LECTURE V 



OXYGEN PRESENT IN THE AIR NATURE OF THE 

 ATMOSPHERE ITS PROPERTIES OTHER 

 PRODUCTS FROM THE CANDLE CARBONIC 

 ACID ITS PROPERTIES 



WE have now seen that we can produce hydrogen 

 and oxygen from the water that we obtained from 

 the candle. Hydrogen, you know, comes from the 

 candle, and oxygen, you believe, comes from the air. But 

 then you have a right to ask me, " How is it that the air 

 and the oxygen do not equally well burn the candle ? " If 

 you remember what happened when I put a jar of oxygen 

 over a piece of candle, you recollect there was a very dif- 

 ferent kind of combustion to that which took place in the 

 air. Now why is this? It is a very important question, and 

 one I shall endeavor to make you understand ; it relates most 

 intimately to the nature of the atmosphere, and is most 

 important to us. 



We have several tests for oxygen besides the mere burn- 

 ing of bodies; you have seen a candle burnt in oxygen or 

 in the air; you have seen phosphorus burnt in the air or in 

 oxygen, and you have seen iron filings burnt in oxygen. 

 But we have other tests besides these, and I am about to 

 refer to one or two of them for the purpose of carrying 

 your conviction and your experience farther. Here we have 

 a vessel of oxygen. I will show its presence to you: if I 

 take a little spark and put it into that oxygen, you know by 

 the experience you gained the last time we met what will 

 happen if I put that spark into the jar, it will tell you 

 whether we have oxygen here or not. Yes! We have 

 proved it by combustion; and now here is another test for 

 oxygen, which is a very curious and useful one. I havt 

 here two jars full of gas, with a plate between them to 



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