Q. Horrock’s apparatus estimates:
a. Free cholorine
b. Combined Chlorine
c. a+b
d. Chlorine demand.
Correct answer : d
Horrocks Apparatus :Â
• It is used to find out the dose of bleaching powder required for disinfection of water.Â
• It consists of :Â
• One black cup (200 ml ) with a marking inside.Â
• Six white cups (200 ml ).Â
• Seven glass stirring rods.Â
• One pipette.Â
• Two droppers.Â
• Starch-iodide indicator solution.Â
• Bleaching powder.
 • Two metal spoons which can hold 2 gms of bleaching powder in each.Â
• Plastic or wooden box container for all these items.