GRAVIMETRIC ANALYSIS
1. In analytical chemistry, gravimetry is the measurement of weight.
2. 1. Introduction
Gravimetric methods are quantitative methods that are based on the determination of the mass of
a pure compound to which the analyte is chemically related. The mass measurements are done
with an analytical balance. Analytical balances are the most highly accurate and precise
instruments in the analytical lab. Hence gravimetric analysis is a very reliable tool in analysis.
3. The term gravimetric pertains to a Weight Measurement. • Gravimetric method is
one in which the analysis is completed by a weighing operation. • Gravimetric
Analysis is a group of analytical methods in which the amount of analyte is
determined by the measurement of the mass of a pure substance containing the
analyte. • Gravimetric Methods can also be defined as quantitative methods based
on the determining the mass of a pure compound to which the analyte is chemically
related
4. 2. Types of Gravimetric Analyses:
a. Precipitation gravimetry – where the analyte is separated from a solution of the sample
in the form of a precipitate and converted to a compound of known composition that can
be weighed. The precipitate from solution is filtered, washed, and purified (if necessary)
before and weighinged.
Example for Precipitation
• Calcium can be determined gravimetrically by precipitation of calcium oxalate and ignition of
the oxalate ion to calcium oxide. This method is an official method for determining calcium in
water. The oxalate ion is obtained from (NH4)2C2O4, generated by bubbling ammonia gas
through oxalic acid.
2NH3 + H2C2O4 → 2NH4+ + C2O42-
• Ca2+ + C2O4 2- → CaC2O4
• CaC2O4 → CaO + CO2 + CO
• The precipitate thus obtained are weighed and the mass of calcium oxide is determined.
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1. In analytical chemistry, gravimetry is the measurement of weight.
2. 1. Introduction
Gravimetric methods are quantitative methods that are based on the determination of the mass of
a pure compound to which the analyte is chemically related. The mass measurements are done
with an analytical balance. Analytical balances are the most highly accurate and precise
instruments in the analytical lab. Hence gravimetric analysis is a very reliable tool in analysis.
3. The term gravimetric pertains to a Weight Measurement. • Gravimetric method is
one in which the analysis is completed by a weighing operation. • Gravimetric
Analysis is a group of analytical methods in which the amount of analyte is
determined by the measurement of the mass of a pure substance containing the
analyte. • Gravimetric Methods can also be defined as quantitative methods based
on the determining the mass of a pure compound to which the analyte is chemically
related
4. 2. Types of Gravimetric Analyses:
a. Precipitation gravimetry – where the analyte is separated from a solution of the sample
in the form of a precipitate and converted to a compound of known composition that can
be weighed. The precipitate from solution is filtered, washed, and purified (if necessary)
before and weighinged.
Example for Precipitation
• Calcium can be determined gravimetrically by precipitation of calcium oxalate and ignition of
the oxalate ion to calcium oxide. This method is an official method for determining calcium in
water. The oxalate ion is obtained from (NH4)2C2O4, generated by bubbling ammonia gas
through oxalic acid.
2NH3 + H2C2O4 → 2NH4+ + C2O42-
• Ca2+ + C2O4 2- → CaC2O4
• CaC2O4 → CaO + CO2 + CO
• The precipitate thus obtained are weighed and the mass of calcium oxide is determined.
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