Nitrotoluene, eutectics

Choice of a suitable solvent, preferably of high polarity, such as PhN02 or sulpholane and for low temperatures S02 or eutectic mixtures of PhNOz with 1,2-dinitrobenzene or nitrotoluenes. [Author s note (2002) Disregard this bad advice )... 

In the system sulphuric acid-m-nitrotoluene the spontaneous formation of the crystals of the compound takes place only by strong cooling of the mixtures containing 60 mole % of sulphuric acid, whereas the crystals of m-nitrotoluene are obtained from all the mixtures containing less sulphuric acid. Even the eutectic Ex between m-nitrotoluene and sulphuric acid was obtained, owing to the strong tendency of the compound to supercool. The crystals of the compound are in... 

Additives used by the US Naval Ordnance Test Station, Inyokern, Calif included 0.5 to 1.0% a-MNN, 0.5% catechol, 0.25% anthracene and 0.25 to 0.75% Span 80A. In addition, small percentages of o- and p-nitrotoluene mixts, such as 3.36/1 were found to be effective. However, the high-melting eutecticforming additives anthracene, a-MNN and cathechol were preferred because little exudation occurred at temps up to within ca 5° of the eutectic temp... 

The solution of the problem was more closely approached by the use of highly nitrated aromatic hydrocarbons, especially the low-melting eutectic mixts of the isomers of di- and tri-nitrotoluenes (such as l,TNT oil" or "drip oil which dissolve readily in NG even at low temps and desensitize it much less than the mono-nitro compds. However, these compds did not produce dynamites which were absolutely non-freezing at the lowest winter temps reached in some countries such as in Canada or Siberia... 

Other data are also available (Refs 42 54) Eutectic Formation. TNT forms binary and ternary eutectics with various types of nitro compds and nitrate esters. Many of these are listed by Urbanski (Ref 29) others have been reported more recently (Ref 25). Since the di-nitrotoluenes and the unsymmetrical TNT isomers form such eutectics with 2,4,6-TNT which melt just above room temp, their removal is necessary to prevent exudation from TNT-based expls. One procedure for purifying TNT takes advantage of the fact that the eutectic containing the undesired isomers migrates to the crystal surface (see discussion under Exudation and Purification )... 

By freezing. When the mixture has been cooled to about -12°C, p- nitrotoluene crystallizes out, while the o- and m- isomers remain liquid. Further cooling results in the crystallization of o- nitrotoluene, while the m- isomer remains liquid, forming an eutectic with the o- isomer. 

Separation of isomeric nitrotoluenes, chloronitrobenzenes, etc. is easily accomplished with columns of this type. Some mixtures, whose constituents have boiling points very close to each other, can be fractionated provided that the substances crystallize so that the pure compounds can be separated from the eutectic mixture by centrifuging. An example is the mixture of nitrochlorobenzenes, described on page 90. 

An example of the use of a ternary eutectic diagram for the assessment of a melt recrystallization process (for nitrotoluene isomers) is given in section 8.2.1. 

The Janecke projection (section 4.4) in Figure 8.16 shows the phase equilibria for the ternary system, ortho-, meta- and pura-nitrotoluene the three pure components are represented by the letters O, M and P, respectively, at the apexes of the triangle. Four different eutectics can exist in this system, three binaries and one ternary ... 

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