LIMIT TEST FOR SULPHATES

 

LIMIT TEST FOR SULPHATES

 

 

AIM: To perform limit test for sulphates in the given sample.

 

APPARATUS REQIURED: Nessler’s cylinder, beaker, pipette, measuring cylinder, glass rods.

 

 

CHEMICALS REQUIRED: BaCl2 solution, BaSO4 reagent, dil. HCl, standard solution of potassium sulphate, distilled water, test sample,

PRINCIPLE: This test is designed for the control of sulphate impurity in inorganic substances. It depends upon the precipitation of the sulphate with barium chloride in the presence of HCl and traces of barium sulphate. The turbidity obtained is compared with standard solution, which contains the known amount of sulphate ions under the same experimental conditions.

SO42- + BaCl2 --------       Dil.HCl-------BaSO₄    +  2Cl^-

PROCEDURE:

 

Preparation of BaSO4 reagent: This reagent must be freely prepared by mixing 10 ml of 25 % solution of BaCl2 and 15 ml of ethanolic sulphate standard solution, which contains 0.10891% K2SO4 in 3% ethanol. K2SO4 has been added to increase the sensitivity of the test. Very small amount of barium sulphate present in the reagent acts as seeding agent for precipitation of barium sulphate. Alcohol helps in preventing super saturation of barium sulphate.

Preparation of test solution:   Dissolve a specified quantity of substance in water or prepare solution as directed by I.P and transfer to Nessler’s cylinder. To this add 2 ml of dilute HCl and make the volume to 45 ml with water. And add 5 ml of BaSO4 reagent. Stir and keep it aside for 5 min.

Preparation of standard solution: Take 1ml of 0.1089% w/v of K2SO4 in Nessler’s cylinder and add 2 ml of HCl and transfer to Nessler’s cylinder and make the volume to 45 ml with H2O. To this add 5 ml of BaSO4 reagent. Stir and keep aside for 5 min. Finally compare the turbidity of two solutions.

SUMMARY:

 

STANDARD SOLUTION	Observation	Inference
Take 1ml of 0.1089 % w/v solution of potassium sulphate in Nessler’s cylinder + 2ml of dilute hydrochloric acid + Dilute to 45 ml in Nessler’s cylinder + 5ml of barium sulphate reagent. Keep aside for 5 min.	The opalescence produced in sample solution is greater than / less than that of standard solution.	The sample passes/ doesn’t pass the limit test for sulphates.
TEST SOLUTION   Take specific weight(1gm) of sample + Add 2ml of dilute hydrochloric acid +Dilute to 45 ml in Nessler’s cylinder + 5ml of barium sulphate reagent. Keep aside for 5 min.

 

 

 

The opalescence produced in the test solution is compared with that produced in standard solution.

 

 

OBSERVATION:

 

 

REPORT: The given sample                  the limit test for sulphates.

 

VIVA QUESTIONS:

 

1.      Write the principle involved in limit test for sulphates.

2.      What forms precipitate in limit test for sulphates?

3.      How barium sulphate reagent is prepared?

4.      The standard solution is prepared with                .

5.      What is the importance of dilute hydrochloric acid in limit test for sulphates?

6.      What is seeding agent?

7.      What is the importance of ethanol in limit test for sulphates?

8.      Write reaction involved in limit test for sulphate.

LIMIT TEST FOR CHLORIDES

 

LIMIT TEST FOR CHLORIDES

 

 

AIM: To perform the limit test for chlorides in the given sample. APPARATUS REQUIRED: Nessler’s cylinders, glass rod, beaker and pipette.

CHEMICALS REQUIRED: Standard Sodium Chloride solution, dilute Nitric acid, 0.1 M Silver natrate solution and Hydrochloric acid.

PRINCIPLE: This test is designed for the control of chloride impurity in inorganic substances. It depends upon the precipitation of chlorides upon reaction with silver nitrate in the presence of nitric acid. The extent of precipitation depends upon the amount of silver chloride formed i.e. on the amount of chloride ions present in the substance. The opalescence produced was compared with a reference standard opalescence having a known amount of chloride impurity.

Cl^- + AgNO3                                  AgCl + NO3-

 

PROCEDURE:

 

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Take two Nessler’s Cylinders, wash th                                              Dil. HNO3nd then label as STANDARD and TEST

 

Preparation of Standard chloride solution: Accurately weigh 0.05845g of NaCl and dissolve in 100 ml of distilled water. (0.05845% w/v of NaCl).

Preparation of standard Solution:

 

Take 1 mL of NaCl solution and transfer into Nessler’s cylinder and add 10 ml dilute Nitric Acid and make up the volume up to 50 mL with distilled water then add 1 mL of silver nitrate solution. Stir well with a glass rod and keep it aside for 5 min.

 

 

Preparation of Test Solution:

 

Weigh a specified quantity of test sample and transfer into Nessler’s cylinder and add 10 ml dilute Nitric Acid and make up the volume up to 50 mL with distilled water then add 1 mL of silver nitrate solution. Stir well with a glass rod and keep it aside for 5 min.

SUMMARY:

 

STANDARD SOLUTION	Observation	Inference
In a Nessler’s cylinder Chloride std. solution (25ppm Cl) 10ml taken. Add 5ml water + 10 ml of dil.HNO3.
Dilute to 50 ml in Nessler’s cylinder + 1 ml of 0.1 M AgNO3 solution.
Stir & allow to stand for 5 min.   Observe the opalescence	The                opalescence produced in sample solution is greater than / less than that of standard solution.	The sample passes/ doesn’t pass the limit test for chlorides.
TEST SOLUTION
Specified substance (1gm) + 10 ml of water + 10 ml of dil.HNO3.
Dilute to 50 ml in Nessler’s cylinder + 1 ml of 0.1 M AgNO3 solution.
Stir & allow to stand for 5 min.
Observe the opalescence

 

The opalescence produced in the test solution is compared with that produced in standard solution.

 

 

OBSERVATION:

 

 

 

REPORT: The sample_              limit test for chlorides.