Limit test for chloride

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BACKGROUND

The quantitative or semi-quantitative tests performed to distinguish minute amount of impurities present in the substance and to control their adverse effects are termed as limit tests. The tests are carried out to detect small impurities in an unknown substance by comparing it with the standard and these impurities gives a specific reaction with some reagents used in the test.¹ The result is evaluated by the visual analysis of the opalescence / turbidity produced and in some cases instrumental analysis were done. The tests are performed in nessler’s cylinder keeping in mind the visual examination of opalescence.

Limit test for chloride gives a silver chloride precipitate upon the reaction of chloride ion with silver nitrate in the presence of dilute nitric acid. Here, the standard solution was prepared by taking 1ml of 0.05845% of sodium chloride solution.

Aim: Aim of this experiment is to carry out the limit tests for chloride of the given samples.

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REQUIREMENTS

Apparatus: Nessler’s cylinder,

Glass rod,

Analytical balance

Sample:     Borax,

Dextrose,

Calcium gluconate,

Sodium bicarbonate,

Magnesium sulphate,

Potassium acetate

Chemicals: Dilute HNO₃,

AgNO₃,

NaCl,

Distilled water

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PROCEDURE

The method for carrying out limit test for chloride requires; a standard and a test solution

Preparation of test solution

Accurately measured quantity of specified sample that is 1 gm was taken and dissolved in 10ml of distilled water with a continuous stirring, then 10ml of dilute nitric acid was added . Silver nitrate 1ml as a reagent was added, volume was made upto 50ml in previously marked nessler’s cylinder. Then, the solution was stirred and kept aside for 5 mins.

Reaction¹

Preparation of standard solution

The standard solution was prepared by taking 1ml of 0.05845% w/v of sodium chloride solution in an another clean nessler’s cylinder to which each of 10ml of dilute nitric acid and distilled water were added.² 1 ml of silver nitrate was added, volume was made upto 50ml with distilled water. The solution was stirred and kept untouched for 5 mins.

Reaction¹

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CONCLUSION

From the above test, it was concluded that the samples used for the presence of chloride as a impurity has passed the test as the opalescence observed was lesser than the standard. Therefore, the samples are of pharmaceutical grade.

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REFERENCES

1. Chatwal GR. Pharmaceutical inorganic chemistry (vol- 1); 2016.
   
2. Indian pharmacopoeia; 2016.