High Quality Content by WIKIPEDIA articles! Red mercury is a 19th-century term for protiodide or iodide of mercury. It was commonly recommended for use as an antisyphilitic as late as 1913, most notably during the early years of the Tuskegee Syphilis Experiments. Taken orally, it caused hematemesis. Today, it continues to be used in some countries for skin lightening, causing some cases of nephrotic syndrome.