Colored
Derivative and Alpha-TNT in Colored Aqueous Alpha-TNT Solutions
TNT
Spectrophotometric Procedure for Quantitative Estimation c. C. RUCHHOFT AND WM. G.MECKLER U. S.
Public Health Service, Water and Sanitation Investigations Station, Cincinnati, O h i o
A simple analytical procedure has been developed for the determination of TNT in uncolored aqueous solutions, which is applicable to polluted water and sewage sampler. A spectrophotometric procedure for quantitative estimation of colored (combined) TNT fraction and the a-TNT fraction (uncombined) in colored TNT waster from shell-loading plants requires determination of extinction values of dilutions of the colored waste as received at 460 and 505 mp, and similar determinations at 505 mp on dilutions after sulfite and hydroxide treatment of the samples.
Observation' of waates at shell-loading plants, and also experiments in the laboratory, have shown that uncolored aqueous solutions of T K T in natural waters slowly become colored. Experiments in the authors' laboratory (discussed below) suggest that this is the result of a reaction bctween T N T and the constituents of the wastes or soil with which the TST comes in contact t o form a colored TST complex. The reaction is hastened by direct sunlight but cannot be induced by sunlight in distilled watchr cont:iining TXT. Distilled water solutions of T N T will become only slightly colored when exposed t o the sun even for long periods of time, compared to the potential possible color. As the react,ion with thc production of the colored T N T complex takes place naturally in the ditches carrying t,he plant T N T wastes, a method of estimating both fractions of T X T in such wastes is desirable.
I
S UNDERTAKIXG a study of the reactions and possible treatment procedures for a-trinitrotoluene wastes a t shell-, bomb-, and mine-loading plants a method for determining the concentration of a-TNT or TST derivatives in such waste was needed. The first part of the study of TST wastes was, therefore, devoted to the development of such a method. (Wherever T N T is mentioned in this paper, a-TST is meant.)
EXPERIMENTAL
T o study various procedures for color formation, solutions of T K T were prepared by placing 1 or 2 grams of flake TNT, of the same quality as used a t the shell-loading plants, in an Erlenmeyer flask containing several liters of distilled water. The water was heated to boiling with stirring to bring the molten T N T into solution, and the solution was cooled. T o assure a solution free from supersaturation, the solution was allowed to stand several hours at room temperature and was then filtered through paper. The solutions so prepared were clear and colorless, and did not resemble in appearance the red waste liquid a t the plant drainage ditches. These solutions remained uncolored indefinitely in the laboratory in the absence of direct sunlight. Aliquots of solutions prepared in this manner were used in the experiments described. The intensity of the color produced in aqueous TST solutions was determined in a Bausch & Lomb visual spectrophotometer. The standard Bauscli 6r Lomb absorption tubes, about 10 cm. (4 inches) in length, as supplied with the instrument, were used and the sample in one tube was compared to a distilled water blank in the other. All extinction readings were made by two observers, and the values recorded in the following tables are the means of such duplicate readings. As preliminary tests showed that maximum absorption occurred between 460 and 505 milli-
.it one plant the chemists estimated the conccntration of TlUT iii the drainage ditches on the basis of the color of the water. I t was stated that the concentrations of T K T in the highly colored water was surprisingly low and that pollution by T X T could be tasted in conwntrations as low as 1 p.p.m. Taylor and Binkenbach ( I S ) , in a study of TST solubilities in water, made gravimetric determinations after evaporation of the solvcnt in a current of air a t 60" C. Such a procedure is time-consuming and hardly applicable to the study contemplated. Pinto and Fahy (10) have recently reported a colorimetric procedure depending upon reduction of the T N T to the triamino compound followed by diazotization and coupling. This procedure could not be easily applied to very dilute aqueous solutions. Copisarow (4)reported that alkalies and alkali compounds produced red colorations in TST and that these were addition, substitution, and condensation compound?;. Giua and Reggiani (7) stated that sodium ethylate formed addition goducts-Le., the mono-, di-, and trialcoholate with TXT. avis (5) mentions both the colored explosive compounds formed with potassium methylate (corresponding to the addition products of Giua and Reggiani, 7') and also the inffammable and explosive products of the reaction of caustic potash with TNT, but does not mention the color of the latter compounds. Davis and Richmond (6) studied the thermotropic color intensification of nitrophenol solutions when treated with sodium carbonate and concluded that the colored addition compounds were sodium nitrophenolates. This reaction is repre.cwttd by Davis :is
I
f0lloa.s:
yf.50
0-fi OH
o=?;=o
HOOH
0
zf
v
p:
1.00
tt
1
/
O=S-OSa.
