An Easily Constructed Trigonal Prism Model Shuklchl Yamana Faculty of General Education. Kinki University, Kowakae, Higashi Osaka 577, Japan
A model of a trigonal prism which is useful for teaching stereochemistry (especially of the neodymium enneahydrate ion, Nd(OH2)93+,' can be made easily hy using a sealed, empty envelope. T h e steps are illustrated i n t h e figure a n d given below.
marked as G , and that of the second vertical line and the base AB i s marked art H. ~
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7) The lower part of the emelope is folded upat I),so that the line UH falls just on the left-hand side of the envelope. The puint correipmding to H is marked as I .
8) The luwer part c,f the envelope ia unfolded. 9) The lower part uf the envelope is folded up, so that the point D falls on I. 10) The points corresponding to the H, B , G , and C on the obverse are marked as H', B', G', and C', respectively. 11) The lower part of the envelope is unfolded. 12) The envelope is folded both backward and forward along the lines IC', DC, and G'G. 13) The upper part of the envelope is cut off along the zigzag course IH'G'B' composed of the three lines IH', H'G', and G'B'. 14) The lower part of the envelope is cut off along the zigzag course DHGB com~osedof the three lines DH. HG. and GB. 16) The rnrre&nding poiots on the reverap'of [he H',G',H, and G , are marked asH'., ti", I / ' , and C'. rerpectrvely. 16) 'Ruo regular triangles on the front, H'IG' and DHG are marked as a, and bl, respectively, 17) Two regular triangles on the reverse, H'*Gr*I and G*H*D, are marked as a3 and bs, resoeetivelv. 18) f w o reguiar triangles on both sides, G'B'Gr* and GBG*, are marked as oa and bz, respectively. I I 19) The left- and right-hand sides of the envelope are pushed toeether so that the thee linen I I ( I b , G'G, and Gf*G*)form a I I trigonsl prism. A H E B 20) Faces marked with a Letter of the alphabet are brought together and stacked in the order given by their numerab to produce a face of the trigonalprism. Thus, the facesol. Q, and a3 are piled on each other in numerical order so that the face having the largest numeral, as, is outside and the others ol and az are folded inside. 21) In step 20, the G' is overlaid with the H'*,and they are fixed with tape to construct the top of the trigonal prism. A H E B 22) Similar procedures are applied to the other regular triangles , and bs. marked with b ~bz, This causes the overlap of the G and H * , which are fixed with tape to construct the bottom of the trigonal prism.
1) The envelope is folded down the center lengthwise. 2) The lower part of the envelope is folded up so that the comer B falls on the center line. The new corner on the right-hand side of the envelope is marked as C . 3) A horizontal line CD, perpendicular to the right-hand side of the envelope a t C , is drawn, and the intersection of the line CD and the base AB is marked as E. The corresponding point on the obverse of the envelope is marked as F. 4) The lower part of the envelope is unfolded. 5) Two vertical lines, perpendicular to the base AB, are drawn, so that one of them passes the point E and the other p a w the point F. 6) The intersection of the first vertical line and the line CD is
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blmholz. L.. J. Amer. Chem. SOC..61. 1544 (1939). Volume 61
Number 12
December 1984
1055
