CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 
2r,3 
and t is the resultant intensity of magnetization induced in the direction of tlie 
external held. The compressibilities will now be different along and perpendicidar to 
this direction, and the change of volume should be proportional to d for the particular 
value of the applied field. This result agrees with experiment.^' 
We can see in a general way how the sign of W on crystallization may sometimes 
be positive and sometimes negative. Usually the molecular packing in the crystalline 
state will be closer than that in the liquid state, but it may happen that the 
conhguration of the molecule is such that, when the parts which have the strongest 
magnetic attraction for eacli other are in the position of minimum potential energy, 
the packing is more open than in the liquid state. The appearance of the internal 
forcive on crystallization will in this case be accompanied by expansion. In the former 
case the appearance of the internal forcive will be accompanied by contraction. 
The region of stability of the crystalline state is represented on the pressure 
temperature diagram by a closed area (fig. 2). 
av=o 
This area will in general be divided into four quadrants l)y the loci of the lines 
dV = 0 and L = 0, where W is the change of volume on crystallization and L is the 
latent heat. 
In the four quadrants the following conditions hold :— 
Quadrant. 
L. 
av. 
dp ■ 
d/- • 
1 
+ 
+ 
-1- 
_ 
2 
+ 
- 
- 
- 
3 
— 
- 
+ 
+ 
4 
— 
+ 
— 
+ 
If the melting-point is at some point along the arc AB of the first quadrant, 
increase of pressure raises the m.p. and W and L are positive. This corresponds 
* Nagaoka and Honda, ‘ Phil. Mag.,’ vol. 46, p. 268, 1898, 
VOL. CCXX.—A. 2 O 
