326
ANALYTICAL CHEMISTRY, VOL. 50, NO. 2, FEBRUARY 1978
Determination of Sulfides and Application to Shale Oil Analysis Raphael P. D'Alonzo,' Alan P. Carpenter, Jr., Sidney Siggia," and Peter C. Uden Department of Chemistry, GRC Tower I, University of Massachusetts, Amherst, Massachusetts 0 1003
Organic sulfides are oxidlzed to the corresponding sulfoxide using aqueous sodium metaperiodate. Simultaneously the perlodate is reduced to iodate which can be quantitatively precipitated by the addition of sllver ion In nitric acid. The precipltate is filtered and dissolved in ammonium hydroxide, and the resulting solution analyzed for its silver content by atomic absorption spectrometry. Sodium metaperiodate is shown to be a good reagent which oxidizes the sulfide completely to the sulfoxide wlthout any further oxidation to sulfone. The sensltlvity of the method is greater than or equal to most existing methods. Selectivity is good; however, compounds such as thlols and diols which are also oxidized will interfere. Also, compounds in the sample which reduce silver Ion will cause high results. The precision of the method Is f2.0-4.0 YO over a range of 1.05.0 ImoVmL of sulfide. The method has been applied to the determination of nonpolar organic sulfides in Green River shale oil.
The goal of this work was to first develop a general method for the determination of organic sulfides with high selectivity and, second, to modify the procedure for sulfide quantitation in shale oil. Past procedures for sulfide analysis have depended heavily upon both chemical and instrumental methods with a strong emphasis on oxidative approaches. The determination of thioethers employing oxidation with bromine has been accomplished using a variety of oxidizing reagents such as: bromine water (I), bromate-bromide mixture (2), and electrically generated bromine (3). The end point can be determined amperometrically, potentiometrically, iodometrically, or by the color of bromine. These reagents react with the sulfide to produce the corresponding sulfoxide.
+ Br, + H,O-
R-S-R'
R-SO-R'
+
2HBr
(1)
However, it has been shown ( 4 ) that bromine oxidations often lead to high results, since some sulfoxide may further oxidize to the corresponding sulfone. R-SO-R'
+
Br,
+ H,O-
R-SO,-R'
+
2HBr
(2)
Since oxidation to the sulfone is seldom complete, stoichiometry is indefinite. A microchemical method based on bromine oxidation was described by Belcher and co-workers (5). Direct titra+' ,ion on small samples (about 50 Fg) was accomplished employing 0.02 N KBr03 However, some problems with overoxidation were also reported. Oxidation of thioethers with hypochlorite has been reported by Leutch (6). This method employs a 0.1 N sodium hypochlorite solution but more dilute hypochlorite solutions were found to rapidly deteriorate. Thus, difficulties were encountered when adapting the method to the micro scale. Lewin (7)presented a macro method for the assay of organic sulfides using perbenzoic acid as the oxidizing reagent. R-S-R'
+
2C,H,03
+
R-SO,-R'
+
2C,H,O,
(3)
'Present address, Procter and Gamble Company, Winton Hill Technical Center, Cincinnati, Ohio 45224. 0003-2700/78/0350-0326$0 1.OO/O
Perbenzoic acid is a strong oxidizing agent, oxidizing the sulfide to the sulfone; thus, any intermediate sulfoxide present will interfere. In this procedure, a measured amount of perbenzoic acid is used, and the excess peroxide is determined iodometrically after oxidation is complete. Once again, this method was not found to be suitable as a micro method, because of the instability of dilute perbenzoic acid solutions. Puchalsky (8) describes a method for the analysis of organic sulfides by titration of their hydrogen peroxide-formed sulfoxides. Sulfides are treated with hydrogen peroxide in acetic acid a t room temperature to produce the corresponding sulfoxide. R-S-R'
+
HOAc
H,O,
R-SO-R'
+
H,O
(4)
Subsequent potentiometric titration of the formed sulfoxide derivative in acetic anhydride is accomplished using HC104. Interference due to overoxidation is prevented, since oxidation to the sulfone is sufficiently slow. The analysis of organic sulfides by column chromatography has been investigated by many authors. For an excellent review of these procedures, see ref. 9. Many instrumental methods for the assay of thioethers have been described. Some of the more interesting techniques involve UV spectrophotometry, gas chromatography, nuclear magnetic resonance, and isotope exchange. Iodine interacts with dialkyl sulfides to produce a complex with a strong absorbance maximum a t 310 nm (10). A spectrometric method, based on the interaction with iodine, for the determination of sulfides in hydrocarbons, has been developed by Hastings (11). Hastings has also pointed out the importance of the free iodine-iodine complex equilibrium (12),and the necessity of a large excess of iodine in the reagent to force the reaction to the right. This complexation has been used analytically, employing both isooctane (11) and carbon tetrachloride (13) as the reaction medium. R-S-R'
