BAIRD &TATLOCK: (LONDON) LTD. 



3559 3559 



3559 s Models for Illustrating Atomic Theory, designed by Professor Collie. Set consisting 

 of one stand, one cube, six tetrahedra, six supports, twelve hooks, and six bands 



2 10 



i 



Fig. i 

 3560 



Fig. 2 3560 Fig. 3 



3560 s A Benzene Model, on one plane, for lecture purposes, by Professor W. R. Lang, University 



of Toronto . . . . . . - - each 15 



The Model is intended as an aid to explaining the theory of the constitution of benzene, based on the following 

 characteristics : 



Each hydrogen atom bearing the same relation to the molecule. 



The formation of benzene as a constant product of the decomposition of other members of the aromatic 



series. 

 The formation of hexa-additive compounds and the ready breaking up of these into a tri-substitution 



product. 



The formation of three isomeric di-substitution products. 

 The evident " saturated " nature of benzene. 



It would be impossible to reconcile these reactions and properties with the carbon and hydrogen atoms 

 arranged as in an open chain. 



Fig. i of the model shows this : the body is evidently unsaturated. Fig. 2 illustrates that the only way in 



which the similarity of the linking of all the carbon atoms can be possible is to have the last one linked to the first. 



The fourth valence of the carbons may be shown as in the Armstrong-Bayer formula as acting towards 



the centre, or the diagonally opposite atoms may be linked together (Claus). If this be done in the model, then 



an exceedingly stable molecule will be represented. Fig. 3. 



CROSS STREET HATTOTST GARDETST, E- C 



663 



