46 Transactions of the Boyal Society of South Africa. 
different forms?" Are chemical and physical properties dependent on 
the aggregation of molecules in a substance, or are they dependent upon a 
change in the structure of the molecule itself ? 
The conceptions of O. Lehmann, which he explained fully in numerous 
works/'' are in direct contradiction to the theory that molecules do not 
change their structures whether the substance be gaseous, solid, aniso- 
tropic, or amorphous, so much so that W. Nernst denies the existence of 
liquid crystals.! 
This theory of the *' identity " of molecules, which is based on 
Avogadro's law, is forced to accept that any change in the space-lattice 
of a crystal must cause a change in the properties of the crystal such as 
melting-point, solubility, and vapour pressure. As these changes are not 
brought about by a plastic deformation of crystals it must be accepted, on 
this theory, that no change has taken place in the space-lattice of the 
crystals whether they are solid or liquid crystals. :!: Consequently the 
pseudo-isotropic structures of liquid crystals cannot exist. 
The pseudo-isotropic layers, which are obtained when the solutions are 
placed between glass plates, and which may be retained by the influence 
of a magnetic field, § when no other force affects the molecules, must have 
a space-lattice. 
D. Vorlander believed that this had been definitely proved by his 
experiments when he had examined such layers in convergent light. || His 
results, however, are also in accordance with Lehmann' s theory of liquid 
crystals. 
The object of my experiments was to determine whether these pseudo- 
isotropic solutions of crystalline substances have a space-lattice or not. 
If there be a space-lattice then they must cause interference phenomenon 
when Rontgen rays are passed through them. 
In order to find such an effect substances whose molecules could be 
influenced by a magnetic field were used. 
In this case, according to Lehmann, only the principal axis of the 
molecules has a fixed direction, viz. parallel to the lines of force, and the 
subordinate axes may lie in any direction, hence the theory of Eontgen- 
ray interference phenomenon cannot predict any definite pattern, except 
that the points on the pattern must trace out symmetrical conic sections. 
This will be the case if there is a space-lattice, according to Vorlander. 
* See 0, Lehmann, Die neue Welt der fliissigen Kristalle, Leipzig, 1911. For a full 
list see " Verzeichuis samtlicher Veroffentlichungen var Dr. Otto Lehmann," Fr. Vieweg 
und Sohn, Braunschweig. 
t W. Nernst, Theoretischen Chemie, 7th Edition, 1913, p. 666. 
+ Compare G. Tammann, Zeitsch. f. Electrochem., 1912, p. 587. 
§ 0. Lehmann, Phys. Zeitsch., 13, 550, 1912. 
II D. Vorlander, Zeitsch. f. phys. Chem., 61, 166, 1907; D. Vorlander and H. Hans- 
waldt, Acta nova, Halle, 90, 1909. 
