<prompt> Ohotolidine test is used to determine-Nitrates in waterNitrites chlorine in waterFree and combined chlorine in waterAmmonia content in water  <response>: 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 