Extraction Efficiency of Solvents. The recovery of sulfur from sediment was carried out initially with a sediment sample of unknown sulfur content. The purpose was to evaluate the efficiency of different solvents in recovering sulfur and to evaluate their suitability for subsequent determinations by both colorimetry and chromatography. The mixture of aniline and benzene performed poorly in both tests. In the colorimetric determination, turbidity occurred and resulted in an unusually high absorbance reading. In the gc method, base line drifts of abnormal proportions made quantitative estimation very difficult. Low recovery values were obtained from both hexane and petroleum ether, probably owing to the relatively low solubility of sulfur in both solvents. Only benzene and toluene exhibited high recovery efficiencies and showed consistent results in both methods. Recovery values of these solvents are listed in Table 1. Additional experiments on extractions were performed, modifying different variables in each test. The maximum recovery values were obtained with 90 min or more of digestion time. Sulfur powder was stirred into an anaerobic sediment suspended in 30 ml of distilled water and allowed to stand overnight. These mixtures were then extracted with 100 ml of solvent using 90-min digestions. The recoveries of sulfur by gc analysis of the benzene layers are shown in Figure 4. Table 11 compares the colorimetric method with the gc method using both benzene and toluene as solvents. Standard deviations for single measurements are shown for each column and row. The difference between the means for the two methods was not significant-even at the 50% level using Student’s T test with lumped variances. The same test on the difference between the benzene and tolu-
ene shows no significance at the 70% confidence level. A study of the calibration curves shows that better responses and linearity were obtained when injections of lower concentrations of standard sulfur solutions were used. The ideal injection contained 1-3 ng; larger amounts caused a loss of linearity owing to the saturation of the EC detector.
Literature Cited ASTM, 1971Annual Standards, Part 17, D 130-68,p 78,1971. Bartlett, J. K., Skoog, D. A., Anal. Chem., 26, 1008’(1954). Berkowitz, J., “Elemental Sulfur,” Beat Meyer, Ed., Interscience, New York, N.Y., 1965. Furman, N. H., Ed., “Standard Methods of Chemical Analysis,” Van Nostrand, New York, N.Y., Vol. 1, p 1003, 1962. Hart, M. G. R., Analyst (London) 86,472 (1961). Hewlett-Packard Cat. No. 5950-8287, “The Electron Capture Detector, Applications and Troubleshooting Manual,” 1972. Juvet, R. S., Jr., Fisher, R. L., Anal. Chem., 38,1860 (1966). Kaplan, I. R., Emery, K. O., Rittenberg, S. C., Geochim. Cosmochim. Acta, 27,297 (1963). Karchmer, J. H., Ed., “The Analytical Chemistry of Sulfur and Its Compounds,” Part I, Wiley-Interscience, New York, N.Y., 1970. McNair, H. M., Bonelli, E. J., “Basic Gas Chromatography,” Varian Aerograph, Walnut Creek, Calif. 1969. Pearson, J. R., Aldrich F. D., Stone, A. W., J. Agr. Food Chem., 15,938 (1967). Struble, D. L., J . Chromatogr. Sei., 10,57 (1972). The Sulphur Institute, “Determination of Sulphur in Soils & Plant Materials,” Washington, D.C., Tech. Bull. No. 14, 1968. Vamos, R., J . Soil Sei., 15, 103(1964). Receiued for reuiew February 28, 1973, Accepted July 2, 1973. This work uas supported in part by the Petroleum Research Fund, a d ministered by the American Chemical Society, and in part by Grant ~04-3-158-45to the C’nicersit?,of Southern California from the National Sea Grant Program, L’.S. Department of Commerce.
