Limit test for chloride

AS PER IP

Apparatus Required  

Nessler cylinders  

Glass rod  

Stand  

Chemicals Required   

Dilute Nitric acid   

Silver nitrate, 0.1M

Sodium Chloride 

Principle

It is based upon the chemical reaction between silver nitrate and soluble chlorides in the presence of dilute nitric acid to give opalescence of silver chloride. 

If the  Opalescence produced is compared with the standard solution.  If the opalescence in the sample is less than the standard,  it passes the test.  If it is more than the standard,  it fails the test. 

Reagents Preparation

Chloride Standard Solution (25 ppm Cl): Dilute 5 volumes of a 0.0824 percent w/v sodium chloride solution to 100 volumes with water.

Silver Nitrate, 0.1 M: Dissolve 17.0 g in sufficient water to produce 1000 ml

Nitric Acid, Dilute: Contains approximately 10 percent w/w of HN03. Dilute 106 ml of nitric acid to 1000 ml with water.

Procedure

Sample Preparation:

Dissolve the specified quantity of the substance under examination in water, or prepare a solution as directed in the individual monograph and transfer it to a Nessler cylinder. Add 10 ml of dilute nitric acid, except when nitric acid is used in the preparation of the solution, dilute to 50 ml with water and add 1 ml of 0.1 M silver nitrate. Stir immediately with a glass rod and allow to stand for 5 minutes protected from light. 

Standard Preparation:

To a mixture of 10.0 ml of chloride standard solution (25 ppm el) and 5 ml of water in Nessler cylinder. Add 10 ml of dilute nitric acid, except when nitric acid is used in the preparation of the solution, dilute to 50 ml with water and add 1 ml of 0.1 M silver nitrate. Stir immediately with a glass rod and allow to stand for 5 minutes protected from light. 

Interpretation 

When viewed transversely against a black background any opalescence produced is not more intense than that obtained by treating a mixture of 10.0 ml of chloride standard solution (25 ppm el) and 5 ml of water in the same manner. 

Note: Nitric acid is added in the limit test of chloride to make solution acidic and helps silver chloride precipitate to make the solution turbid at the end of the process.

=======================================================

AS PER BP 

Apparatus Required  

Nessler cylinders  

Glass rod  

Stand  

Chemicals Required   

Dilute Nitric acid (10%)  

Silver nitrate 0.1M

Sodium Chloride 

Principle

It is based upon the chemical reaction between silver nitrate and soluble chlorides in the presence of dilute nitric acid to give opalescence of silver chloride. 

If the  Opalescence produced is compared with the standard solution.  If the opalescence in the sample is less than the standard,  it passes the test.  If it is more than the standard,  it fails the test. 

Reagents Preparation

Chloride Standard Solution (5 ppm Cl): Immediately before use, dilute with water R to 100 times its volume a  solution containing sodium chloride R equivalent to 0.824 g of  NaCl in 1000.0 mL. 

Silver Nitrate: Dissolve 17.0 g in sufficient water to produce 1000 ml

Nitric Acid, Dilute: Contains about 125 g/L of HNO3 (Mw: 63.0). Dilute 20 g of nitric acid to 100 mL with water. 

Procedure

Sample Preparation:

To 15 mL of the prescribed solution add 1 mL of dilute nitric acid and pour the mixture as a single addition into a test-tube containing 1 mL of silver nitrate solution.

Standard Preparation:

Prepare a standard, in the same manner, using 10 mL of chloride standard solution (5 ppm Cl) R and 5 mL of water and add 1mL of dilute nitric acid and pour the mixture as a single addition into a test tube containing 1 mL of silver nitrate solution.

Interpretation 

After standing for 5 min protected from light, any opalescence in the test solution is not more intense than that in the standard. 

=========================================================

AS PER USP

Silver Nitrate: Dissolve 17.5 g in sufficient water to produce 1000 ml

Sample Preparation:

Dissolve the specified quantity of the substance under test in 30 to 40 mL of water, or, where the substance is already in solution, add water to make a total volume of 30 to 40 mL, and, if necessary, neutralize the solution with nitric acid to litmus. Add 1 mL each of nitric acid and silver nitrate TS and sufficient water to make 50 mL. Mix, and allow to stand for 5 minutes protected from direct sunlight. 

Standard Preparation:

Unless otherwise specified in the monograph, compare the turbidity, if any, with that produced in a solution containing the volume of 0.020 N hydrochloric acid specified in the monograph.