V O L U M E 27, N O . 2, F E B R U A R Y 1 9 5 5 hypocliloritc hnd been added. If a n end point could be olwrved at all, it came far too early. With formate, methanol, ethyl alcohol, or tert-butyl hydroperoxide, no osidation occuricd under the conditions of the titration, since the first additions of reagent gave proportionate increases of current,. Under more strongly alkaline conditions, hypolxomite reactions might he espected to be more rapid and stoichiometric. IIowver, a t higher p H values hypobromit’e yields no ditrusion current a t potentials more positive than the region corresponding to oxygen reduction. Such titrations, particularly in dilute solutions, would therefore have to be carried out in air-free solutions. LITERATURE CITED
(1) Bitskei, J . , and I’etrich, K., M a g y a r Kdmikusok Lapja, 2, 230 (1947). (2) Haller, J. F., and Listek, S.S.,. ~ N A L .CHEM.,20, 639 (1948).
217 (3) Kolthoff, I. X I . , and Furman, N. H., “Potentiometric Titrations.” p. 257, Wiley, S e w York, 1926. (4) Kolthoff, I. M., and Stenger, V.-4., ISD. ENG.CHEM., ANAL.E D . , 7, 79 (1935). (5) Kolthoff, I. hl., Stricks, W., and hIorren, L., A n a l y s t , 78, 405 (1953).
(6) Xarks, H. C., and Bannister, G. L., ANAL. CHEM.,19, 200 (1947).
(7) Marks, H. C., and Glass, J. R., J . Am. Water Works Assoc., 34, 1227 (1942). (8) Muller, E., “Die Elektrometrische Massanalyse,” p. 207, Theodor Steinkopff, Dresden, 1942. (9) Tomicek, O., and Filipovic, P., CoZZection Czechoslou. Chem. Commzins., 10, 340 (1938). (10) Ibid., p. 415. (11) Tomicek, O., and Jasek, h l . , J . Am. Chem. Soc., 57, 2409 (1935). (12) Treadwell, W. D., Hela. C h i m . Acta, 4 , 396 (1921).
RECEIVED for review June 23, 1954. .4ccepted November 15, 1954.
Infrared Method for Determination of 0-, m-,and p-Mononitrotoluene and 2,l-Dinitrotoluene in Mixtures FRANK PRISTERA and MICHAEL HALIK Picatinny Arsenal, Dover,
N. 1.
For the efficient study of the nitration of toluene an exact knowledge of the nitration products formed in the first stage of nitration is necessary. Such products consist essentially of 0 - , m-, and p-mononitrotoluene with small amounts of dinitrotoluene. For the analysis of such products, as a mixture, an infrared spectrophotoInetric method has been developed which is fast, rather accurate and precise, and applicable over very wide ranges of concentration for each ingredient. The method involves making absorbance measurements of a 20y0solution of the sample in Cyclohexane at the peaks of the 8.49-, 8.10-, 9.39-, and 12.49-micron bands which are those of p - and o-nitrotoluene, 2,4-dinitrotoluene, and m-nitrotoluene. Using the method of successive approximations, the measured absorbances, after beng corrected for solvent and cell absorbance,were calculated to per cent of the ingredients. Since this method was first developed, it has been extended to include also 2,6dinitrotoluene, which is determined by measuring a 25% benzene solution of the sample at the peak of the 11.22-micron band.
’
I
X THE manufacture of trinitrotoluene by the nitration of toluene, o-, m-,and p-mononitrotoluene are produced in the first stage of nitration. The nieta isomer on further nitration yields trinitro isomers other than thed esired 2,4,6-trinitrotoluene. These isomers are generally undesirable as they cause exudation i n trinitrotoluene and therefore must be removed. A method of iiitration that n-ould produce the least amount of m-nitrotoluene, :it the first stage of nitration, would therefore be desirable. The (+llcient development of such a nitration method requires a nicthod of a n s l > - h of iiiisturcs of 0-,ni-, and p-nitrotoluene and alpo 2,4-dinitrotoluerie, which is prohahly present to some extent in the first stage of nitration of toluene. Such a method of i in addition, can be advantageously used to study nitration kinetics which in turn can be used for the establishment of an effirient nitration method. -1s no method of analysis of mixtures of 0-, m-,and p-nitrotoluene, and 2,4-dinitrotoluene has been found in the literature, it \ v a ~considered desirable to develop one. Considering the
successful use of infrared spectroscopy in t h e analysis of trinitrotoluene isomeric mixtures ( I ) , it was considered advisable t o investigate the use of this tool in the development of a method for the analysis of mixtures of 0-, m-, and p-nitrotoluene and 2,4-dinitrotoluene. An examination of the infrared spectrograms (see Figures 1 through 4) of the ingredients confirmed the feasibility of using infrared spectroscopy for the analysis of such a mixture. SURIMARY OF METHOD AND RESULTS ON SYNTHETICS
The developed method involves preparation of cyclohexane solutions of the sample of suitable concentration; measurement of the prepared solutions a t the peaks of absorption bands occurring at about 8.70 for o-nitrotoluene, 12.49 microns for mnitrotoluene, 8.49 microns for p-nitrotoluene, and 9.39 microns for 2,4-dinitrotoluene; and relating the absorbances t o concentrations from previously established relationships (absorptivities) using the method of successive approximations for calculations. The developed method was applied t o seven synthetic samples containing various amounts of o-, 711-, and p-nitrotoluene and 2,4dinitrotoluene. The results obtained are listed and treated statistically in Table I. -4summary of the statistical values is shown in Table 11. Since the method was first developed it has been extended to include 2,6-dinitrotoluene, which is determined by measuring a 25% benzene solution of the sample a t the peak of the 11.22micron band. I n this connection the following absorptivity data supplement Tables I11 and I\-. The average absorptivities of 2,6-dinitrotoluene a t the peaks of the 8.49-, 8.70-, 9.39-, 11.22-, and 12.40-micron bands are, respectively, 0.36, 0.53, 0.20, 12.5, and 0.49. The average absorptivities of 0-, m-, and p-nitrotoluene and 2,4-dinitrotoluene a t 11.22 microns are, respectively, 0.18, 0.60, 0.18, and 0.55. Also the cell absorbance a t 11.22 microns is 0.04, and the absorptivity of benzene is 0.06 per 0.10 mm. T h e infrared spectrograms of 0-, m-, and p-nitrotoluene, 2,4-, 2,6-dinitrotoluene, and the solvents cyclohexane and benzene are included in this report (see Figures 1 through 7). EXPERIMENTAL PROCEDURE
Instrumentation. The infrared work was performed using a Perkin-Elmer Double Beam infrared spectrophotometer (Model
ANALYTICAL CHEMISTRY
218
Figure 1.
