Aluminum and Iron in Atlantic and Gulf of Mexico Surface Waters Determination and Occurrence L. H. SIMONS, P. H. MONAGHAN, A N D RI. S. TAGGART, Humble Oil & Re$ning Co., Houston, Tex.
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water contains many elements in ionic solution. Some of thesr elements such as chlorine, sulfur, sodium, calcium, and magnesium are present in large concentrations; others such as aluminum and iron are present only in trace Concentrations. In the ecology or geology of the sea, the latter elements are no less important because they occur in minute quantities. Their accurate determination in rea water, however, is usually more difficult.
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to inteifere. -4lthough it is possible that sea water contains some organic material having masking power for aluminum, the presence of such a substance has not been demonstrated. Although the sulfide coprecipitation method for iron is sensitive, it is relatively time-consuming and possibly prone to some error because of the number of manipulations involved. The tripyridyl method is satisfactory, but the reagent is not as readily available as o-phenanthroline. Fortune and Mellon ( 2 ) have shown that o-phenanthroline is remarkably sensitive for the colorimetric determination of ferrous ions and that relatively few other ions interfere. Due to this sensitivity, it is not necessary to concentrate the soluble iron in sea water prior to addition of the reagent. The method appeared t o be applicable to the determination of soluble iron in sea water. Sea water may contain aluminum and iron in the form of buspended particles as well as in the soluble form. For example, the elements may be present in suspended clay particles or in the remains of plankton. Although the water may be filtered prior to analysis, the possibility remains that some of the finer particles may pass through the filter and may cause error by solution in the chemical reagents used in testing. An advantage of the use of Blue Black R for aluminum and o-phenanthroline for iron is that no strong acids or alkalies need be added to sea Tvater after filtration. .\mmonium acetate and acetic acid may lie added to buffer the pH a t 5 in the aluminum determination, and no ndjustment of the pH is necessary in the iron determiiiation.
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SOLUTIObS 4 V D 4PP4RATUS
Figure 1.
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Locations from Which Water Samples Were Taken
A411solutions n ere made with reagent grade chemicals with the exception of the solution of Blue Black R, which was made from the dye as receired from the Du Pont Co. For the aluminum determination, a 0 . 1 7 solution of Blue Black R in 95% ethanol m-as prepared. I n the determination of iron, a 10% hydroxylamine hydrochloride solution and a 0.1 % o-phenanthroline solution were used. Solutions of aluminum potassium sulfate dodecahydrate [AIK(S04)2.12H?O]containing 2, 5, 10, and 15 micrograms of aluminum per liter and solutions of ferrous ammonium sulfate hexahydrate [Fe(SH4)2(SO4)?6H20] containing 2, 5, 10, and 15 micrograms of iron per liter were prepared for standards, respectively, of aluminum and iron. Nessler tubes were used for the visual comparison of colors in both determinations. The fluorescence developed in the aluminum determination was compared in 50-ml. Sessler tubes under a General Electric B-H4 mercury vapor lamp. The red color developed in the iron determination was compared in 100-ml. Nessler tubes under ordinary light.
