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208 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Thus, nitro compounds with a great number substituents, for example trinitro-

mesitylene, do not give any colour reactions. Compounds with nitro groups

located in the 2,4-positions, produce colours that depend to a considerable extent
on the substituent in position 1. The presence of the OH or NH 2 group interferes

with the colour reaction. The situation remains unchanged after both of the groups

have been acylated, while alkylation of a phenol restores the ability to produce

colour.

Newlands and F. Wild [59], when investigating maxima of the absorption

spectra of coloured solution, obtained with various dinitro compounds, found

that some of them produce two maxima.

T. Urbanski, Kwiatkowska and Kutkiewicz [60] came to similar conclusions.

Table 26 lists some of the results obtained.

TABLE 26

ABSORPTION SPECTRA OF COLOURED COMPOUNDS PRODUCED BY THE JANOVSKY REACTION

Compound

m- Dinitrobenzene

o- Dinitrobenzene

p- Dinitrobenzene

2,4-Dinitrotoluene

3,5-Dinitrotoluene

1,3,5-Trinitrobenzene

1,2,3-Trinitrobenzene

1,2,4-Trinitrobenzene

2,4,6-Trinitrotoluene

2,3,4-Trinitrotoluene

2,4,5-Trinitrotoluene

1-Fluoro-2,4-dinitrobenzene

1,3-Dichloro-4,6-dinitrobenzene

2,4-Dinitrophenetole

2,4-Dinitroaniline

2,4-Dinitrophenylamine

2,4-Dinitrophenylhydrazine

Colour

violet

none

none

bluish-violet

reddish-violet

reddish-violet

reddish-violet

red

blood red

violet

yellow-green

greenish-blue

deep blue

reddish-violet

red

red

blood red

Absorption maxima Reference

mμ

570-573

570-575

450-460 and 575

562 and 573

562

525

460 and 540

550

425-430 and 630

430 and 550

640

560

560

590

570

[60]

[60]

[60]

[60]

[60]

[60]

[60]

[60]

[60]

[60]

[60]

[59]

[59]

[59]

[59]

[59]

[59]

Abe [61] investigated the rate of the colour development with m- dinitrobenzene
in acetone in the presence of sodium hydroxide by examining the intensity of the

band 560 mμ against time. The maximum intensity occurs after 9 min. The

more concentrated the solution of sodium hydroxide the more quickly the
colour fades.

According to Cone [62] it is advisable to use butanone (methyl ethyl ketone)

instead of acetone, because the former gives a more stable colour and the reaction
can be used for colorimetric determination of TNT in air.