impurity

Ren's group, however, suspected the problem wasn't the material's intrinsic ability but the impurities within it.

Normally, nuclear reactors use purified water, which runs through a closed system to ensure that none of the water from the reactor can get out—and that no impurities can get in.

These effects are also very sensitive to impurities, strain, and external conditions, which makes them difficult to study.

He feeds her salmon and bottled water; no impurities for his girl, who has Russian and Danish lineage and is as smart as she is sweet, according to the proudest of dog owners.

Molten iron then separates from impurities and can be tapped off.