What is the principal use of gravimetric analysis?

Gravimetric analysis is primarily concerned with the measurement of mass, which is fundamental to quantifying the amount of an analyte in a sample. In this technique, a specific substance is isolated and converted to a stable, pure solid form, often a precipitate. The mass of this precipitate is then accurately measured to determine the content of the analyte in the original sample.

This method is highly precise because it relies on the concept that mass is a conserved quantity and can be measured with great accuracy using analytical balances. The solid precipitate represents the analyte or a derivative of it, allowing chemists to calculate the proportion of the target substance present based on the stoichiometry of the reaction involved in forming the precipitate.

In contrast, the other choices do not relate directly to the primary function of gravimetric analysis. For example, determining pH levels pertains to acidity or basicity rather than mass measurement. Measuring temperature changes is related to thermodynamic investigations rather than a direct measurement of mass. Identifying color changes in solutions is associated with qualitative analytical methods, not the quantitative aspect that gravimetric analysis emphasizes. Thus, measuring the mass of solid precipitates is the correct and principal use of gravimetric analysis.