Gravimetric Analysis

At the end of this unit , the student is expected to be able to: 

1- Understand the fundamentals of gravimetric analysis. 

2- Follow the steps of the gravimetric analysis. 

3- Choose the appropriate precipitating agent for a certain analyte. 

4- Avoid or at least minimize the contamination of the precipitate. 

5- Optimize the precipitation conditions in order to obtain a desirable precipitate. 

6- Do all sorts of calculations related to gravimetric analysis.

Introduction 

Gravimetric methods are quantitative methods that are based on measuring the mass of a pure compound to which the analyte is chemically related. Since weight can be measured with greater accuracy than almost any other fundamental property, gravimetric analysis is potentially one of the most accurate classes of analytical methods . However it is lengthy and tedious as a result, only a very few gravimetric methods are currently used . There are three fundamental types of gravimetric analysis . In precipitation gravimetry, which is our  subject  in  this  unit  ,  the  analyte  is  separated  from  a  solution  of  the  sample  as  a precipitate and is converted to a compound of known composition that can be weighed. 

In volatilization gravimetry, the analyte is separated from other constituents of a sample by conversion to a gas . The weight of this gas then serves as a measure of the analyte concentration.  

In  electrogravimetry,  the  analyte  is  separated  by  deposition  on  an electrode by an electrical current. The mass of this product then provides a measure of the analyte concentration.