Determination of Chlorine in Water Suggested Use of 3,3’-Dimethylnaphthidine RONALD BELCHER, ALBERT J. NUTTEN, and WILLIAM 1. STEPHEN D e p a r t m e n t of Chemistry, The University, Edgbaston, Birmingham 15, England
M
A S Y reagents have been proposed for the determination
of chlorine in water, but only two, benzidine and its 3,3 ’-dimethyl-derivative (o-tolidine), have achieved widespread use. The yellow colors produced when these substances are treated with oxidizing agents (in this case, chlorine water) are not very stable and fade rapidly. In their studies of substituted benzidines and related compounds as reagents in analytical chemistry the authors have recommended 3,3’-dimethylnaphthidine (3,3’-dimethyl-4,4’-diamino-1,l’-dinaphthyl) as a reagent for the detection of zinc (1) and vanadium (2) and a8 a redox indicator in the titration of zinc (S), cadmium, calcium, indium ( d ) , and gallium ( 6 ) , with potassium ferrocyanide. In the presence of oxidizing agents this compound gives an exceptionally stable, purple-red meriquinonoid product. The reaction is very sensitive, exceeding that of any other benzidine-type compound for the many oxidizing agents examined. The sensitivities of 3,3’-dimethylnaphthidineand certain other substituted benzidines towards chlorine have now been determined. These values are recorded in Table I with those of benzidine and 3,3’-dimethylbenzidine included for comparison. These figures give some indication of the relative sensitivities of the various amines under the experimentalconditionsemployed. I t is seen that the reagents a t present in use are neither the most sensitive nor the most suitable. From the standpoint of color stability, the N - and N,N’-alkylated benzidines are superior to the simple diamines-a fact which has been observed from their behavior towards many other oxidizing agents (6). None, however, is as sensitive as 3,3’-dimethylnaphthidine. The favorable characteristics of high sensitivity, stability of color, and ease of color measurement make the reagent ideally suited to the colorimetric determination of chlorine.
Table I.
Comparative Sensitivities Com-
parative Amine Sensitivity Color 1.O Pale yellow, fades rapidly 1. Benzidine 2 3 3’-Dimethylbenzidine 1 .O Pale yellow: fades rapidly 3: 3lMethvlbenzidine 0.5 Pale yellowf fades rapidly 4 3 3’-Di&h lbenaidine 0.5 Pale yellow: fades rapidly 5: i-Methylzenzidine 0.5 Pale yellow. fades slowly 6. N ”-Dimethylbenzidine 0.25 Pale yellow. iades very slowly 7. N’N’-Tetramethylbenzidine 0.20 Pale yellow: fades very slowly 8 N’N’-Diethylbenzidine 0.25 Pale yellow. fades slowly 9: N:N’-Tetramethylbenzidine 0.5 Pale yellow! fades slowly 10. Naphthidine 1 .O Transient pihk 0.1 Pink-red: very stable 11. 3,3 -Dimethylnaphthidine
Table 11. Limiting Sensitivities under Conditions for Determination of Chlorine Amine Sensitivity,p.p.m. chlorine
3 4 5 6 7 8 9 1 0 1 1 1 2 0.1 0.07 0 . 1 0.5 0.1 0.2 0.1 0.08 0.07 0.5 0.04
The usual procedure in water analysis necessitates a Nessler tube comparison. Under these conditions the sensitivities are improved, as shown in Table 11. The colors obtained with 3,3’-dimethylnaphthidineand a range of standard chlorine solutions measured using the EEL photoelectric colorimeter (Evans Electroselenium, Ltd., Harlow, Essex, England) show that Beer’s law is obeyed and that the colors
formed are sufficiently reproducible to enable accurate results to be obtained on as little as 0.05 p.p.m. of chlorine. A typical curve is shown in Figure 1. The E E L colorimeter is a simple single-cell, direct-reading instrument; using a more sensitive absorptiometer it should be possible to detect less than 0.01 p.p.m. of chlorine. REAGENTS AND SOLUTIONS
Chlorine waters of appropriate strength are obtained by the dilution of a strong solution of chlorine in water the strength of which is accurately known by thiosulfatimetric titration.
