1 40 Scientific Proceedings, Royal Dublin Society. 



In alcoholic solution neither phenylurea nor s-diphenylurea was nitrated. 



All the ureas reacted with nitric acid at low concentrations in carbon 

 tetrachloride suspension. s-Diphenylurea and triphenylurea nitrated easily. The 

 former gave mono-, di-, and tetranitro derivatives, and the latter di-, tri-, and 

 pentanitro derivatives. Phenylurea gave phenylurea nitrate as well as p-nitro- 

 phenylurea and 2-4-dinitro-phenyl-nitro-urea. as-Diphenylurea, however, did not 

 react with one or two molecular amounts of nitric acid, and with four and six gave 

 products from which no pure compound was obtained. Phenylurea was unique in 

 being nitrated in the amino group. 



The direct action of nitric acid on these ureas was also examined. Phenylurea 

 and s-diphenylurea yielded a tri- and a tetranitro derivative respectively, whereas 

 as-diphenylurea and triphenylurea gave as a decomposition product 2-4-2''4'- 

 tetranitro-diphenylamine. 



The nitric acid used in this investigation contained oxides of nitrogen, and its 

 specific gravity was 1'51. 



1. — Phenylurea. 



The action of the oxyacids of nitrogen on phenylurea has been incidentally 

 examined in some previous work. 



Walther and Wlodkowaki [Journ. f. pr. ch. (2), 59, p. 282], by the action of 

 nitrous acid on phenylurea in glacial acetic acid solution, obtained nitroso-phenylurea 

 as light yellow needles, melting with decomposition at 95° C, and in a similar 

 experiment we obtained the same result. 



J. L. F. lleudler [Rec. trav. chim. Pays-Bas, 33 (1913), pp. 35-84] examined 

 the direct action of nitric acid, both alone and in the presence of sulphuric acid, on 

 phenylurea and ortho- and paranitro-phenylurea. He obtained in every case a 

 compound which decomposed at 142° C, with formation of a red sublimate, and 

 melted at 154°-157°C. with decomposition. When heated with water it was 

 decomposed, giving 2-4 dinitrauiline. With alcohol it formed 2'4-dinitro-phenyl- 

 urethane, aird when treated with ammonia in ethereal suspension at 0° C. for three 

 and a half hours it was converted into 2'4-dinitro-phenylurea. He regarded the 

 substance therefore as 2'4-dinitro-phenyl-nitrourea. 



Reudler nitrated the phenylurea at low temperature with twelve molecular 

 amounts of nitric acid, and obtained the above-mentioned compound by precipita- 

 tion with water and subsequent crystallisation from acetone, using 99 '7 per cent, 

 nitric acid free from nitrous acid. 



Working under the same conditions, but using nitric acid (sp. gr. 1'51) 

 containing some nitrous acid, we got a separation of a colourless substance in 

 prisms melting at 164° C. (uncorr.) with decomposition. By boiling with acetone 

 it assumed a yellow colouration, and crystallised as needles, the melting point being 

 lowered. It contained a percentage of nitrogen corresponding to a trinitro 

 derivative of phenylurea. Boiled with water it gave 2'4-dinitraniline, and, treated 

 in hot ethereal suspension with ammonia for a quarter of an hour, it gave 2-4- 

 dinitro-phenylurea. The original substance was therefore 2'4-dinitro-phenyl-nitro- 

 urea. The yellow colour and somewhat low melting point of this substance as 

 prepared by Eeudler was probably due to a slight decomposition of the body by 

 the hot acetone. 



The action of nitric acid on phenylurea in the presence of solvents has not 

 been previously examined, When dissolved in acetic acid or alcohol, and on allow- 

 ing to remain at room temperature for two months, phenylurea at 5 per cent. 



