DETERMINATION OF DISSOLVED OXYGEN IN WATER.
1.Narrow mouth ground glass stoppered dust proof test tube of capacity 60 ml.
2.Pipette capacity 10 ml.
Indigo Carmine Solution - Dissolve 0.0108 gm of indigo carmine and 0.12 gm of dextrose in 3.0 ml of demineralized water. When completely dissolved add 45 ml. of glycerol. This reagent is stable for two weeks only.
- Pottasium Hydroxide – 5 gm KOH (Pottasium Hydroxide) is dissolved in 10ml of demineralised water.
- About half an hour before testing for dissolved oxygen add 20ml of the indigo carmine solution as prepared in the 20.2 and 5 ml of KOH to a small beaker. The solution will change colour from deep red to a lemon yellow in about 15 minutes and then it is ready for use.
- Collect the sample through the cooler filled with ice on the spot by overflowing the sample from the test tube for about 5 minutes.
- After sufficient volume of water has passed through the test tube immediately remove the test tube and insert the pipette filled with the indigo carmine reagent prepared
- Add about 4 ml of indigo carmine solution from the pipette.
- Match the colour developed in the test tube with the colour of standards prepared in the following way.
Red Colour Standard No. CS – A : Dissolve 59.29 gm of cobaltous chloride (COCl2 . 6H2O) in 1:99 hydrochloride acid and make the volume 1 litre.
ANALYSIS OF OIL CONTENT IN WATER
Procedure
One separating funnel of 1litre capacity, concentrated sulphur acid, petroleum ether, beaker and a funnel are required.
Take 500 cc. of water sample to be analysed for oil content in a one litre separating funnel.
- Add 5 cc. of conc. sulphuric acid and shake well.
- Add 20 ml petroleum ether in the separating funnel and shake well for 5 minutes. Release the pressure formed inside the funnel cautiously by opening the stop cock after inverting the funnel.
- After shaking well keep the funnel on stand and allow the petroleum ether layer to separate from water layer.
- Take out the water from the separating funnel leaving behind the petroleum ether.
- Then filter the petroleum ether through filter paper in the funnel into a 100 cc beaker of known weight.
- Keep the beaker containing petroleum ether and oil in a drying chamber for two hours at 110oC.
- When beaker is dried take it out, cool in a desecrator to room temperature and weigh the beaker with oil.
- Weight of oil mg x 2 = oil in ppm (parts per million).
ANALYSIS OF -CN & -CNO OF SALT
- Dissolve 100 gms calcium Nitrate in 900 ml. of D.M. water (Deminerlised water).
- Dissolve 26.1 gm of silver Nitrate in 1 liter of demineralised water in a volumetric flask and mix well by shaking.
- Dissolve 2 gm of phenolphtalein in 1 liter of Methyl alcohol.
- Prepare 5% aqueous solution of potassium chromate (K2CrO4).
- Crush sample in a mortor. Take 5 gms of crushed sample in a 250 c.c volumetric flask.
- Add 50 c.c D.M. water to dissolve the sample.
- Add 60 c.c. Calcium Nitrate Solution. Make the volume to 250 c.c with D.M. water and shake well to mix the contents.
- Allow the ppt. to settle.
- Filter the solution through filter paper
- Take 25 c.c of the filtrate. Add 5 drops of phendphtatein and Titrate against standard AgNO3 solution till the solution becomes colourless. Note the reading. (a)
- Add 5 drops of K2CrO4 to the same solution. Titrate against AgNO3 till the colour changes from yellow to brown.
- Note the reading (b).
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