A HARD-WORKING DIET. 343 



there is nothing to be seen, but if we raise the tern- Oxidation of 



Carbon and 



perature by applying a highly heated wire or a Hydrogen 

 light the Carbon and Hydrogen both begin to unite carbonic acid 

 with the Oxygen of the air and "burn." Hydrogen and water< 

 and Oxygen when combined form Hydrogen-Oxide or 

 "water," as mentioned before, and, if a plate or any- 

 thing cool be held over the flame, drops of water 

 can be collected. The Carbon which thus loses its 

 companion Hydrogen, and has not united with the 

 Oxygen of the air, can be collected in a solid form, 

 and, indeed, smuts and smoke are small particles of it. 

 It has travelled through the pipes, however, as a gas. 

 The Carbon which does unite with Oxygen forms car- 

 bonic acid, with which everybody may be familiar 

 (though it is a gas which cannot be seen), and a test 

 for its presence is given below. Thus from the gas there 

 is obtained by "splitting up " by heat, a solid (carbon), 

 a liquid (water), and a gas of totally different composi- ^J^j[h 

 tion (carbonic acid). This is a rough chemical analysis, analysis. 



The same results can be obtained from an oil lamp 

 where the Carbon and Hydrogen are present as fluid, 

 or from a candle where the Hydrogen and Carbon are 

 present as solid. 



The water and carbonic acid can be collected most 

 conveniently, perhaps from a candle, as the experiment 

 can be made on a table. For observing the formation 

 of the water it will be an advantage to support the 

 plate slightly tipped on one side as the drops will run 

 together, and also to keep the plate cool by putting 

 cold water in it. The fact of being able to collect solid 

 Carbon is mentioned for the sake of the illustration of 

 an element being present in a compound without its 

 being recognised till it is separated out. It can only 



