CHEMICAL HISTORY OF A CANDLE 167 



could take the oxygen from the hydrogen. Now, suppose we 

 do something of the same kind here with this carbonic acid. 

 You know carbonic acid to be a heavy gas: I will not test 

 it with lime-water, as that will interfere with our subsequent 

 experiments, but I think the heaviness of the gas and the 

 power of extinguishing flame will be sufficient for our pur- 

 pose. I introduce a flame into the gas, and you will see 

 whether it will be put out. You see the light is extinguished. 

 Indeed, the gas may, perhaps, put out phosphorus, which 

 you know has a pretty strong combustion. Here is a piece 

 of phosphorus heated to a high degree. I introduce it into 

 gas, and you observe the light is put out, but it will take 

 fire again in the air, because there it re-enters into combus- 

 tion. Now let me take a piece of potassium, a substance 

 which even at common temperatures can act upon carbonic 

 acid, though not sufficiently for our present purpose, be- 

 cause it soon gets covered with a protecting coat ; but if we 

 warm it up to the burning point in air, as we have a fair 

 right to do, and as we have done with phosphorus, you will 

 see that it can burn in carbonic acid; and if it burns, it 

 will burn by taking oxygen, so that you will see what is left 

 behind. I am going, then, to burn this potassium in the 

 carbonic acid, as a proof of the existence of oxygen in the 

 carbonic acid. [In the preliminary process of heating the 

 potassium exploded.] Sometimes we get an awkward piece 

 of potassium that explodes, or something like it, when it 

 burns. I will take another piece, and now that it is heated 

 I introduce it into the jar, and you perceive that it burns in 

 the carbonic acid not so well as in the air, because the 

 carbonic acid contains the oxygen combined; but it does 

 burn, and takes away the oxygen. If I now put this potas- 

 sium into water, I find that besides the potash formed 

 (which you need not trouble about) there is a quantity of 

 carbon produced. I have here made the experiment in a 

 very rough way, but I assure you that if I were to make it 

 carefully, devoting a day to it instead of five minutes, we 

 should get all the proper amount of charcoal left in the 

 spoon, or in the place where the potassium was burned, so 

 that there could be no doubt as to the result. Here, then, 

 is the carbon obtained from the carbonic acid, as a common 



