Yes. The most practical check is a fixer clearing test.

Mix a small amount of the powder in water, then drop in a small clipped piece of undeveloped film leader. If the film clears and becomes transparent, the solution is fixer. If it stays opaque, it is not fixer and is likely the developer.

A second clue is pH: many developers are alkaline, so red or purple litmus paper will turn blue in developer solution. Fixer generally will not show that alkaline reaction.

Smell may help, but it’s less reliable than testing. Avoid inhaling chemical dust directly. Mix only a small test batch, handle it carefully, and discard it safely if you’re still unsure.