Does the mere introduction of ill-gotten money – even a small amount – into lawful money make it all unlawful?

The inclusion of some ill-gotten money into a lawful earning makes it mixed money, comprising both lawful and unlawful components. Its owner is obligated to extract the unlawful money and return it to its rightful owner or his heir. If the owner is unknown, or if returning it to him is impossible, then he must give it away in charity on their behalf.