Gravimetric

Gravimetric refers to phenomena or methods related to gravity. In science and engineering, gravimetric analysis is a classical quantitative chemical technique for determining the amount of an element or compound by weighing a solid that contains the analyte. In geophysics and surveying, gravimetric methods measure variations in the Earth’s gravity field to infer subsurface density contrasts and structure.

The principle of gravimetric analysis is to convert the target analyte into an insoluble compound of known composition. The precipitate is separated by filtration, thoroughly washed, dried, and weighed to a constant mass. By applying stoichiometry, the mass of the precipitate is related to the amount of analyte in the original sample. Common precipitates include barium sulfate for sulfate determinations and silver chloride for chloride determinations; in some cases the precipitate is converted by ignition to a stable oxide or carbonate for weighing. The procedure typically requires careful control of solvent conditions, pH, and temperature to minimize side reactions and ensure a pure, well-defined product.

Gravimetric methods offer high accuracy and are less susceptible to interference from some matrix components, but they are time-consuming and labor-intensive. Potential sources of error include incomplete precipitation, co-precipitation of impurities, moisture, and losses during filtration or drying. Proper method development and routine quality control are essential to obtain reliable results.

In gravimetry within geophysics, gravimeters measure the local acceleration due to gravity. Absolute gravimeters compare gravity to a standard, while relative gravimeters monitor changes over time or between locations. Applications span mineral exploration, geodesy, groundwater studies, and monitoring mass changes in natural and engineered systems.