148 Scientific Proceedings, Royal Dublin Society. 



An analysis of this substance gave the following result : — 



0*1680 g. of the substance gave 31-3 of moist nitrogen at 17° C, and 756 mm., 

 corresponding to N 21-50. 

 (JuHsOsNe required N 21-43. 

 The compound vs^as, therefore, 2-4-2'-4'-tetrauitro-s-diphenylurea, as described 

 by Eeudler. 



D.— ACTION OF NITROUS ACID ON SYMMETRICAL DIPHENTLUREA. 



(a) One molecular part of sodium nitrite dissolved in the least quantity of 

 water was added, a little at a time, and with constant shaking, to 2 g. of 3-diphenyl- 

 nrea in 100 g. of glacial acetic acid. The mixture was allowed to remain at the 

 temperature of the room for three days, when the liquid had assumed a deep 

 green tint. All the urea was, however, recovered unchanged. 



(b) Two molecular parts of sodium nitrite dissolved in the least quantity of 

 water were added, a little at a time, and with constant shaking, to 2 g. of glacial 

 acetic acid. All the urea dissolved, and a cream-coloured substance separated and 

 remained in suspension throughout the solution. After continued shaking for an 

 hour it was added to water, when more of the substance separated as needles. It 

 decomposed at 100°-103°C. Crystallised from ether it decomposed at 103° C, 

 and a mixture of it with dinitroso-s-diphenylurea also melted at the same 

 temperature. The substance was, therefore, dinitroso-s-diphenylurea. 



(c) Dinitroso-s-diphenylurea was also obtained by the action of four and six 

 molecular parts of nitrous acid on s-diphenylurea in acetic acid solution. 



^.—ACTION OF NITRIC ACID ON DINITROSO-S-DIPHENYLUREA. 



(a) To ten molecular parts of nitric acid, cooled in salt and ice, 1 g. of 

 dinitroso-s-diphenylurea was added in small quantities. It dissolved easily, 

 giving a red solution. This was allowed to remain overnight at the temperature 

 of the room. By adding to much water, and crystallising from acetone the 

 precipitate thus obtained, 2-2-2'-4'-tetranitro-s-diphenylurea was got. The yield 

 was theoretical. 



(5) One, two, four, and six molecular parts of nitric acid were added respec- 

 tively to four solutions, each containing 2'5 g. of dinitroso-s-diphenylurea in 

 100 g. of glacial acetic acid. On the addition of the nitric acid the undissolved 

 nitroso compound went into solution in every case, and later a precipitate began 

 to separate. 



The bottles were allowed to remain at the room temperature for two months. 

 A large quantity of substance had separated in every case. This was found to 

 consist mainly of 4-4'-dinitro-s-diphenylurea. 



3. — ASYMMETKICAL DiPHENYLUEEA. 



Michler [Ber. d. Dtsch. Chem. Ges., ix, 715] obtained asymmetrical diphenyl- 

 urea by heating diphenylurea chloride in a sealed tube with alcoholic ammonia at 

 100° C. 



We found, however, that the reaction 



(C6H5)2N . CO . CI + 2NH3 = (CgHs)^ . N . CO . NH^ + NH.Cl 



proceeded in the cold, though somewhat slowly. In boiling spirit solution the 

 reaction went easily, and by passing ammonia into a hot solution of the chloride 

 the urea was readily formed. 



