LAVOISIER 49 



Some idea of the sco pe o f Priestley's researches may be inferred 

 from the mere catalogue of his discoveries. He is^ -credited with dis- 

 covering^ dephlogisticated air toxygen) hydrochloric acid, sulphur 

 dioxide, nitrosulphuric acid, sulphuretted hydrogen, and the isolation 

 of amonia gas. 



/^Lavoisier and His Work. — Antoine Laurent Lavoisier was born 

 in( i^ari^^in 1742^ jben years later than the date on which Priestly first 

 saw^thcr^M of day. As scientist his career was practically contem- 

 poraneous with that of Priestly, who made the same momentous 

 discovery, working independently. In 1775, a year after Priestly had 

 prepared his dephlogisticated air (oxygen), Lavoisier published his 

 paper "On the nat ure and principle which combines with metals dur- 

 ing t heir ca lcinat ionT" Irfthis paper he showed that metals on being 

 "burnt did not give up phlogiston to the air but took something from 

 the air; they on becoming metallic oxides, increased^ iiTweighT. La- 

 voisier deall-the death- blow jto the phjogiston theory and was in a 

 sense the real discover of oxygen. ~Iltl)r6ved'Ehat the principle which 

 combined with metals when calcined was the principle of acidity. He 

 says: "I shall therefore designate dephlogisticated air, air eminently 

 respirable, when in a state of combination or fixedness by the name of 

 'acidifying principle,' or, if one prefers the same meaning in a Greek 

 dress, by that of 'oxygine' principle." Lavoisier discovered oxygen 

 and gave it the name by which it will henceforth be known. He made 

 further experiments in connection with respiration which he con- 

 cluded to be "a combustion, slow it is true, but otherwise perfectly 

 similar to the combustion of charcoal." He eventually saw, however, 

 that some of the oxygen inspiredhad other use than the production 

 of carbon dioxide. 



It was not, however, until the early decades of the nineteenth 



century that the view that oxidation took place in the lungs gave 



way to the accurate theory of tissue respiration. In 1837, Gustave 



Magnus proved that both venous and arterial blood contained oxygen 



^and carbon dioxid. 



Hydrogen was discovered by Cavendish in 1781, when he also 

 discovered the composition of water. Nitrogen was discovered in 

 1772 by Rutherford. Oxygen was prepared by Priestly in 1774 and 

 recognized by Lavoisier the following year. Carbonic acid gas, or car- 

 bon dioxide was first discovered by Van Helmont in 1640 and redis- 

 covered and defined by^lack in 1757. 



7^ 



