122 
ME. A. E. OXLEY ON THE INFLUENCE OF MOLECULAR 
subtracting the ordinates, we get the values of d — d x at different temperatures. 
These, in conjunction with the value of d 2 —d x for water at air temperature, give the 
specific susceptibility* of nitrobenzene at different temperatures. The two curves in 
fig. 8 show how the specific susceptibility of nitrobenzene varies with temperature ; 
curve (a) for phial of type (a), curve (b) for phial of type (b). 
5-0 
4-5 
40 
As the crystals were very gradually melted by heat conducted through the walls of 
the phial, no effect due to latent heat would be expected to enter. Moreover, if the 
crystals were taking heat from the phial faster than it was supplied by the surrounding 
enclosure, the temperature of the phial would be colder than that indicated by the 
thermometer. The phial could not get hotter than the enclosure unless the latent 
heat were negative. The only way in which latent heat might affect the observations, 
therefore, is by cooling the phial below the temperature indicated by the thermometer. 
But this effect would increase the deflection due to the glass and accordingly reduce 
that due to the diamagnetic substance contained in it. This result would make any 
correction due to latent heat of opposite sign to the difference actually found. A good 
test of the absence of any error due to this cause is obtained by showing that the 
change of susceptibility is permanent. If the effect were due to absorption or emission 
Curve a x and © , Curve b. o 
o 
X 
I —©e- 
-i-1-r- 
G O —& -©£ 
-o-GE>— 
160 140 120 100 80 60 40 20 
20 40 60 80 
- Temperature (°C) 
FI G. 8 
* The calculation is as follows :— 
d 2 for O - 75 gr. water = 80 scale divisions. 
do-di = 80 + 28 = 108 scale divisions; d — d x = 76 + 28 = 104 scale divisions. 
M = 2"273 - 1 - 223 = 1-050 gr.; m w = O'75 gr.; density of nitrobenzene = 1-22. 
Using equation (y), we find 
1 
1-050 
0-2o x 1-OuO _ |7.25 x o-75 + O-25 x 0-75}^ 
1 * 22 108 
10~" = - 4 - 98 x 10~ 7 . 
Also 
3 X = _L_ 10• 253V a - 7 ' 5 * a °' 75 . 8(d-d x )\. 10- 7 . 
1-050 
108 
At the fusion-point 
Hence 
3V a A 0'08; S(d-di) =13 scale divisions. 
3 xlx A 12 per cent. 
