MAGNETIC PROPERTEEy OF LIQUID OXYGEN. 



185 



tube begins to fill uj) with liquid atnios|)lieric air, produced at the ordi- 

 nary barometric pressure. 



Dr. Janssen had recently been making prolonged and careful experi- 

 ments on Mont Blanc, and he found that these oxygen lines disappeared 

 more and more from the solar spectrum as he reached higher altitudes. 

 The lines at all elevations come out more strongly when the sun is low, 

 because the rays tlien have to traverse greater thicknesses of the earth's 

 atmosphere, 



Micliael Faraday's experiments made in 1849 on the action of mag- 

 netism on gases opened up a new field of investigation. The following- 

 table in which + means " magnetic " and — means " negative," sum- 

 marizes the results of Faraday's experiments. 



Mayneile relations of (jascs (Farada;/). 



Air 



Xitrogen 



Oxygen 



Carbonic acid . . . -. 



Carbonic oxide 



JTitric oxide 



Ethylene 



Ammonia 



Hj^drochloric acid 



In air. 



+ 



In carbonic In hydro- 

 acid, gen. 



+ weak. 

 — strong. 

 -|- strong. 



weak. 



+ 



-f- strong. 



— weak. 



— weak. 



— weak. 



Becquerel was before Faraday in experimenting nj)on this subject. 

 Becipierel allowed charcoal to absorb gases, and tlien examined the 

 ]>roperties of such charcoal in the magnetic field. He thus discovered 

 the magnetic properties of oxygen to be strong, even in relation to a 

 solution of ferrous chloride, as set fortli in the following table: 



Specific mar/vcfism, equal weights (Becquerel). 



Iron + 1,000,000 



Oxygen -f 377 



Ferrous chloride solution, sp. gr. 1'4334: -|- 140 



Air + 88 



Water — 3 



The lecturer took a cu]) made of rock salt and put in it some liquid 

 oxygen. The liquid did not wet rock salt, but remained in a spheroidal 

 state. The cup and its contents were placed between and a little below 

 the poles of an electro magnet. Whenever the circuit was completed 

 the liquid oxygen rose from the cup and connected the two poles, as 

 represented in the cut, which is copied from a photograph of the phe- 

 nomenon. Then it boiled away, sometimes more on one pole than the 

 other, and when the circuit was broken it fell off the pole in drops 

 back into the cup. He also showed that the magnet would draw up 

 liquid oxygen out of a tube. A test-tube containing liquid-oxygen, 



