He developed ideas on the attractive and repulsive forces involved in chemical affinity, which later had influence on his successors William Cullen and Joseph Black. He compounded "Plummer's pills", a mixture of calomel and antimony sulfide with guaiacum; the pills were originally compounded to treat psoriasis but were used for more than a century as an antisyphilitic.
He developed concepts about attractive and repulsive forces in chemical affinity, which later influenced his successors William Cullen and Joseph Black. He created "Plummer's pills," a mixture of calomel and antimony sulfide with guaiacum; these pills were initially intended for psoriasis treatment but were used as an antisyphilitic remedy for over a century.