enthalpy functions of Drago e t al. (111, Gutmann ( 1 7 ) , or Arnett et al. (12) were found. The same conclusion applies to the entropy changes for eq 1 as well. However, when solvatochromic red shifts (as E T ) for each of the three dyes are plotted as a function of AGfo for the equilibrium in eq 1, the regular nonlinear correlations in Figure 3 are obtained. Another test of the uniformity of the red-shift data for the three indicators was applied to the empirical curves in Figure 3. The parallel character of the family of curves was verfied by determining differences, A = (E& - ET)^, for each of the solvents in Table I with a given pair of indicators (1 and 2). For the pair, NBAO-PB, the mean value of A (or is 4.63 f 0.15 kcal/mol (S.D.) with all solvents included, and, for the remaining combinations, a ( P B - X R ) is 3.7 f 0.9 and a ( N B A 0 - X R ) is 8.3 f 1.0 kcal/mol. The statistical variation within a set of differences is definitely random and the poorer precision for the last two pairs arises from the larger uncertainties in the Brooker X R data. For the more extended lower portions of the curves (beyond -AGfo = 1.60), the correlations become essentially linear and conform t o a simple additivity of free energies
a)
-(ET + AGf") = c
(2)
given by eq 2. The computed values for the constant, c, are: 55.20 f 0.26 (NBAO); 50.60 f 0.15 (PB); and 46.6 f 0.6 (Brooker's dye VII).
LITERATURE CITED (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17)
E. M. Kosower, J. Am. Chem. Soc.. 80, 3253 (1958). K. Dimroth et al., Justus Liebigs Ann. Chem., 861, 1 (1963). C. Reichardt. Angew. Chem., lnt. Ed., Engl., 4, 29 (1965). L. G. S. Brooker et al.. J. Am. Chem. SOC.,87, 2443 (1965). J. Figueras, P. Scullard, and A. Mack, J. Org. Chem.. 36, 3497 (1971). J. Figueras. J. Am. Chem. SOC.,93, 3255 (1971). 0. Kolling and J. Goodnight, Anal. Chem., 45, 160 (1973). 0. Kolling and J. Goodnight. Anal. Chem., 46, 482 (1974). E.G. McRae, J. Phys. Chem.. 61, 562(1957). M. M. Davis and H. Hetzer, Anal. Chem., 38, 451 (1966). R. Drago, G. Vogel. and T. Needham. J. Am. Chem. SOC., 93, 6014 (1971). E. Arnett, E. Mitchell, and T. Murty, J. Am. Chem. Soc., 96, 3875 (1974). J. F. Thorpe. J. Chem. SOC.,324 (1907). 0. Kolling, Anal. Cbem., 38, 1424 (1966). F. Fowler, A. Katritzky. and R. Rutherford, J. Chem. Soc. E, 460 (1971). T. Krygowski and W. Fawcett. J. Am. Chem. Soc., 97,2143 (1975). V. Gutmann and R. Schmeid, Coord. Chem. Rev., 12, 263 (1974).
RECEIVEDfor review August 8,1975. Accepted February 3, 1976. Partial financial assistance for this project was supplied by a National Science Foundation Grant GP-27634.
Decomposition and Analysis of Refractory Oceanic Suspended Materials D. W. Eggimann" and P. R. Betzer Department of Marine Science, University of South Florida, 830 First Street South, St. Petersburg, Na. 3370 7
A new technique for the decomposition of refractory oceanic suspended matter has been developed and tested using samples of certified standard materials, W-1 and Plastic Clay. Decomposition is carried out in a sealed, all-Teflon (T.F.E.) vessel using high-purity HCI, "03, and HF. Eliminating boric acid from the digestion procedure and only using highly purified acids produces extremely low blanks, improves signal-to-noise ratios, and minimizes interferences for flameless atomic absorption analyses. Aluminum, calcium, iron, magnesium, manganese, and silicon were quantitatively recovered from standards whose weights (100 to 2000 gg) were representative of the amounts of suspended matter which would normally be filtered from open-ocean waters.
