licate measurements were made on another sample of the standard alloy. A mean of 78.5 5 0.7% was obtained. General Evaluation. This nondestructive method of analysis gives results accurate t o within a t least 5 t o 6% for all three techniques. T h e sample size was limited t o about 2 to 3 grams in the gross-decay and manualsweep-spectrometer methods, but could be increased to about 6 grams in the automatic scan technique. Because the precision of the measurement is a direct function of the total number of counts accumulated, it is advantageous to use the maximum sample size for analysis. Of the t\Vo typical spectrometer assemblies, the automatic recording instrument has better resolving power (about loyo, since a well crystal was not used), shorter scan time, and has the additional advantage of automatic recording and measurement, but it is more costly ( ~ $ 5 5 0 0 )than the other spectronieter ( ~ $ 3 1 0 0 ) . The 60-day half life and the highenergy ganiina rays of the antimony are definite disadvantages in using this type of neutron source for activation analysis, although its relative
cheapness and unrestricted availability tend t o compensate. Other neutron sources without these disadvantages such as polonium-beryllium ( l l ) , actinium-beryllium ( I S ) , plutonium-beryllium (15), and californium-252 spontaneous fission ( l a ) , may soon help to answer the demand for portable sources of higher neutron flux for use in routine analysis. ACKNOWLEDGMENT
The authors wish to thank the Michigan Memorial Phoenix Project for its generous support of this work. They also acknowledge the help of I. B. Ackermann in designing the irradiation chamber, and in making preliminary measurements. LITERATURE CITED
(1) Hughes, D. J., Harvey, J. A., U. S.
Atomic Energy Commission, Rept. BNL-325 (July 1955). (2) Jenkins, E. I., Smales, A. A., Quart. Rw. (London) 10, 83-107 (1956). (3) Loveridge, B. A,, Smales, A. .4., “Activation Analysis and Its Application to Biochemistry,” Methods of Biochemical Analysis, Vol. 5 , pp. 225-72, Interscience, Sew York, 1957.
(4) Mayr, G., Nucleonics 12, No. 5, 58-60 (1934).
(5)’ Miyr, G., Brunner, H. D Brucer, M., Ibid., 11, No. 10, 21-5 (1953). (6) Meinke, W. W.,AKAL. CHEY. A ,
736-56 (1956). (7) Ibid., 30, 686 (1958). (8) M$nke, W.K., ilnderson, R. E., Ibid., 25, 178-83 (1953). (9) Ibtd., 26, 907-9 (1954). (10) Meinke, W. K.,Maddock, R. S., Ibid., 29, 1171-4 (1957). (11) Mound Laboratory, U. S. Atomic Energy Commission, Rept. TID-5087 (July 1952). (12) Sucleonzcs 14, NO. 6 , 105 (1956). (13) Ibzd., 15, NO. 9, 192-3 (1957). (14) Oak Ridge Katiorfd Laboratory, Oak Ridge, Tenn., Radio-isotopes, Special Xaterials and Services,” Cataldg, 1957. (15) Sheldon, J., Williams, J., Brit. -4tomic Energy Research Establishment, Rept. AERE-M/M-80 (August 1954). (16) Sullivan, \I-. H., “Trilinear Chart of Kuclides,” U.S. Government Printing Offire, TTashington 25> D. C., January 1957. (1;) Tavlor, T. I., Havens, K. R.,Jr., “Berl’s Phvsical Methods in Chemical .4nalysis,” Vol. 3, -pp. 539-601, Academic Press, Sew E ork, 1956. (18) Wanke, H Monse, E. U., 2. Naturforsch. loa, 6$7-9 (1955). RECEIVED for review January 28, 1958. Accepted April 7, 1958.
Chemical Oxygen Demand of Petrochemical Wastes Modification of the Standard Catalytic Reflux Pro’cedure F. W.
BERTRAM,
0.T.
