88 Mr Oxley, Magnetic Susceptibility with Temperature. 
groups are unstable and rapidly break up as the temperature is 
increased. Hence vy is large, and it is reasonable to expect a high 
value of the constant B. 
Another property of the constant B is that it never acquires a 
large negative value. Values of B have been obtained for solutions 
of the sulphates, chlorides and nitrates of all the ferromagnetic 
elements and the largest negative value found is 0:86 x 10~ for a 
0°79 normal solution of ferric chloride. This value is only 12°/, 
greater than the value of the diamagnetic susceptibility of pure 
water. The positive values, on the other hand, have been shown — 
to range from zero to 75 x 10° a quantity which is ten times as 
great as the numerical value of the susceptibility of water. The 
preponderance of large positive values of B is to be expected if 
the curve of fig. 1 represents the change of molecular complexity 
with change of temperature. 
Conclusion. 
In this paper and in an earlier investigation (“The Variation 
of Magnetic Susceptibility with Temperature,” Proc. Camb. Phil. 
Soc. Vol. XVI. p. 486) an attempt has been made to represent the 
variation of magnetic susceptibility with the temperature, taking 
into consideration the formation of complex aggregations of mole- 
cules and the effect such aggregations have in modifying the 
magnetic properties. It is believed that if due account be taken 
of the characteristic properties of substances, the work of du Bois 
and Honda does not prove that the foundations of the Curie- 
Langevin theory are unsound. 
Hitherto, the relation representing the variation of the 
susceptibility of solutions with the temperature has been an 
empirical one and of the simplest form—linear. Assuming the 
truth of the Curie-Langevin laws for groups of particles whose 
complexity does not vary with the temperature, the para- 
magnetism of any substance will follow a simple hyperbolic law 
Y= - and the diamagnetism will be constant as the temperature 
‘y varies. If the groups vary in complexity as the temperature 
changes, these laws will be modified in a manner depending on 
the characteristic changes of constitution possessed by the sub- 
Stance. 
For the general case of aqueous solutions, treated in the present 
paper, the rate of variation of the molecular complexity with the 
temperature has been shown to be approximately linear, The 
modified relations have been applied to represent the variation of 
the susceptibilities of solutions of ferric chloride, ferrous sulphate 