Suspended materials in open-ocean waters can vary from as little as 0.5 pg/l. to as much as 1000 fig/l. (1-6). The greatest portion of ocean waters, however, is characterized by suspended particle loads of less than 20 pg/l. (2-5). Since the largest volume water sampler which is routinely used by oceanographers collects 30 1. of seawater, the total mass of suspended material which can be collected for analysis will almost always be less than 600 pg. A large fraction (usually more than 50%) of the suspended material is made up of organic compounds; the remainder is composed mostly of alumino silicates, quartz, carbonates, and amorphous silica ( I , 2, 5, 7-9). Many of the techniques which have been applied to the decomposition and analysis of oceanic sediments (10-12) 886
ANALYTICAL CHEMISTRY, VOL. 48, NO. 6, MAY 1976
or suspended material from rivers and other near-shore oceanic areas (13-16) are not suitable for use with samples of suspended matter collected from the open ocean because: (1)they are designed for larger sample sizes (1mg or more of suspended matter) than are normally collected and available for analysis (10-12); (2) they use relatively large amounts of impure reagents which contribute substantial amounts of several geochemically important minor elements, including six (aluminum, calcium, iron, magnesium, manganese, and silicon) which we were interested in measuring (9-16); and (3) the samples are decomposed in open vessels which provide an avenue for atmospheric contamination and the loss of volatile species (13-18). The object of this work was to develop a suitable method for dissolving and analyzing small quantities (less than 2 mg) of oceanic suspended matter for aluminum, calcium, iron, magnesium, manganese, and silicon.
EXPERIMENTAL The suspended material is dissolved as follows: An Eppendorf pipet is used to inject 750 p I of concentrated (ULTREX J. T . Baker Chemical Co.) HC1 into an all-Teflon bomb (Figure 1) containing the suspended matter and Nuclepore filter membrane (47mm diameter, 0.4 pm pore size) on which it was collected. The bomb is then sealed, submerged in a hot-water bath, and heated for 30 min a t 90-100 O C . The bomb is then transferred to a freezer and cooled for 15 min a t -45 O C . After cooling, the bomb is opened, injected with 250 pl of concentrated, ULTREX " 0 3 using an Eppendorf pipet, sealed, and submerged for an additional 30 min in the hot-water bath. Following a second cooling in the freezer, 50 pl of concentrated, ULTREX H F is injected into the bomb with an Eppendorf pipet. The bomb is then resealed and
LUCITE RETAINING COLLAR
TEFLON CAP
TEFLON DIGESTION CUP
TEFLON DIGESTION
BOMB
Flgure 1. Diagram of Teflon vessel used to digest refractory susDended matter
heated for 60 min in the hot-water bath. After final cooling in the freezer, the sample is diluted to 100 ml with doubly deionized water. T h e final solution is thus 0.75% HCl, 0.25% " 0 3 , and 0.05% HF. Samples were analyzed for aluminum, iron, and manganese with a Perkin-Elmer Model 403 atomic absorption spectrometer equipped with a Model 2000 heated graphite furnace, a deuterium arc background corrector, and a Model 56 recorder. Magnesium and calcium measurements were made on the same instrument using an air-acetylene flame instead of the heated graphite furnace. T h e volatility of SiFd precluded any silicon measurements by flameless atomic absorption. Instead, a colorimetric procedure which utilized the formation of the silicomolybdate blue complex and employed ascorbic acid as the reducing agent was adapted to a Technicon AutoAnalyzer. Instrumental settings for the atomic absorption unit, heated graphite furnace, and Technicon AutoAnalyzer are listed in Table I. Primary standards (10 mg/ml) for all six elements were prepared from reagent grade chemicals. T o minimize viscosity and matrix differences between standards and samples, combined secondary standards were prepared so that the six elements were present in essentially the same proportions and with the same matrix as the samples. Secondary standards were prepared fresh every third day in concentrations which closely bracketed the samples. To eliminate as much operator bias as possible, all the data were reduced on an IBM 360/65 computer. Standard curves of absorbance vs. concentration were constructed from first- or secondorder regression equations. Sample absorbance was converted to concentration using the regression equation. T o obtain fig of each element, sample concentrations were multiplied by the solution volume (100 ml) and then corrected for the filter blank by subtracting the amounts of aluminum, calcium, iron, magnesium, manganese, and silicon which the Nuclepore filter membrane contributed to the sample (Table 11).
