Method for Water-Soluble Chloride Analysis Test in Soil
Loading ... Civil Engineers Blog

top page

Latest News

top post page

Home Method for Water-Soluble Chloride Analysis Test in Soil

Method for Water-Soluble Chloride Analysis Test in Soil

Font size

 


Method for Water-Soluble Chloride Analysis Test in Soil 


Principle.

Chlorides are extracted from dry soil sample by solution in a mass of water equal to twice that of the sample. Results are expressed as the chloride ion content.

The water- extract method is applicable only to soils in which the chloride content
derives directly from  recent contact with, or immersion in, saline water. 




Reagents and Apparatus.


I. Burette, 50 mL 






II. Weighing balance 



III. Stoppered conical flask, 500 mL 






IV. Wide mouth screw-capped plastic or metal bottle,


2L capacity.







V. Measuring cylinder 



VI. Filter paper, medium grade  



VII. Filter funnel 




VIII. Mechanical shaker 




IX. 6 M Nitric Acid Solution 


X. 0.1 N Silver Nitrate Solution 


XI. 0.1 N Potassium Thiocyanate Solution  


XII. 3-5-5-Trimethylhexan-1-ol 


XIII. Ferric alum indicator  



Procedure: 


Standardization of thiocyanate solution 

Transfer 25 mL of the silver nitrate solution into a 250 mL conical flask, using a 
pipette, and  add 5 mL of the nitric acid solution and 1 mL of ferric alum indicator solution.

Add  thiocyanate solution from a burette until the first permanent color change occurs, that is  from colorless to pink. Record the volume of thiocyanate
solution added V1 (in mL).

Calculate the concentration C (in mol/L) of the solution from the following equation:

 C =2.5/  V1 






 

Preparation of test specimen. 


Obtain an initial sample. Dry this sample in an oven at 105 °C to 110 °C and allow to cool to  room temperature in the desiccator. Sieve the sample on a 2 mm test sieve (if appropriate,  guarded by a test sieve of larger aperture) and crush retained particles other than stones to pass through the 2 mm test sieve. Reject the stones, ensuring that no fine material adheres  to them, e.g., by brushing.

Record the mass m2 (in g) of sample passing the 2 mm test sieve  to the nearest 0.1 %. Throughout these and subsequent operations ensure that there is no  loss of fines.

Divide the material passing the 2 mm test sieve by successive riffling through the 15 mm divider to produce the following: a) a test specimen of about 500 g; and b) a specimen of about 50 g for a qualitative check test to determine whether chlorides are present. 

Dry the specimens in the oven at 105 °C to 110 °C. The specimens are deemed to  be dry when the differences in successive weighing carried out at intervals of 4 h, do not  exceed 0.1 % of the original mass of the sample.

Allow the specimens to cool to room  temperature in the desiccator.




Qualitative check for chlorides.


Place the 50 g check specimen in a 500 mL conical flask and add to it an approximately  equal mass of distilled water. Agitate the contents intermittently for 4 h, allow to settle and  pour off some of the supernatant solution into a beaker.

Obtain about 25 mL of clear solution  by filtering, if necessary, through a medium grade filter paper, e.g., Whatman No. 40.

Acidify  the liquid with nitric acid, add about five drops of the silver nitrate solution and allow to stand  for 10 min.

 If no turbidity is apparent after this time the soluble chloride ion content of the soil  is negligible and the test for chloride content is not necessary.



Preparation of water-soluble chloride extract. 


Weigh a clean and dry screw-capped bottle to 1 g and record its mass. Place the test  specimen in the bottle and weigh the bottle and contents to 1 g.

Calculate the mass of soil  by difference m (in g). Add to the bottle a mass of distilled water mw equal to twice the mass  of the test specimen.

Fasten the watertight caps securely.

Secure the bottle to the shaking  apparatus and shake for at least 16 h.

When convenient the soil can be left shaking  overnight.

Filter the suspension through a medium-grade filter paper into a clean beaker until at least 100 mL of clear filtrate has been collected.

If the filtrate is not completely clear,  filter through a fine-grade filter paper.

 


Analysis of extract.  


Take 100 mL of the filtered extract by means of the pipette and transfer to the 250 mL  conical flask.


Add 5 mL of the nitric acid solution to the flask followed by silver nitrate solution from a burette until all the chloride has been precipitated, and then add a little  excess silver nitrate.


Record the total volume V (in mL) of silver nitrate solution added.


Add  2 mL of 3,5,5-trimethylhexan-1-ol, fit the stopper, and shake the flask vigorously to  coagulate the precipitate.


Carefully loosen the stopper, avoiding loss of solution, rinse with  distilled water, and collect the washings in the solution.


Add 5 mL of the ferric alum indicator  solution, followed by the standardized thiocyanate solution from a burette until the first  permanent color change occurs, that is from colorless to brick-red. Record the volume V3  (in mL) of thiocyanate solution added. 





Calculation.


Chloride Content= 0.007092(V2-10CV3)

Where: V2= volume of silver nitrate solution added 

V3= volume of standardized potassium thiocyanate solution added 

C= concentration of standardized potassium thiocyanate solution


 

Reference.  


BS 1377 Part 3:1990 Amd 9028 :1996  

No comments
Post a Comment