A science historian and an art historian team up to produce this excellent illustrated essay on Alchemy and how it was the beginning of modern chemistry.

From page 3: "In 1600, chymists knew of just seven metals - gold, silver, iron, copper, tin, lead, and mercury ... All have some properties in common: they all are shiny, and they all (except for the liquid metal mercury) can be hammered, shaped, and cast. This commonality of properties implied to early thinkers a commonality of composition, and thus it was theorized that all the metals were composed of the same essential ingredients in different proportions and degrees of purity. The Arabic writers of the Middle Ages, who laid the foundations of chymistry, cited two hypothetical ingredients and named them "Mercury" and "Sulphur." This so-called Mercury and Sulphur combined underground naturally to produce metals. If there is too much Mercury - the fluid principle - then tin and lead - the two most easily melted metals - result. If there is too much Sulphur - the dry, inflammable principle - then iron and copper - the two hardest metals and the two that will burn most easily in air - will be formed. Only when very pure Mercury and Sulphur combine thoroughly in just the right proportion will gold be the product. Given this theory of the generation of metals, turning one metal into another was a simple (in theory) matter of learning by what means to purify and adjust the proportions of Mercury and Sulphur in a given metal."

https://maryoverton.wikispaces.com/The+Distracted+Driver