Here are the basic steps in gravimetric analysis, explained:
1. Preparation of solution
- The sample is dissolved in water or another suitable solvent to form a clear solution.
- Any interfering substances are removed before starting the analysis.
2. Precipitation
- A reagent is added to the solution to form an insoluble solid (precipitate) containing the substance to be measured.
- The reagent is added slowly to get a pure and easily filterable solid.
3. Digestion
- The mixture is kept warm for some time so that small particles combine to form larger, purer crystals.
- This helps in easy filtration and removes trapped impurities.
4. Filtration
- The precipitate is separated from the liquid using filter paper or a crucible.
- The solid is then washed to remove impurities and leftover ions.
5. Drying or Ignition
- The washed precipitate is dried in an oven or ignited in a furnace to remove all moisture or volatile substances.
- This ensures the solid has a constant weight.
6. Weighing
- The dried solid is cooled in a desiccator and then weighed accurately using an analytical balance.
7. Calculation
- From the weight of the pure compound, the amount of the element or ion in the original sample is calculated using stoichiometry.
In short:
Dissolve → Precipitate → Digest → Filter → Dry/Ignite → Weigh → Calculate