Additional Notes. 485 



in the same year. M. Lavoisier, in 1773, made known 

 this gas as a component part of atmospheric air. About the 

 same time it was procured by Scheele, and proved to be a 

 distinct fluid. Its specific gravity has been investigated and 

 determined by Kirwan and Lavoisier, the latter of whom 

 makes it 0.001 15, or to common air as 942.6 to 1000. The 

 combustibilitij of azotic gas, and the pioduction of nitric 

 acid by this process, were first discovered by Mr. Caven- 

 dish, and communicated to the Royal Society in 1785. The 

 name Azote was given to tl;is gas by the l^iench Academi- 

 cians, and is derived from its incapacity to support Hfe. 



Oxygen, p. 83. 



The gas, the base of which is commonly known by this de- 

 nomination, was discovered by Dr. Priestley, on the 1st of 

 August, 1774, and called by him dephlog'isticated ai)'. Mr. 

 Scheele, of Sweden, discovered it in 1773, without any pre- 

 vious knowledge of what Dr. Priestley had done ; and gave 

 it the name of empyreal air. Condorcet gave it first the 

 name of vital air, and M. Lavoisier afterwards gave it 

 the name of oxygen gas, which is now generally ado])ted. 



The discovery of this substance, and the investigation of 

 its properties, deserve to be ranked among the most important 

 events recorded in the history of chemistry. The explana- 

 tion which they have afforded to the principles of combus- 

 tion, respiration, acidity, &:c. place their value in a most 

 interesting point of light. To this discovery, and these in- 

 vestigations, we may trace the commencement of that grand 

 revolution in chemical science, which was triumphantly con- 

 firmed by the discoveiy of the composition of water in 1781, 

 though not presented to the world in a complete and systema- 

 tic form until 1787. 



Paracelsus believed that there was only one acid princi- 

 ple in nature, which communicated taste and solubility to the 

 bodies in which it was combined. Becher embraced the 

 same opinion, and added to it, that this acid principle was a 

 compound of earth and water, which he considered as two 

 elements. Stahl adopted the theory of Becher, and en- 

 deavoured to prove tiiat the acid principle Is sulphuric acid, 

 of wliich, according to him, all the other acids are mere 

 compounds; but his proofs were only conjectures or vague 

 experiments, from which nojthing could be deduced. Neverrr 