lo/
09
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2 3 4 5 6 7 8 9 / ABSORPTIOMETER READING
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Figure 1. Typical Curve Obtained in Determination of Chlorine Using 3,3Dimethylnaphthidine With the exception of 3,3’-dimethylnaphthidine (0.1% in glacial acetic acid), all the amine reagents are used as 0.1% solutions in 1 N hydrochloric acid. This compound was synthesized b the authors according to the method of Fries and Lohmann &). I t is now available commercially from British Drug Houses, Ltd., Laboratory Chemicals Group, Poole, Dorset, England. PROCEDURES
Determination of Sensitivities. To 10 ml. of chlorine solution contained in a test tube, add 1 ml. of the amine reagent and observe the color. Dilute the chlorine solution until the color is just detectable when viewed against a white background. Detection of Chlorine under Conditions of Actual Analysis. Place 100 ml. of the chlorine solution in a Nessler tube, add 1 ml. of reagent, and mix thoroughly. Allow to stand for 1 minute and observe the color. Repeat with more dilute chlorine solutions until the color is just apparent. Determination of Chlorine (0.05 to 1.0 P.P.M.)in Water Using 3,3’-Dimethylnaphthidine. To 100 ml. of sample contained in a graduated flask, add 1 ml. of 0.1% solution of 3,3’-dimethvlGaphthidine in glacial acetic acid andmix the solution thoroughly. Allow to stand for 5 minutes and record the intensity of the color, photoelectrically, using a green filter-e.g., Ilford 404 Green. Compare with values obtained from standard calibration curves. DISCUSSION AND RESULTS
Of the several amines examined, all are more sensitive than either
benzidine or
3,3’-dimethylbenzidine. In
particular,
3,3’-dimethylnaphthidineis the most sensitive, and it is recom-
V O L U M E 26, NO. 4, A P R I L 1 9 5 4
113
mended as a reagent for the detection and determination of chlorine. Accurate results are obtained with as little as 0.05 p.p.m. of chlorine and the color formed is more stable than that given by any of the other amines. The color begins to fade only after 15 t o 20 minutes, and then only a t a very slow rate. Reproducible results are obtained, even in the lowest range of 0.05 to 0.5 p.p.m. examined. Comparisons can be made using standard calibration curves. Acetate buffers retard the development of the color and mineral acid interferes even in 0.0LV concentration. Other oxidants present in the solution will also interfere, but the procedures used in water analysis take full account of these interferences. I n
general; treated waters do not contain significant amounts of oxidants, other than chlorine. LITERATURE CITED
(1) Beloher, R.,Nutten, A. J., and Stephen, W. I., Analyst, 76, 375 (1951). (2) Ibid., p. 430. (3) Belcher, R., Nutten, 4.J., and Stephen, W. I., J . Chem. SOC., 1951,1520. ( 4 ) Thid.. D. 3444. I m . ; i952,2438. (6) Belcher, R., Nutten, A. J., and Stephen, W. I., unpublished work. (7) Fries, K., and Lohmann, N., Ber., 54, 2912 (1921). RECEIVED for review ,March 6, 1953. Sccepted January 27, 1954.
