Pharmaceutical analysis sem 1 (unit3) hand written notes pdf

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Precipitation titration is a type of volumetric analysis in which a precipitate is formed after adding a reagent to the solution. The amount of the reagent added is based on stoichiometric calculations to ensure complete reaction and formation of the precipitate.

The principle behind precipitation titration is that the endpoint is reached when the reaction between the analyte and the titrant has produced a stoichiometric amount of the precipitate. At this point, any excess of the titrant will result in the formation of a noticeable excess of precipitate.

Precipitation titration is used to determine the concentration of certain analytes, such as chloride, sulfate, or carbonate ions, in an unknown sample. The procedure usually involves adding a standard solution of a titrant to a known volume of the unknown sample. The titrant reacts with the analyte in the sample to form a precipitate which is then filtered, dried, and weighed. The mass of the precipitate formed is then used to calculate the concentration of the analyte in the original sample.

One common example of precipitation titration is the determination of chloride ion concentration by the Mohr method. In this method, a known volume of the sample is treated with a silver nitrate solution to form a silver chloride precipitate. Excess silver nitrate is titrated with a standard solution of potassium thiocyanate until all the silver ions have reacted to form a soluble complex. The endpoint is reached when the red-brown color of the complex changes to a colorless solution.

Precipitation titration is generally less sensitive than other types of titrations but is useful when the analyte cannot be detected easily by other methods, or when the analyte is not stable in solution.