Chloride is one of the most and easily available in many forms like as a Sodium chloride, calcium chloride, Ammonium chloride, Magnesium chloride, etc. Here, we are going to see how to check the chloride in a given water / waste water / soil sample. If you want to check your water contains chloride or not, you may follow the following steps.
Needed chemicals : Silver Nitrate 0.02 N solution, 10% Potassium Chromate solution (indicator), Sodium chloride (For standardization of Silver nitrate solution), Distilled water.
Required Glassware /equipments: 50ml Burette with stand, funnel, 250ml conical flask (Erlenmeyer flask), 1000ml Standard Measuring flask, 02 litre amber color bottle, Volumetric pipette 10/25ml, pipette bulb, weighing balance.
Preparations : 0.02 N Silver nitrate solutions are available in market Or you may easily prepare that solution in lab. Take 3.3974g of Silver nitrate and dissolved in small quantity of water and poured it into the 1000ml Standard measuring flask and add the distilled water and make up the mark. Now your solution is ready for titration. You may be cross verify your prepared solution by standardization against 0.02 N of sodium chloride solution.
Standardization of Silver nitrate solution By Standard Sodium chloride solution :
Take previously heated and dried, cooled salt of sodium chloride 0.709g by using analytical weighing balance and dissolved by small quantity of distilled water and poured it into a 1000ml standard measuring flask and make up to the mark.
Now, take 20ml of the prepared 0.02 N of Sodium chloride standard solution in a conical flask and add 1ml of potassium chromate indicator and titrate against the prepared silver nitrate solution. End point is yellow colour changes to a reddish brown colour.
Now, using V1N1 = V2N2 formula, you will get the exact normality of your prepared silver nitrate solution.
V1 = volume of standard sodium chloride solution taken to the analysis.
N1 = Normality of standard Sodium chloride solution.
V2 = Titre volume of silver nitrate solution.
N2 = Normality of Silver nitrate.
here, we need N2.
So, N2 = V1*N1 / V2
Chloride Analysis in the given Sample :
Now, take that silver nitrate solution into the 50ml Burette. Take 10 or 25ml water sample in conical flask and add 1ml Potassium chromate indicator and see the color differences. (Actually, potassium chromate is a yellow coloured solution. It will react with silver nitrate and immediately produce a reddish brown precipitate). If your sample turns reddish brown colour without adding silver nitrate, your sample contains no chloride minerals. Otherwise, if sample remains appear as yellow color by addition of indicator, shows chloride is present and it will be estimate by addition of Silver nitrate. Now, slowly added the silver nitrate solution into the conical flask containing the measured quantity of sample till the appearance of reddish brown color as end point.
For chloride analysis in a given soil sample, just prepare 5 / 10% solution . chloride will be easily dissolved in a water. You will be filter through filter paper and doing the above method to find out the chloride estimation in given soil samples.
Calculation :
Titre value*35.45*0.02*1000/ volume of sample taken.
Results will come as mg/L.
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