COLOR AND CHEMICAL CONSTITUTION 135 



the para-position. Now the activity of these oxygen atoms is to be 

 attributed to the residual affinity which each is known to possess, and 

 hence by the assertion of this affinity when in close proximity to each 

 other, followed quickly by a break in the same, we arrive at the condi- 

 tion known as isorropesis, upon which form of oscillation the color 

 depends. It is necessary in this process that the active groups under- 

 going isorropesis should be adjacent. The pulsations of the benzol 

 ring readily furnish the means by which the two para-atoms are suc- 

 cessively brought under the influence of each other, and hence their 

 positions will approach more nearly to that of adjacent atoms, a point 

 that was confirmed by the similarity in the absorption spectra between 

 para-benzo-quinone and compounds where the two carbonyl groups 

 were actually adjacent. The study of ortho-quinones falls in the same 

 category as the para-quinones and may be explained in a similar 

 manner. Meta-quinones, however, can exist, but momentarily on the 

 hypothesis of the benzol pulsations and hence are unstable. 



Isorropesis, as has just been indicated, occurs between adjacent 

 atoms possessing residual affinity. It is also to be remembered that 

 some disturbing force must be brought to bear upon these atoms, for 

 otherwise no make-and-break and consequently no oscillation can take 

 place. In the simplest case studied, that of diacetyl (CH 3 — CO — 

 CO — CH 3 ), the disturbing influence rests undoubtedly with the 

 hydrogen atoms of the methyl groups which from their electro-positive 

 nature exert a strong attraction for the electro-negative atoms of 

 oxygen. This constitutes a sort of keto-enol tautomerism, the presence 

 of which should certainly be accounted for in the appearance of the 

 absorption-curve; indeed, the slight extension of the absorption-curve 

 of this compound near the oscillation frequency 3,800 corresponds 

 exactly to the location of a band due to keto-enol tautomerism. The 

 cause of isorropesis in a compound rests, then, upon the disturbances 

 of the residual affinities of the two atoms in juxtaposition. In the 

 examples already cited, those of pyruvic acid and oxalic acid, the 

 hydroxyl group is next to the active carbonyl group. The slight posi- 

 tive nature of the hydrogen atom in this capacity will diminish its 

 disturbing effect upon the second oxygen atom, or that of the carbonyl 

 group, and consequently only the slightest amount of isorropesis will be 

 possible. With the alkyl ester of pyruvic acid the conditions will 

 favor a slight isorropesis, as we have seen, but with oxalic acid there 

 should be none at all. In quinones the residual affinities of the benzol 

 ring constitute the disturbing factors. The hydrogen atoms of the 

 benzol molecule may also exert some disturbance. In general, we may 

 say that the amount of isorropesis must rest upon the disturbing in- 

 fluences which can be brought to bear upon the active groups showing 

 residual affinity, or those susceptible of this new kind of oscillation. 



Isorropesis need not always be confined to residual affinities between 