A number of other yorkers h:Lve studied the formation of colored compounds by the reaction of nitro compounds in ketones or alcohols with alkalies. Bost and Xicholson (2) present a qualit,ative teht for the identification of mono-, di-, and trinitro compounds, depending upon the color obtained when an acetone solution of the compound is treated with sodium hydroxide. Quantitative colorimetric procedures for nitro comounds developed by Kay ( S ) , Baernstein ( I ) , and lloss with bellon (9) all depend upon similar reactions. The red stream water a t shell-loading plants and the work of Davis (6) suggested that a simple procedure without the introduction of any additional organic reagent should be possible for aqueous TST solut,ions.
WAVE Figure 1.
430
L E N G TH - M I L LI MI C R 0 N S
Extinction Curve for Aqueous TNT Solution Treated with Sulfite and Hydroxide and Diluted
43 1
ANALYTICAL EDITION
July, 1945
microns. readinns were made a t 460. 475., 490., and 505 millimicrons. I n the first experiment, various inorganic salts were added to 50-ml. aliquots of a solution containing about 70 mg. of T N T per liter and observations for color development were made after various treatments. Where colors developed with apparent maximum intensity for the treatment after about 10 or 15 minutes, the colored solutions were diluted with distilled water and extinction value. were determined. The results obtained indicated that only a few of the reagents tried were ,satisfactory for rapid maximum color production and that the reaction must be controlled to hold the color a t a maximum until the reading can be made. The color intensity obtained with sodium sulfite and hydroxide together was the most satisfactory. This mixture produced a stronger color than the sulfite alone, and a different color than with hydroxide alone (maximum absorption a t 505 mp, shown in Figure 1, as contrasting with maximum absorption a t 460 mp with hydroxide alone), and one more independent of sulfite concentration, temperature, and reaction time. I t was also noticed that there was an apparent fading of color5
Table
I.
as a result of dilution of the colored T N T solutioii with distilled water to make a reading. Consequently aliquots of an aqueous TST solution, colored b;I with and hydroxide, were diluted in seven different dilution waters (Table I). On the basis of constant color characteristics for a t least 40 minutes, and because it was less complex than others tried, the 0.01 N and o.m5 hydroxide solution (No. 7) was selected as the best dilution water. Variations of the sulfite-hydroxide treatment were tried in another series of experiments. These data (Table 11) show that procedure 3, involving treatment with sulfite followed by hydroxide, was preferable to the others tried. Faster reaction and a maximum intensity a t 505 mp were obtained. Procedure 3 of Table I1 was studied on known concentrations of a-TNT in Cincinnati t a p water and in domestic sewage. These experiments indicated t h a t because of precipitation due to the water-softening effect of the sulfite-hydroxide treatment, natural water and sewage samples containing a-TNT must be filtered after treatment for color production. Maximum color production was not obtained in undiluted samples. Check
treatment
iv
Effect of Dilution Waters on
TNT Sulfite-Hydroxide Color
(.\liquet portions of colored T N T solution diluted 1 t o 50 in water described)
l I e a n Extinction Coefficients for Indicated Wave Length after Indicated Time After 10 >Iinutes h f t e r 40 Minutes .4fter 6 Hours
Dilution Coillposiriuii of Dilution Water Experiment Water Used 1 Distilled water
460
475
0.61
0.62
490 0.64
505 0.61
460 0.48
475 0.50
0 50
490
505 0.47
0.43
460
475 0.45
490 0.46
505 0.44
2
Mineralized (11' dilution wnter
0.70
0.70
0.69
0.68
0.5i
0.63
0 62
0.58
0.62
0.63
0.59
0.57
3
0.01 N NazSOr
0.56
0.59
0.63
0.64
0.51
0 53
0 54
0.50
0 44
0.42
0.42
4
0.01 N NaOH
0.61
0.66
0.66
0.63
0.69
0 73
0.70
0 66
0 85
0.77
0.73
5
p H 9.6 borate buffer (3)
0.55
0.58
0.60
0.59
0 45
0.47
0.41
0 43
0 14
0.40
0.41
0 41 0 66 0 38
6
Mineralized water NanSOa
0.69
0.73
0.73
0.71
0.75
0.78
0.77
0 73
0.78
0 75
0.72
0 70
7
0.01 S SanSOa, 0,005A' N a O H
0.67
0.66
0 62
0.61
0.64
0.64
0.64
0 59
0.66
0 61
0.60
0 58
4- 0.01 A-
~~
Table
II.
