186 



MAGNETIC PROPERTIES OF LIQUID OXYGEN. 



wlieii placed in the Hnglies balance, produced no disturbing effect. 

 The magnetic moment of liquid oxygen is about 1,000 when the mag- 

 netic moment of iron is taken as 1,000,000. On cooling, some bodies 

 increased in magnetic power. Cotton wool, moistened with liquid 

 oxygen, was strongly attracted by the magnet, and the liquid oxygen 

 was actually sucked out of it on to the poles. A crystal of ferrous 

 sulphate, similarly cooled, stuck to one of the poles. 



The lecturer remarked that fluorine is so much like oxygen in its 

 properties that he ventured to predict that it will turn out to be a mag- 

 netic gas. 



Nitrogen liquefies at a lower temperature than oxygen, and one 

 would expect the oxygen to come down before the nitrogen when air 

 is liquefied, as stated in some text-books, but unfortunately it is not 

 true. They liquefy together. In evaporating however, the nitrogen 

 boils off before the oxygen. He poured two or three ounces of liquid 

 air into a large test tube, and a smouldering splinter of wood dipped 

 into the mouth of the tube was not re-ignited; the bulk of the nitrogen 

 was nearly five minutes in boiling off, after which a smouldering si)linter 

 dipped into the mouth of the test tube burst into flame. 



Magnetic properties of liquid oxygen. 



Between the poles of the magnet all the liquefied air went to the 

 poles; there was no separation of the oxygen and nitrogen. Liquid 

 air has the same high insulating power as liquid oxygen. The phe- 

 nomena j)resented by liquefied gases present an unlimited field for 

 investigation. At — 200° C. the molecules of oxygen had only one- 

 half of their ordinary velocity, and had lost three-fourths of their 

 energy. At such low temperatures they seemed to be drawing near 

 what might be called "the death of matter," so far as chemical action 

 was concerned; liquid oxygen, for instance, had no action upon a piece 

 of phosphorus and potassium or sodium dropped into it; and once lie 

 thought, and publicly stated, that at such temperatures all chemical 

 action ceased. That statement required some qualification, because a 

 photographic plate placed in liquid oxygen could be acted upon by 



