Step 1: Understanding the Concept.
Gravimetric analysis finds the amount of a substance purely from the mass of a solid it forms, unlike titrimetric methods that rely on measuring volumes and spotting an endpoint colour change.
Step 2: Key Approach.
List out the standard sequence of a gravimetric procedure and check which of the four given options does not belong in that sequence.
Step 3: Detailed Explanation.
A gravimetric procedure typically runs through precipitation of the analyte, digestion to grow larger and purer crystals, filtration and washing to isolate the solid, then drying or igniting it before a final weighing.
Precipitation, digestion, and filtration all appear directly in that sequence and are needed to obtain an accurate, weighable precipitate.
An indicator, by contrast, is a tool for spotting a colour-change endpoint in a titration, a completely different analytical technique that measures volume of titrant rather than mass of precipitate.
Since gravimetric analysis never needs a visual endpoint, an indicator plays no part in it.
Step 4: Final Answer.
The step not involved in gravimetric analysis is the use of an indicator.