144 Scientific Proceedings, Royal Dublin Society. 



By precipitation with water a further quantity of this substance was obtained 

 from the nitric acid, but it could not be obtained in a colourless condition. 



2. — Symmetkical Diphenylukea. 



Hantzch [Liebeg's Annal. d. Chem., 325, 244, 1903], by the action of nitrous 

 fumes on s-diphenylurea in glacial acetic acid solution, obtained nitroso-diphenyl- 

 urea as yellow needles melting with decomposition at 82° C. 



We did not obtain this substance, but got in glacial acetic acid solution 

 dinitroso-s-diphenylurea as cream-coloured prismatic needles decomposing at 

 103° C. 



By acting on s-diphenylurea in acetic acid solution with nitrogen peroxide we 

 obtained successively dinitroso-s-diphenylurea, and 4'4'-dinitro-s-diphenylurea 

 melting with decomposition at 320° G. [Struve, Eadenhauser, J. f. pr. chem (2), 

 52, 233]. This latter compound we also obtained by the condensation of two mole- 

 cules of p-nitraniline with one of urea. 



The direct nitration of s-diphenylurea has been examined by several investiga- 

 tors with varying results. 



Losanitch [Ber. d. Utsch. Chem. Ges., x, p. 690] dissolved it in cold nitric acid, 

 and warmed the solution to complete the reaction. He obtained a product melting 

 about 200° G., which, according to analysis, was a tetranitro-s-diphenylurea. An 

 alcoholic potash solution of it gave a dipotassium derivative which on boiling with 

 water gave 2-4-dinitraniline. The compound was therefore 2-4'2'-4'-tetranitro-s- 

 diphenylurea. 



Fleischer and Nemes [Ber. d. Dtsch. Chem. Ges., x, p. 1295] have also described 

 this reaction, but their results do not appear to have been reliable. 



A. a. Perkin [J. Chem. Soc, 63 (1893), p. 1068] treated the tetranitro derivative 

 obtained by Losanitch with a mixture of equal parts of nitric acid (sp. gr. 1'5) and 

 sulphuric acid, which did not dissolve it, but transformed it, on heating, into a 

 substance melting at 203° G. with decomposition. This compound, on treatment 

 with ammonia, gave 2"4'6-trinitraniline melting at 186"^ G., and was therefore 

 2'4'6'2''4''6'-hexanitro-s-diphenylurea. 



Cur tins [J.f.pr. chem. (2), 52, p. 513], working at a lower temperature, obtained a 

 result different from that of Losanitch. He nitrated s-diphenylurea in the cold, and 

 obtained a yellow substance melting at 247-270° C., evidently impure, as his 

 analysis indicated. By heating it in a sealed tube with hydrochloric acid he got 

 m-nitraniline. 



J. L. F. Eeudler [Eec. trav. chim. Pays-Bas, 33 (1913), pp. 35-84] added 

 s-diphenylurea to nitric acid (997 p.c.) at a low temperature, and obtained a 

 compound as fine yellow needles, in which decomposition began to take place at 

 150° C, and which melted at 218° G. with decomposition. This substance was a 

 tetranitro-s-diphenylurea, and when boiled with potash gave 2'4-dinitrophenol, and 

 with aqueous ammonia gave 2-4-dinitraniline. It was therefore 2'4-2'-4'-tetranitro 

 s-diphenylurea. 



Working under similar conditions, with twenty molecular parts of acid to one 

 of the urea, we obtained 2-4-2'-4'-tetranitro-s-diphenylurea using acid (sp. gr. 1-51) 

 containing some oxides of nitrogen. It was also observed that 4-4'-dinitro-s- 

 diphenylurea was formed as an intermediate product in this reaction. 



The action of nitric acid on s-diphenylurea in the presence of solvents has not 

 been previously examined. 



In glacial acetic acid and in alcoholic solution at low concentration, and with one, 