Fortunately. as new and better reagents become availalile from time to time, it is possible to analyze sea water for trace elements more accui ately and more conveniently. In regard to aluminum and iron. the most reliable pievious investigations ( 1 , 3, 4) have indicated that the concentration of soluble aluminum in sea water is variable but averagrs about 0 5 mg. per liter and that the soluble iron concentration varies from zero to about 0.01 mg. per liter. Soluble aluminum Tvas determined by isolation of aluminum as the ouinate, liberation and diazotization of the ovine in the aluminum salt, and colorimetric estimation of the diazotized o\ine. Soluble iron was determined either by piecipitation ns sulfide follon ed by colorimetric estimation with thiocvanate or bv direct colorimetric estimation with 2,2',2"tripyridyl. Preliminary work in this laboratory with the ovine method disclosed that aluminum ovinate is too soluble for the quantitative determination of soluble aluminum in the concentration range from 0 to 1 mg. per liter. A further objection to this ieagent is that it is a general precipitant for many metallic ions. On the other hand, the new fluorimetric reagent, Pontachrome Blue Black R (5, 6 ) , appeared to have adequate sensitivity and selectivit: This reagent reacts solely with aluminum ions to produce an orange-red fluorescing complex under ultraviolet light. Interference by other ions, therefore, can result only from relatively high concentrations of colorific ions or from sequestering agents, such as the fluoride ion and possibly organic materials. In sea water, colorific elements are present in concentrations which are too low to interfere, and the high calcium concentration of sea m-ater ensures that the fluoride concentration will be too low
PROCEDURES
Aluminum. To a 50-ml. sample filtered through Whatman S o . 42 paper, 0.5 gram of ammonium acetate and 0.06 ml. of glacial acetic acid were added to buffer the pH a t 5. Then 1.5 ml. of Blue Black R solution Fas added. -4fter standing 2 hours, the fluorescence i ~ a sobserved under the mercury vapor lamp, and its intensity was compared visually with that of standard solutions treated in the same manner. Iron. To 100 ml. of sea xvater filtered through Whatman S o . 42 paper, 1 ml. of hydroxylamine hydrochloride solution was added and then 5 ml. of the o-phenanthroline solution. The intensity of the color was compared visually with that of standard solutions treated in the same manner. SUITABILITY O F METHODS FOR AYALYSIS O F SEA W4TER
In order to determine the suitability of the methods for the analysis of soluble aluminum and iron in sea water, recovery studies were made by adding definite quantities of aluminum 989
ANALYTICAL CHEMISTRY
990
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Table I. Sample S o 1
2 3 4
5 6
7 8
9 10 11
I2 13 14 I5 16
17 18 19
20 21 22 23 24 ”5
26 27 28 29 30 31
Concentrations of Soluble Ahminun1 and Soluble Iron in Sea W-ater Date Collected Hour Day 9AM 4 2/52 9. P .U.. 4/2/i2 4/3 j i ; 9 A.M. 9 P.M. 4/3/52 4/4/52 9 A.M. 4/4/52 9 P.M. 4/3/52 9 A.31. 4/5/52 9 P.>l, 4/6/52 9 A.M. 4/6/52 9 P.I. 4/7/52 9 A.M. 4/7/52 9 P.M. 4/11/52 9 A.M. 4/11/52 9 P.M. 4/12/52 9 A.M. 4/12/52 9 P.M. 4/13/52 9 A.X. 4/13/52 9 P.X. 4/14/52 9 A.M. 4/14/52 10 P . M . 4/15/52 11 A.M. 4/15/62 9 P.M. 9 A.M. 4/16/52 4/16/52 9 P.M. 1,0/12/50 l/IO/51 ~
1/10/31 1/11/51 1/10/5l 1/12/51
1/13/51
Chloroqlty Grams/Liter 20 05 19
xi
i9.60 19.71 19.70 19.52 19.78
19.60 19.80 19.40 18.05 17.10 17.20 19.70 19 95 20.00 19.80
20.00 l9,75 19.87 19 80 14.67 20.08 20.00 30 65 39 30 31 90 18.60
39.00 2.5.70 24. 76
11g /Litel 4lnminriin Iron 0 002 0 007
o
002
0.002 0 .005 0.002 0.002 0 002 0.002
0.000 0.002
o ooi
00.002 .002 0.005 0.002 0.000 0 00% 0.002 0.002
0 002
0.002 0.002
n 005 0 nnn
n nn.; 0.005
0 002
0 002 o0 002 002 0 002 0 002 0 002 0 002 0 000 0 007 0 005 0 002 0 002 0 005 0 005 0 003
0.002
60 60i 00 00002 002 o0
007
005 0 005 0 002 0 002 0 002 0 002 0 010 0 000 0 005 0 010 0 005 0 000 0 000
and iron to a synthetic sea water and to a sample of natural sea water, The synthetic sea mater contained sodium, potassium, calcium, and magnesium ions in the proportions found in ordinary sea water but in somewhat greater absolute concentrations. The solution wa5 prepared from the chlorides of these ions, and the total chloride content was 33,600 mg. per liter. The natural sea water sample was of lagoonal origin and had a “chlorosity” of 30.65 giams pel lite1 (C‘hlorosity, a term peculiar to oceanograph\-. is dehned a- the total amount in prams of chloride, bromide, and iodide in 1 liter of sra Tvater a t 20” C.$a-suming that the bromide and iodide have been replaced by chloride.) Its salinity m s greater than that of open ocean water as a result of natural evaporation in the lagoon. Quantities of aluminum and iron equivalent to those contained in the standard solutions were added to aliquots of these two samples of water, and the color or fluorescence developed in each test was compared with the standards which had been prepared from distilled water. I n each instance, the aluminum or iron concentration of the synthetic sample was found to be identical with that of the corresponding standard solution, having the same aluminum or iron content. For the natural sea water sample, however, aluminum and iron contents were found to be somewhat higher than those of corresponding standard solutions, in agreement with the sum of the original contents of these ions, as determined by analysis, and the added contents. S o precipitate was observed on addition of o-phenanthroline to the natural sea water sample, indicating that the ions found by Fortune and JIellon ( 2 ) to precipitate the reagent were not present in sufficient amount to interfere. It is apparent from the recovery studies that no interference was evident in the determination of either aluminum or iron in sea water.