TNT Colored Solutions Formed b Treatment with Various Combinations of Sodium Hydroxide, Carbonate. and tulfite
Description of Treatment Procedure (to 50-MI. Aliquot6 of T N T Solution) 1 pellet NaOH plus 1 gram SazSOs added together. stirred until solution complete
Wave Lengths Used
1 pellet S a O H : after solution complete, 1 g r a m NazSOa, stirred as in 1
3
Treatinelit Procedure NO. 1
460 475 490 505
Extinction Coefficient Readings ( l f e a n s of 2 Observers) Dilutions >fade U p 5 Minutes after Color Formation Treatment Completed. Dilutions Made U p 2 Hours after Color Readings on 1/50 Dilution after Formation Completed. Readinqs on Indicated Time" 1/50 Dilution after Indicated Time" Within 10 Immediate minutes 1 hour 24 hours reading 10 minutes 20 minutes 24 hours after after after after after after after dilution dilution dilution dilution dilution dilution dilution 0.67 0.80 0.42 0.90 0.80 0.80 0.43 0.75 0 37 0.96 0.85 0.88 0.86 0 37
0.81 0.90
0.92 0.94
0.32 0.26
1.04 1 08
0.92 0.97
0.90 0.93
0 31 0 28
460 475 490 505
0.75 0.74 0.72 0.71
0.86 0.90 0.89 0.86
0.54 0.48 0.42 0.36
0 68 0 72 0 72 0 69
0 74 0 73 0 74 0 73
0 0 0 0
74 76 75 76
0 56 0 49 0 43 0 38
1 gram NazSOa: after solution complete, 1 pellet NaOH stirred as in 1
460 475 490 505
0.87 1.01 1.04 1.08
0.80 0.81 0.88 0.94
0.49 0.42 0.37 0 32
0.88 0.94 1.02 1.06
0.78 0.87 0.93 0.95
0 76 0.83 0.89 0.93
0.48 0.42 0.36 0.32
4
1 pellet S a O H stirred a s in 1
460 475 490 505
0.88
0.82 0.66 0.55
0.84 0.78 0.68 0.56
0.65 0.62 0.52 0.44
0 65 0.56 0.48 0.40
0.64 0.55 0.48 0.40
.. .. .. ..
0 60 0.53 0.42 0.35
5
1 gram 9azSOs stirred as in I
460 475 490 505
0.35 0.44 0.49 0.55
0.98 1.00 1.04 1.07
0.61 0.55 0.48 0.40
0.33 0.34 0.34 0.35
0.73 0.83 0.86 0.92
0.79 0.82 0.91 0.98
0.35 0.32 0.27 0.24
6
1 gram NazCOa plus 1 gram
460 475 490 505
0.72 0.78 0.86 0.90
0.806 0.84b 0.89b 0.94b
0.63 0.66 0.73 0.76
.. ..
0.70 0.76 0.80 0.55
..
2
7
a
Comparative Experiments with
NazSOa added stirred as in 1
together,
1 gram XazSOa; after solution complete 1 gram NarCOs stirred R S in 1
460 475 490 505
0.60 0.64 0.68 0.72 .ill dilutions were made u p in a water of 0.01 .V NanSOa and 0.005 N NaOH. Two-hour reading.
0.76b 0.80b 0.876 0.85b
..* .
.. ..
0.726 0.78b 0.82b
0 86b
.. .. ..
.. .. ....