Competitive Binding of Mercuric Chloride in Dilute Solutions by Wool and Polyethylene or Glass Containers Merle Sid Masri’ and Mendel Friedman W e s t e r n Regional R e s e a r c h Laboratory, Agricultural R e s e a r c h S e r v i c e , U.S. D e p a r t m e n t of Agriculture, Berkeley, Calif. 94710
Comparison of binding efficiencies of native, reduced, and S+-( 2-pyridylethyl) wool for mercuric chloride over a wide concentration range shows that the modified wools are more effective than native wool in the parts-per-million range but that the three wools are nearly equivalent in the parts-per-billion range. The modified wools thus have a greater total capacity for mercury salts at the higher (parts-per-million) mercury levels. Competitive sorption of mercuric chloride by polyethylene and glass surfaces of containers may take place at low mercury salt levels. The results show that mercuric chloride is distributed between the liquid phase, wool, and the container and that wool competes effectively with the container for mercuric chloride. Chloride ions and hydrochloric acid desorb mercuric chloride from the container. In a previous communication (Friedman and Waiss, 1972), we have shown that wool is a promising filter material to remove and recover mercuric and methylmercuric chloride from contaminated sources. As the concentration of mercuric salt decreased, sorption by wool became very efficient since the partition coefficient-i.e., the relative distribution of mercuric salt between the aqueous phase
and the solid (wool) phase-reaches very high values at equilibrium. Because of the potential utility of wool for adsorbing mercury salts from contaminated waters and beverages and because of the potential value of wool as an analytical tool to concentrate mercury salts in the partsper-billion range, we wished to determine whether competitive sorption of HgC12 by polyethylene or glass containers may take place at low mercury levels. Wool is highly efficient in binding mercuric chloride from dilute solutions and effectively competes with polyethylene or glass container surfaces for mercuric ions. This information is fundamentally interesting and practically useful for testing whether wool or any other adsorbent may be used to concentrate mercury salts a t low levels. Binding studies of HgClz to native wool ( N ) ,to wool in which the disulfide bonds have been reduced to sulfhydryl groups ( R ) , to wool in which the SH group of reduced wool have been alkylated with 2-vinyl-pyridine ( P ) were carried out as previously described (Friedman and Waiss, 1972; Masri and Friedman, 1972). Additional details are given in the table legends. To whom correspondence should be addressed. Volume 7 , Number 10, October 1973
951
Results of a series of experiments on the binding of mercuric chloride over a wide range of concentrations to native, reduced, and S-(2-pyridylethyl) wools (Tables I111) suggest that the binding efficiency, defined as a partition coefficient or partition ratio, increases as the initial concentration of mercury salts in solution decreases. This phenomenon was previously shown to be valid for native wool and is implicit in the previously derived isotherm for wool (Friedman and Waiss, 1972). The present results suggest that the same trend operates for reduced and pyridylethyl wool and may generally be valid for modified wools with new chelating sites. An examination of the partition ratios suggests that the
modified wools have a greater capacity for HgClz a t the parts-per-million mercuric ion levels. However, at the parts-per-billion level, the three wool types studied apgear equally effective, possibly because covalent binding to residual S H groups takes place. During the course of the present and earlier studies it became apparent that some mercuric salt was being lost to the container on prolonged storage of mercury salt solutions in the parts-per-billion range. Since such losses have wide-range practical and theoretical implications, a series of experiments was carried out to delineate this problem. These experiments are summarized in Table IV and Figure 1.
1
I 110-
Table Ill. Hg2+ Uptake by Reduced Wool
-
110
(HgC12-Hz0, 20 hours, 25')
-
Conc. range Hg2+ in medium Initial
i 0 " i l i -1100
*prr '.IF
I d
I
jll
llll, 06, l,.lll
L01.IIIl
OtIOIP>#O*(
Llljll
I1100
c-2
Figure 1. HgCI2 desorption from polyethylene tank by NaCl 0.05M HCI
-
Table I V . Loss of HgCIz to Polyethylene Tank Surface
Table I. Comparison of Hgz+ Uptake by Native ( N ) , Reduced ( R ) , and S-Pyridylethyl ( P ) Wool
+ Hg2+ to 30 ppb + Hg2+ to90 ppb
(HgCI2-H20, 50 rnl/g, 24 hours, 25") Hg2+ uptake
Wool
Initial
Final
Mg/g
%
R P N R P N R P N R P N R P N R P
0.1 (100 ppm) 0.1 0.1 1 1 1 2 2 2 4 4 4 8 8 8 40 40 40
0.0017 0.0002 0.0003 0.2 0.001 0.016 0.8 0.0016 0.218 1.7 0.042 0.79 3.4 1.5 2.5 21.5 19.5 25.2
4.9 5 5 40 50 49.2 60 99.9 89.1 115 198 160.5 230 325 276 925 1025 740
98 99.8 99.7 80 99.9 98.4
60 99.9 89.1 58 99 80.2 57 81 69 46 49 37
Partition ratio" 3,000 25,000 17,000 200
+
100 mg P Filter Empty, rinse Refill 50 I. H20 HN03(0.05N)
50,000
3,100 75 62,000 41 0 67 5,000 202 67 21 0 110 43 53 29
+
423 ppb
Event Start 50 I.