+
I, 3 (R-S-R'
. I)+I-
(5)
The method to be described utilizes atomic absorption spectrometry for the analysis of some selected aliphatic and aromatic thioethers, as well as potassium penicillin G. An aqueous sodium metaperiodate reagent oxidizes the organic sulfide to the corresponding sulfoxide. The reduced periodate is quantitatively precipitated in the form of silver iodate, which is removed from the reaction mixture by filtration using a fine glass frit filter. After washing to remove excess silver, the filtered silver iodate is dissolved in ammonia, and the resulting solution analyzed for its silver content by means of atomic absorption spectrometry. Sodium metaperiodate is found to be a good reagent to oxidize the sulfide completely to the sulfoxide without any further oxidation to produce sulfone. The reagent, unlike periodic acid, is stable to light. The reaction conditions are mild with quantitative oxidation accomplished a t low temperatures (0-25 "C). The general procedure calls for a reaction time of 15 h. The sensitivity of the method is greater than or equal to most existing methods and selectivity is quite good, since many other functional groups such as benzyl, phenyl, and carboxyl do not interfere. The adjacent hydroxyl group is known to interfere, but these groups and sulfides are rarely found in the presence C 1978 American Chemical Society
c4NALYTICAL of each other. The precision of the method is f2.&4.0% over a range of 1.0-5.0 pmol/mL of sulfide. T h e refining of petroleum and shale oils by catalytic cracking procedures is adversely affected by the presence of heteroatom compounds. I n particular, t h e problems due t o t h e presence of sulfur compounds in petroleum oils and t h e need t o study their structure has been discussed (14). This difficulty is also common t o t h e refining of crude shale oils because of t h e presence of sulfur compounds. For example, one of t h e potentially most useful sources of oil, the Green River oil shale deposit, yields oil with sulfur levels between 0.61 t o 0.87% (15). Green River shale oil sulfur compounds have been determined as being predominately thiophenes and sulfides, with traces of disulfides and mercaptans also present (16-19). T h e absence of more highly oxidized forms of sulfur is due t o t h e pyrolysis conditions present in t h e production of t h e shale oil. T h e study of sulfide sulfur compounds in petroleum and shale oil distillates has been performed in t h e past with a n emphasis on reactive extraction techniques. Complexation with metal salts (17,18,20), extraction with strong acids such as HI (18,20) and H2S04(21), and the formation of sulfonium salts using methyl iodide or sodium-p-toluenesulfonate (18, 20), have all been used as methods to separate sulfides from t h e oils studied. The sulfides are then regenerated from the salts and recovered by extraction or distillation. The amount of sulfur (from elemental analysis) in each distillate fraction gives a n estimation of t h e amounts of sulfur compounds present (18). T h e limitations of these methods are: the less than quantitative yield obtained in derivatization and regeneration of t h e sulfides (18,20), the contamination of the extracts of t h e oil with unsaturates (18,20), and the lack of a suitable method for measuring the total sulfur present (20). In this study, a crude shale oil obtained from The Oil Shale Corporation (TOSCO) was fractionated using a silica gel adsorption column, as has been done in past work (18,22-24). This was done in order to separate the nonpolar sulfur compounds from t h e bulk of t h e polar constituents, such as t h e nitrogen components, which are found in shale oil. This step removed any polar materials which might cause reduction of t h e silver ion in t h e precipitation step. T h e isolation of the aromatic and nonpolar sulfur compounds was followed by reaction with NaI04. This initial preparative separation in combination with NaIO., oxidation is quite specific for the determination of neutral organic sulfides in Green River shale oil. A check of the percent recovery of sulfides from the silica column separation procedure was undertaken using standards of butyl sulfide and phenyl sulfide. The quantitative elution of these standards from the adsorption column with a benzene eluent indicates the validity of this procedure.