0.80b 0.80h
0.84b 0.90h
INDUSTRIAL AND ENGINEERING CHEMISTRY
432 Table Ill. a-TNT
Extinction Coefficient Readings Obtained with Standard
Concentration in Standard At 460 J1illiinicron.Solutiona, Reading CalcuP.P.1.I. obtained latedh Deriatiuii 4.88 1.76 1 771 - 0 011 4.40 1.44 1.591 -0151 4.04 1.60 1.466 + O 134 3.32 1.11 1.205 - 0 095 0 93 0 976 - 0 046 2 69 0 91 0 965 -0 055 2 66 2 44 0 89 0 886 1 0 004 2 21 0 78 0 802 - 0 022
1.22 1.11 0.95 0.81 0.49
0.48 0.46 0 40 0 33 0.24
0 443 0 403 0 345 0.294 0.178
+ O 037 f O 057
+O 055 f 0 036 10.062
TNT
A t 475 Millimicrons Reading Calcuohtained latedb Deviation 1 90 155 1.62 1.23 1 04 1 05 0 99 0 82
1.932 1.742 1600 1.315 1065 1 053 0 966 0 875
0 53 0.48 0 41 0 36 0 25
0 0 0 0 0
483 440 376 321 194
- 0 032 -0.192
Vol. 17, No. 7
Solutions after Sulfite-Hydroxide Treatment and Dilution A t 490 .\Iillimicrons Reading Calcuobtained latedb Deviation
At 505 Jlilliinicrons Reading Calcuobtained latedb Derintioii
+ O 020 -0.085 - 0 025 - 0 003 + O 024 - 0 055
1.98 1.67 1.74 1.33 1 11 1 11 1 06 0 87
2.059 1.857 1.705 1.401 1 135 1 123 1 030 0 933
-0 079 -0,187 + O 035 - 0 071 - 0 025 - 0 013 + O 030 - 0 063
2.07 1.74 1.75 1.39 1 18 1 15 1 14 0 83
2.135 1.925 1.768 1.453 1 177 1 164 1 068 0 967
-0,065 -0,185 -0,018 -0,063 4-0 003 - 0 014 + O 072 - 0 037
10.047 4-0.040 10.034 +0.039 + O 056
0.57 0 51 0.44 0 375 0.25
0.515 0.468 0.401 0 342 0.207
f O 055 1 0 04% +0.039 + O 033 +O 043
0.46
0.59 0.51
0.534 0 486 0.416 0.354 0,214
f0.056 f O 024 f O 044 + O 046 f0.046
0.40 0.26 a Solutions obtained by diluting standard solutions containing 24.4 40.4 and 66.4 nig. of a-TNT per liter of distilled water. b Calrulated on basis of mean results for TNT concentration from'0.95 io 4.04 p.p.m. on assumption that Beer's I R U applies.
results, however, were obtained in natural waters and sewage when the color treatment procedure was followed by filtration and dilution in the sulfite-hydroxide dilution water. CORRELATIONS O F CY-TNT C O N C E N T R A T I O N S AND EXTINCTIONS A T SEVERAL W A V E LENGTHS
The extinction curve obtained between 460 and 700 mM on an aqueous T N T solution treated for color production with sulfite and hydroxide and diluted in the sulfite hydroxide dilution water is shown in Figure 1. On the basis of this curve, i t is evident that extinction determinations should be made around 505 mp. This extinction curve differs considerably from the curve for T N T wastes (12) from T X T manufacture and from the curve for a-TNT treated with caustic only, which has its maximum a t 460 or below as nearly as can be determined visually. Thp extinction curve obtained from the water in the shell-loading plant ditches resembles that obtained in the laboratory from caustic or carbonate treatment. As the latter treatment gives higher extinctions a t 460 than a t 505, i t was decided to study extinction values obtained by the procedure developed here a t 460, 475, 490, and 505 mp. The trend of the values obtained a t these four wave lengths should enable one to determine whether a sulfite-hydroxide T X T color or a caustic T X T color is being dealt with. Three standard solutions were prepared, containing 24.4, 40.4, and 66.4 mg. of T N T per liter. The T N T recrystallized from alcohol was introduced into liter quantities of distilled water in Pyrex bottles and the bottles were warmed on a water bath until complete solution was obtained. After the standard solutions had cooled to room temperature, 50-ml. aliquots of each standard were treated by the sulfite-hydroxide procedure and then diluted with the 0.01 N suWite-0.005 N hydroxide dilution water. By this procedure, 17 colored solutions were prepared containing from 0.49 to 4.88 mg. of T N T in the diluted sample. These colored solutions were prepared and examined, one a t a time, to obtain maximum color intensities, but it is realized now that the exact time requirements to obtain the maximum color may not always have been met. The extinction readings were made a t the four wave lengths previously selected and the result3 are given in Table 111. Inspection of these data indicates close agreement with Beer's law, excessive deviations being shown only a t a T N T concentration of 4.4 p.p.m. A N A L Y T I C A L PROCEDURE F O R U N C O L O R E D a - T N T S O L U T I O N S
The rate of color formation by the procedure developed was studied on a solution containing about 10 p.p.m. of TNT. One gram of sulfite was added to the solution and the extinction value rose from 0.07 for the untreated solution to 1.18 after one minute