Hg2+ conc. (mg/ml)
Partition ratioa
Conditions
200 m g wool 98,000 14 I. medium 20 hr, 25" 103 ppb 58 ppb 14 I. medium f 20 m g wool 543,000 20 hr, 25" a Partition ratio: (pg Hg2+/g w o o l ) / b g Hg2+/ml (final)]
1016 ppb rg60Sf
Final
+
-t500 m g P Filter Empty, rinse
Sampling, time, hr to t72 t120
to
Hg2+, ppb 10 3 2
30
10 to 90 ti7 57 t64 18 t24 12 Wool has 300 p g Hg2+
Balance Hg2+,c(g +500
+ 1400
f43
1.5 1.5 f24 4 t66 2.5 Wool has 500 p g Hg2+
+4000
-300 -600
tl8
f2
-500 -125 +4375 p g
(4375 pg Hg2+)/(surface6900cm2) = 0 . 6 3 p g Hg2+/cm2
(Mg Hg2+/g wool)/[mg Hg2+/ml (final)].
a
Table II. Hgz+ Uptake by Reduced Alkylated Wool ( P ) (S-pyridylethyl wool) (HgC12-H20, 20 hours, 25") Hg2+ conc. initial
1 PPm 100 ppb a
Final 0.616 ppm 61 P P ~
952
+ +
Partition ratioa 44,000
(47,000)b
447,000
(360.000)c
Partition ratio (pg Hg2*/g/ wool)/[pg Hg2+/ml (final)] 29 pg Hg2+/mg wool (5 8 mg Hg2+/sample vs 5 4 mg theoretical) Direct analysis of wool-22 pg H2+ /mg wool (0 44 mg Hg2+/samplevs 0 55 mg Hg2+ theoretical)
* Direct analysis-
C
Conditions 200 m g Pb 14 I. medium 20 hr. 25' 14 I. medium 20 m g F 20 hr. 25"
Environmental Science 8 Technology
The mercuric chloride balance during the described events, shown in the right-hand column of Table IV indicates that a total of 4375 gg of mercuric ion was lost to the container. Additional studies, summarized in Figure 1, demonstrate that nearly all of the mercuric chloride that has been lost to the container can be recovered with the aid of NaCl and/or HCI. Chloride ions in aqueous and in acid solution appear to prevent binding of HgZT to the container. We also examined the sorption of mercuric chloride by glass containers. In typical experiments, the Hg2+ concentration of a 12-ppb mercuric chloride solution in a 10-liter glass carboy dropped to 10 ppb after 24 hr. This corresponds to a 17% loss or 0.008 gg HgZ+/cmz. Similarly, a 30-ppb mercuric chloride solution in a 1-liter volumetric flask lost about 35% of its Hgz+ after 9 days, corresponding to 0.02 +g Hg2+/cmz. Additional experiments have shown that it is relatively safe to store mercuric chloride in the ppm range, since the total loss falls within the experimental error of the analyses. Precleaning the glassware with 5% to 10% " 0 3 , followed by rinsing of the container with a 0.1N HC1 solution
containing IN NaC1, effectively removes any adsorbed mercury from the surface. Similarly, addition of NaCl and/or HC1 to dilute mercuric ion solutions prevents loss of mercury to container. Sorption of mercuric ion on glass has been considered as a source of error in analyses since the eighteen hundreds. However, we have not seen any quantitative studies which show distribution of mercuric ion between plastic or glass containers and the solvent, except for a recent report (Carr and Wilkaiss, 1973) which appeared after this work was completed. Our results show that it is possible to desorb nearly all of the mercuric salt from the container with the aid of chloride ion and hydrochloric acid and that wool effectively competes with the container for mercuric ions. This observation is not only of theoretical interest but of obvious practical importance. Literature Cited
Carr, R. A,, Wilkaiss, D. E., Enuiron. Sci. Technol., 7,62 (1973). Friedman, M., Waiss, Jr.. A . C., ibid.,6,457 (1972). Masri, M. S., Friedman, M., ibid.,6,745 (1972). Received for reuieu February 20, 1973. Accepted July 16, 1973.
