To find out whether teh w ater has been properly chlorinated, the test used is -
Horrock's test
Oho-toluidine test
Presumptive coliform test
Total bacterial count
After chlorination,tge residual chlorine is tested at the end of one hour contact period.If free residaul chlorine level is less than 0.5 mg/litre, the chlorination procedure should be repeated before water is drawn.Reagent used in OT test is analytical grade ohotoluidone dissolved in 10% hydrochloric acid.On addition of reagent to water containing chlorine it turns yellow. Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 718
Environment and health