Final answer:
The arsenic compound effective for treating syphilis was called Salvarsan, discovered by Paul Ehrlich and his assistant after systematic screening.
Step-by-step explanation:
The arsenic compound that proved highly effective in treating syphilis was called Salvarsan. In the early 1900s, the German scientist Paul Ehrlich and his assistant Sahachiro Hata discovered this compound after screening over 600 arsenic-containing compounds. Marketed under the name Salvarsan, this compound garnished the title of the first real antimicrobial agent, providing a remedy for syphilis. Although today, penicillin, specifically parenteral penicillin G, is the drug of choice for treating syphilis, Salvarsan was the initial breakthrough in syphilis therapy.