RESULTS AND DISCUSSION Following a review of techniques which have been applied to the decomposition and analysis of sediments and suspended matter in rivers and near-shore oceanic areas, we chose t o apply Buckley and Cranston's (12) procedure t o our samples of oceanic suspended matter. Their decomposition technique was favored because it was carried out in a sealed Teflon bomb and required relatively small amounts of reagents. Thus, both volatile and nonvolatile elements could be measured while reagent blanks and contamination from the digestion vessel and laboratory atmosphere could be minimized. Although their technique is ef-
fective for decomposition and analyses of 100-mg samples of marine sediment, it was immediately apparent from our experiments that there were a t least four major changes needed before it could be applied to our small samples of oceanic suspended matter. These included: (1) the elimination of boric acid, which contributed significant amounts of the elements we were measuring and provided uncorrectable interferences in the measurement of aluminum, iron, and manganese in the heated graphite atomizer; (2) the use of ULTREX grade, rather than reagent grade, HCl, "03, and H F which contain large amounts of silicon and iron; (3) the reduction of the amount of H F from 6 ml to 0.05 ml to eliminate interferences in the measurement of silicon and aluminum; (4) the alteration of the sequence of addition of the reagents t o ensure dissolution of iron. Although several authors have discussed the use of boric acid to dissolve insoluble metal fluorides for samples larger than 100 mg (10-12), we found its use undesirable because even small amounts resulted in intense light scattering which precluded compensation by the deuterium background corrector. In addition, even had we been able to compensate for the light scattering during atomization, the concentrations of aluminum, calcium, iron, magnesium, manganese and silicon contained in even the purest available boric acid would have substantially increased the reagent blank. For example, 1-g samples (representative of a minimum amount which is employed during digestion of refractory materials) of Specpure (Johnson Mathey Co., Ltd., London, England) boric acid were dissolved and then analyzed. When compared to the average mass of these elements in oceanic suspended matter from 20 1. of seawater (Table 11),the contribution from boric acid makes up 12, 28, 2, 9, 24, and 7% of the aluminum, calcium, iron, magnesium, manganese, and silicon, respectively. If this calculation is repeated for the amount of boric acid (5.6 g) used in the procedure we are modifying (12), these levels become 68, 158, 11, 50, 134, and 39%, respectively, of the average amount of these elements in oceanic suspended matter. Thus, even the highest purity boric acid that was available was unsatisfactory due to the levels of each of these elements it contained, as well as the interferences it created in the heated graphite atomizer. While boric acid may be necessary for digestion and complete recovery of certain metals in larger samples, our good recovery for these elements (Table 111) without the use of boric acid indicated that, in samples smaller than 2 mg, insoluble metal fluoride formation was undetectable