used to avoid contact of the water with metals. The samples \\?re stored prior to analysis in polvethylene bottles to avoid contact a i t h glass. Samples 25 through 31 were fiom the Laguna Madre, a shallow lagoon lying along the southwest coast of Texas. These lagoonal samples were taken b> means of an enameled bucket, from which they were transferred immediately to paraffin-coated bottles for storage prior to analysis. The soluble aluminum content of the open ocean samples was. found to vary from 0 to .007 mg. per lit’er and averaged .0025 mg. per liter, The total soluble iron in these samples varied over the same concentration range and averaged .0026 mg. per liter. Both aluminum and iron concentrations averaged higher in lagoonal waters, in accord with the increased salinity of these samples. The results of the present n-ork indicate an average aluminum content of sea water two orders of magnitude less than that reported by earlier investigators. On the other hand, the results of the iron determinations confirm the results of earllet invcstigations. CONCLUSIONS
Relatively new and rapid methods of analysis have been found suitable for the determination of soluble aluminum and soluble iron in sea water. For aluminum the results indicate an average content of about 2.5 micrograms per liter. This concentration is two orders of magnitude less than the concentration reported by previous xvorkers in sea waters from other localities. The present work substantiates previous determinations of the concentration of soluble iron. The concentration of this element averaged about 2.6 micrograms per liter. LITERATURE CITED (1) Cooper, L. H .
(2) (3)
(4) (5) (6)
ii.Proc. , R o y , Soc. ( L o n d o n ) ,B118,419 (1935). Fortune, m.B., and JIeilon, 11. G . , IYD.EXG. HEM., . 1 ~ . 4 L . ED.,10, 60 (1937). Haendler, H. AI., and Thompson, T. G., J . M a r i n e Research (Sears Foundation), 2, 12 ( 1 9 3 9 ) . Rakestraw, K. W,, llahncke, H. E., and Beach. E . F., IND. ENG.CHEM.,AXAL.ED.,8, 136 (1936). Weissler, Alfred, and White, C . E., ~ A L C .H E Y . , 18,530 ( 1 9 4 6 ) . White. C. E., and Lowe, C . S.,IND. ESG. CHEM.,ASAL.ED.,9,430 (1937).
RECEIVED for review Septcinber 13, 1932. Accepted February 24. 1933.
CORRECTIONS Colorimetric Determination of Fluorine In the article on “Colorimetric Determination of Fluorine” [IxD. ESG. CHEM.,AKAL.ED., 5, 300-2 (1933)], on page 301, hrst column, the third paragraph under the heading “-ipparatus and Procedure” should read: “ACETYLACETOYE.Prepare a 0.057, aqueous solution from the freshly distilled product.” W, D. ARVSTRONG
RESULTS OF ANALYSES OF SEA WATER
The locations of sea water samples analyzed for soluble aluminum and iron are shown in Figure 1, and the results of analyses are presented in Table I. Samples 1 through 24 were taken during April 1952, on a voyage of the tanker Esso Cumberland, from Baytown, Texas, to Halifax, Nova Scotia. These surface samples of open ocean water were taken aboard ship by means of a canvas bucket loaded with cement. This sampling device was
Modification of Determination of Urea by the Diacetyl Monoxime Method In the article on “Modification of the Determination of Urea by the Diacetyl Monoxime Method” [Friedman, H. 9.. ASAL. CHEM.,25, 663 (1953)] in Table I1 the last figure in the first column should be 20 instead of 29.