CARLISLE, J. E. MURRAY, and G. W. WARREN‘
Union Carbide Chemicals Co., Texas City, Tex.
C. H. CONNELL University of Texas Medical Branch, Galveston, Tex.
,A modification eliminating chloride interference in the determination of chemical oxygen demand by the standard dichromate reflux procedure with silver sulfate catalyst is presented. The conventional procedure is altered, so that chlorides are first quantitatively oxidized by refluxing the sample in the absence of silver sulfate catalyst. The catalyst is then added, and refluxing is continued to complete the oxidation. An inorganic chloride correction, based on an independent determination, can then be accurately applied to the total chemical oxygen demand. Applications of the modified procedure are evaluated, showing that all the advantages offered b y the standard dichromate catalytic reflux method plus an elimination of interferences due to inorganic chlorides may be expected. 1482
ANALYTICAL CHEMISTRY
A
of industrial wastes have far-reaching significance in monitoring water pollution and efficiency of operations. I n working with waste water streams from petrochemical industries, the test results of most general interest are usually the chemical oxygen demand (C.O.D.) and the biochemical oxygen demand (B.O.D.) ( 2 ) . A determination of the waste’s C.O.D. is made when a quick estimate of the strength of industrial wastes is desired. Such a determination does not differentiate between biochemically stable and unstable components, and may not be directly correlated with B.O.D. but instead represents a more nearly accurate measurement of the contaminants present. Most of the procedures originally proposed for C.O.D. used permanganate, chromate, or iodate as the NALYSES
oxidizing agent, none of which gave complete oxidation or consistent results except with a few specific wastes. A dichromate reflux procedure (4) introduced in 1949 gave a high degree of oxidation of certain types of compounds, but was ineffective in oxidizing completely the organic aliphatic aoids. and numerous other compounds. The use of silver catalyst with the dichromate reflux method Ivas investigated and in 1951 results were published ( 5 ) , which showed that nearly complete oxidation was accomplished with most compounds including aliphatic acids. The presence of chlorides in appreciable quantities caused lorn and unpredictable results, and no remedy was proposed. This procedure was, 1 Present address, Union Carbide Chemicals Co , South Charleston, W. Va.
aninionium sulfate, using o-phenanthroline ferrous complex as the indicator, The titration is accomplished in the reaction flasks. A blank, in which 50 nil. of distilled water is substituted for the sample, is treated in the same way. An inorganic chloride correction, based on duplicate determinations by a convenient method on the original sample, is applied to the chemical oxygen consumed value. Some minor modifications reduced the blank correction and improved the reproducibility. Sulfuric acid addition is made through the condenser. This Figure 1. Chemical and biochemical oxygen demands of a plant waste water stream A.
Modified dichromate catalytic reflux
B
therefore, of little value for use with plant waste water streams which may contain up t o 10,000 mg. of chloride per liter. A study of the dichromate reflux procedures (both with and without silver sulfate catalyst) showed that inorganic chlorides are oxidized quantitatively to free chlorine by dichromatesulfuric acid in the absence of silver sulfate, and that the chlorine is removed from the reaction mixture by diffusion from the condenser. A method was devised whereby the chlorides present were compensated for by initial oxidation of the sample with standard dichromate in the absence of silver sulfate catalyst. The catalyst was then added, and refluxing continued to complete the oxidation of the organic niaterials. An inorganic chloride correction, based on duplicate chloride determinations [usually by Mohr titration (1, 611 on the original sample, was subtracted from the gross C.O.D. The dichromate reflux procedure, thus modified, is free from chloride interference, and offers the advantage of inore complete oxidation through the use of silver sulfate catalyst. RECOMMENDED APPARATUS AND PROCEDURE
The procedure adopted is the method of JIoore, Ludzach, and Ruchhoft (6), modified by introduction of the catalyst after a period of initial reflux, The Moore method (3) depends on the dichromate consumed when a n appropriate amount of sample (diluted to 50 ml. with distilled water), 75 ml. of concentrated sulfuric acid, 25 ml. of 0.2500 N potassium dichromate, and 1 gram of silver sulfate are refluxed for a total of 2 hours, I n this procedure, a 500-ml. Erlenmeyer flask, equipped with a standardtapered glass joint to fit the condenser, and with a glass-stoppered side arm, is substituted for the round-bottomed flask. Suitable boiling stones are added to the flask, and the mixture is refluxed for 1 hour without the silver sulfate catalyst. It is then cooled to minimize loss of volatile unoxidized organics and 1 gram of catalyst is added through the
