20 THE ABSORPTIOX SPECTRA OF SOLUTIONS. 



one form to the other, the final state being unaffected by the catalytic agent. 

 This latter condition means that the direct and reverse actions are equally 

 changed. If now intra-molecular change is the source of the absorption 

 bands, then a catalytic agent should affect the persistence of the band. Experi- 

 mental results verified these conclusions. Other compounds were tried with 

 similar results. 



From these results it follows that there must exist, in connection with 

 the reversible transformation of one tautomeric form into the other, a system 

 that is synchronous with the light absorbed. This can not be a vibration of 

 the labile atom itself, since the oscillation frequency of the absorption band- 

 does not bear any direct relation to the mass of the labile atom, and the fre- 

 quency of atomic motions is never so high as these. The absorption must be 

 due, however, to the oscillation of linking of the keto-enol tautomers: 



H 



CH = C <=> C C , or, symbolically, CH fi- 

 ll I 

 OH H O O* 



where the asterisks indicate the points where the migrations of linkages occur. 

 From a summary of work previously done on ultra-violet absorption spectra, 

 it was seen that most of the compounds showing absorption also were tau- 

 tomeric. As was also seen, an increase in the mass of the molecule in general 

 decreased the oscillation frequency of the absorbed light, although by only a 

 small amount. 



Assuming the saturnian form of atom similar to the arrangement assumed 

 by Sir J. J. Thomson, chemical bonds would simply consist of Faraday tubes 

 of force. By a rearrangement of Faraday tubes, it is quite probable that 

 a vibrational disturbance would be set up. If Hewitt's explanation of the 

 origin of fluorescence is correct, it would follow that disturbances set up by 

 isodynamic changes are of the same frequency as light waves. The lumin- 

 osity due to thermal or electric action is caused by rapid changes of stress 

 or of the electric action to which the atoms are subjected. Here the disturb- 

 ances of the electrons are due to the oscillation of linkages within the mole- 

 cule. The comparatively small displacement of the absorption band by a 

 change in the mass of the molecule is to be expected, since an increase in the 

 mass of matter near a vibrating electron has the effect of retarding its motion, 

 the oscillation frequency becoming less. For instance, the spectral series of 

 Kayser for various related elements show a displacement towards the red on 

 increasing the atomic mass. This is in general true for all emission spectra 

 and for the absorption spectra of the rare earths and organic dyes. 



The sodium and aluminium derivatives of ethyl acetacetate show the 

 enolic and ketonic modifications in dynamical equilibrium. The sodium com- 

 pound is found to be easily decomposed into sodium hydroxide and ethyl 

 acetacetate, whereas the aluminium derivatives show dissociation and hydrol- 

 ysis to only a very slight extent. The absorption spectrum is not dependent 

 on ionization or hydrolysis. Hartley has found that the ultra-violet absorp- 

 tion spectra of metallic nitrates is exhibited even on very great dilution, show- 



