During Wollaston's researches into the purification of platinum by dissolution of native platinum ore in aqua regia, a large amount of insoluble black powder remained as a byproduct of this operation. While Wollaston concentrated on the soluble portion, Tennant examined the insoluble residue. In the summer of 1803, Tennant identified two new elements, iridium and osmium. This was documented in the paper he read to the Royal Society in 1804 (31)