A system of physical chemistry - Index of

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A system of physical chemistry - Index of

APPENDIX III 20 1

symmetrical gyroscope. Owing to this lack of symmetry more complex

relations are to be expected. In the case of an asymmetric gyroscope

with three different moments of inertia, we find in place of the regular

precession of the figure-axis describing a circular path on a surface, the

more complicated form of the general Poinsot vibration. Such movement

possesses three degrees of freedom as the molecular heat of water

vapour requires. In the case of the water molecule the electrons do

not all revolve in the same plane. These new modes of motion and

interaction may be expected to give rise to a number of .bands so that

the spectrum of water vapour would be expected on these grounds to

be complex. There is a further point. The measurements of Rubens

and Hettner have shown that the bands are fairly broad. This is not

easy to reconcile with the Bjerrum rotation theory. The breadth of the

bands is attributed by Kriiger to certain of the molecules which possess

a value for the angle ^ which is far from the mean value.

If we consider the difficulties which surround the application of the

quantum theory to rotation frequencies, it would appear that precessional

movement with complex vibrational form is the more plausible hypothesis.

Possibly an intensive examination of the dependence upon

with a com-

temperature of the wave-lengths of rotation bands, together

plete discussion of the form of vibration of the water molecule, might

serve to decide between the two views.

is,

Tlie Quantity

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