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BACKGROUND
In this limit test, the iron reacts with thioglycollic acid in the presence of citric acid and in alkaline medium develops a pale pink to deep reddish purple colour due to the ferrous compounds might be present in the sample.
As this test is very sensitive, citric acid 20% has been added which doesn’t permit the pptn of iron by ammonia by forming a complex with it and the colour formed due to ferrous compound gets damaged by oxidising agents and alkalies.1
Aim: Aim of this experiment is to carry out the limit tests for iron of the given samples.
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REQUIREMENTS
Apparatus: Nessler’s cylinder,
Glass Rod,
Analytical balance
Sample: Potassium bromide(1gm),
Sodium chloride(0.5gm),
Borax(0.5gm),
Sodium carbobate(0.2gm)2
Chemicals: Thioglycollic acid,
Iron free ammonia solution,
Iron free citric acid,
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
The specified amount of sample was taken and dissolved in some few ml of distilled water followed by addition of 2ml of 20% w/ citric acid and 0.1ml of thioglycollic acid, then the solution was made alkaline with iron free NH3 solution, and the volume was made upto 50ml with distilled water.
Reaction
Preparation of standard solution
1ml of 0.1089% w/v of pot.sulphate was taken in a clean nessler’s cylinder to which few ml of distilled water and 2ml of dil.HCl were added2. Then the volume was made upto 45ml with distilled water and barium sulphate 5ml was added at last , after which it was kept still for 5mins.
Reaction
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CONCLUSION
After performing the above test, it was observed that the samples are of pharmaceutical mark as the opalescence of the test samples are lesser tan tat of standard solution.
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REFERENCES
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Chatwal GR. Pharmaceutical inorganic chemistry (vol- 1); 2016.
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Indian pharmacopoeia; 2016.