282 Mr Osaley, The Influence of Molecular Constitution 
The Influence of Molecular Constitution and Temperature on 
Magnetic Susceptibility. Preliminary Note. By A. EK. OXtey, B.A., 
Coutts Trotter Student, Trinity College. 
[Received 14 July 1913.] 
IN a former paper* the author has shown how the observed 
departure from the Curie-Langevin laws for paramagnetism and 
diamagnetism may be explained in terms of the variation of the 
nature of the molecular complexes with temperature. Later, the 
influence of such aggregations has been considered by Holmf, 
Weiss and Piccard}, and Piccard§; the last physicist showing that 
the variation of the diamagnetic susceptibility of water with the 
temperature can be interpreted as due to the presence of two 
types of complexes. The idea of the coexistence of different types 
of complexes has been satisfactorily applied to the case of aqueous 
solutions of salts of the ferromagnetic elements||. 
The present note is intended to contain a preliminary account 
of further experiments which have been made to test the effect 
of the presence of molecular complexes on the susceptibility. 
We shall denote the specific diamagnetic susceptibility by y. 
About thirty organic and several inorganic substances have 
been investigated and the variation of . with temperature has 
been examined over a range of 250°C. It is found in general { 
that there is a decrease in the value of y during the passage from 
the liquid to the crystalline state. This decrease amounts to 
5°/, (approx.) of the value of x. If the substance supercools or 
passes into a gel as the temperature is lowered there is no dis- 
continuity, but when crystallisation does take place the value of y 
is found to decrease. If the substance is now heated y remains 
constant until the normal melting point is reached but increases 
during fusion. A hysteresis loop due to temperature is thus 
obtained, similar to those which Hopkinson** discovered for the 
passage from the paramagnetic (non-crystalline) to the ferro- 
magnetic (crystalline) state in the case of nickel-steels, the critical 
temperature in the latter case corresponding to the temperature 
of fusion of the diamagnetic crystals in the former case. 
With regard to the continuity found when the substance passes 
* Proc. Camb. Phil. Soc., Vol. xvi. p. 486, Mareh 1912. 
+ Ark. for Mat., Stockholm, 8, 16, 1912. 
+ Comptes Rendus, t. 155, p. 1234. 
§ Comptes Rendus, t. 155, p. 1497. 
|| Proc. Camb. Phil. Soc., Vol. xv1t. p. 65, Dec. 1912. 
{| There are a few exceptional cases which are not discussed here. 
** Proc. Roy. Soc., Vol. xuvit. p. 1, 1890; or Hwing’s Magnetic Induction in 
Iron and other metals (third edition), p. 184 et seq. 
