Wrote Letter L-433 of 1705-03-03 to the members of the Royal Society about silver deposits on his own hands after he mixed gold and silver with acid and treatment of a callous on his own finger with vitriol and then acid
Text of the letter in the original Dutch and in English translation from Alle de Brieven. The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren
Leeuwenhoek wrote this letter about silver deposits on his own hands after he had experimented with mixtum (mixture of gold and silver) and aqua regia (mixture of nitric acid and hydrochloric acid). Treating a horny induration on his own third finger with vitriol and then with aqua fortis (nitric acid and sulphuric acid).
Recovering silver from little pieces of skin from L.'s own fingers, which had been blackened through contact with aqua regia. Treatment of a callous spot, which had been cut open, with vitriol and aqua fortis.