Ultraviolet Photography of Sulfur Dioxide Plumes Gary M. Klauber D e p a r t m e n t of Electrical Engineering, The J o h n s H o p k i n s University, B a l t i m o r e , M d . 21218
A method to image normally invisible SO2 plumes on photographic film, using the sun's ultraviolet light in the absorption band of SO2 near 300 nm, is described. Design of a primitive SOz plume camera is described, and a sample uv SO2 plume photograph is presented. A knowledge of the geometry and ultimate rise of smoke plumes is necessary to predict the ground level concentrations of sulfur dioxide downwind of tall, stationary sources. This has typically been done (Hoult et al., 1969) by shutting off the electrostatic precipitators to release visible particulates and photographing this soot plume. This note describes a novel technique for photographing SO2 plumes using the ultraviolet light of the sun and exploiting the uv absorption properties of S O z .
Theory SO2 gas absorbs light in the 232-315-nm wavelength range, with a typical Beer-Lambert law absorption coefficient of 0.013 cm-I torr-I a t 304 nm (Warneck et al., 1964). Daytime sunlight typically arrives at the earth's surface only at wavelengths above 295 nm, increasing in intensity with increasing wavelength (Coblentz and Stair, 1936; Knestrick and Curcio, 1970). In principle, if a camera body were fitted with a lens which passes uv light and an interference filter which admits only those wavelengths absorbed by SO2, photographs of SO2 plumes are possible. The absorption bands of C02, CO, 0 2 , H20, KzO, "3, and N O fall outside of the SO2 band of interest (Thompson et al., 1963). Absorption of NO2 is typically a factor of three lower than that of SO2 near 300 nm (Hall and Blacet, 1952). Nitrogen oxides are less than 10% NO2 near the stacks, and the stack exit NO, concentration is typically one third of the SO2 concentration (Cuffe and Gers-
tle, 1967). Therefore, NO2 interference is two orders of magnitude below SO:! signals near the stack. In the region of ultimate plume rise in urban atmospheres, NO2 interference may be as much as 107'0, due to rapid oxidation of NO to NO2 in the plume. Apparatus
A fused quartz simple lens, with focal length 9.5 cm in the ultraviolet, was mounted on a single lens reflex camera body at a lens-to-film distance equal to the focal length. A 10-nm bandwidth interference filter centered a t 298 nm was mounted immediately behind the lens. The entrance aperture was fl6. T o estimate exposure and to adjust the focus, a series of trial exposures was made. Kodak High Contrast Copy Film 5069, processed according to manufacturer's directions, was used. The apparatus was then used to photograph power plant plumes perpendicular to their axes. Resul t s
A series of pictures was taken of the H. A. Wagner power plant, southeast of Baltimore, Md., on Monday, April 16, 1973, from 11:05to 11:lO A.M. EST. The bearing of the stacks from the camera was 285" a t a range of 1.1 km. Surface winds 10 min earlier a t Friendship Airport, 11 km to the east, were 220" a t 4 m sec-I. Skys were partly cloudy, with a 40% cirrus cover. Figure 1 shows an ordinary visible light photograph of the scene, taken through a standard 50-mm camera lens, where no smoke is visible above the stacks. Figure 2 is an ultraviolet photograph, exposed for 2 sec, taken about 2 min after Figure 1. Note that one of the stacks, number 1 (left), is not in operation. Superposition of absorption by plumes from units 3 and 4 is apparent. The Volume 7. Number 10, October 1973
953
