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How does gravimetric analysis determine the amount of a substance?

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A strip of pH paper rests on the rim of a container holding a yellow liquid, with a color comparison chart and several unused pH strips nearby. — chemical analysis Strip of pH paper resting on specimen, with a comparison chart.

Gravimetric analysis is a method of quantitative chemical analysis that determines the amount of a substance by converting it into a product of known composition that can be isolated and weighed.12

The process generally follows these steps:
* Preparation: A solution is prepared using a known weight of the sample.1
* Separation: The desired constituent is isolated from the sample. Common techniques include:
* Precipitation: Adding a reagent to form an insoluble compound, which is then filtered, washed, and dried or ignited.1
* Volatilization: Converting the constituent into a gaseous compound, such as evolving carbon dioxide with an acid, and measuring the weight gain of an absorbent.1
* Electrodeposition: Using an electric current to plate out metals from a solution.1
* Measurement and Computation: The isolated substance is weighed, and the amount of the original constituent is calculated based on that weight.1

Accuracy depends on the purity of the isolated substance, as achieving a composition that perfectly matches a chemical formula can be challenging.1