ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 153 



The absorption curves for the ketonic and enolic forms are shown in 

 the diagram on p. 156. 



When the solution of the a-ester was allowed to stand, and photo- 

 graphs were taken after successive intervals of time, the transition from 

 the enolic to the ketonic form could be clearly traced. After an interval 

 of only three hours, the absorption band of the enolic ester had almost 

 entirely disappeared, ichilst the amount of general absorption had also 

 appreciably diminished. Solutions containing 1 milligram-mol. in 100 

 and 500 c.c. respectively showed after forty-eight hours a great diminution 

 in the amount of the general absorption, whilst after three weeks the 

 curve coincided almost exactly with that of the /3- and y-esters, as shown 

 on p. 155. 



The result of this investigation exemplifies the value of the spectro- 

 graphic method, and shows how it might be applied with advantage 

 to the investigation of similar cases of isomerism either to guide the 

 chemical investigation or to confirm the conclusions drawn from it, 

 especially when any doubt exists as to whether the isomerism is due 

 to a diSerence in constitution or merely to a difference in the arrange- 

 ment of the atoms in space. The amount of substance required for the 

 experiments is small, and can generally be recovered again from the solu- 

 tion. 



The esters were prepared by the method described by Knorr.' 

 The preparation of the /3- and y-esters offers no difficulty : the 

 a-ester is only obtained when strict attention is paid to all the details 

 given by Knorr. Two distinct preparations of each of the ketonic 

 esters and three preparations of the a-ester were made. Each prepara- 

 tion was photographed several times without any difference being ob- 

 served in the photographs of the same substance. In the case of the 

 o-ester the photographs were taken immediately after the completion 

 of the preparation, as the change to the ketonic form sets in almost at 

 once. 



II. A Study of the Absorption Spectra of o-Oxycarbanil and its 



Alkyl Derivatives.^ 



The substance o-oxycarbanil, C7H5O.2N, and its alkyl derivatives form 

 a group of compounds which stand in the same relation to one another as 

 isatin, carbostyril, and their respective alkyl derivatives. 



o-Oxycarbanil can be prepared by the fusion of o-aminophenol hydro- 

 chloride with urea, or from its lactim ether by the action of concentrated 

 hydrochloric acid."* It can also be obtained by the distillation of o-amino- 

 phenyl ethyl carbonate."* Two ethyl derivatives of o-oxycarbanil are 

 known. One of these is prepared by boiling o-oxycarbanil for some time 

 under a reflux condenser with equivalent quantities of ethyl iodide and 

 alcoholic potash, the other by the interaction of o-aminophenol and ethyl 

 iminocarbonate. The ether obtained by the first method is considered 

 to be a lactam, that is, to have the ethyl group directly attached 

 to the nitrogen atom, because on heating for some time with hydrochloric 

 acid it takes up water and decomposes into carbon dioxide and the hydro- 



' Log. cit. 



^ Hartley, Dobbie, and Paliatseas, Trans. Chem. Soc, vol. Ixxvii. 



» Sandmeyer, £er., 1886, 19, 2650. * Bender, £er., 1886, 19, 269. 



