Chemistry Labs

Analytical chemistry

Gravimetric analysis

Convert analyte ions into a pure, stable solid of known composition, then weigh it.

1 Lower secondary2 Upper secondary3 Undergraduate4 Advanced5 Research

IntuitionIntuition: the measurement idea

Gravimetric analysis turns an ion into a weighable solid. The method is exact because mass is measured directly and because the weighed compound has a defined composition.

Explore the Gravimetric analysis measurement concept in this interactive signal.

SchoolSchool level: signal and result

Gravimetric analysis is a classical method based on precipitation, filtration, washing and weighing. Its gravimetric factor converts the mass of a weighed form into the mass of the analyte.

Definition:

Convert analyte ions into a pure, stable solid of known composition, then weigh it.

First identify the measurand, choose a signal that responds to it, and compare the sample with a calibrated standard or a validated model.

$m_A=m_P\,\dfrac{M_A}{M_P}

Example: Worked analytical example

Calculate the analyte result from the stated measurement and method relation.

Solution

A 0.4660 g BaSO₄ precipitate corresponds to 0.1918 g sulfate because 96.06/233.39 = 0.4116.

Method checkpoints
StagePurpose
PrepareControl matrix and contamination
MeasureAcquire a calibrated response
ValidateCheck recovery and uncertainty

UndergraduateUniversity: quantitative method

Quantitative precipitation, particle growth, coprecipitation, peptization, washing and ignition must all be controlled; constant mass is the evidence that the weighed form is stable.

Calibration, selectivity, sample preparation and uncertainty belong to the method itself, not to afterthoughts. Report units, conditions and the calibration range.

$m_A=m_P\,\dfrac{M_A}{M_P}

References