a h r n all the sulfite was in solution. Thereafter there was no change in the extinction. The same quantity of sulfite in a water blank gives an extinction of 0.08. All the color produced by the sulfite treatment is apparently formed within tho time required to dissolve the sulfite, and apparently i t makw littlr difference whether the hydroxide is added immediately aftc,r the sulfite is dissolved or 10 minutes later. I n either case thc extinction increases to between 1.25 and 1.45 in the time requirt4 to add the hydroxide, mix, and transfer the solution to thc instrument. Thereafter the extinction value slowly riscs for 10 to 15 minutes and in this case reached a maximum of 2.30 after 13 minutes. When the alkalinized solution is further diluted with the sulfite-hydroxide dilution water, a further total increase in extinction values is obtained. If the T N T sulfite-caustic solution is diluted within the firht 6 or 7 minutes before the maximum color intensity ha3 been reached, the dilution continues to increase in color intensity for 10 minutes or more until its maximum is reached. If, hon.erc~i., the alkalinized solution is diluted when its color i- a maximum, the maximum color is obtained immediately after dilution anti, thereafter, the color slowly fades. I n the case used for illu.tration, the extinction value obtained on a 1 to.5 dilution of the fully treated sample after 5 minutes was 0.75 which increased to 0.85. When the dilution was made after 15 minutes, extinction values of 0.86 to 0.88 were obtained. As the undiluted treated sample had a maximum extinction of 2.30, an extinction valuc ( i t about 0.46 would be expected after a 1 to 5 dilution if the procesh were a simple dilution. The intensification reaction obtained during dilution is shown by the fact that an extinction value almost double that expected is actually obtained. To check with the extinction values shown in Table I11 it s necessary t o dilute the sample treated for color production a t least 1 to 1 before the extinction values are read.
REAGENTS,Sodium sulfite, anhydrous, C.P. Approximately 2 N sodium hydroxide solution, prepared by
dissolving 80 grams of C.P. sodium hydroxide in 1 liter of distilled water. Approximately 0.01 N sodium sulfite and 0.005 N sodium hydroxide dilution water. The dilution water should be freshly prepared each day by dissolving 0.2 gram of sodium hydroxide and 0.6 gram of sodium sulfite in 1 liter of distilled water. Aeration of the dilution water by shaking, which will cause oxidation of the sulfite, should be avoided after the sulfite is added. PROCEDURE. To a 50-ml. sample of the water or sewage in a small Erlenmeyer flask 1 gram of anhydrow sodium sulfite (weighed on a rough balance) is added and the flask swirled gently until i t is dissolved. Five minutes after the sulfite, 1 ml. of approximately 2 N sodium hydroxide solution is added and mixed. rlfter the hydroxide has been in contact with the sample for
ANALYTICAL EDITION
July, 1945
-_ . \ I l s t u r e Lsed,
Table
433
IV. Test Data, Spectrophotometric Procedure for Colored and a-TNT
(Usine definite mixtures of known colored T N T solution and standard a - T N T solution) .4nalyticai Quantities on Basis of Observed E Deviations betweeii Ratio of Solutions colStandDilu- Readings and Calculations as Described, P.P.R.1. Quantities Calculated on Observed and Calculated Uncolored Mean Talues Basis of Mixture, P.P.M. Values, P.P.M. Percentage Errors ored ard tion TNT a-TST OhColored a-TNT Colored Uncol- Total Colored UncolTotal Colored Uncol- Total Colored Uncol- Total sulutioii solution served complex a b complex ored a T N T complex ored a T N T complex ored a T N T complex ored a T N T 2.1 0.12 10.7 2.0 0.1 2.2 84.6 20.5 105.1 18.9 84.7 18.3 103.0 19 1 1/25 85.5 18.9 1/50 84.0 18.3 17.2 7.9 0.7 0.7 1.4 1.1 1.8 22.9 103.0 80.1 102.3 J 1 1/25 81.5 20.6 20.6 61.2 21.1 81.0 ?0.6 22.8 1/50 0.1 6.0 13 8 4.3 4.4 0.1 27.8 99.0 71.2 98.9 24.6 75.5 23.4 4 1 1/25 76.0 22.2 75.0 22.8 24.0 1/50 2.9 16.0 10.0 3.4 7.1 4.2 44.5 42.2 86.7 89.6 1 1 1/25 51.5 35.5 36.6 51.6 38.0 40.0 1/50 51.8 40.0 2.2 4.2 3.3 15.0 4.4 1.1 50.2 79.6 29.4 82.9 33.8 49.1 1 2 1/25 36.6 46.8 46.8 50.3 1/50 31.0 52.6 4.6 7.9 5.7 6.2 1.4 3.2 56.7 74.5 17.8 79.1 1 4 1/25 21.2 57.2 58.3 19.2 59.9 61.5 1/50 17.2 62.8 0.4 36.0 4.6 0.6 3.2 2.8 61.6 70.5 8.9 70.9 10.6 56.6 56.6 12.1 58.8 1 9 1/25 1/50 13.6 61.6 60.5 0 . 9 0.9 0 . 6 2 7 . 0 0.6 64.0 68.5 1.2 4.5 69.1 60.7 5.7 63.4 1 19 1/25 5.6 61.8 1/50 5.8 66.3 65.0 2.8 2.5 1.8 13.7 7.0 2.3 Nean Gbiiig E values obtained with colored blank of same dilution. b Using E values obtained with distilled water blank. Q
