u00b0 c for 24 hours and at 0 u00b0 c for 1 hour the precipitated product is removed by filtration through a sintered glass funnel and washed with concentrated h 2 so 4 additional product is obtained by extraction of the filtrate with methylene chloride the extracts should be worked up immediately and not stored it is dissolved in pure dry warm chloroform and the solution is decanted through a short column of anhydrous mgso 4 the filtrate after concentration at 25 u00b0 c to a volume of 10 ml and chilling at 0 u00b0 c for several hours deposits small chunky pale yellow prisms of hexanitrobenzene 0 63 g 58 mp 240 u00b0 265 u00b0 c dec concentration of the filtrate gives 0 14 g of additional product mp 195 u00b0 245 u00b0 c the first crop on sublimation gives very pale yellow prisms mp 246 u00b0 262 u00b0 c lit mp 240 u00b0 258 u00b0 c moisture must be excluded during the isolation operations 13 c nmr cd 2 cl 2 u03b4 138 7 relative to tetramethylsilane o lit 139 0 ir kbr 1560 1320 887 cm 1 mass spectrum strong m e at 348 with very little fragmentation anal calcd for c 6 n 6 o 12 c 20 70 n 24 14 found c 20 67 h 0 00 n 23 74 in carrying out the foregoing procedure 100 h 2 so 4 may be used in lieu of the fuming h 2 so 4 specified also the times of reaction 24 hours at 25 u00b0 30.