Ryan & 0' Toole — Action of Oxides, ^c, on the Phenylureas. 147 



parts of nitric acid. After allowing the bottles to remain at the temperature of 

 the room for two months their contents were examined : — 



(1) The bottle to which one molecular part of nitric acid had been added con- 

 tained a red solution, with a yellow solid in suspension. From the solution a trace 

 of red oil was obtained, and from the solid, by extraction with hot alcohol, some of the 

 unchanged urea was obtained. After repeated extraction with hot alcohol a 

 yellow substance remained. This after crystallisation from nitro-benzene decom- 

 posed at 320° C, and was 4-4'-dinitro-s-diphenylurea, a mixture of it with this 

 substance melting at the same temperature. 



The alcoholic extract gave a reddish-brown substance melting at 140°-170 C, 

 from which no pure substance was isolated. 



(2) The bottle containing two molecular amounts of nitric acid gave a red 

 solution and a greenish-yellow solid. The former yielded only a little red oil. 

 As in the previous case, 'i'4'-dinitro-s-diphenylurea was obtained from the solid 

 by thoroughly extracting it with alcohol. From the alcoholic extract a yellowish- 

 brown substance was obtained, from which no crystallising substance could 

 be got. 



(3) The bottle which contained four molecular parts of nitric acid gave a red 

 solution and a greenish-yellow solid. The solution v^as filtered from the solid, 

 and gave, on shaking with barium carbonate, filtering, and evaporating to dryness, 

 a small quantity of red oil. The solid was well extracted with alcohol, and a 

 substance, which was found to be 4'4'-dinitro-s-diphenylurea, remained. From 

 the red oil obtained from the carbon tetrachloride solution, and also from the 

 brown substance contained in the alcoholic extracts, a compound, crystallising 

 in yellow needles, and melting with decomposition at 212° C, was obtained 

 by fractional crystallisation from alcohol. This substance was probably 4-nitro-s- 

 diphenylurea. 



(4) The bottle to which six molecular amounts of nitric acid had been added 

 contained a red sohition and a brown solid. The former, on filtering from the 

 solid, was shaken with barium carbonate, filtered, and evaporated to dryness. 

 It yielded only a trace of a red oil, from which no crystalline product was 

 obtained. 



By extracting the solid with alcohol as before, 4-4'-dinitro-s-diphenylurea was 

 left. From the alcohol extract, using acetone as solvent, a small quantity of 2'4'2''4'- 

 tetranitro-s-diphenylurea was obtained. From this also a small quantity of a 

 substance was obtained, using a mixture of carbon tetrachloride and chloroform 

 as solvent. This substance melted at 212° C, and was probably 4-nitro-s- 

 diphenylurea. 



II. — In the Absence of Solvents. 



s-Diphenylurea (5 g.) was added slowly to twenty molecular parts of nitric 

 acid cooled in salt and ice. At first the urea dissolved easily, giving a red solution. 

 Later on, however, a precipitate formed after each addition of the urea, and this 

 dissolved with increasing difficulty towards the end of the operation. When all 

 the urea had been added, a considerable quantity of the precipitate was present. 

 Some of it was removed, and was found to possess all the properties of 4'4'- 

 dinitro-s-diphenylurea. On standing overnight all the precipitate dissolved, 

 giving a deep red solution, from which, by precipitation with water and crystal- 

 lisation from acetone, yellow needles were obtained. These began to decompose 

 about 150° C, and melted with decomposition at 218° C. 