5 t o 10 minutes, the sample is filtered through a No. 1 Whatman paper. As soon as the sample is filtered, and in no case over 15 minutes after the hydroxide is added, the sample is diluted with the sulfite-hydroxide dilution water to the proper extent for examination. The dilution should be a t least 1 to 4 and may be 1 to 50, and the result can still be interpreted on the basis of the correlation data given. The diluted sample may be introduced in the spectrophotomcltrr and readings, preferably a t 505, may be made every minute o r two for 10 minutes or until the maximum extinction values are obtained. The dilution should be made to hold extinction readings between 0.5 and 1.6 for the best results. If the color obtained by the standard treatment is too low for tiilution, an approximate result can be obtained if a new 50-ml. portion of sample is treated with 0.25 gram of sodium sulfite fullowed by 0.25 ml. of the 2 N sodium hydroxide solution. The c d o r will form under these conditions a t a much lower rate and \vi11 not reach a maximum for 30 to 40 minutes, after which the ..ample may be examined undiluted. If a spectrophotometer or photoelectric colorimeter is not available, color standards can be prepared for visual matching. In this case it is best to prepare a standard T N T solution of 20 to 40 p.p.m. A 50-ml. portion of the standard solution is treated at the same time and in the same way as the sample. After the color treatment, color standards containing 0.5, 1, 2, 3, 4, and 5 p.p.m. are prepared with this solution and the sulfite-hydroxide dilution water in 50-ml. Sessler tubes. The color-treated sample is diluted a t the same time the standards are prepared and the colors should be matched within 30 minutes of the preparation of the dilute standards. Standards higher than 5 p.p.m. cannot be used. ANALYSIS OF COLORED (Y-TNT SOLUTIONS
Experiments have indicated that, once the colored complex is formed by nature, or by carbonate or hydroxide in the laboratory, this complex cannot readily be altered even by prolonged treatment with sulfite and hydroxide to produce the complex with a maximum absorption a t 505 mp. rlny remaining uncombined T N T , however, still reacts under the sulfite hydroxide treatment to give the complex with maximum absorption a t 505 mp. Upon the basis of these observations a procedure for estimating both the colored complex and the uncolored a-TST has been devised. PROCEDCRE FOR COLORED T K T SOLUTIOKS.A 50-ml. aliquot with sulfite and hydroxide is treated as described and after 10 minutes filtered if necessary. During the time required to treat the above portion, a portion of the colored sample (also filtered if necessary) is diluted with a dilution water containing 300 p.p.m. of sodium carbonate. The dilutions should be such that E readings between 0.5 and 1.6 are obtained if possible. Simple exact dilutions of 1/5, 1/10, 1/25, and 1/50 can be easily made with volumctric pipets and 50- or 100-ml. volumetric flasks. I t
is necessary to make these direct estimation readings a t both 460 and 505 mp in two proper dilutions such as 1/25 and 1/50 or 1/10 and 1/25, etc. The spectrophotometric examination of the untreated sample should be made immediately after dilution. When the sulfite-hydroxide treated sample has been filtered and has had the proper contact time (10 to 15 minutes), it is diluted with the sulfite-hydroxide dilution water and examined a t 505 mp every 2 minutes for 6 to 10 minutes or until a maximum E reading is obtained, with a distilled water blank. If the original solution was highly colored, so that a direct dilution of the same strength has been examined, this is introduced into the distilled water tube and with it as a blank several additional readings are made a t 505 mp. When this is completed, it is desirable to make another dilution of the treated sample and again make two sets of readings a t 505 mp, one with the distilled water blank and one with the colored sample of the same dilution in the carbonate water as a blank. .4 typical set of readings as follows might be obtained:
Dilution Used 1
E
1 50
Wave Length Used 460 505 460 505
Untreated Colored Sample 0.85 0.55 0.47 0.31
Sulfite-Hydroxide Treated Sample With distilled With diluted water untreated colored blank sample as blank 0.84
0.37
0.44
0.18
On the basis of the authors’ experiments, the colored complex formed with carbonate does not exactly conform to Beer’s law, so t h a t two factors were worked out for different dilutions at 460 mp.
