1922] 



on The Structure of Organic Crystals 



587 



which is nearly the width of the benzene ring. From these and 

 various other indications we build a structure such as is represented 

 in Figs. 3 and 4. It would seem that the molecules are linked 



Fig. 3. — Showing mutual relations of three naphthalene 

 molecules and parts of others. 



The unshaded circles between the two cleavage planes represent a 

 molecule as at Q (Fig. 1). The shaded represent molecules B and F 

 in the same figure. The small circles represent hydrogen atoms, but 

 their size is uncertain. 



Diameter of carbon atom = 1*50. BH = 4*92. Projection of 

 AD on the plane of the diagram = 2*50. Benzene ring consists of 

 atoms A-F only. 



together side by side more strongly than from end to end, and that 

 is why these and similar crystals cleave across the end or ft position. 

 If we examine a-naphthol in which hydrogen at the side of the 

 naphthalene molecule has been replaced by an OH group, we find 



Fig. 4.— Section of naphthalene cell perpendicular to the 

 axis of c, showing a-hydrogens connecting the molecules 

 side to side. 



that the standard cell contains four molecules, which is what we 

 should expect, for each of the four a positions must be represented. 

 When the OH group is taken from the side and put at the end, we 

 find that the cell has shrunk sideways and grown lengthways by the 

 amount we should expect to result from the addition of an oxygen 



