Chemistry. — "On Phenyl Carbaininic Acid and its Homohgues" . 

 By Prof. F. E.G. ScHEFFER. (Communicated bj Prof. Böeseken.) 



(Communicated in ttie meeting of September 29, 1918). 



1 . Introduction. 



It was observed by Dittk in 1887 that under high pressure and 

 at temperatures lower tliau room temperature aniline with carbonic 

 acid can react under formation of a solid compound which consists 

 of equal molecular quantities of aniline and carbonic acid ^). It may 

 besides be inferred from his paper that unmixing takes place at 

 ordinary temperature. Some years ago Dr. J. J. Polak carried out 

 a number of experiments with the same system of substances in the 

 organic chemical Laboratory of the Amsterdam University'); he too 

 succeeded iri ascertaining the existence of a compound, and the result 

 of his analysis pointed to the same composition as was given by 

 DiTTE. It further appeared in his researches that the compound melts 

 on being heated in the presence of a liquid and a vapour rich in 

 carbonic acid, before the meniscus liquid-vapour disappears, with 

 formation of a second liquid layer; this suggested the thought to 

 me that the system aniline-carbonic acid would present an analogy 

 in its behaviour with Bakhuis Roozkboom's gas-hydrate systems and 

 with the system sulphuretted hydrogen-water, the phenomena of 

 which I have fully described in These Proceedings '). It will appear 

 from the below-menlioued obsei'vations that the compound, which 

 in my 0[)inion is to be considered as a carbaminic acid, gives rise 

 in the P-T diagram to the appearance of a quadruple point, where 

 solid compound, two liquid layers, and gas coexist, and that the 

 three-phase lines which intersect in this quadruple point, can be 

 determined with sufficient accuracy. This system also furnishes a 

 new application of the quadruple point rule, drawn up by me in 

 1912 '), which was described by Schreinemakers in the Zeitschrift 

 fur physikalische Chemie almost at the same time '). 



1) Gompt. rend 105. 612. (1887). 



^) Not published. The results of his research have been kindly put at my disposal 

 by Dr. Polak, for which 1 gladly express my indebtedness to him here. 

 ») These Proc. 13. 829 (1910/11) and 14 195 (1911/12). 

 4) These Proc. 15 389 (1912/13). 

 6) Zeilschr. f. physik. Chem. 83. 59 (1913). 



