<prompt> If the second cup of Horrocks apparatus show blue color after 3 drops of starch-iodine indicator, what dose of bleaching power is required to disinfect 910 L?8gm30gm4gm15gm  <response>: Dose n x 2 gm for 455 litres n no, of first cup which show distinct blue colour n2 2nd cup - color change n x 2 for 455 litres 4 gm for 455 litres 455 litres - 4 gm 