CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 
279 
that of the line then the molecular diamagnetic susceptibility of hydrogen 
(-61-0 X 10-^) can be accounted for, and each electron orbit of radius 10cm. has a 
magnetic moment +16'3 x 10"^^, nearly equal to that of the magneton, +18'5 x 10~“ 
The atomic susceptibility of carbon in combination is sliown by Pascal to lie 
— 62 5 X 10“’, and in connexion with tlie additive law this value is consistent with the 
expelimental values of the molecular susceptibilities. The mean experimental value 
of the atomic susceptibility of diamond is — 59‘Ox 10“’."^ The mean of these values 
is -607x10-’, which is probably as accurate a value as is available at present. But 
this value is almost exactly twice that of the atomic susceptibility of hydrogen 
— 305x 10 ’. Probably therefore the atom of carbon contains two magnetons. As to 
the period of revolution we have 
M l 2 TTe}'^ 
= ^ . WV = - 
T 
where 
M = moment of orbit, 
e = electron charge in e.m.u., 
r = radius of orbit, 
T = period, 
and this implies that the period t for the carbon atom is not equal to that of the line 
Ha unless r — 10“® for the carbon atom. 
f he sum of the atomic susceptibilities of the atoms in the group CH 2 is 
-123-5 X 10-’. 
Experimentally, Pascal showed that the difference of molecular susceptibility in a 
number of compounds whose constitution differed by this group was 
-118-7x 10-’. 
The mean of these two values is —121’lxlO ’ which is probably very near the true 
value. But this is almost exactly four times the value of the atomic susceptibility of 
hj^drogen, viz., —30 5x 10-’, and in this combination, CHg, we may say that each 
hydrogen atom has one magneton and the carbon atom has two magnetons. 
An ethylene linkage, according to Pascal, lowers the diamagnetic molecular 
susceptibility of the compound by +57 x 10-’, while two or more such linkages lower 
it by +110 X 10-’. These values are respectively nearly equal to twice and four times 
the atomic susceptibility of hydrogen. 
As the additive law holds in the case of the simpler liquid hydrocarbons, it will hold 
for all the others which differ only by CH 2 groups, and therefore, taking the values of 
X into account, any member of the three homologous series 
C„. H.. 
271 + 2 ? 
a.H 
271? 
ri TT 
• -^ 271-2 
* Honda, ‘Ann. der Rhys.,’ vol. 32, p. 1044, 1910, gives -59-5x10-"; Owen, ‘Ann. der Phys..’ 
vol. 37, p. 693, 1912, giv^es -58-5x10-". 
VOL. CCXX.-A. 
2 Q 
