Which set of procedures correctly describes the official USP gravimetric methods?

Which set of procedures correctly describes the official USP gravimetric methods?

• A. I, III, and IV
• B. II, III, and IV
• C. I, II, and IV
• D. I, II, and III

Answer: (A)

Gravimetric analysis hinges on obtaining a solid product whose mass directly reflects the amount of analyte, then weighing that solid after proper isolation. In the official USP gravimetric methods, you form a stable precipitate of known composition, collect it by filtration, wash it thoroughly to remove impurities, and dry (or ignite) it to a constant mass before weighing. This sequence—producing a definite solid, isolating it cleanly, and weighing the final mass—translates the measured weight into the quantity of the target substance via stoichiometry. Any step that stays in solution, relies on a color change, or uses a non-weight-based measurement would not fit gravimetric principle. Therefore, the correct combination is the one that includes making the solid, filtering and washing, and drying/ignition with weighing.

Gravimetric analysis hinges on obtaining a solid product whose mass directly reflects the amount of analyte, then weighing that solid after proper isolation. In the official USP gravimetric methods, you form a stable precipitate of known composition, collect it by filtration, wash it thoroughly to remove impurities, and dry (or ignite) it to a constant mass before weighing. This sequence—producing a definite solid, isolating it cleanly, and weighing the final mass—translates the measured weight into the quantity of the target substance via stoichiometry. Any step that stays in solution, relies on a color change, or uses a non-weight-based measurement would not fit gravimetric principle. Therefore, the correct combination is the one that includes making the solid, filtering and washing, and drying/ignition with weighing.