DELETERIOUS CONTENTS OF SOILS.

DELETERIOUS CONTENTS OF SOILS.

I. Determination of Total Soluble Sulphates by Volumetric Method: (IS : 2720 – Part – 27)

Object:

Determination of total soluble sulfate content of soil by Volumetric method.

Sample Preparation: Take about 100 grams of oven dried soil sample and sieve it in a 425 micron IS Sieve.

Preparation of Reagents:

1. Barium Chloride Solution (N/4): Dissolve 30.5 grams Barium chloride in one liter of distilled water.

2. Potassium Chromate Solution (N/4): Dissolve 24.275 grams of Potassium chromate in a small amount of distilled water. Add few drops of Silver Nitrate solution to it to remove any Chloride, filter and dilute to 250 ml.

3.Silver Nitrate Indicator: Dissolve 500 mg of Silver Nitrate in 100 ml of distilled water.

4.Dilute Solution of Ammonium Hydroxide: (Sp.Gr 0.888) Mix Ammonium Hydroxide and distilled water in the ratio of 1:2.

5.Concentrated Hydrochloric acid: Sp.Gr 1.11.

Test Procedure:

1. 10 grams of soil sample taken in to beaker.

2. Add 50 ml water, stir well, allow decanting and filtered.

3. Take 10 ml filtrate sample by pipette in a conical flask.

4. Make it slightly acidic by adding concentrated hydroelectric acid (i.e.: few drops) and heat to boiling.

5. Add Barium Chloride solution (N/4) from the Burnett till the precipitation is complete, measure the volume in ml and recorded it as ‘X’.

6. Neutralize the solution with Ammonium hydroxide (i.e.: few drops).

7. Tit rate the excess of Barium chloride against Potassium Chromatic solution(N/4), measure the volume in ml and recorded it as ‘Y’. the end point may be confirmed, if considered necessary, by using Silver nitrate solution as an external indicator.

Calculations:

Sulfates as Sodium Sulfate in Soil, percent by mass = 0.0177 x (X – Y)

II. DETERMINATION OF ORGANIC MATTER IN SOILS ( IS: 2720 – Part – 22)

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Total weight of original soil sample (Oven dried) – W1 grams.

2. Sieve the sample on 10 mm IS sieve and weighed the passing material – W2 grams.

3. Then sieve the sample on 425 micron IS sieve and take the soil sample for the test – Approximately 5 grams – W3 grams.

Preparation of Reagents:

1. Potassium Dichromate Normal solution: Dissolve 49.035 grams of Potassium Dichromate in one liter of distilled water.

2. Ferrous Sulfate 0.5 N solution: Dissolve 140 grams of Ferrous Sulfate in 0.5 N Sulfuric acid to make one liter of solution (Add 14 ml of concentrated Sulphuric acid to distilled water to make one liter of solution for 0.5 N Sulfuric acid).

3. Concentrated Sulfuric acid: Sp.Gr 1.83.

4. Or tho Phosphoric acid: Sp.Gr 1.70 to 1.75.

5. Indicator: 0.25 grams of Sodium Diphemylamine-Sulphonate dissolved in 100 ml of distilled water.

Standardization of Ferrous Sulphate Solution:

1. Take 10 ml of Normal Potassium Dichromate solution in to 500 ml conical flask.

2. Add 20 ml concentrated Sulfuric acid and swirled and allowed to cool for some times.

3. Add 200 ml of distilled water, 10 ml of Or tho Phosphoric acid and 1ml of the Indicator and the mixture shall be shaking thoroughly.

4. Ferrous Sulfate solution added through Burnett in 0.5 ml increments, up to the solution changes from blue to green.

5. Add 0.5 ml Potassium Dichromate, then solution changing the color back to blue.

6. And then Ferrous Sulfate added drop by drop until the color of the solution changes from blue to green. Measure the total volume of Ferrous Sulfate solution in ml and recorded it as ‘X’.

Procedure:

1. Take 5 grams of soil sample of 425 micron IS sieve passing in 500 ml conical flask.

2. Add 10 ml of Potassium Dichromate solution.

3. Add 20 ml of concentrated Sulphuric acid and allowed to 30 minutes on a heat insulating surface like asbestos sheet.

4. Add 200 ml distilled water, 10 ml of Ortho Phosphoric acid, 1 ml of the Indicator and the mixture shall be shake vigorously.

5. Ferrous Sulphate solution added through burette in 0.5 ml increments, up to the solution changes from blue to green.

6. Add 0.5 ml Potassium Dichromate, then solution changing the color back to blue.

7. And then Ferrous Sulphate added drop by drop until the color of the solution changes from blue to green. Measure the total volume of Ferrous Sulphate solution in ml and recorded it as ‘Y’.

Calculations:

1. The Volume of Potassium Dichromate used to oxidize organic, V= 10.5(1 – Y/X).

2. Percentage of Organic Matter in soil = (0.67W2V) / (W1W3)

III. DETERMINATION OF CHLORIDE AND SALINITY IN SOILS

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Take the oven dried soil sample and sieve it on 2 mm IS sieve.

2. Take 50 grams of 2mm passing material in conical flask and add the distilled water with 1:5 ratio, allowed to 16 hrs, so that the salts are extracted by the distilled water completely.

Preparation of Reagents:

1. Chloride free distilled water.

2. Potassium Chromate – color Indicator.

3. Standard Silver Nitrate (0.0141N / 0.0156N): Dissolved 2.395 grams Silver Nitrate in one liter of hot distilled water to prepare 0.0141N solution. Alternatively, dissolve 2.65 grams of Silver Nitrate in one liter of hot distilled water to prepare 0.0156N  solution. 

Procedure:

1. Take 25 ml of filtered sample in a conical flask.

2. Adjust the PH in the range of 7 to 8 by adding Sulphuric acid or Sodium Hydroxide solution.

3. Add 1 ml of Potassium Chromate – Yellow color develops.

4. Take 0.0156N Silver Nitrate solution in burette and titrate till brick red color develops. Measure the volume in ml and recorded it as ‘X’.

Calculations:

1. Chloride(mg/l or ppm),  Y = (X x 35.46 x 1000 x 0.0156) / (ml of sample taken)

2. Salinity (ppt or gms/lt) = 0.03 + 1.806 x Chlorides in g/lt.

3. Total Chlorides in soil sample = 5 x Y.