Pharmaceutical analysis sem 1 (unit3) hand written notes pdf

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Precipitation titration is a type of titration in which a precipitate is formed during the reaction. The precipitate is then measured, either gravimetrically or by its turbidity or color, in order to determine the amount of analyte present.

The principle behind precipitation titration is to add a titrant solution of a known concentration to a sample solution containing an analyte. The titrant is added until a point is reached where a precipitate is formed. The amount of titrant required to cause precipitation is correlated to the amount of analyte present in the sample.

There are several types of precipitation titration, including:

1. Mohr method: This method involves titrating a solution of an unknown concentration of chloride ion with silver nitrate until precipitation occurs.

2. Volhard method: This method is used to determine the concentration of chloride ions in a sample by adding excess silver nitrate and then back-titrating with a standard solution of potassium thiocyanate.

3. Fajans method: This method involves adding a small amount of a chromate or dichromate indicator to a sample containing chloride ions. Silver nitrate is then added until the endpoint is reached, which is indicated by a color change.

4. Argentometric method: This method involves titrating a solution containing chloride ion with silver nitrate in the presence of a complexing agent, such as ammonia or potassium dichromate.

Precipitation titration is commonly used in analytical chemistry for the determination of anions and cations. It is particularly useful for determining the concentration of ions that do not have suitable indicators for other types of titrations. However, precipitation titrations are often time-consuming, and the precision and accuracy can be affected by the presence of interfering substances in the sample.