CHEMISTRY: GOMBERG AND SCHOEPFLE 
463 
equilibrium of this nature might be expected to shift in favor of dis- 
sociation with dilution, as is actually the case with these compounds. 
2. When in triphenylmethyl two phenyl groups become joined 
through an oxygen atom and thus give rise to a xanthone ring, the 
tendency of the new compound, phenyl-xanthyl, towards dissociation 
increases to a marked extent, approximately threefold. 
3. A phenyl and a ^-tolyl group are apparently equivalent in 
their influence for dissociation when linked to a xanthone ring; a 
/>-chlorphenyl group is of somewhat lesser influence, as can be seen 
on comparing the dissociation curves of the three corresponding 
aryl-xanthyls. This equality of influence of a ^-tolyl and a phenyl 
group would not necessarily have been anticipated. Tolyl-diphenyl- 
methyl differs very much from triphenylmethyl, and tri-^-tolylmethyl 
is so unstable that it is apparently impossible to isolate it, owing to 
the tendency to isomerize or polymerize. 
4. An a-naphthyl group when replacing a phenyl group in tri- 
phenylmethyl exerts upon the dissociation equilibrium of the com- 
pound a very decided influence in favor of the monomolecular phase — ■ 
a-naphthyl-diphenylmethyl appearing as wholly dissociated. This 
favorable influence of the naphthyl group is still retained when the 
group is linked to a xanthone ring, the resulting compound being also 
dissociated to the extent of 100%. And yet, when the naphthyl 
group enters as a component in the formation of the xanthone ring 
itself, it depresses very decidedly the dissociation tendency of the 
compound, as is evident on comparing the two isomers, a-naphthyl- 
xanthyl and phenyl-pheno-jS-naphtho-xanthyl. 
5. It has been established that the triarylmethyls are, in the solid 
state, almost wholly devoid of color, being, like triphenylmethyl 
itself, only pale-yellow; but their solutions differ very much, being 
yellow, orange, brown, red, or green, according to the individual 
compound. Schlenk has described tribiphenyl methyl, 100% dis- 
sociated, as a dark green powder. Whether this difference in color 
from our completely dissociable radicals is real or only apparent 
we cannot at present say. The fact that triarylmethyls, colorless 
when solid, give color only when in solution, lends support to the 
hypothesis that the triarylmethyls do undergo tautomerization when 
dissolved. Not dissociation alone into triarylmethyl, but, in addition 
thereto, the consequent tautomerization of this into its quinonoid 
of the color phenomenon. Tautomerization commonly occurs, indeed, 
constitute a satisfactory explanation 