Dichromate standard reflux
C. 5 - d a y B.O.D.
side arm. Refluxing is contiiiued for an additional hour. The mixtllre is cooled and the condenser assembly is washed down with distilled water to dilute the mixture to approximately 360 nil. The excessdichromate is titrated with ferrous
Table I.
Extent
~$~~!~{~"hu,c,e, ~ ~ - $ ~ $ ~
Silicone stopcock grease can be oxidized by this procedure; therefore no grease is used on the condenser and side arni joints. A drop of sulfuric Or Phosphoric acid may be used to lubricate thc joints. CALCULATIONS
1. Total O.C., mg./liter
=
of Dichromate Oxidations by Various Methods (Chloride corrections applied)
% Theoretical Oxygen Demand by Standard Reflux ical Synthetic Oxygen Without With Catalyst Modified Reflux Demand, Catalyst, Standards in Distilled Water Mg./Liter -4 A B C A B C 100 95 66 101 98 96 Acetic acid 1065 15 Bcetone 92 74 99 95 92 2200 62 99 Ethanol 2085 98 97 94 39 99 92 76 A. No chlorides added. B. 500 mg./liter C1- added. C. 2500 mg./liter C1- added, Table II.
Effect of Chloride ion and Catalyst on C.O.D. Determinations
% o/o Oxidized after . - Compd. C1: Correction
Compound Methyl isobutyl ketone
C1- Correction Conventional Methods With Without Concn., Mg./Liter on Sample Basis" Modified catalyst catalyst Compd. c1method (6) (4)
100 to 300 180 to 10,000 77 300 C1- free 76 87 Propyl propionate 75 to 225 169 to 10,000 94 C1- free 225 20 Propylene dichloride 95 t o 285 100 to 10,000 C1- free 19 285 94 Sodium acetate 100 to 300 100 to 10,000 300 98 C1- free 92 Ethylenediamine 160 to 480 160 to 10,000 96 C1- free 480 200 to 600 93 160 to 10,000 Triethanolamine 95 C1- free 600 81 180 to 540 140 to 10,000 Sodium formate 85 540 C1- free 96 110 to 330 160 to 10,000 1-Butanol 97 C1- free 330 101 160 to 10,000 110 to 330 Methanol 99 C1- free 330 101 156 to 10,000 90 to 270 Acetic acid 100 C1- free 270 53 161 to 10,000 75 to 225 Isopropyl ether 52 C1- free 225 Sample size adjusted to ensure a sufficient excess of dichromate.
Si1
77 Nil 92 Nil 23 Nil 97 Nil 94 Nil 96 Nil 85 Xi1 97 Nil 100 Nil 99 Nil
54
VOL. 30, NO. 9, SEPTEMBER 1958
63 62 78 63 21 7 27 35 88 90 94 92
62 67 81
77 96
100
23 28 47 46
1483
( A - B ) X normalityof F ~ ( N H O ~ S O ~ ) Z ( SxO8000 ~)Z sample volume
where O.C.
tone, and ethanol were prepared. These solutions were used in the initial studies, either with or without known amounts of chlorides added, to determine the effectiveness of the several C.O.D. methods. In these studies and throughout the work t h a t followed, the theoretical oxygen demand for each compound was based on a n assumption that maximum oxidation was obtained, except in the case of amines, where the calculations were based on the oxidation of the contained nitrogen to free nitrogen. Table I summarizes the results using the standard reflux methods, both with and without silver sulfate catalyst, and the modified version of the standard catalytic reflux method.
