Our online medical glossary of medical terms and definitions includes definitions for terms related to treatment, and general medicine
BLACKWASH
1. A lotion made by mixingcalomel and lime water.
2. A wash that blackens, as opposed to whitewash; hence, figuratively, calumny. "To remove as far as he can the modern layers of black wash, and allow the man himself, fair or foul, be seen." (C. Kingsley)
Source: Websters Vocabulary