Chapter Xi 167

Priestley as a man of science--His characteristics as a philosopher--Experiments and Observations on Different Kinds of Air--His discovery of the influence of vegetation on vitiated air--Atmospheric air not elementary--His researches on nitric oxide--Eudiometry--Nitrous oxide--Discovers hydrogen chloride--Prepares oxygen from nitre (1771)--Isolates ammonia gas--Discovers sulphur dioxide--Dephlogisticated air (oxygen)--Discovers silicon fluoride--Intra-diffusion of gases--Respiration--Priestley's opinions of the value of experimental science in education--Discovers nitrosulphuric acid--Notes the constancy of composition of the atmosphere--Prepares chlorine--Sound in "air"--Experiments relating to phlogiston--The seeming conversion of water into air--Watt and the compound nature of water--Discovers sulphuretted hydrogen--Priestley's confession of faith in phlogiston.

Index 225

LIST OF ILLUSTRATIONS

Joseph Priestley, from the portrait in Dr Williams' Library by Artaud (Photogravure) Frontispiece Birthplace of Priestley, from a drawing by J. A. Symington after a photograph page 5 The Pillaging of Priestley's House during the Birmingham Riots facing page 120

Joseph Priestley