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A LECTURE ROOM PERIODIC TABLE' FREDERIC B. DUTTON Michigan State College, East Lansing, Michigan
T o SATISFY a desire for a lecture room periodic table the rear and passing a tape carrying the desired numbers which would be visible to all students in the room, which next to the glass. The tape is passed from one spool to would permit focusing attention on a desired item, and another by rotating the drive spool with a selsyn motor yet would not be so complex as to be distracting, there which is controlled by a similar motor on the control has been erected in the lecture room of the Kedzie panel. The idler spool is operated by a counter weight. Chemical Laboratory a t Michigan State College the Motor driven tapes are behind the four openings to the right. The three openings a t the left carry the fixed periodic table shown above. The data for the table are painted on ground glass numhers 2, 8, 18 painted on the glass and are used only mounted in front of a network of metal boxes housing when elements in the fifth period and higher are being 71/%-wattlight bulbs. The titles, period numhers, and discussed, i.e., when more than four numbers are r e group numbers are illuminated when a master switch is quired to express the electronic configuration, in which closed. By closing individual switches on a control case the first three electronic levels are full. The table is supported from tweby-fours bolted to panel a t the lecture table the symbols for each element the wall and carrying a S/rinch plywood back. A may be illuminated. The electronic configuration for any element under heavy 16-gage galvanized iron channel forms the outer discussion can be indicated in the seven squares shown periphery. It is 5l/# inches deep with the front side 1 in the open space above Cr, Mn, Fe, and Co in the inch wide a t the sides and bottom and l1/2 inches wide table. This is done by illuminating- the openings from a t the top. This permits the glass sections to be raised 'Presented a t the 118th meeting of the American Chemical and swung out a t the bottom for removal. The plywood back was covered with sheet aluminum and the netSociety in Chicago, September, 1950.
FEBRUARY, 1951
the lecture table. The selsyn motors were driven through a transformer. They are rated a t 110 volts, 400 cycles but operate satisfactorily a t 16 volts on 60 cycles. They are the war surplus Model 2JDlJl. The selsyn motors are manufactured by General Electric and others.
Lecture Table Control Boord
work of boxes, which are 6l/2 X 91/2 inches each, constructed of 22 gage galvanized iron strips running vertically. The horizontal dividers were of the same material and were fastened in place with sheet metal screws after a hole was punched in the center of the rear edge for a rubber grommet, through which the electrical connections were made. The depth of the boxes was 58/18 inches and was calculated so that there would be just room for the a/ls-inch glass to rest against the boxes a t the back side and be retained in place by the channel frame in front, thus holding the glass in place. The glass was cut in s t r i ~ s .each striv carrsine: two of elements with one narrower strip a t the left for the period numbers. The 7'/2-watt light bulbs were mounted in standard cleat receptacles in the center of the boxes and similarly spaced for the titles. The bulbs were dipped in Christmas tree lamp lacquer that had been thinned and tinted by mixing the various colors available. Each group was assigned a different ~ o l o r .A ~ thin layer of glass wool was placed in each box over the light bulbs to increase the diffusion of the light and minimize bright spots. The lettering was painted in reverse on the smooth side of the glass and the frosted side was exposed to avoid reflections. The space over the 7 squares for the electronic configuration was lacquered to make it transparent. All lamp sockets were wired with one side in common. All socket terminals were brought to a connector strip a t the top of each group, from which a multiwire cable led to the control panel on A
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Kodachmme slides of the table and control panel are available from the writer on loan
sELrv~ i SELSYN *2 ON aNTROL PANEL Wiring Diagram
ACKNOWLEDGMENT
Grateful acknowledgment for assistance is due to many members of the staff and particularly to Drs. Byerrum, McCarty, Pitha, Stone, and Schuetz, who took many evenings away from their families and their research to help build the assembly.
Motors and Tape Mechanism
