CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 
123 
of heat on change of state, this could not be the case. The change of susceptibility 
cannot be ascribed to an alteration of thermal conductivity for, as will be seen later, 
the same difference has been obtained at air temperature between crystals and super¬ 
cooled liquid, each having stood long enough to take up the temperature of 
the room. 
The experiments on about twenty substances'* will now be briefly summarised, for 
the most part in the order in which they have been investigated. In one or two cases, 
substances, which are chemically closely related, have been classed together. 
The results are shown graphically in figs. 8-14. A short account of any peculiarity 
will be given and the curves will be more fully discussed later. For brevity, in what 
follows, the specific diamagnetic susceptibility will be referred to generally by the 
absolute temperature by b, and a curve showing the relation between x and 3- will be 
called a x~b- curve. 
About seventy experiments have been made and some of the substances have been 
investigated several times, using both types of phial described above (fig. 3). 
(a) A Study of Benzene Derivatives. 
For the most part, the simpler benzene derivatives have been selected, because in 
many cases their crystalline forms have been investigated and it was hoped that an 
interpretation of the results would thereby be rendered more feasible. 
Toluene. 
/\/ 
CEL 
Liquid toluene is more diamagnetic than crystalline toluene, 8x/x amounting to 
5 per cent. Two curves for this substance have been obtained and the break in the 
curve occurred in each case at —96° C. The melting point is at —92° C. (fig. 9a). 
Ortho-xylene. 
/X/CH3 
I I 
The liquid is more diamagnetic than the crystals, the change of x taking place at 
— 26° C. and c\/x = 4’8 per cent. The melting point of the crystals is at —28° C. 
(fig. 96). 
/\/ULK 
Oymene. I I '~' JLL 3. 
The curve for the phial filled with cymene was parallel to that for the empty phial 
over the interval 20° C. to —150° C. (see note under pyridine below). 
* Over thirty substances have been investigated. An account of these additional experiments will be 
given in a future paper. 
R 2 
