Isaac Newton was doing chemistry with a range of nasty heavy metals for years. A sample of his hair was analysed some time ago and found to contain significant levels of lead [1].
Boyle, Cavendish and their cohorts investigated a variety of sources and were not empiricists in the modern sense. Remember that they had e.g. no concept of yeast, bacteria, and yet saw the daily baking of bread and brewing of beer. Not surprising perhaps that they saw similar processes in the chemical realm? A flavour of the times slightly earlier can be seen in the use of astrology for medical purposes [2]
Boyle, Cavendish and their cohorts investigated a variety of sources and were not empiricists in the modern sense. Remember that they had e.g. no concept of yeast, bacteria, and yet saw the daily baking of bread and brewing of beer. Not surprising perhaps that they saw similar processes in the chemical realm? A flavour of the times slightly earlier can be seen in the use of astrology for medical purposes [2]
[1] https://web.pa.msu.edu/courses/2008spring/ISP213H/welcome/we...
[2] http://theshakespeareblog.com/2014/06/shakespeare-and-the-al...