140 PROCEEDINGS OF THE AMERICAN ACADEMY 



the same time. The crystallization from chloroform was continued 

 until the substance showed the constant melting point of 285° ; it was 

 then dried at 100°, and its composition determined by the following 

 analyses.* 



I. 0.2310 grm. of the substance gave 19.6 c.c. of nitrogen under a 

 pressure of 765 mm. and a temperature of 21°. 

 II. 0.1688 grm. of the substance gave, according to the method of 

 Carius, 0.2128 grm. of argentic bromide. 



Found. 



II. 



53.64 



The yield was far from satisfactory, amounting on the average from 

 about 15 to 20 per cent of the theoretical, although on one occasion 

 we obtained 40 per cent. As, however, the tribromdinitrobenzol used 

 in this case was the residue from the alcoholic extracts derived from 

 previous preparations, we think that a considerable part of this large 

 yield consisted of tribromtrinitrobenzol from the previous processes, 

 which had been dissolved by the hot alcohol, since, although nearly 

 insoluble in hot alcohol, it is not completely so. It follows from this 

 that it is well to use the tribromdinitrobenzol obtained in purifying 

 the crude product with alcohol as material for a new preparation. 



Properties. — The tribromtrinitrobenzol forms good-sized, well- 

 developed white crystals, with perhaps a slight yellowish tinge, which 

 differ in habit according to the solvent from which they have been 

 crystallized. From benzol, hexagonal prisms terminated by hexag- 

 onal pyramids are deposited, which look very much like some forms 

 of quartz crystal ; from a mixture of benzol and alcohol, long, slender, 

 tapering prisms are obtained, which under the microscope seem to be 

 made up of rows of hexagonal pyramids united as in cap quartz, so 

 that the edges of the prisms are bluntly serrated ; crystallized from 

 chloroform, the prisms are not so slender as from benzol and alcohol, 

 and the twinning just described is much better marked. These crys- 

 tals, furrowed by numerous re-entering angles parallel to the basal 

 plane, are very characteristic. The substance melts at 285° (uncorr.), 

 and sublimes to a slight extent when heated in an air-bath, even at as 



dotrinitrobenzol, it is not necessary to purify it completely from tetrabromdi- 

 nitrobenzol. See page 143. 

 * See also page 142. 



