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184 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Both cryometric (Gillespie [60]) and spectrographic (Brand, Horning and Thorn-

ley [17]) investigations of nitro compounds indicate that in sulphuric acid solutions

mononitro compounds behave like weak bases (p. 174). Thus it follows from

cryometric measurements that nitromethane in 100% sulphuric acid solution is 20%

ionized, and nitrobenzene 40%. Nitrobenzene is a stronger base than nitromethane.

The pale yellow colour of nitrobenzene or p- nitrotoluene turns more intense

when the compound is dissolved in sulphuric acid, while solutions of nitromethane

and other nitroparaffins are colourless. The yellow colour of the aromatic nitro

compounds is due presumably to an ionic structure containing a quinonoid ring.

Primary and secondary nitro compounds also react with acids, while tertiary

compounds show considerable resistance to them.

Primary nitro compounds, when treated with nitrous acid, give nitrolic acids

(VI).

The reaction leading to the formation of nitrolic acids was described for the

first time by V. Meyer [49]. The compounds are formed by treating aci-forms of

primary paraffins with NaNO 2 , followed by acidification of the whole mass. Ac-

cording to Veibel [61], the mechanism of the reaction may be presented by the

following multistage scheme :

aci-nitro compound Colourless salt

Red salt

Colourless product

(4)

Nitrolic acids, when reacted with sodium or potassium hydroxide, produce

a reddish-brown colour. The reaction is used for the detection of primary
nitroparaffins. Secondary. nitroparaffins form pseudonitroles with nitric acid

(VII)