OF ARTS AND SCIENCES. 3 



convenient proportions : 20 grm. of tribromdinitrobenzol, 16 grm. of 

 raalonic ester dissolved in 100 to 150 c.c. of absolute alcohol and 

 treated with 2.4 grm. of sodium as sodic ethylate. It was not neces- 

 sary to add the ester gradually, and there was no perceptible evolution 

 of heat during the reaction. The mixture was allowed to stand in a 

 corked flask at ordinary temperatures for three or more hours, and 

 the dark blood-red liquid thus obtained filtered from the precipitate 

 of sodic bromide, which had been deposited, acidified with dilute sul- 

 phuric acid, which changed the dark red color to pale yellow, and 

 filtered once more to remove the sodic sulphate formed. The filtrate 

 was then distilled on the water bath until most of the ether had passed 

 over, when the residue in the flask deposited, as it cooled, crystals of 

 the new substance mixed with a large quantity of unaltered tribrom- 

 dinitrobenzol. The mother liquor from these crystals was allowed to 

 evaporate spontaneously, and left a red or yellow oil mixed with a 

 small additional quantity of the crystals, which were separated from 

 it, and the oil allowed to stand in an, open dish for some weeks, when 

 it deposited an additional quantity of the crystals. The crystals, 

 whether obtained by cooling the hot alcoholic solution, or from the 

 oil by long standing in the cold, were purified by dissolving them in 

 a little hot alcohol, and adding a moderately strong aqueous solution of 

 sodic hydrate (the common laboratory solution diluted with its own 

 volume of water), which converted the new substance into its soluble 

 sodium salt, but left the tribromdinitrobenzol unaltered, the red solu- 

 tion was then poured into a large quantity of water, and the tribrom- 

 dinitrobenzol removed by filtration. If the solid crystals were treated 

 directly with the aqueous solution of sodic hydrate, the tribromdinitro- 

 benzol was left in a form which clogged the filter very badly, whereas 

 when an alcoholic solution was used, as directed above, no difficulty 

 was encountered in the filtration. The red filtrate was acidified with 

 dilute sulphuric acid, and the precipitate purified by crystallization 

 from hot alcohol until it showed the constant melting point 75°-76°. 

 After being dried in vacuo, its composition was determined by the 

 following analyses. 



I. 0.2061 grm. of the substance gave on combustion* 0.2910 grm. 

 of carbonic dioxide and 0.0602 £rm. of water. 

 II. 0.2013 grm. gave 0.2827 grm. of carbonic dioxide and 0.0511 

 grm. of water. 



* Care must be taken to heat the substance very gradually, as it shows a 

 tendency to explode in the combustion tube. 



