1870.] Dr. A. W. Hofmann on the Aromatic Cyanates. 109 



the phenylurethane of the ethyl series, phenylcarbaminic ether, has been 

 carefully investigated by Messrs. Wilm and Wischin*, who obtained it by 

 the action of chlorocarbonic ether upon aniline. 



I have repeated the experiment of Messrs. Wilm and Wischin, and can 

 fully confirm their results. The body prepared in this manner is identical 

 with that which I formerly obtained. The melting-point of the substance, 

 after repeated crystallization, was found to be 51°; Messrs. Wilm and 

 Wischin gave 51 0, 5-52°. The boiling-point was about 237°, the same as 

 that found by those gentlemen. 



Messrs. Wilm and Wischin state that the phenylcarbaminic ether 

 (which they call carbanilidic ether) is volatile without decomposition. I 

 find that although the greater portion escapes decomposition when dis- 

 tilled, yet part of it splits up into phenylic cyanate and alcohol, 



C 9 H u NO a =C 7 H fl NO + C a H e O, 

 which is perfectly in accordance with what I expected from the study of 

 the half-sulphuretted phenylurethane. On distillation, the well-known 

 and familiar odour of the phenylic cyanate is immediately developed ; and, 

 in fact, Messrs. Wilm and Wischin must also have observed it ; for they 

 say of the carbanilidic ether, " the vapour of this body excites a copious 

 flow of tears, but when diffused has a faint resemblance to bitter almond- 

 oil." What Messrs. Wilm and Wischin smelt was the phenylic cyanate. 

 If the mixture of phenylic cyanate and alcohol, obtained along with a large 

 quantity of phenylurethane by the distillation of the latter, be allowed to 

 stand for twenty-four hours, the odour of the cyanate will have disap- 

 peared entirely ; the cyanate and alcohol have recombined with formation 

 of phenylurethane. 



After these results of the behaviour of phenylurethane under the influ- 

 ence of heat, there could be no doubt that phenylic cyanate would be ob- 

 tained by the employment of phosphoric anhydride. 



Experiment has fully confirmed this expectation. 



Phenylic Cyanate. — When phenylurethane is heated with anhydrous 

 phosphoric acid, a considerable quantity of a colourless liquid distils over 

 of great refractive power, having a pungent odour, and attacking the eyes 

 strongly. This liquid is phenylic cyanate, which only requires redistilla- 

 tion to be obtained pure. As in all operations in the aromatic series in 

 which phosphoric anhydride takes part, the quantity obtained is by no 

 means that required by theory, although it approaches it. 



For more than one reason I had desired to discover a method for the 

 preparation of the phenylic cyanate. I was now enabled to determine 

 more accurately the boiling-point of the body ; it is 163°. In my former 

 determination, for which only a few grammes were available, I had found 

 it to be 178°. 



The specific gravity of the phenylic cyanate at 15° is 1*092. Its vapour- 



* Ann. Chem. Pharm. vol. cxlvii. p. 157. 

 VOL. XIX. s K 



