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

The expansion of soil containing high sulphates occurs during ambient temperature drops from daytime temperatures of roughly 30 degree to below 5 degree at night. This expansion caused structural damage to single storey house in particular and to interior concrete bottoms and asphalt driveways. This phenomena, herein appertained to as” salt heave,” . Only by early recognition of the presence of water-soluble sulphate in the soil to control structural damage building or pavement. The final test procedure described herein provides a system to estimate soils containing sodium sulfate.  In this session we will learn how to determine total soluble sulphates by volumetric system as per( IS 2720 – Part – 27).

Object: Determine total soluble sulphates by volumetric method as per  (IS : 2720 – Part – 27)

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 5 grams Barium chloride in one liter of distilled water.
2. Potassium Chromate Solution (N/4): Dissolve 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: Gr 1.11.

Test Procedure:

1. 10 grams of soil sample taken in to
2. Add 50 ml water, stir well, allow decanting and
3. Take 10 ml filtrate sample by pipette in a conical
4. Make it slightly acidic by adding concentrated hydrochloric acid (i.e.: few drops) and heat to
5. Add Barium Chloride solution (N/4) from the burette 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. Titrate the excess of Barium chloride against Potassium Chromate 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:

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