Horrocks Apparatus
Introduction : Ancient method to test the amount of bleaching powder required to chlorinate a given quantity of water.
Apparatus :contains the following items 1.one Black cup and 6 white cups(200ml) 2.2 metal spoons(each holds 2gms) 3.7 stirrers 4.bleaching powder 5.Starch iodine indicator solution 6.distilled water 7.two droppers
Method: 1.Take one spoonful of bleaching powder (2g) in the black cup and make a thin paste using distilled water. Add more distilled water to make the volume up to the brim of black cup-stock solution. 2.Fill the water to be tested in the 6 white cups upto 1cm below the brim 3.With a pipette add 1 drop of stock solution to the first white cup, 2drops to the second,3 drops to third and so on. 4.Stir the water in each cup using a separate rod 5.Wait for half an hour for the action of chlorine 6.Add 3 drops of starch iodine indicator to each white cup and stir Development of blue colour indicates the presence of free residual chlorine. 7.Note the first cup which shows distinct blue colour. Suppose 4th cup, then 4 spoons or 8gms of bleaching powder required to disinfect 455 litres of water.