(5j
Sulfuric Acid-Induced Fluorescence of Corticosteroids MAX
L. SWEAT'
Department o f Pharmacology, University o f Utah College o f Medicine, Salt Lake City, Utah
0
F THE relatively large number of corticosteroids tested by Reichstein and Shoppee ( 5 ) and by Wintersteiner and Pfiffner ( 9 ) , only three substances, corticosterone, 17-hydroxycorticosterone, and 4-pregnene-llp,li~,2Op,21-tetrol-3-one, were found to exhibit sulfuric acid-induced fluorescence. 17-Hydroxy-11-dehydrocorticosterone, an 11-keto compound, was included in the group of fluorescent steroids by Wintersteher and Pfiffner (9). However, if purified by chromatography, 17-hydrosy-11-dehydrocorticosterone does not fluoresce when treated with sulfuric acid ( 1 ) . Sulfuric acid-induced fluorescence has been confined to the qualitative analysis of cortical steroids. The esperimental results presented demonstrate that the phenomenon may be adapted to the quantitative anal>-sis of corticosterone and l i li~-drorycorticosteroricb>- reacting ethnnolic solutions of these steroids with sulfuric acid. EXPERI3IENTIL
Relation Between Wave Length of Excitatory Beam and Intensity of Fluorescence. Three light sources were used to determine the wave lengths of light which excite ethanolic sulfuric ncid solutions of l;-h~-drosycorticosterorie to a maxiilinl degree ~f HuorcPcc.nce: an -1H-13 Hnnovia mercury arc lamp, a I3ecliniaii h>di,ogen discliargc tui)r, aiid a Beckman tungsten filament 1:~nip. ~ I C R C T - RARC Y Lim. Various conibinationp of primary filterc: were introduced into the path of light emitted by the mercury arc of a Farrand 1Iodc.I -1fluorometer. The secondary light, filter was fixed (a combination of TTratten gelatin S o . 16 and So. 74 secondary light filters). d 10 x 75 nim. Corning S o . 9820 test tube containing a mixture of 0.1 nil. of ab3olute ethj-1 iil(who1 and 1.0 ml. of concentrated sulfuric acid was placed i n the cxriage compartment and the sensitivity dial adjusted to a rending of 5 on the galvanometer scale. To an optically matched tube containing 0.25 y of 1'7-hydroxycorticosterone dissolved in 0.1 ml. of ahsolute ethyl ;ilcohol was added 1 ml. of concentrated sulfuric wid; the mixture was Ptirred and the tube placed in the p a t h of the excitatory light beam. Maximal galvanometer deflectioii above the blank reading of 5 was obtained with a combination of Corning S o . 5113 and S o . 4489 filters which limited tmismission to the region of the -136 mp mercury line. HYDROGEN AXD T u TES 1 ~ 3 1 ~ s A . standard 4-mI. quartz n1)sorption cell containing 50 y of 17-hydroxycorticosterone in 3 nil. of 1 to 10 ethanolic sulfuric acid solution was placed in the ciirriage compartment of a Beckman DU ppectrophotometer. A plate containing an upright metal tube 6 inches long and 1 inch in diameter was substituted for the regular carriage top plate. The intensity of fluorescence emitted by the steroid solution was e d n i a t e d by eye for the various settings of the m v e srlector dial of the spectrophotometer. .~ ~
I Present address, D e p a r t m e n t of Physiology, !Vestern sit>-,Clereland, Ohio.
Reserve Cnirer-
With a slit width of 0.015 mm., those wave lengths of light from the hydrogen discharge tube which excited maximal degrees of fluorescence in the steroid solutions appeared to be in the spectral region 470 to 480 mp. K a v e lengths of light greater than 535 mp or less than 440 mp failed to excite visible fluorescence. Studies with the tungsten filament lamp were in essential agreement with those which employed the hydrogen lamp. The ethanolic sulfuric acid solution of 17-hydroxycorticosterone had a distinct absorption peak a t 4iS mp. This observation indicates that light energy is absorbed from the same region of the spectrum which excites maximal fluorescence of the steroid. The discrepancy between the results obtained with the mercury arc lamp and those obtained with the tungsten and hydrogen lamps deserves comment. The tungsten and hydrogen lamps emit a continuous spectrum, Tvhereas the mercury lamp emits a discontinuous spectrum which is characterized by the fact that a relatively large fraction of the total energy is in the 436 nip area. JTave lengths less than 440 mp did not excite visible fluorescence in the Beckman wit,h the t,ungsten and hydrogen lamps. The fact that the mercury lamp induced fluorescence a t this wave length is probably due to the fact that the emission at 436 nip is GALVANOMETER DEFLECTION
m s Figure 1. Emission Spectrum of Fuorescence Produced by 17-Hydroxycorticosterone in Ethanolic Sulfuric Acid Solution
