" It also included an experiment where he focused the sun's rays on mercuric oxide to produce a substance he referred to as dephlogisticated air.
This scientist created a forerunner of a eudiometer, using a pneumatic trough to test the "goodness" of air.  While in Calne, this scientist published Experiments and Observations on Different Kinds of Air, a work which further debunked the classical idea of the four elements and reported on substances like "alkaline air." It also included an experiment where he focused the sun's rays on mercuric oxide to produce a substance he referred to as dephlogisticated air. For 10 points, name this 18th century British chemist known for his discovery of elemental oxygen
This scientist created a forerunner of a eudiometer, using a pneumatic trough to test the "goodness" of air.  
Joseph {Priestley}