Concept:
Salvarsan is an arsenic-containing antimicrobial drug historically used for treatment of syphilis.
Step 1: Identify arsenic-containing drug.
Salvarsan contains arsenic in its structure.
Step 2: Historical use.
It was used as an antimicrobial agent, especially against syphilis.
Step 3: Conclusion.
Therefore, the correct answer is Salvarsan.