oxygen consumed ml. of Fe(NH4)z(S04)2 used for blank B = ml. of Fe(NHp)2(S04)2 used for samDle 2. Chloride coriection = chlorides, mg./ liter X 0.225 3. C.O.D., mg./liter, due to organics present = total O.C., mg./liter, chloride correction A
=
=
EXPERIMENTAL EVALUATION OF MODIFIED PROCEDURE
T o determine the C.O.D. as per cent of the theoreticnl oxygen demand, standard solutions of acetic acid, ace-
Table 111.
Chloride Interference vs. Chloride Concentration
Total C1-, Mg. in Reaction Mixture
Total CI-, Mg./Liter on Sample Basis
1.78 3.55 7.10 10.6 35.5 71.0 177.5
120 237 473 707 2,370 4,730 11,820
Table IV.
C.O.D., as c1-, Mg./Liter With Without catalyst catalyst
(4)
(6) 83 106 235 41 1 887 1110 3320
(4)
(6) 68 45 50 58 37 24 28
116 246 474 707 2,400 4,800 10,000
97 104 100
100 101 101 85
Precision of Chloride Determinations on Waste Waters by Mohr Titration
Sample as Received 95%
Av. mg. Cl-/l. 1 2 3 4
% Oxidation With Without catalyst catalyst
1968 760 9562 4759
Std. dev.
limits. mg. ' Cl-/l.
7.34 3.1 66.5 8.6
&20 1 9 zk148 124
Table V.
Sample Al(OH)3 Treated, Filtered
Sample Filtered 95%
Av. mg. Cl-/l. 1951 745 9310 4622
95%
Std. dev.
limits. mg. Cl-/l.
Av. mg. Cl-/l.
2.19 1.8 0 9.1
&6 it5 0 f22
1965 757 9373 4689
Std. dev.
limits. mg. Cl-,'l.
3.9 1.3 49.2 9.5
fll &4 A116 &26
Error of Oxygen Correction of C.O.D. Due to Chlorides
(95% limits)
Samde as Received Mg. Ci-/l. Mg. 0/1. 120 f 9 it 148 124
1 2 3 4
Table VI.
14.5 h2.0 it33.4 it5.4
Sample Al(OH)s Treated, Samde Filtered Filtered Mg. Cl'/l. Mg. 0/1. Mg. Cl-/l. Mg. 0/1. f6
f 5 0 122
it1.4 11.1 0 A5.0
it11 &4 it116 A26
&2.5 hO.9 dz26.2 15.9
Reflux Time vs. Per Cent Oxidation, Modified Method
Av. % Compd. Oxidized
Compound Methyl isobutyl ketone Propyl propionate Sodium acetate Ethylenediamine Triethanolamine 1-Butanol Methanol Acetic acid Isopropyl ether Sample size adjusted to 0
1484
0
(Cl- Corr. Applied) after
Concn., Mg./Liter on Sample Basiss Compd. Chloride
1.5
2.0
hr.
hr.
200; 300 147; 213 200; 300 320; 480 393; 593 220; 327 220; 327 127; 200 147; 213
78 71 97 86 92 97 98 96 42
77 76 98 99 94 96 98 100 52
1800; 3600 1760; 3410 600; 1200 1600; 3840 980; 3560 1540; 3590 1540; 3590 1650; 3800 1640; 3210
Refluxing
ensure a sufficient excess of dichromate.
