HORROCK’S APPARATUS.pptx

1. Dr. Vishal Pahune

2.  Horrock’s water testing apparatus is designed to find
out the dose of bleaching powder required for
disinfection of water

3.  6 White cups 200 ml capacity each
 One black cup with circular mark in the inside
 2 metal spoons each holds 2g of bleaching powder
when its fill level with the brim
 7 stirring rods
 One special pipette
 Two droppers
 Starch-iodine indicator solution
 Instruction folder

5.  1) Take one level spoonful (2g) of bleaching powder in
the black cup
make it into thin paste with little water
add more water to paste and make up the volume up to
circular mark with vigorous stirring.
Allow it to settle. This is stock solution
 2) fill the 6 white cups with water to be tested, upto
about a cm below the brim
 3)with special pipette provided add one drop of stock
solution in 1st cup, 2 drops in 2nd cup, 3 drops in 3rd
cup,….so on upto 6 drops in the 6th cup

6.  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 iodide solution in each of the
white cups and stir it again. Development of the blue
color indicate the presence of the free residual of
chlorine
 7) note the first cup which shows distinct blue color,
supposing the 3rd cup shows blue color, then 3 level
spoonful or 6 gms of bleaching powder would be
required to disinfect 455 liters of water