Japanese doctors in the eighteenth and nineteenth centuries made use of a number of toxic mercury chloride compounds for the treatment of syphilis. Some of these compounds were produced using Chinese methods that had been known in Japan for more than a thousand years, but others were produced using newer methods that had been introduced more recently from China or Europe, and they were known by a bewildering variety of names of Chinese or European origin depending on the methods by which they were produced and the circumstances in which they were employed. There was considerable confusion about which of these compounds were distinct and which should be considered as mutually equivalent, and about the extent to which different methods of production yielded different levels of therapeutic efficacy or toxicity. European methods for the production of mercury chloride compounds became widely known in Japan only towards the end of the eighteenth century, prior to which the compounds produced by these methods could be obtained only through trade. However, as Japanese doctors began to show a growing interest in European medicine in the late eighteenth century they also began to familiarize themselves with these methods of production and to make direct comparisons between the compounds produced by Chinese and European methods.

This talk will compare production methods for mercury chloride compounds in early modern Europe, China and Japan, showing how the ability of Japanese doctors and patients to make use of these compounds depended on global trading networks for raw materials and finished drug products. It will show how the tendency to maintain secrecy surrounding the production of these compounds was gradually disrupted by an increasing willingness to publicize their knowledge about production methods, and examine how this increasingly open circulation of knowledge helped transform the ways people thought about these compounds and used them for treating syphilis and other diseases.