ANALYTICAL CHEMISTRY
3.0 hr. 77 82 101 94 89 89 92 100 55
4.0 hr. 78 86 98 97 94 98 97 99 57
The various C.O.D. tests were also used to determine the C.O.D. of a plant waste water stream. Because there is no practical way to determine the theoretical oxygen demand of such a stream, no comparison between the actual and theoretical oxygen demands could be obtained. Figure l shows that the results obtained by using the modified catalytic procedure were consistently higher than those obtained by the other procedures, being 1.6 to 3.0 times that of the B.O.D. and 1.4 and 1.8 times that of the uncatalyzed reflux method. The various oxidation methods were studied t o determine the effect of chlorides upon completion of oxidation of the organic compounds in selected waste water streams. Duplicate C.O.D. results were obtained on several standard samples to n-hich different amounts of inorganic chlorides had been added (Table 11). The concentrations, shown as milligrams per liter on the sample basis, represent from 1.1 to 13.2 mg. of organics in the reaction mixture together with as much as 150 mg. of chloride. INTERFERENCES BY INORGANIC CHLORIDES
I n considering interferences effected by inorganic chlorides toward quantitative oxidation when silver sulfate catalyst is used, work was done to determine if the chloride concentration w'as a t a level that would result in a significant effect on the oxidation of the organic. C.O.D.'s were obtained in duplicate on aliquots of standard solutions of sodium chloride in distilled water, containing from 1.8 to 1?7.5 mg. of chloride, by refluxing for 1 hour in the presence, and in the absence, of silver sulfate catalyst. These chloride concentrations represented approximately 100 to 12,000 mg. of chloride per liter in samples as routinely analyzed (Table 111). Because the data obtained through the use of silver sulfate catalyst do not form a smooth curve, a suitable correction factor cannot be applied, and the modified method involving oxidation of the chlorides prior to addition of the catalyst must be followed. The highest chloride concentration (177.5 mg. in the reaction mixture, or about 12,000 mg. per liter on a sample basis) appears to be near the maximum quantitatively oxidized in the absence of catalyst by this procedure. PRECISION OF CHLORIDE CORRECTIONS
The precision and accuracy of the Mohr volumetric method for chlorides, as used to correct C.O.D. values, were determined. Replicate determinations by the Mohr method were made on waste water samples containing varying
amounts of inorganic chlorides. Chlorides were also determined on each of the samples after filtration, and after treatment with aluminum hydroxide with subsequent filtration, to eliminate interference due t o turbidity. Results shown in Tables IV and V are a t the 95% confidence level. They show that single chloride determinations by the Mohr method yielded results within =t4 to 1 2 6 mg. per liter of the average chloride content a t concentration levels from 760 to 4759 mg. per liter. This would result in an error of hO.9 to h 5 . 9 mg. of oxygen per liter correction of the C.O.D. The precision of chloride determinations a t the 9400 mg. per liter level mas found to be less. A single determination would be viithin 1 1 4 8 mg. per liter from average, yielding an error of 1 3 3 mg. of oxygen per liter correction of the C.O.D. REFLUX TIME REQUIREMENTS
The reflux time required to obtain maximum oxidation was determined by studying limitations of the modified
method for C.O.D. It has been established (Table 111) that a t least a 1-hour reflux period before catalyst addition is necessary to oxidize inorganic chlorides completely in concentrations up to 12,000 mg. per liter. Several standard samples, to which varying amounts of inorganic chlorides had been added, were analyzed in duplicate by the modified procedure. The total reflux time was varied from 1.5 to 4.0 hours with the reflux time prior to catalyst addition kept a t 1.0 hour for each determination. The results as shown in Table VI indicate that the oxidation obtained within a total reflux time of 2 hours is near the maximum level and that there is little gain in extending the time beyond 1.5 hours for most of the compounds tested.
ferences due to inorganic chlorides. This method should be of value in EStimating the strength of wastes, especially those resulting from petrochemical industries, whose process and cycle waters may contain appreciable amounts of chlorides. LITERATURE CITED
(1) American Public Health Association, New York, “Standard Methods for the Examination of Water, Sen-age and Industrial Wastes,” 10th ed., p. 60,
1955.
12) Ibid.. D. 260. (3j Ibid.; ‘p. 333.
