and Manganese).