might be cited are > C = C <; = CO; > C = NH,— N =; — N = O; = C = S, etc, A bathochrome introduced into an organic compound causes the absorption band to become wider. An auxochrome causes the intensity of the absorption to be greater.
Baly and many others have supported the view that the absorption of many organic compounds is due to a change in the valency linking of a compound. This dynamic isomerism is known to take place in many chemical compounds in the presence of a catalytic agent or at high temperatures. Take the case of acetylacetone and ethyl acetoacetate. The absorption in this case may be due to a reaction changing the ketonic (1) into the enolic (2) form and some experimental evidence favors this view.
From the above brief account of our knowledge concerning the nature of the absorption and emission centers of light and heat radiations it will be noted that many advances have been made toward the solution of this problem in recent years. The existence of "electron" atmospheres in many solids, liquids and gases has explained the emission and absorption of spectra that are ordinarily described as continuous; the existence of negative electrons serves to explain many phenomena such as those of the Zeeman effect, etc.; models containing elementary magnets arranged in various ways have been used by Ritz to explain the series classification of spectrum lines; the various phenomena of ionization are being found to be intimately correlated with the phenomena of light emission and much evidence is being accumulated to show that light and heat centers may ultimately be identified as consisting of certain kinds of ions; a very large amount of experimental data has been accumulated concerning absorption spectra of solutions of organic and inorganic compounds and the centers of this absorption seem to consist in certain "aggregates," "chromophores," etc., which can be studied from other points of view; much evidence is found to point to the view that light and heat centers depend upon certain dynamic conditions and are not stable systems such as we usually conceive atoms and molecules to be.