142 REPORTS ON THE STATE OF SCIENCE. 
I 
$0,C1 
4. 0-8552 :1706876,B=95°29. . » ~—- «182°. 
i 
I 
80,Cl 
5. 07288 : 1 2 0°6544, B=99° 42’ . 3 3 - 69°. 
a 
Br 
‘ SO,NHPh 9.9576 : 1 : 08364, B=99° 30’ ee 
; (labile form) ake EG 
Br 
The following compound crystallises in the orthorhombic system :— 
Br Melting point. 
~ ‘ 
SO,OEt 
if OH90Es 1: O6257 =. .0. ain 2 eee 
br 
The substances numbered 1, 2, and 3 form a well-defined isomorphous 
series as is immediately indicated by the close approximation of the 
axial ratios quoted. The compounds 4 and 5 differ entirely in crystalline 
character from the foregoing but the similarity of the ratio ¢/b in the 
two cases suggests an intimate morphotropic relation as existing between 
their crystalline structures. 
In a series of papers Barlow and Pope have pointed out that the 
whole space occupied by a crystalline substance can be conveniently 
regarded as parcelled out amongst the various atoms composing the 
material and have shown that this mode of treatment leads to the con- 
clusion that the volumes thus allocated to atoms of different elements 
are, in any one substance, approximately proportional to their valencies. 
A crystallme substance is thus to be regarded as a close-packed assem- 
blage of spheres of atomic influence in which each of the latter has a 
volume directly proportional to the fundamental valency of the atom 
which it contains. The close-packed assemblages referred to are geo- 
metrically partitionable into units representing individual molecular 
aggregates ; these should represent in composition, constitution and con- 
figuration, the chemical molecules of the substances concerned. 
From the study of the crystalline forms of benzene and its derivatives 
Barlow and Pope have deduced a form of assemblage for the hydrocarbon 
which is partitionable into units of the composition C;H; and have 
described the configuration of the molecule as thus derived. In the 
crystalline assemblage the carbon spheres of influence are arranged in 
columns, of which each link consists of three spheres in_ triangular con- 
tact; it has been concluded that these columns remain intact in the 
crystalline derivatives of benzene: the passage from the hydrocarbon 
to any derivative thus involves the moving apart of the columns of carbon 
