A Simple, Effective Demonstration of Magnetic Properties of Materials With the importance of magnetic properties in the arguments associated with the development of bonding theory a t the introductory chemistry level, effect.ive demonr+,rations of diamagnetism and paramagnetism are needed. Demonstrations such as the ones found in "Tested Ilemonstrations in Chemistry," compiled and edited by H. N. Alyea snd F. B. Dutt,on and ihe instructor's manuals to accompany the numerous texts written by Seinko and Plane, either involve a waiting period or are difficult to project for a. large class. A simple modification of the demonstration suggested by Seinka and Plane greatly enhances the sensitivity and, therefore, allows one to illustrate diamagnetism. In addition, it requires only a magnet of a few kilogauss st,rength. The other materials are not critical and are available in any laboratory. The important modification is the manner in which the tube is bung from the support,ing rod. mrl.allge lnr "11paratus a s shown in the photograph by hanging the test tube wit,h string or thread. Allow the test tube l o w m c ii,mst in the position shown. Cellophane tape with adhesive on both sides may be used to attach t,he string tr, the rod and this technique facilitates orienting the test tube. The string is wrapped over the tape and is easily twisted an the surface of the tape. The effect of the maenetic field on substances in the tube is easilv demonstrated. The maenet is hroueht close to
the demonstration tolsrge classes. Both solid and solution samples of the salts of transition metals may be used. The apeed with which the field attracts samples of very different numbers of mispaired electrons is quite apparent, e.g., solid N:S0,,7H20 and MnSOI.7H~0. Liquid oqygen and liquid nibrogen may be put in a simple cryostat and measured. An adequate rrvostat, mav be made bv insertine a .$-in. test tube into a &in. t,est tube with a sliehtlv lamer inside diameter. Since Science Foundation, College of Science Improvement. Program.
568 / journal o f Chemical Educafion
