Tyndall beam which we use, but we have been able to determine its rate of coagulation with Mr.Green's condensation apparatus."Likewise, the electrification produced upon the disruption of materials and surfaces is well known.7

By ERNST FISCHER and (MRs.) YAEL F. FREI.4-Phenylazo-l-naphthol (I) exists in solution as an equilibrium mixture with its tautomer, a-naphthaquinone phenylhydrazone (11). On cooling, this equilibrium shifts towards the latter (in methylcyclohexane) or towards the former (in alcohol). The alcoholic solution a t -140" contains practically only the former (I), which on irradiation with light a t various wavelengths is photoequilibrated with its cis-isomer, in analogy with other azo-compounds.Between -135" and -90" the unstable cis-isomer is thermally converted into the stable trans-isomer via the phenylhydrazone. Each step has an activation energy of about 11 kcal./mole, as compared with about 23 kcal./mole for the normal cis + trans conversion. No direct photoconversion involving the hydrazone seems to take place. Similar results were obtained with solutions in tetrahydrofuran-methyltetrahydrofuran. KUHN and B A E R ~were the first to point out that 4-phenylazo-l-naphthol (I) exists in solution as a tautomeric equilibrium mixture with the phenylhydrazone (11). Their results were confirmed and extended by several authors2One would expect tautomer (I) to exist in a cis-and a trans-form (Ia and b) in analogy with azobenzeneJ3 the a~onaphthalenes,~ and 4-hydro~yazobenzene,~*~ but attempts to achieve such isomerisations have hitherto been ~nsuccessful.~

No abstract

No abstract