Intermediate Topic 933 of 1102 Analytical, Lab & Spectroscopy
Gravimetric Analysis
Determining amount of analyte by weighing a precipitate.
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In-depth explanation of Gravimetric Analysis
Gravimetric analysis determines the amount of an analyte by converting it into a pure, stable compound of known composition, which is separated, dried or ignited and weighed. The precipitate must be sparingly soluble, form filterable particles and be free of coprecipitated impurities, which is controlled by slow precipitation from hot dilute solutions followed by digestion. The mass of the precipitate, combined with its formula and the stoichiometry, gives the mass of analyte in the original sample through a gravimetric factor. The method is highly accurate and does not require calibration against standards, but it is slow and labour intensive. It remains a reference method for some determinations.
Going deeper: Gravimetric Analysis
Key ideas: Mass of analyte = mass of precipitate x gravimetric factor, where factor = (molar mass of analyte form)/(molar mass of precipitate) x stoichiometric ratio. Dry or ignite to constant mass (successive weighings differing by under 0.3 mg). Precipitate from hot dilute solution with slow addition of precipitant and digest, so crystals grow larger and purer. Common forms: BaSO4, AgCl, Fe2O3, Mg2P2O7.
Common mistakes and connections: Students forget the stoichiometric ratio in the gravimetric factor (such as 2 Fe per Fe2O3), weigh a precipitate that is still wet, or lose fine particles during filtration. Coprecipitation of impurities causes high results. Adding the precipitant too quickly gives colloids. AgCl must be protected from light. Related to solubility product, Ksp, filtration and stoichiometry.
Visualization of Gravimetric Analysis
Weighing dried BaSO4, which is 13.74 percent sulfur by mass, converts its mass directly into the sulfate originally present. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Sulfate is determined by precipitating it as barium sulfate and weighing the dried BaSO4 solid.
Frequently asked questions about Gravimetric Analysis
What is Gravimetric Analysis?
Determining amount of analyte by weighing a precipitate.
Is Gravimetric Analysis a beginner, intermediate or advanced topic?
Gravimetric Analysis is a intermediate topic in Analytical, Lab & Spectroscopy. It builds on the vocabulary of beginner topics in this area.
What should I learn before Gravimetric Analysis?
Study these earlier topics in Analytical, Lab & Spectroscopy first: X-ray Crystallography, Electron Microscopy, Scanning Tunneling Microscopy.
What comes after Gravimetric Analysis?
The next topics in Analytical, Lab & Spectroscopy are Titrimetric Analysis and Back Titration.
Can I practise Gravimetric Analysis with quizzes?
Yes. The interactive lesson includes a self-check question on Gravimetric Analysis, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Gravimetric Analysis fits in Analytical, Lab & Spectroscopy
Gravimetric Analysis is topic 57 of 99 in Analytical, Lab & Spectroscopy.