by our method of analysis. Despite the elimination of boric acid, the blank remained unacceptably high due to the use of reagent grade acids. The maximum limits of impurity for ACS reagent grade HC1, "03, and H F exceed the maximum limits of impurity of ULTREX HCl, "03, and H F by a t least ten times for iron and more than 100 times for silicon. If 50 ~1 of reagent grade H F were added during digestion to samples of suspended matter from T R 111, the silicon in this small amount of acid would contribute over 5 fig, or 25%, of the average silicon in these oceanic samples. By using ULTREX grade reagents, we were able to reduce the acid blanks to less than the detection limit of our analytical methods. In addition to these refinements, we found it necessary to reduce the amount of H F used in the digestion procedure. Our data showed that aluminum and silicon signals were a function of the concentration of H F and were, in fact, suppressed by excesses of HF. By adding small increments of H F to solutions (which were 0.75% HC1 and 0.25% "03) containing equivalent amounts of silicon, the influence of H F on the absorbance of the silicomolybdate blue complex was determined. These data (Figure 2) show that ANALYTICAL CHEMISTRY, VOL. 48, NO. 6, MAY 1976
887
Table I. Operating Parameters for Atomic Absorption and Autoanalyzer Systems Program settings for HGA Dry Element
Light source
Ash
Wavelength, nm
Slit width, nm
Temp (GC), C
Time,
Atomization Time,
S
Temp (qC), C
Time,
S
Temp (?C), C
Comments
S
A1
HCa
309.2
0.7
150
25
1000
20
2600
12
Fe
HC
248.3
0.2
150
25
1200
20
2500
10
Mn
HC
279.5
0.2
150
25
1000
20
2400
10
Purge gas, nitrogen+ purge gas flow is interrupted for 7 s at the beginning of each atomization cycle
Flame settings
Ca Mg
HC HC
422.7 285.2
1.4 0.7
Oxidant
Flow rate, l./min
Fuel
Flow rate, l./min
Air Air
22 22
Acetylene Acetylene
4 3
Reducing flame Oxidizing flame
Autoanalyzer settings Sampling cycle
Pump rate
Si
Tungston 660 Sample 1 min 1 5 cm3/h 5-cm flow cell lamp (filter) Blank 1 min a Hollow cathode lamp. b For aluminum measurements in Nuclepore filters, and in reagent blanks, argon was used as the purge gas.
____
___
_
_
-
~
_______
Table 11. Elemental Composition of 47-mm Diameter, 0.4 pm Pore Size Nuclepore Filters, W-1 and Plastic Clay Standards, and Samples of Open-Ocean Suspended Matter
Element
Method of analysis
Detectiona limit, pg
Composition of 47-mm diameter Nuclepore Membrane filters Range reported by General Electric, pg This anal, pg (SD)
Composition of standards w-l and
Plastic Clay, Range in pg from Table IV
Composition of suspended matter collected o n Trident Cruise 11I , Atlantic Ocean Average, Range, Pg !-e
AI HGAb 0.02 0.05-0.1 0.07 (0.003) 10-333 5.3 0.1-31.0 0.0 5-0.1 G0.3 0.5-127 3.4 0.4-15.5 Ca Flamec 0.3 Fe HGA 0.02 0.1 -0.5 0.22 (0.03) 1.9-128 4.1 0.4-23.1 Mg Flame 0.004 0.05-0.1 0.03 (0.01) 0.5-65 1.4 0.2-6.4 Mn HGA 0.0003 0.01-0.05 0.0018 (0.0002) 0.1-2.1 0.086 0.00 2-0.3 59 0.1 -0.5 0.56 (0.33) 27-400 19.9 4.8-11 8.0 Si Colord 0.3 a Detection limit is defined as twice the standard deviation of the blank. b Atomic absorption, heated graphite atomizer (HGA 2000). C Atomic absorption, air-acetylene flame. d Silicomolybdate/ascorbic acid colorimetric procedure adapted to Technicon AutoAnalyzer.