If a dilution of 1/50 is used the quantity of colored TST in E p.p.m. equals - X dilution factor. On the other hand, if the 0.29 sample is examined undiluted or with l / 3 to 1/25 dilutions, a factor of 0.26 is used in place of 0.29 in the equation. However, if the E values obtained a t 460 mp are less than 0.30, a correction must be made for the instrument, which in the authors’ case is 0.06. Under these circumstances the above equation becomes P.p.m. of colored TST =
2 0’06 X dilution factor
The K values of 0.26 for undiluted samples or dilutions up to 1/25 and 0.29 for 1/50 dilutions to be used in the above equation are considered tentative values. On the basis of the data above, the colored T N T present was as follows: 0.85
For 1/23 dilution, o.26
X 25 = 81.5 p.p.m.
INDUSTRIAL AND ENGINEERING CHEMISTRY
434
For 1/50 dilution,
0 47 0.29
x
50 = 81.0 p.p.m.
For determining the uncombined a-Ti\‘T that remains in the colored sample, it is necessary to determine the net increase in extinction a t 505 mp due to the sulfite hydroxide treatment. The general equation for calculating the a-TNT is P.p.m. of TST =
*
0.437
X dilution factor
When the untreated colored solution in the same dilution as the treated sample is used as a blank, the E as read is substituted in the above formula. When distilled water is used as a blank, the increased extinction due to sulfite-hydroxide treatment is determined as follows from the E values of the untreated and treated samples of the same dilution.
E Net gain due to sulfitehydroxide treatment
= E - (E Sulfite-hydroxide Untreated sample of treatment with same distilled water dilution blank
-
0.06)
If the E of the untreated sample was not obtained in the same dilution as the E for the sulfite-hydroxide treated sample, the above correction can be estimated. In such a case the E for any dilution of an untreated sample without any deduction is divided by the factor necessary to bring it to the dilution of the sulfitehydroxide treated sample that was examined. Applying these rules to the data given above, the calculations for alpha T N T become: First for the E readings obtained with the untreated colored dilution as a blank, For the 1/25 dilution,
0 37 - X 25 = 21.2 p.p.m. 0.437
For the 1/50 dilution,
E7
X 50 = 20.6 p.p.m.
Using the E data for the untreated colored sample and the sulfite-hydroxide treated sample with the distilled water blank,
For the 1/25 dilut,ion,
- 0.437 (0‘55 -0’06)
X 25 = 20.0 p.p.m.
