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272 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

increase of the factor Φ. Figure 57 gives the proportion of m- nitrotoluene when

acids with 10% HNO 3 and various concentrations of H 2 SO 4 were used at 55°C

for a period of 100 min. The factor varied from 46% to 82.7%.

FIG. 57. Influence of the factor Φ (nitrating activity)

on the yield of m- nitrotoluene (Orlova [2a]).

According to Ingold [9a], the relative rate of nitration on each nuclear posi-

tion of toluene can be illustrated by the diagram where the rate of attack on one

nuclear position of benzene has been made the unit:

R. M. Roberts, Browder, and Kobe [10] carried out a number of experiments

using isotope dilution analysis to determine the proportion of m- nitrotoluene

formed in the course of nitration of toluene.

They nitrated radioactive toluene-l-^14 C with a mixture of nitric and sulphuric

acid at 0°, 30°, 45° and 60°C. After nitration the whole was diluted, with water

and steam distilled. Thus mononitro-products were separated from unnitrated

toluene and dinitro products. The weighted sample of isomeric mononitro-

toluene was diluted with a known quantity of non-radioactive m- nitrotoluene

and the mixture was distilled through an efficient micro-fractionating column in

order to recover a pure sample of m- nitrotoluene. The m- nitrotoluene was oxi-

dized by dichromate-sulphuric acid mixture to m- nitrobenzoic acid and this material

was radio-assayed. The proportion of m- nitrotoluene in the mixed nitrotoluenes

was calculated from the formula

% m- nitrotoluene =

100x

where

y(a/b-1)

x is the weight of m- nitrotoluene diluent,

y is the weight of mixed nitrotoluenes diluted,

a is the molar radioactivity of the toluene-1-^14 C nitrated,

b is the molar radioactivity of the m- nitrobenzoic acid.