as HF concentrations increase beyond 0.05%, there is a significant reduction in the absorbance of the silicomolybdate complex. Therefore, we reduced the amount of H F used in the digestion procedure from 6 ml to 50 111. This very small amount of HF is sufficient to digest approximately 18 mg of a typical aluminosilicate, which is about 450 times more than the average amount present in 20 1. of seawater. The sequence of addition of reagents was also changed from that specified by Buckley and Cranston. Duce and Hoffmann (personal communication) suggest that if iron is to be completely dissolved from airborne particulate matter, HC1 should be added to and reacted with the material before any concentrated HNOs is used. Thus, instead of initially adding 1 ml of aqua regia (as specified by Buckley and Cranston, 1971), we add 750 ~1 of concentrated HCl to the sample. After the sample has been heated and subsequently cooled down, 250 pl of concentrated " 0 3 is added. Finally, to complete the breakdown of the aluminum oxygen octahedra, 50 p1 of concentrated H F is added. Because an extra heating and cooling cycle is required, the stepwise addition of acids does extend the time required for sample preparation, but the selective chemical attack 888
ANALYTICAL CHEMISTRY, VOL. 48, NO. 6, MAY 1976
ensures complete dissolution of iron in the sample. The use of Teflon bombs with steel jackets has resulted in the contamination of samples with iron and manganese (Buckley and Cranston, personal communication) and with nickel and chromium (12). Our bomb is made entirely of Teflon except for a lucite collar which provides mechanical rigidity to the top. It has been our experience that, without a retaining collar, the tops of all-Teflon bombs tend to distort and lose their sealing capacity after relatively few digestions. With a lucite collar in place, we find that our first group of Teflon bombs is still functioning effectively after 100 complete digestions. The bomb is valuable for most trace element work because it is suitably inert and free of contaminating elements. We were unable to detect any contribution of aluminum, calcium, iron, magnesium, manganese, or silicon from the bomb. In addition, the natural rejection of the Teflon for the acids used in the digestion aids in keeping the sample in contact with the small quantity of reagents. Finally, the sealing capacity of the bomb is important to any study of elements such as silicon, aluminum, vanadium, and titanium which could form volatile species during decomposition (12).
1
100
Ox)
030
010
Table 111. Elemental Recovery of USGS W-1 and U.S. Bureau of Standards 98a Plastic Clay0
1
1
1
1
070 1
I10
090
1
1
7 5 PPY S I
1
Silicon
109 197
100 101
203*
100
275* 336
100 100 99 106
Aluminum
Iron
Manganese
Magnesium Calcium 70
433 472* 527 607 626 64 2 720
840 885 897 966*
1104 1627 1891*
100 96 98 96 95 105 101 98
103 102 103 99
100 98 98 95 91 97
93 99 99 108 91
94
99 102 97 99 110 101 99 94 96 99 101 103 93
98 97 100
88 100 94 95 90 98
101 97
98
104
98 101
100 102
97 100 97 10 5 98
103
102 101 98 97 97 99 101 104
100 103 101 102
A1203
CaO Fe203
MgO
MnO SiO,
16.9 10.96 11.2 6.6 0.16 52.6
1
1
GAIN 2
A
6AY 8 IEXPANDEO SCALE1
1
~
5 I PPY 5 1
20
-
100
100 102
(83)
97
0
100 101 101 92
I
I ,020
I
I ,040
'
I .060
X HF IN
101
Table IV. Standard Reference Material (Average Percent Composition) Survey Diabase W - l
IS0 1
2 6 PPY SI
102 101
100 100 105
1
103
96
100 99 101 100 96 99 Av 4 5 3 5 2 OneSD 3 QSamples are USGS W-1, except those designated by an asterisk which are U.S.National Bureau of Standards 98a Plastic Clay.
