Estimation of sodium chloride by Precipitation titrations
Precipitation titration is a technique used to determine the amount of a substance in a solution by reacting it with a reagent to form a precipitate. The most commonly used precipitation titration method for estimating sodium chloride is the Mohr method.
The Mohr method involves adding a known quantity of silver nitrate solution to the sample solution containing sodium chloride. The addition of silver nitrate results in the formation of a white precipitate of silver chloride. The endpoint of the titration is reached when all the chloride ions in the sample have reacted with the silver ions, forming the silver chloride precipitate.
To carry out the Mohr method, a known quantity of the sodium chloride sample is dissolved in distilled water and a few drops of potassium chromate indicator solution are added. The silver nitrate solution is then slowly added to the sample solution until the endpoint is reached. At the endpoint, the color of the solution changes from yellow to red, indicating the formation of silver chloride precipitate.
The amount of silver nitrate solution added to the sample can be used to calculate the amount of sodium chloride present in the sample, using stoichiometry of the reaction.
It is important to ensure that the reagents used are of high purity and that the sample solution is free from any other interfering substances that may affect the accuracy of the titration. Additionally, the silver nitrate solution should be standardized against a known quantity of sodium chloride before use to ensure accurate results.
Overall, precipitation titration, particularly the Mohr method, is a reliable and widely used technique for the estimation of sodium chloride in various industries, including food and pharmaceuticals.
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