Social & Preventive Medicine General 74585ba6 Indicator solution in Horrock’s Apparatus contains A Ortho-toulidine B Bromocresol purple C Ortho-toulidine arsenite D Starch iodide High-Yield Explanation Indicator in Horrock’s apparatus: Starch iodide. Indicator in Presumptive coliform test (MPN Multiple Tube Method): Bromocresol purple.