Indicator solution in Horrock’s Apparatus contains: (A) Ortho-toulidine, (B) Bromocresol purple, (C) Ortho-toulidine arsenite, (D) Starch iodide
Answer is D. Indicator in Horrock’s apparatus: Starch iodide.
Indicator in Presumptive coliform test (MPN Multiple Tube Method): Bromocresol purple.