A Jig for Making Styrofoam Molecular Models The availability of inexpensive styrofoam spheres hay been a great stimulus to the constntction of molecular models. An inexpensive method of quickly and accurately producing holes in these s ~ h e r e is s essential if full use is during the last fifteen years. to be made of this material. Many devices have been described in THIS JOURNAL H., J. CHEM.EDUC., 34,99(1957)). Some are excellent but rather expensive to build (GIBE,T . R. P., JR., AND BOSSOW, Others require considerable time if many spheres are to he used. Far a elass of 200 or more students we have found 6in., 4-in., and 3-in. spheres with 12-in. dowels as bonds very suitable for discussions of small molecules. On the other hand n model of a fat with Zin. and 1-in. spheres gives a structure several feet long. With s. few scraps of wood, a couple of rods, and common shop tools a jig can be constructed which will handle spheres of a variety of sizes and allow holes to he produced in a sphere in but a few seconds. As indicated in the sketch two vertical brass rods, A, serve as; a guide for s slide, f3, which carries a "V" with the point st the Lop, C. A similar "V" is mounted a t right angles on the base with the point down, D. Holes are drilled perpendicular to the sides of the upper and lower "V" throogh which the punch passes. When a. sphere is placed in the bottom "V" and the slide lowered the sphere is accurately centered. A few details of construction may be of help. We happened to find hexagonal brass rod about 2 em in diameter which served well for the guides. The base and slide as well as the two "Vns were made of oak. The guide rods were about 45 cm long and were placed 20 cm apart. The two "T"s are attached by means of screws making them easy to remove for new holes or to replace with other goides for octahedral holes. For tetrahedral holes i t is convenient to make the interior angle 70" 32' in order that the guide hales can be drilled a t right angles to the surface of the wood. Since spheres of various diameters are likely to be used a series of holes is needed The horizontal distance between these hales is 0.814 of the diameter of the sphere. We have found it convenient to use '/,-in. wood dowel for the punches and for the bonds between atoms. The punch can he sharpened with pencil sharpener and a smooth hole produced using a rotary motion. The dowels used for bonds can have their sharp corners removed with the aid of a drill press and sandpaper. C. R. CONARD H. E. BENT UNIVERSITY OF MISSOURI 65201 COLUMBIA,
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Journal of Chemical Educafion
