How was syphilis treated in the 1700 and 1800?

Answer 1

From the Journal of Military and Veteran's Health:

Gerhard van Swieten (1700-1772), an Austrian army surgeon, introduced the internal use of corrosive sublimate, mercuric chloride, or liquor Swietenii, which stayed in use as treatment for syphilis for many years, and Guido Bacelli in 1894 developed it as an injection. [11] In the late 19th century, calomel, mercurous chloride, a purgative and laxative, was used as an inunction and in tablet form and later as an injection. Ammoniated and salicylated Mercury ointments were developed and the pharmaceutical formulae for unguentum hydrargyri ammoniateand unguentum hydrargyri salicilate were still in the Australian Pharmaceutical Formulary in 1955. Mercury stayed in favour as treatment for syphilis until 1910 when Ehrlich discovered the anti-syphilitic effects of arsenic and developed Salvarsan, popularly called the “magic bullet”.