Ohotoluidine Arsenite test determines -: (A) Free residual chlorine, (B) Combined chlorine, (C) Free and combined chlorine separately, (D) Free and combined chlorine together
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)