OXYGEN. 143 



for reasons not well understood, the admixture of this 

 or any other infusible powder, facilitates the evolution 

 of this gas from the chlorate. At a red heat, part of 

 the double portion of oxygen which the black oxide 

 contains is expelled in a gaseous form. 



332. A SIMPLER METHOD. The above 



Give a, simpler 



method of pre- method, for preparing oxygen, is here 



paring oxygen ^^ becauge it iU ustrates t he mode of 



collection of gases in large 

 quantities, and makes its 

 accumulation visible to the 

 eye. The oxygen needed 

 for the following experi- 

 ments will be more con- 

 veniently prepared by pla- 

 cing the mouth of the test-tube, containing the proper 

 materials, in a wide-mouthed vial, and heating, as be- 

 fore. As the gas is evolved, it will expel the air, and 

 soon fill the vial. 



333. IRON BURNED IN OXYGEN. Make 



How cm iron 



be burned in a coil of very fine iron wire, by winding 

 the latter around a pencil ; fasten one end 

 into the middle of a cork, by slitting the lat- 

 ter, and attach a fine splinter to the other end. 

 Light the splinter, and introduce it into a vial 

 of oxygen. The wire itself will take fire, 

 and burn with brilliant scintillations. In this 

 and the following experiments, the cork is to 

 be placed loosely over the mouth of the vial, to pre- 

 vent its violent expulsion by the heated gas. 