U.S. Geological
-
130 1
0
Elemental %recovery Sample size in, fig
1
National Bureau of Standards Plastic Clay 98a 33.19
0.31 1.34 0.42 48.94
As a check on the new procedure, 15 samples of the United States Geological Survey W-1 standard and five of the National Bureau of Standards Plastic Clay (98a) standard, whose compositions are listed in Table IV, were digested. Measurements of the concentration of aluminum, iron, magnesium, and silicon were made on both standards. In addition, manganese was measured on the samples of W-1, which is certified for this element. Calcium was measured on some of the W-1 samples, but was not abundant enough in the small amounts of Plastic Clay to be measured accurately. The average chemical compositions for the W-1 and Plastic Clay standards (Table IV) were used to compute a percent recovery for each element (Table 111). The average recovery for each of the six elements listed is within a single standard deviation of 100% recovery. Because of the great variability in the concentration of oceanic suspended materials with depth and with location ( I , 3-5, 8 , 9 ) , the digestion procedure was tested for samples ranging from approximately 100 to 2000 pg. T h e results of the tests (Figure 3)show that, over the entire range of weights, digestion was complete for each of the standard materials. T o correct the analyses for the elemental contributions of the Nuclepore filter membranes, three filters from each of three batches were digested and analyzed. The average contribution for each element as determined from these
I
I ,080 SAMPLE
I ,100
' ' ' I .I20
1 ,140
I
1
1
160
SOLLITION
Figure 2. Effect of the presence of HF on the absorbance measurement of silicon by the silicomolybdatelascorbic acid colorimetric
method
nine filters is listed in Table I1 along with compositional data supplied by General Electric. Robertson (13)reported Nuclepore filter membranes contained 28 and 0.13 wg/g of iron and manganese, respectively. Using his data for these elements, and the average mass of a 47-mm Nuclepore membrane (19 mg, determined from the average desiccated weight of 751 filters from 10 batches), .a 47-mm filter should contain 0.53 pg of iron and 0.0025 pg of manganese. Our findings are in reasonable agreement with these values and, with the exception of manganese and magnesium, the ranges suggested by General Electric. Both our determinations and those of Robertson (17) indicate that manganese levels in Nuclepore membranes are much lower than those reported by General Electric. In addition, we found significantly lower amounts of magnesium in the batches of membranes we analyzed than General Electric suggests. Our data for aluminum and iron are all within the ranges they suggest, and silicon, while slightly higher, is still within one standard deviation of their range. The low calcium levels in single, 47-mm diameter Nuclepore membranes precluded the measurement of this element by atomic absorption spectroscopy using an air-acetylene flame. The level of calcium we report is less than or equal to the detection limit of the analysis (0.3 pg). The levels of aluminum, calcium, iron, magnesium, manganese, and silicon in single, 47-mm diameter, Nuclepore filters are insignificant when compared to their levels in the W-1 and Plastic Clay standards we digested or to the average amounts of these elements associated with the suspended matter in 20 1. of open-ocean water (Table 11).For example, the average elemental mass contributed by one of these filters ranges from a minimum of 0.7 to a maximum of 2.6% for aluminum and iron, respectively, in the smallest W-1 standard we tested (109 kg). When compared to the average amounts of these elements in the suspended matter from 20 1. of open-ocean water, the blank represents 1.3, 2.9*, 5.4, 2.2, 3.1, and 2.8%, respectively of the average amounts of suspended aluminum, calcium (calculated using the maximum calcium content reported by General Electric for a single, 47-mm diameter Nuclepore filter), iron, magnesium, manganese, and silicon. Our methods of digestion and analysis were applied to several hundred samples of suspended matter taken from ANALYTICAL CHEMISTRY, VOL. 48, NO. 6, MAY 1976
889
I
1
1
1
1
J.1
I
1
1
1
1
.1
110-
,
1
1
1
1
1
1
.1
-
0
>
.
105A
0 X
a: W
x
100-
0
+
1
.1
a
m
x
0
A
a
0
m
o
A 0 0
95-
a
0
X
0
RECOVERY OF ELEMEKTS SILICON
0
W U
0 AWYINUY
90-
85
0
i
I
0
I
100
1
200
1
300
1
400
1
500
1
600
1
roo
1
1
800
MlCROGRP.YS
900
1
1
1
1000 1 1 0 0
STANrhWO
OF
X
WGNESlUY
A
CALClul Y p -
*
1
1200
1
1300
1
1
1400 1500
I
1
1600
1
1 1700 moo
I ROO
CLAY
Figure 3. Recovery of silicon, aluminum, iron, manganese, magnesium, and calcium from standard reference materials
Table V. The Precision and Signal-to-Noise Ratios for Samples Collected on Trident Cruise 111 Element ~
Av signal-tonoise ratio Av precision of instrumental anal., %Q No. of samples
(n) Type of analysis
~
Silicon
Aluminum
Iron
Manganese
Magnesium
Calcium
10
12
10
7
4
9
5
6
4
11
8
6
20 8
208
211
194
209
77
At. absorption (graphite furnace)
At. absorption (graphite furnace)
Colorimetric (Technicon r Auto n Analyzer)
At. absorption (graphite furnace)
At. absorption At. absorption (air-acety(air-acetylene flame) 1 lene flame)
