Water Water PracticalsPracticals

HORROCKS APPARATUSHORROCKS APPARATUS

Designed to find out the dose of Designed to find out the dose of bleaching powder required for bleaching powder required for disinfection of water.disinfection of water.

CONTENTSCONTENTS

6 white cups( 200ml capacity)6 white cups( 200ml capacity) 1 black cup with circular mark inside1 black cup with circular mark inside 2 metal spoons(2g capacity)2 metal spoons(2g capacity) 7 glass stirring rods7 glass stirring rods 1 special pipette1 special pipette 2 droppers2 droppers Starch– iodide indicator solutionStarch– iodide indicator solution Instruction folderInstruction folder

PROCEDUREPROCEDURE

Take 2g of bleaching powder in Take 2g of bleaching powder in the black cup, make it into a thin the black cup, make it into a thin paste with little water.paste with little water.

Add more water to paste & Add more water to paste & make up volume up to circular make up volume up to circular mark with stirring.mark with stirring.

Fill 6 white cups with water to Fill 6 white cups with water to be tested up to 1 cm below the be tested up to 1 cm below the brim.brim.

With the special pippette provided With the special pippette provided

add one drop of stock soln to 1add one drop of stock soln to 1stst cup, 2 drops to the 2cup, 2 drops to the 2ndnd cup and so cup and so on..on..

Stir the water in each cup with Stir the water in each cup with separate rod.separate rod.

wait for half hour for the action of wait for half hour for the action of chlorine.chlorine.

Add 3 drops of starch– iodide Add 3 drops of starch– iodide indicator to each. indicator to each.

Development of blue color Development of blue color indicates presence of free residual indicates presence of free residual chlorine.chlorine.

CalculationsCalculations

Suppose 3Suppose 3rdrd cup develops blue color. cup develops blue color. Then 3 x 2 g of bleaching powder is Then 3 x 2 g of bleaching powder is

needed to disinfect 455 l of water.needed to disinfect 455 l of water. Therefore the quantity needed (x) to Therefore the quantity needed (x) to

disinfect (y) l of water will be =disinfect (y) l of water will be = 6 y / 455 6 y / 455

Orthotoludine testOrthotoludine test

0.1ml OT reagent to 1 ml of water.0.1ml OT reagent to 1 ml of water. Yellow colour develops proportionate Yellow colour develops proportionate

to cl concentration.to cl concentration. Measured by chloroscope.Measured by chloroscope.

SAMPLINGSAMPLING FOR PHYSICAL & CHEMICAL FOR PHYSICAL & CHEMICAL

ASSESMENTASSESMENT sample collected in clean glass sample collected in clean glass

stoppered bottles made of neutral stoppered bottles made of neutral glass of capacity not less than 2ltrs.glass of capacity not less than 2ltrs.

FOR BACTERIOLOGICAL EXAMINATIONFOR BACTERIOLOGICAL EXAMINATION sample collected in clean sterilized sample collected in clean sterilized

bottles made of neutral glass, capacity bottles made of neutral glass, capacity of 250ml, with a ground glass stopper of 250ml, with a ground glass stopper having a overlapping rim. having a overlapping rim.

SAMPLE FROM TAP WATERSAMPLE FROM TAP WATER

Tap opened fully, let water run to Tap opened fully, let water run to waste for 2 min.waste for 2 min.

Bottle held near the base with one Bottle held near the base with one hand & the stopper & paper cover hand & the stopper & paper cover over it removed together & held in over it removed together & held in fingers.fingers.

Bottle should be filled from a gentle Bottle should be filled from a gentle stream of water from tap, avoiding stream of water from tap, avoiding splashing. splashing.

Sampling from rivers, wells Sampling from rivers, wells etcetc

Tie additional string to the bottle Tie additional string to the bottle string.string.

Dip bottle with string not with hands.Dip bottle with string not with hands. Face mouth of bottle towards streamFace mouth of bottle towards stream Generate current in still water.Generate current in still water. Location for the sampling Location for the sampling

Transport & storage of Transport & storage of SamplesSamples

the bacteriological examination the bacteriological examination of the sample should be of the sample should be commenced asap after commenced asap after collection.collection.

Water should be kept in ice until Water should be kept in ice until it is taken for analysis within it is taken for analysis within 48hrs of collection.48hrs of collection.

Samples not preserved in this Samples not preserved in this manner should be rejected.manner should be rejected.

THANKYOUTHANKYOU