SUMMARY.
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| C_{6}H_{5}(N0_{2}) Nitro-benzene.  Liq.  B.Pt. 206 deg.  C.               |
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| C_{6}H_{4}(NO_{2})_{2} Ortho-, meta-, and para- di-nitro-benzenes. |
| Solid.  M.P. 118 deg., 90 deg., and 172 deg.  C.                                 |
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| C_{6}H_{3}(NO_{3})_{3} S.-Tri-nitro-benzene.  Solid.  M.P. 121 deg.  C.   |
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| C_{6}H_{4}(CH_{3})NO_{2} Ortho-, meta-, and para- nitro-toluenes.  |
| B.P. 218 deg., 230 deg., and 234 deg.  C, Para compound solid.                  |
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| C_{6}H_{3}(CH_{3})_{2}NO_{2} Nitro-xylene.  Liquid.                 |
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| C_{6}H_{2}(CH_{3})_{3}NO_{2} Nitro-mesitylene.  Solid.              |
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| C_{6}H_{3}(CH_{3})(NO_{2})_{2} Di-nitro-toluenes.                  |
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| C_{6}H_{4}Cl(NO_{2}) Nitro-chloro-benzenes.                        |
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| C_{6}Br_{4}(NO_{2})_{2} Tetra-bromo-di-nitrobenzene.               |
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The nitro compounds are mostly pale yellow liquids, which distil unchanged, and volatilise with water vapour, or colourless or pale yellow needles or prisms.  Some of them, however, are of an intense yellow colour.  Many of them explode upon being heated.  They are heavier than water, and insoluble in it, but mostly soluble in alcohol, ether, and glacial acetic acid.

Nitro-benzene, C_{6}H_{5}(NO_{2}), was discovered in 1834 by Mitscherlich.  It is a yellow liquid, with a melting point of +3 deg.  C. It has an intense odour of bitter almonds.  It solidifies in the cold.  In di-nitro-benzene, the two nitro groups may be in the meta, ortho, or para position, the meta position being the most general (see fig., page 4).  By recrystallising from alcohol, pure meta-di-nitro-benzene may be obtained in long colourless needles.  The ortho compound crystallises in tables, and the para in needles.  They are both colourless.  When toluene is nitrated, the para and ortho are chiefly formed, and a very little of the meta compound.