TRANSACTIONS OF SECTION B. 481 
a carboxyl group. For if a salt be prepared the resulting ions are of a lighter 
colour, or even colourless. 
Ionisation produces a redistribution of the partial valencies in such a manner 
that the chromophore becomes attached to the benzene nucleus with fewer 
valencies, and is therefore weakened as regards its colour-producing properties, 
The electrically charged valencies of the ions behave as free valencies, and like 
these are used for the saturation of other valencies. There is therefore a very 
close connection between chemical lines of force and electrical lines of force, the 
former being a consequence of the divisibility of valency and the latter of the 
electrical charge of the ions. 
(v) Valency. By Dr. F. M. JAucur. 
(vi) Note on the Intimate Structure of Crystals, 
By Professor W. J. Sottas, Se.D., PLS. 
In attempting to arrive at a knowledge of the intimate structures of crystals 
it is essential to examine the validity of two assumptions which form the basis of 
certain proposed systems: one of these is the principle of closest packing, the other 
the notion of valency volumes. In some few cases closest packing might be re- 
garded as highly probable; as,for instance, in that of the diamond; but such minerals, 
and particularly the diamond, were distinguished by exceptional properties, not the 
least remarkable of which is an unusually high surface tension, a peculiarity taken 
advantage of on the automatic separation of the diamond from its less valuable 
associates in the South African mines. The second assumption introduces us to an 
absolutely new conception, the truth of which is not self-evident but open to 
question. 
In studies of this kind, where the constructive imagination necessarily plays 
a great and dangerous part, it is essential in the case of any structural system 
which might be proposed to show in the first place that it is not opposed by 
irreconcilable exceptions. This is the first step ; the next, quite as essential, is to 
prove that no other system is capable of affording equally satisfactory results. As 
an example of an inconsistent fact, silver iodide may be cited, for the sudden 
passage of this salt from the hexagonal to the cubic system is accompanied by con- 
traction in volume amounting to 16 per cent. Closest packing will not account 
for this, since the shear which is invoked to explain the transformation leaves the 
assemblage as close packed after the transformation as it was before. On the other 
hand, an open packed configuration consistent with the crystalline symmetry of the 
salt may be conceived, and has indeed been described, which involves of necessity 
a change of volume similar in amount to that observed. If this configuration 
should be supported by subsequent inquiry it would be sufficient of itself to destroy 
the universality of the two assumptions of closest packing and valency volumes, for 
it cai on the opposed conceptions of molecular volumes and a remarkably open 
packing. 
As regards the structure of benzene many configurations could be devised to 
represent the single molecule, and before accepting any one of these it would be 
necessary to show that none of the others afforded equally satisfactory results. 
It is not a substance favourable for testing the truth of the notion of valency 
volumes, for it is possible that in this and most organic compounds carbon does 
indeed possess a molecular volume approximately four times as large as that of 
hydrogen. The real difficulty in this case arises when other monovalent elements 
are substituted for hydrogen; thus on the valency-volume hypothesis it is necessary 
to suppose in the case of CBr, that the volume of bromine on entering into com- 
bination diminishes from 20 to about 6, while that of carbon increases from 12 to 
about 24, and this although three of the bonds of each atom of carbon are united 
with carbon and only one with bromine. The difliculty becomes greater when com- 
pounds like C,H,Br, and C,H,Br, are taken into consideration, The moleculai 
1907. II 
