A L'LIVING" PERIODIC CHART OF THE ELEMENTS*
A modern revision of the Mendeldeff periodic chart has been duplicated in the form of a large display cabinet for the elements and their ions. Plateglass sheleres form the horizontal lines between the different series of the chart. A small glass bottle containing a sample of each element sits in its proper cornpartment so that the cabinet appears as a wall chart plus a n actual sample of the element. Samples of sixty-fiere of the ninety-two elements are now i n the cabinet. The cabinet also contains solutions of the salts of the elements showing the characteristic colors of the ions. We have designed a large periodic chart display cabinet which may prove of interest to chemistry departments in other colleges and universities.
ELEMENTS
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The accompanying photograph will show that the cabinet is a reproduction of a revised Mendeleeff chart of the elements, but a brief description of it will clarify some ?f the points about the cabinet and some of the ideas we had in building it.
* Presented at the Virginia Academy of Science at its meeting at Hollins College. April 2 S 2 3 , 1932.
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By outside measurements the cabinet is 165 cm. by 200 cm. with a depth of 10.5 cm. A copy of the periodic chart was painted in black by a local sign painter on a white enameled back prepared by the cabinet maker before the cabinet was built onto it. Plate glass shelves mark the horizontal lines between the series of elements and a sliding plate glass door protects the materials of the cabinet. The framework of the cabinet is wood with mahogany finish. The section allotted to each element is sufficiently large to accommodate several bottles on the shelf ,of each "compartment" without hiding from view the number, the symbol, or atomic weight of the element. The samples of the elements are in 30-gram glass-stoppered bottles or in sealed tubes in these bottles. At the present time there are samples of sixty-five of the ninety-two elements in the cabinet. Samples-of solutions of salts of the elements in which the elements occur alone in either the positive or negative radical of the compound sit in &gram glass-stoppered bottles beside the bottles containing the elements. The student can, therefore, see the colors of the ions of the elements as well as the free elements when studying the periodic chart. Since the accompanying photograph was taken a set of blank radium tubes, and solutions of several salts have been added to the cabinet. The set of radium tubes consists of the following: a glass tube filled with phosphorescent zinc sulfide which is an exact replica of a twenty-five milligram radium tube, a screw-cap silver protective tube, a screw-cap brass screen tube into which the silver tu$e fits, and a lead storage cylinder for the whole which has a wall one cm. thick. One of the special features of the display is the arrangement of the samples of five of the rare gases of the earth's atmosphere, or the zero group of elements. These gases are in partially evacuated tubes made by a local neon sign company spelling the symbol of each of these elements and are electrically connected so that the colors produced by an electric discharge through the tubes may be seen. Incidentally, we find that these tubes accompanied by a small direct vision spectroscope give a most convenient method of demonstrating bright-line spectra to large groups of elementary students. Allotropic modifications of carbon, phosphorus, and those of sulfur sufficiently stable to remain a t room temperature for a few days are in the cabinet. Rhombic sulfur is, however, the only one of the last-mentioned which we shall attempt to keep permanently in the cabinet. It is hoped that allotropic forms of other elements can be put into tfie cabinet a t some time in the future. In order to increase the value of this display as a tool for study a large chart giving some of the uses of the free elements has been prepared by (Continued on page 1810)
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cost in nnts
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the general chemistry class to hang a t one side of the cabinet. In design this chart is a smaller copy of the periodic table with some of the uses of the free elements listed in the rectangular block devoted to each element. This "living" chart of the elements is proving to be not only a beautiful display, but also a valuable instrument of study. When convenient to do so students are studying this "chart" rather than the ones in their texts or the ones in the lecture room or laboratories. Students and friends have contributed samples of some of the elements to the cabinet, which has greatly increased the interest and pride of the students in the work. In fact, the author does not know of any equipment in the department which has stimulated as much interest in the work of the department as this project has created.
. . . . . Note: The author will appreciate information which will lead to the location o f any o f the "missing elements" or allotropic modifications o f the elements at reasonable prices.