EXPERIMENTAL Reagents. Periodate Reagent. Sodium metaperiodate (certified ACS) was obtained from Fisher Scientific Company. A 15 pmol/mL solution of this reagent is prepared by dissolving approximately 0.78 g in 250 mL of distilled deionized water. This reagent is reported to be stable (25),but was stored in the dark if it was to be used over an extended period of time. Acid-Silver Reagent. Silver used for precipitation of the iodate formed was prepared by mixing equal volumes of a 3:l concentrated nitric acid (Baker Analyzed Reagent) solution with 2 M silver nitrate solution. Silver nitrate, 2M, (Fisher) was prepared by dissolving 84.94 g AgNO3 in 250 mL of distilled deionized water. This reagent was stored in the dark for no more than two weeks before use. Silver Stock Solution for AAS. A stock solution of AgN03 (Fisher) was prepared according to guidelines given in ref. 26. Standard solutions for calibration were prepared by diluting appropriate aliquots of stock solution in 100-mL volumetric flasks. All silver solutions were protected from light and fresh standards were prepared from the stock weekly.
CHEMISTRY, VOL. 50, NO. 2, FEBRUARY 1978
327
Standard Sulfide Solutions. Phenyl sulfide (gold label-99+ %) was obtained from Aldrich. Butyl sulfide, isobutyl sulfide, hexyl sulfide, benzyl sulfide, L-(-)-methionine, DL-methionine, and N-acetyl-DL-methionine were all received from Eastman Kodak Co. A sample of penicillin G potassium salt was obtained from Wyeth Laboratories. This sample was refrigerated to prevent degradation of its @-lactamring. All sulfides purchased were the purest grades available. Microanalysis for sulfur was carried out on all sulfides as a purity check, percent purities greater than 98% being obtained. Standard sulfide solutions were prepared by weighing out 10-50 mg of the compound, dissolving in either distilled water or 2:l acetone (Fisher spectro grade)-water solution, and diluting to volume in a 100-mL volumetric flask with the solvent. These solutions were used immediately after preparation. Apparatus. A Perkin-Elmer 403 Atomic Absorption Spectrophotometer was used to measure all absorbances at 328.1 nm with a single element silver hollow cathode lamp at an operating current of 20 mA. All determinations were made using an airacetylene flame in accordance with the guidelines given in reference 26. All absorbances measured were an average of 100 readings. A filtering apparatus consisting of six fine frit (4-5:5 pm) Pyrex glass funnels was used for simultaneous filtering of 1-6 samples. Eppendorf pipets (Brinkmann Instruments) were used to pipet all reagent and sample solutions. A Mettler microbalance was used for weighing all sulfide samples. Procedure. General Method. A 1-mL sample of sufide solution is pipeted into a 50 X 150 mm test tube. The amount of sulfide taken should range between 100 to 500 pg, this corresponding to a concentration of 1-5 pmol/mL for a sulfide of molecular weight 100. One milliliter of reagent sodium metaperiodate solution is added to the sample, and the top of the test tube sealed with parafilm. This provides a 3-15 times molar excess of periodate to sulfide. The test tube is placed on a mechanical shaker and allowed to shake overnight (15 h). After shaking, 1 mL of acid-silver reagent is pipetted into the reaction mixture to precipitate the iodate formed. The test tube is again shaken for an additional 10 min to flocculate the AgI03 precipitate. The test tube is then placed in a freezer, maintained at -15 "C, for 30-60 min to promote further coagulation and suppress solubility of the AgI03 The test tube is removed from the freezer and its contents are immediately transferred, with a 3-mL rinse of 1:l acetone-water (0 "C), to the filtering apparatus. The precipitate is rinsed three times with acetone-water washing portions from the test tube. Each washing portion is allowed to pass completely through the filter before the next portion is added; otherwise, high blank values will result due to incomplete washing of the excess AgN03. After fiitering and washing of the precipitate is completed, clean filter flasks are transferred to the filtering apparatus after rinsing of the