Does impurity cease upon the mere disappearance of its physical substance, even if its trace remains? And what is the most preponderant opinion on this matter?

The removal of the substance of the impurity and its traces (color or odor) is a condition for achieving purity. However, if the removal of the traces becomes difficult and arduous, then it is excused, and purity is decreed. This is the view of the majority of jurists.