82 Mr Piirvis and Miss Homer, The absorption spect7'a of 



The absorption spectra of solid tetramethylpicene and of its 

 solutions. By J. E. Purvis, M.A., St John's College, and Miss A. 

 Homer, Fellow of Newnham Colleg-e. 



[Bead 8 February 1909.] 



From the products of the action of aluminium chloride on 

 naphthalene investigated by one of us (Homer, Trans. Chem. Soc. 

 1907, vol. xci. p. 1103) there was isolated a new hydrocarbon whose 

 empirical formula was CosHno. It was suggested that this sub- 

 stance was an alkyl derivative, probably tetramethyl, of dinaphth- 

 anthracene, CooHi^. 



In a later paper by the present authors (Homer and Purvis, 

 T7'ans. Chem. Soc. 1908, vol. xciii, p. 1319), it was thought that 

 further evidence as to the constitution of this hydrocarbon might 

 be obtained from a comparative study of the absorption spectra of 

 its solutions with the spectra of solutions of the supposed parent 

 substance, dinaphthanthracene, and of picene the isomeride of 

 dinaphthanthracene. Benzene solutions of these hydrocarbons 

 were compared because picene and dinaphthanthracene are practi- 

 cally insoluble in alcohol. As a result of the investigation it 

 was found that the absorption curve of the hydrocarbon CseHgs 

 exhibited the same type of curve as picene, and therefore the 

 substance was considered to be an alkyl derivative of picene. 



Some comparative experiments were conducted about the same 

 time, both with solutions in alcohol and in benzene, with the 

 solid and with the vapour of the hydrocarbon CogHos. With 

 regard to the solutions, A7IOOO solutions in benzene and in alcohol 

 were taken and the absorption curves plotted in the same way 

 as is described in the previous paper {loc. cit.). The solid 

 hydrocarbon CobH^ liquefies at 49 — 50° C, so that it was quite 

 easy to melt a little of the substance on microscopic glass cover- 

 slips, by which a ver}^ thin layer was uniformly spread over the 

 surface of the glass : the layer was quite translucent. The glass 

 was then clamped before the slit of a spectroscope and the light of 

 a Nernst lamp, of an iron arc, and of a condensed iron spark were 

 used as the sources of light. Photographs were taken of the 