CONCLUSION
(4) Moore, IT,-4., Kroner, R. C., Ruchhoft, C. C., ANAL. C m M . 21, 953 (1949). (5) Moore, W. A., Ludzach, F. J., Ruchhoft, C. C., Ibid., 23, 1297 (1951). (6) Pierce, W. C., Haenisch, E. L., “Quantitative Analysis,” 2nd ed., p. 258, Wiley, New York, 1937.
This modification of the standard dichromate reflux method for determining C.O.D. of industrial wastes offers all the advantages of the standard method plus a n elimination of inter-
RECEIVED for review September 9, 1957. Accepted April 28, 1958. Divisions of Industrial and Ennineerine Chemistrv and Water, Sewage, aGd Sanit&on Chemistry, 132nd Meeting, ACS, New York, N. Y., September 1957.
Cellulose Supported Thorium-Alizarin Red S Reagent for Fluoride Ion Determination STANLEY K. YASUDAl and JACK L. LAMBERT Department of Chemistry, Kansas State College, Manhattan, Kan.
b The reagent and procedure described are the result of a study of colorimetric methods to produce a color in solution directly proportional to fluoride ion concentration. Fluoride ion in the concentration range to 15 p.p.m. reacts selectively with the reagent to release the thorium-Alizarin Red S chelate (absorption maximum, 520 mp) into solution. Concentration limits for a number of possible common interfering ions were determined. A polymeric structure for the reagent and a mechanism for the ion exchange reaction are proposed. The combining ratio of thorium to dye was found to be 1 to 2 by gravimetric and spectrophotometric methods. Chelation of thorium through a carbonyl oxygen and the 1-hydroxy group in the Alizarin Red S was substantiated by infrared absorption data. The method should be convenient for rapid visual or spectrophotometric determination of fluoride ion within the conditions specified. Present address, Los Alamos Scientific Laboratories, Los Alamos, N. M.
T
colored compounds obtained in solution or suspension from the reaction of thorium or zirconium salts with hydroxyanthraquinone dyes have been described as reagents for fluoride ion determination (2, 4, 8-15). These methods generally involve a change in hue of the sample solution as a measure of fluoride ion concentration. I n an investigation of metal-dye compounds as analytical reagents ( l e ) , thorium-Alizarin Red S compound supported on filter paper was found to undergo rapid and selective exchange with fluoride ion to release anions into solution. Preliminary work (6) had indicated the potential usefulness of thorium-Amaranth compound supported on filter paper as a reagent for fluoride ion, and this Tvork extended the study to include a number of dyes of various types. HE
SPECIAL REAGENTS AND EQUIPMENT
Thorium nitrate tetrahydrate, reagent grade, 1% solution buffered to p H 1.8 to 1.9 with 0.2M hydrochloric acid0.2M potassium chloride buffer solution.
Alizarin Red S, indicator grade, filtered 1% solution. Standard fluoride ion solution, 100 p.p:m., 0.221 gram of reagent grade sodium fluoride per liter of solution. Amberlite IR-120 (H) nuclear sulfonic cation exchange resin, analytical grade. PROCEDURE
Prepare the thorium-Alizarin Rcd S reagent paper by treating 1.5-inch squares of Whatman No. 42 filter paper individually with 1% Alizarin Red S solution. Blot between filter paper to remove excess dye solution, and dry a t room temperature. Store in a brown glass container. Prepare each reagent paper immediately before use by immersing in 1% thorium nitrate solution buffered to p H 1.8 to 1.9. Remove excess thorium ion solution by washing with several changes of distilled water and blot free of water before use. Convert a 6-inch column of Amberlite I R 1 2 0 in a 250-ml. buret (inside diameter approximately 3.1 cm.) to the acid form by treatment with hydrochloric acid solution, and rinse with distilled water until the eluate no longer tests acid. Pass 75 ml. of sample VOL. 30, NO. 9, SEPTEMBER 1958
0
1485
