<prompt> The amount of good quality bleaching powder required for chlorinating a round well measuring 4 mtrs diameter and depth of water column 6 mts, to get PPM of residual chlorine when the Horrok;s test gives definite blue colour in the 3rd cup onwards, is -993.8 grams99.38 grams9.938 grams0.9938 grams  <response>: Simple solution: The 3rd cup becomes blue in Horrocks apparatus 3x2 6 gm of bleaching powder required to disinfect 455 L of water. That means 6455 gmL of Bleaching powder is required The volume of well V p r2 h, here r d2 2m h 6m V 3.14 x 4 x 6 75.36 m3 75.36 x 1000 L 75360 L Total Bleaching powder required for well 75360 x 6455 993.75 