Ohotolidine test is used to determine-: (A) Nitrates in water, (B) Nitrites chlorine in water, (C) Free and combined chlorine in water, (D) Ammonia content in water
Answer is C. Oho-toluidine test is used to determine both free and residual chlorine with speed and accuracy. It is done using oho-toluidine dissolved in 10 per cent solution of hydrochloric acid. When added to water containing chlorine it turns yellow and its intensity varies with the concentration of the gas. Oho-toluidine Arsenite test is used to determine free and residual chlorine separately. (PARK TB (25th edition pg 775)