Infrared spectrogram of o-nitrotoluene
Figure 2. Infrared spectrogram of m-nitrotoluene
Table I.
Values Obtained on Synthetics of id$d
Sample I o-Nitrotoluene m-Xitrotoluene p-Nitrotoluene 2,4-Dinitrotoluene Sample I 1 o-Piitrotoluene m-Xtrotoluene p-Nitrotoluene 2,4-Dinitrotoluene Sample I11 o-Nitrotoluene m-Sitrotoluene p-Nitrotoluene 2,4-Dinitrotoluene
Sample Y o-Sitrotoluene m-h-itrotoluene p-Xtrotoluene 2,4-Dinitrotoluene Sample VI o-Sitrotoluene m-Sitrotoluene p-Nitrotoluene 2,4-Dinitrotoluene
c
Standard deviation =
Found, 7
0-,
m-, and p-Yitrotoluene and 2,4-Dinitrotoluene Standard Deviationc
Coefficient of Variationd
2.98 6.97 -5.59 18.4
2.38 0.22 0.49 0.32
4.63 2.51 1.30 12.0
-0.29 -0.G9 -0.05 -0.03
-0.49 -3.57 -0.33 -0.58
2.25 0.08 0.18 0.23
3.79 0.42 1.20 4.39
56.73 0.99 39.81 4.91
2.20 -0.02 0.16 0.10
3.88 -2.02 0.40 2.04
1.43 0.07 1.37 0.13
2.52 7.10 3.45 2.65
61.03 4.25 35.95 2.18
G O . 09 4,ll 34.94 2.35
1.38 0.17 -0.06 0.00
2.30 4.14 -0.17 0.00
1.02 0.39 1.21 0.47
1.70 9.49 3.46 20.0
31.90 0.52 57.40 9.74
31.82 0.52 57,81 9.82
1 80 -0.11 -2.24 0.52
5.66 -21.2 - 3 88 5 29
0 70 0 03 0 09 0 23
2.20 5 78 1 19 2 36
___.
Absolute Errora. %
C
d
Ar.
87.20 7.80 3.40 4.45
87.20 7.80 3.25 4.50
87.20 7.80 2.90 4.55
87.04 7.89 3.28 4.48
48. d5 8.80 37.80 2.30
53.90 8.60 38.40 2.50
50.50 8.80 37.60 3.00
52.50 8.80 37.20 2.85
51.36 8.75 37.75 2.GG
1.53 0.61 -2.11 0.49
59.69 20.04 15.02 5.24
57.70 19.35 15.05 5,35
59.75 19.45 15.17 5,45
62.45 19.25 14.75 5.02
57.70 19.35 11.90 5.00
59.40 19.35 11.97 5.21
64.20 30.56 2.04 3.14
01.75 32.00 3.15 3.85
66.45 32,40 2.52 2.99
63.05 32.50 3.33 3.91
0 0 . 45 32,l5 2.98 2.97
G4.42 32,2cI 3.00 3.43
54.53 1.01 39.05 4.81
5 0 . .5G 0.913 37.87 4.78
57.24 1.00 40.30 1.85
58.26 0.93 40.00 4.94
54.87 1.09 41.09 5.08
58.71 3.94 35.00 2.35
58.64 3.74 33.83 3.03
60.34 4.20 33.96 1.95
60.34 4.27 36.02 2.24
30.02 0.63 G O . 05 9.30
31.90 0.3 57.06 10.14
30.89 0.52 58,40 9.82
32.59 0.49 58.40 9.59
/c
a
b
85.74 7.51 2.01 4.74
8G,5 3 8.13 3.58 4.40
49,83 8.14 39.86 2.17
i(xi
