28 SMITH'S INTERMEDIATE CHEMISTRY 



since wood, coal, and gas will not burn without it, and even for 

 light where oil, gas, or a candle is used. 



We wish to know with which substances it can combine, as well 

 as the substances on which it has no action. This information will 

 show us how to work, in future, without interference from the 

 oxygen in the air and whether oxygen has probably played a part 

 in some experiment or not. 



Let us take up, then, (1) the history of the element, (2) what 

 materials contain oxygen (occurrence), (3) how we can obtain it 

 in a pure state (preparation), (4) what its specific physical proper- 

 ties as a substance are, and (5) what it does, and what it cannot do 

 in nature and in the laboratory (chemical properties). The 

 classification of the facts about this, and other substances under 

 five heads, is somewhat mechanical, but has the advantage of 

 enabling the reader quickly to find any required information. 



History of Oxygen. Leonardo da Vinci (1452-1519) seems 

 to be the first European to mention the presence of two gases in 

 the air. Mayow (1669) measured the proportion of oxygen in the 

 air and discussed fully its uses in combustion, rusting, vinegar- 

 making, and respiration, but did not make a pure sample. Hales 

 (1731) made it from saltpeter, and measured the amount obtain- 

 able, but did not see any connection between it and the air! 

 Bayen (Apr., 1774) was the first to make it by heating mercuric 

 oxide. Priestley (Aug. 1, 1774) made it 

 by heating the same substance and quite 

 purposelessly, as he admits, thrust a lighted 

 candle into it and was delighted with the 

 extreme brilliance of the flame. Scheele, a 

 Swedish apothecary, had made it in 1771-2 

 from no less than seven different sub- 

 stances and understood clearly that atmos- 

 pheric oxygen combined with metals, phosphorus, hydrogen, 

 linseed oil and many other substances. Finally, Lavoisier 



