LN2 demos: pewter bell and spring, color change tube, LN2 cannon.

Liquid Nitrogen Demos:Lead bell & spring, color change tube, liquid N2 cannon. The lead (solder) spring, after immersion in liquid nitrogen, is quite springy. The cooled lead bell rings when tapped. The glass tube filled with red mercury iodide turns bright yellow when cooled. Cooled flowers become brittle, and break when dropped. An air-filled balloon shrivels to small size when cooled, and expands when warmed up. Liquid nitrogen poured into the cannon evaporates and shoots the cork. LIQUIFICATION OF A GAS.