CONSTITUTION AND TEMPEEATURE ON MAGNETIC SUSCEPTIBILITY. 
281 
Thus iron-carbonyl (Fe (CO)^) and nickel-carbonyl (Ni (CO)J are diamagnetic* * * § ; 
potassium ferri-cyanide is paramagnetic, while potassium ferro-cyanide is diamag¬ 
netic, t It would appear that in these cases the loss of magnetic property of the iron 
and nickel atoms is due to a transfer of valency electrons, i.e., it involves an electric 
charging up of the atoms. The behaviour of the oxygen atom in organic compounds, 
in compounds with chlorine and in metallic oxides, where it acts always as an 
electronegative element, may possibly be accounted for in the same way. Free oxygen 
and ozone are strongly paramagnetic, but no semblance of an additive nature of the 
magnetic property is found in any of the oxygen compounds. 
The appearance of strong magnetism in the Heusler alloys and its disappearance in 
manganese steels, are similar effects, dependent on the formation of intermetallic 
chemical compounds accompanied l)y an electron transfer. 
There are many paramagnetic sulistances which possess molecular magnetic 
moments comparalde with, and in some cases much superior to, those shown by ferro¬ 
magnetic substances. The apparent feeble susceptilulity they possess is due to the 
fact that, with the largest magnetic field which can be applied, we can never produce 
anything like a saturation effect. In fact, according to Weiss, the molecule of cobalt 
chloride, C 0 .CI 2 contains 25 magnetons, while an atom of cobalt below the critical 
temperature contains 9 magnetons. We may well ask ourselves—what is the nature 
of the process by which the addition of a diamagnetic substance, H.Cl to cobalt, 
produces such a large increase in the number of magnetons per molecule.^ Assuming 
the work of W eiss holds good, and there is certainly a very considerable amount of 
evidence in favour of his theory, we can interpret this result either by supposing that 
the atom of cobalt really contains more than 9 magnetons,§ or else that the 
diamagnetic acid supplies the additional magnetons when it acts on the cobalt to form 
the chloride. In either case, it seems that we must admit that a molecule may 
possess systems of magnetons which, in certain circumstances, are so arranged to 
counterbalance one another, producing no additional moment of the molecule.|| These 
magnetons would contribute nothing to the paramagnetic or ferro-magnetic property 
of a substance and could not be included in Weiss’s theory. The grouping of these 
“ latent ” magnetons, according to our extended view, would be perturbed by the 
union of the cobalt atom with the Cl ion, in a manner similar to that by which an 
external field reveals the spontaneous magnetization in iron (as interpreted on Ewing’s 
theory) by orientating groups which were formerly so-constituted as to show no 
magnetic effect externally. If this is so, then we are only justified in assuming that 
purely diamagnetic molecules contain groups of magnetons so arranged that the 
* A. E. Oxley, ‘ Proc. Camb. Phil. Soc.,’ vol. 16, p. 102, 1911. 
t J. S. Townsend, ‘ Phil. Trans. Roy. Soc.,’ A, vol. 187, p. 547, 1896. 
I The specific susceptibility of cobalt chloride is 90 x 10“®, that of hydrochloric acid -0'80 x 10“L 
§ Some of which are self-compensated. 
II I.e., of the molecule as a whole. 
2 Q 2 