J
1 SD of 3 to 5 absorbance signals for sample ilmean absorbance for sample i ) / n samples 100.
shallow (1km) waters with 30-1.Niskin bottles during R/V Trident cruise 111 to the North Atlantic Ocean and then collected on 47-mm diameter, 0.4 wm pore size Nuclepore membranes. The average signal-tonoise ratios and the average precision of the analyses (Table V) indicate the method is a suitable means of preparing and analyzing particulate matter from clear openocean waters for these elements. It is particularly important to note that the calculation of signal-to-noise ratios included instrumental, filter, and reagent contributions to the denominator. Since instrument noise was often more than half of the total blank, the application of an analytical technique (possibly instrumental neutron activation or electrochemistry) with less instrumental noise than the atomic absorption and colorimetric techniques we employed could further increase signal-to-noise ratios.
ACKNOWLEDGMENT Many valuable suggestions for improving the manuscript were made by Susan B. Betzer and Linda Bell and came out of discussions with Ray Cranston of the Bedford Oceanographic Institution.
LITERATURE CITED (1) F. T. Manheim, R. H. Meade. and G. C. Bond, Science, 167, 371 (1970). (2) P. E. Biscaye and P. Varlamoff. 1975 Spring Annual Meeting of the
800
ANALYTICAL CHEMISTRY, VOL. 48, NO. 6, MAY 1976
American Geophysical Union, June 16-19, Washington, D.C., "Suspended Particulates in Seawater: A World of Geochemical Diversity", oral presentation. P. R. Betzer, K. L. Carder, and D. W. Eggimann, "Suspended Solids in Water", R. Gibbs, Ed., Plenum Press, New York. N.Y., 1974, pp 295314. P. R. Betzer. P. L. Richardson, and H. B. Zimmerman, Mar. Geol., 16, 21 (1974). F. T. Manheirn, J. C. Hathaway. and E. Uchupi, Limnol. Oceanogr., 17, 17 (1972). P. E. Biscaye and S. L. Eittreim, ref 3, pp 227-260. D. C. Gordon, Deep-sea Res., 17, 233 (1970). R. H. Meade. P. L. Sachs, F. T. Manheim, J. C. Hathaway. and D. W. Spencer, J. Sediment. Petrol., 45, 17 1 (1975). R. A. Feely, W. M. Sackett, and J. E. Harris, J. Geophys. Res., 76, 5893 (1971). B. Bernas, Anal. Chem., 40, 1682 (1968). F. J. Langmyhr and F. E. Paus, Anal. Chim. Acta, 43, 397 (1968). D. E. Buckley and R. E. Cranston, Chem. Geol., 7, 273 (1971). W. Sacked and G. Arrhenius, Geochim. Cosmochim. Acta, 26, 955 (1962). L. P. Atkinson and U. Stefansson. Geochim. Cosmochim. Acta, 33, 1449 (1969). T. Joyner, J. Mar. Res., 22, 259 (1964). P. R. Betzer, Ph.D. Thesis, University of Rhode Island, 1971. D. E. Robertson, Anal. Chem., 40, 1067 (1968). D. E. Robertson, "Ultrapurity-Methods and Techniques", M. Zief and R. Speights, Ed., Marcel Dekker, New York, N.Y., 1972, pp 207-253.
RECEIVEDfor review September 10, 1975. Accepted February 3, 1976. This work was supported by the Office of Naval Research under Contract N00014-72-A-0363-0001.
