Ignition of Magnesium in ~orcelihn To demonstrate the presence of nitrogen in air, laboratory directions often call for the ignition of magnesium ribbon in a covered porcelain crucible. This usually produces a black stain on the porcelain that is virtually impossible to remove without ruining the glaze. To avoid this, the fallowing modification is suggested. Fold a 1 5 to 20-em strip of magnesium ribbon into 5-cm lengths. Clamp one end in a test tube holder suspended from a ring stand so that the other end hangs just over a porcelain crucible. Using a burner held in the hand ignite the magnesium carefully, hut avoid looking at the burning metal. Raise the crucible and dislodge the fragile ash into it, being careful not to lose any of the ash. If necessary, break up the ash with a stirring rod. Cover the crucible with a small watch glass having a niece of moistened red litmus on its underside. Raise the watch elass sliehtlv. add several d r o ~ of s water to the ash. and more or less uniformly, change it to blue 'Present address: 10411 Forest Ave., Fairfax, VA 22030. H. I. Feinstein' George Mason University
Fairfan, V A 22030
Volume 59
Number 2
February 1982
159
