A system of physical chemistry - Index of

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A system of physical chemistry - Index of

APPENDIX III.

Kruger's Theory of Gyroscopic Molecules.

[This appendix represents the substance of two papers by F. Kriiger,

Annalen Fhysik, [iv.], 50, 346; ibid., 61, 450 (19 16), on "The vibra-

tions of free gyroscopic molecules," and on " Molecular precessional

vibrations and specific heat."]

Maxwell pointed out that a magnet must behave as a gyroscope if

the ampere molecular stream (the origin of magnetisation) be of a

material nature, and he carried out an experiment to decide this point

with an electromagnet, without, however, finding the expected result.

The electron theory has referred the ampere (magnetic) current to^

rotating electrons. But the electrons possess mass, and therefore their

circulatory motion gives to the molecule containing them a certainangular

momentum. O. W. Richardson {Phys. Rev., 26, 248, 1908)

showed in the case of a freely hanging magnetised iron wire that, owing

to the angular momentum N of the molecules, a torsion must manifest

itself, although he was unable at first to obtain a definite result owing

to experimental difficulties. Recently Einstein and J. W. de Haas

{Verh. d. D. phys. Ges., 17, 152, 203 (1915)) have succeeded in giving,

an exact calculation of the torsion which the wire should experience, and

have also succeeded in overcoming the great experimental difficulties.

They have in fact employed their method to calculate the ratio of the

charge to the mass of an electron. Further, S. J. Barnett {Phys. Rev.

[ii.], 6, 239 (1915)) has shown that magnetic effects can be produced inan

iron wire by rapid rotation of the wire. Also Maxwell's originalexperiment

has been taken up again by W. J. de Haas and by G. L. de

Haas and Lorentz {Proc. K. Akad. Wetenschap., 24, 398 (19 15)), whO'

have shown that the effect can scarcely be expected to be experimentally

detectable. The gyroscopic characteristics and properties of the atoms

of metallic iron due to the existence of molecular currents, i.e. the

rotations of electrons in the atoms, can now be considered to be

definitely demonstrated.

In addition to magnetic investigations there have sprung into existence

in the last few years certain optical theories in connection with the

laws of line spectra which have rendered very probable the existence of

rotating electrons even in the case of those molecules whose magnetic

character is by no means pronounced. Such electron planetary systems

have formed the basis of the atomic models of Rutherford and ol

Nicholson. Based on such, Bohr has constructed a model atom by

VOL. III. 193 13

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