Gravimetric Analysis
Gravimetric methods of analysis are based on the measurement of mass.
There are two major types of gravimetric methods:
Precipitation methods: in this method the analyte is converted to a sparingly soluble
precipitate. This precipitate is then filtered, washed free of impurities, and
converted to a product of known composition by suitable heat treatment, and the
product is weighed.
Volatilization methods: in this the analyte or its decomposition products are volatilized at a
suitable temperature. The volatile product is then collected and weighed, or,
alternatively, the mass of the product is determined indirectly from the loss
in mass of the sample.
Properties of precipitates and precipitating reagents
A gravimetric precipitating agent should react specifically, and
selectively with the analyte. The ideal precipitating reagent would react with
the analyte to give a product that is
1.
Readily
filtered and washed free of contaminants
2.
Of
sufficiently low solubility so that no significant loss of the solid occurs
during filtration and washing
3.
Unreactive
with constituents of the atmosphere
4.
Of known
composition after it is dried or, if necessary, ignited
No comments:
Post a Comment