Paramagnetism and color of liquid oxygen: A lecture demonstration

Abstract

When liquid nitrogen is poured between the poles of a powerful magnet, the liquid is not held in the pole gap. When liquid oxygen is poured between the poles of the magnet, some of the liquid is held in the pole gap until the liquid evaporates. This demonstration also displays the characteristic blue color of liquid oxygen. MaterialsLiquid nitrogen (5-8 1) 02 gas (cylinder with pressure regulator) 2 Dewar flasks (11 capacity) Large test tube (38 mm o.d. X 300 mm long) Ring stand and clamp to hold the large test tube Rubber tubing (7-8 mm o.d. X 30 cm long); 2 pieces Glass tubing (7-8 mm o.d. X 30 cm long) Glove (to protect hand from cold) Permanent magnet Copper coil Unsilvered Dewar, 250-ml capacity (optional) 250 ml beaker cigarette (optional) Several types of magnets may be suitable for this demonstration. The permanent magnet used at the University of Wisconsin-Madison is a "Horn Gap" magnet with an original field strength of 1.8 kilogauss. Conical pole pieces machined

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