For the 1/50 dilution, 0’44 - (0‘31 - o*06) X 50 = 21.2 p.p.m. 0.437 Using the mean of all values obtained, this sample contained 81.2 p.p.m. of colored T X T and 20.7 p.p.m. of uncombined aT X T or a total of 101.9 p.p.m. The K values used in all these calculations apply only to the authors’ instrument and for accurate determinations with other instruments these values must be redetermined on prepared standards. To test the value of this analytical procedure, two samples, one containing only a-TST and the other containing largely colored TXT, were mixed in definite proportions and analyzed. The colored TiTT sample was 29 days old and, on the basis of the same analytical procedure, was found to contain 89 p.p.m. of colored T N T and 18.1 p.p.m. of CY-TNTwhen it was used in this experiment. The a-TNT sample was a carefully prepared standard containing 66.4 p.p.m. of a-TNT and was uncolored. The data in Table I V show that good estimates of the two forms of T N T were obtained in all mixtures when the data obtained as described for two dilutions were averaged. I n all cases slightly higher values for the colored T N T were obtained than calculation indicated. This is to be expected, as the mixture of the solutions would naturally favor the reaction with the production of more colored TNT. Again, in all cases except one the quantity of uncolored a-TNT found in the mixture was less than the value calculated. The errors in the determinations of the colored and uncolored fractions, therefore, seem to be compensating. As a result, the deviations between the values for total T N T as observed and calculated varied between 0.1 and 4.6 p.p.m., with a mean deviation of only 1.8 p.p.m. The percentage errors in the results for total T N T varied between 0.1 and 6.2%, with a mean of 2.3 for the eight mixed solutions
Vol. 17, No. 7
analyzed. These data seem to indicate that the procedure described can be safely relied upon to give reasonable estimates of the uncolored a-TNT and the colored T X T complex in water containing mixtures of the two. SUMMARY
a-TNT in aqueous solutions reacts with sulfite and hydroxide to form a colored compound and the color so obtained can be intensified by dilqion in a weak sulfite-hydroxide solution. The rates of the color formation in each step of this reaction have been studied and it has been shown that the correlation between the T N T concentration and the color intensity of the sulfite and hydroxide treated and diluted samples conforms to Beer’s law. On the basis of these reactions, a simple analytical procedure for the determination of TST in uncolcred aqueous solutions has been developed which is applicable to polluted water and sewage samples. Correlation between T N T concentrations of standard solutions and extinction values of the samples after treatment by the recommended procedure are presented for four wave length?. Examination of samples a t 505 mp is recommended as optimum. If spectrophotometer equipment or a photoelectric colorimeter is not available, the method is applicable by simple color comparison with prepared standards. A spectrophotometric procedure for the quantitative estimation of the colored (combined) T X T fraction and the (uncombined) or-TNT fraction in colored T N T wastes from shell-loading plants has been described. The procedure requires the determination of extinction values of dilutions of the colored waste as received a t 460 and 505 mp; and similar determinations a t 505 mp on dilutions after sulfite and hydroxide treatment of the samples. The quantity of colored and P T S T can be estimated from the E values obtained substituted in two equations, Analytical data on eight different mixtures of colored and standard wTST solutions show that good estimates of each of the two forms of TST were obtained in such mixtures by the procedure described. The procedure is being used and has proved extremely valuable in a study of the reactions and possible treatment procedures of TST wastes from hhell-loading plants. LITERATURE CITED
Baernstein, H. D., IND.ENG.CHEM.,ANAL.ED., 15, 251 (1943). Bost, R. W.,and Nioholson,Frank, Ibid., 7, 190 (1935). Clark, W. M.,“Determination of Hydrogen Ions”, p. 107, Baltimore, Williams & Wilkins Co., 1922. Copisarow, M.,Chem. News, 112, 283-4 (1915). Davis, T. L., “Chemistry of Powder and Explosives”, pp. 149, 150, New York, John Wiley & Sons, 1941. Davis, T. L., and Richmond, J. L., J . A m . Chem. SOC.,62, 75663 (1940). Giua, blichele, and Reggiani, Giulio, Atti. accad. sei. Torino, 62, 333 (1927). Kay, Kingsley, Can. J . Research, 19, B86-9 (1941). Moss, M.L., with Mellon, >I. G., ISD.ENG.CHEM.,ANAL. ED., 14, 861-2 (1942). Pinto, S. L., and Fahy, J. P., J . Ind. Hyg. Tozicol., 24, 24-6 (1942). Ruchhoft, C. C., Sewage Works J . , 13, 669 (1941). Schott, Stuart, Ruchhoft, C. C., and Megregian, Stephen, IND. ENG. CHEM.,35, 1122 (1943). Taylor, C. A., and Rinkenbach, W.H., J . Am. Chem. SOC.,45, 44-59 (1923). PREEENTED before the Division of Water, Sewage, and Sanitation Chemistry CHEMICAL SOCIETY, New York. N. Y. a t the 108th Meeting of the AMERICAN
CORRECTION. I n the article “A Specific Spot Test for Vanadium” [IND.ENG.CHEbf., ANAL. ED.,17, 63 (1945)] the last sentence should read: By use of comparative tests, it will detect vanadium in 500 times its weight of Ni++, 100 times its weight of Co++ or Cu++, and 10 times its weight of Cr+++ or WO4-J. H. REEDY
