CH. XXVII. MODERN CHEMISTRY. 



CHAPTER XXVII. 



SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED). 



Birth of Modem Chemistry — Discovery of * Fixed Air,' or Carbonic 

 Acid, by Black and Bergmann — Working out of * Chemical 

 Affinity ' by Bergmann — He tests Mineral Waters, and proves 



* Fixed Air ' to be an Acid — Discovery of Hydrogen by Cavendish 

 — He Investigates the Composition of Water — Oxygen discovered by 

 Priestley and Scheele — Priestley's Experiments — He fails to see the 

 true bearing of his Discovery — His Political Troubles and Death 

 — Nitrogen described by Dr. Rutherford — Lavoisier lays the 

 Foundation of Modem Chemistry — He destroys the Theory of 



* Phlogiston ' by proving that Combustion and Respiration take up a 

 Gas out of the Air — Discovers the Composition of Carbonic Acid 

 and the nature of the Diamond — French School of Chemistry — 

 Death of Lavoisier. 



During the last half of the eighteenth century, while Hunter 

 and Linnaeus were adding to our knowledge of living beings, 

 and Werner and Hutton were reading the history of the 

 crust of the earth, a little group of men in England, France, 

 and Sweden were making discoveries which entirely altered 

 the science of chemistry. These men were Bergmann and 

 Scheele in Sweden ; Black, Cavendish, and Priestley in Eng- 

 land ; and Lavoisier in France. 



In order to understand what their discoveries were, and 

 what they taught us, it is necessary to bear in mind that up 

 to this time chemists had believed fire, air, and water to be 

 simple substances which could not be decomposed or split 

 up into any other kind of matter. Mayow, indeed, had 