filter stems before transfer to prevent any possibility of contamination. Concentrated ammonium hydroxide (5 mL) is added to the test tube and transferred to the filter funnel to dissolve the AgI03 precipitate. Suction is applied and the filter rinsed with three 15-mL portions of distilled deionized water from the test tube. The suction flask is then removed from the filtering apparatus and its contents are transferred to a clean 100-mL volumetric flask, which is made up to volume with distilled deionized water rinsings from the filter flask. The silver content of the resulting solution is then determined by atomic absorption spectrometry. For further procedural details, see reference 27. Silica Column Separation of Shale Oil Sulfur Concentrate. A 2-3 g sample of crude shale oil (from TOSCO; Golden, Colo.) is placed on a 2 cm X 25 cm column of silica gel (60-200 mesh, Fisher Scientific) previously activated at approximately 130 "C for 24 h. Hexane (100 mL) is passed through the column to remove the paraffin portion of the oil. Spectrograde benzene, 150 mL, (Fisher Scientific) is then passed through the column and collected, the eluate containing the aromatic and sulfur compounds of the oil (18). Other more polar constituents of shale oil, such as oxygen- and nitrogen-containing compounds remain adsorbed on the column during the separation. Reaction of Sulfides i n Shale Oil with NaI04. The benzene eluent from the silica column preparative separation is divided into three 50-mL volumes and the benzene evaporated to 2-5 mL on a hot plate held at 50 "C. Blanks are prepared using 50 mL of benzene solvent. At this point, the sulfur concentrates and
328
ANALYTICAL CHEMISTRY, VOL. 50, NO. 2, FEBRUARY 1978
Table I. Determination of Organic Sulfides by Atomic Absorption Spectrometry Micromoles Concentration, Compound pmol/mL Taken Found 5.015 5.015 5.145 Butyl sulfide 4.476 4.476 4.610 Isobutyl sulfide 1.547 1.547 1.524 Hexyl sulfide 3.688 3.688 3.577 Phenyl sulfide 3.207 3.207 3.095 Benzyl sulfide L-(-)-Methionine 2.746 2.746 2.716 2.611 2.611 2.663 DL-Methionine 1.151 1.151 1.105 Potassium penicillin G a Figures in parentheses indicate number of determinations.
Recovery, %a 102.6 :3 . 2 ( 6 ) 103.0 t 4.8 ( 6 ) 98.5 = 4.4 ( 6 ) 97.0 = 3.2 ( 6 ) 96.5 t 2.2 (6) 98.9 t 2.2 ( 6 ) 102.0 = 2.4 ( 6 ) 96.0 I 6.0 ( 5 )
Table 11. Determination of Total Sulfide in a Mixture Concentration, pmol/mL 4.7455
Mixture Butyl sulfide, 2.5075 pmol, + isobutyl sulfide, 2.2380 pmol Hexyl sulfide, 1.739 pmol, + 4.081 benzyl sulfide, 2.342 pmol Figures in parentheses indicate number of determinations. blanks are placed in 125-mL Erlenmeyer flasks and 10 mL of NaI04 (70 Mmol/mL) added with 20 mL of acetone. The flasks are stoppered and shaken on a mechanical shaker for 12-16 h. The H20/acetone/benzene layer is then separated from the dark surface oil layer using a separatory funnel and the formed iodate then precipitated by 2 mL of acid-silver reagent. The flasks are then placed in a refrigerator at -10 "C for 30 min. After cooling, the samples are filtered through fine fritted glass funnels and the AgIO3 precipitate is washed three times with 1:l acetone:H,O (at 0 O C ) . The AgI03 is then dissolved in 10 mL of concentrated ammonia and diluted to a final volume of 100 mL with distilled, deionized water. Blanks are treated in an identical manner. The resulting solutions are analyzed for their silver content by atomic absorption spectrometry. Standard Addition Method. To each of the 50-mL portions of the benzene eluent from the silica column separation is added 10 mL of 0.22 mg/mL phenyl sulfide in benzene. Each sample is then evaporated down to 2-5 mL volume and treated as described earlier. Calculations for the level of sulfides present in shale oil by this method assume that the 2.2 mg of phenyl sulfide added is completely reacted. The total equivalents of sulfide found minus the equivalents of sulfide added equals the equivalents of sulfide in the oil sample.
RESULTS AND DISCUSSION Calibration Curve. Appropriate dilutions of silver nitrate stock solution were used for the construction of a calibration curve. Absorbances were measured a t 328.1 nm and were found t o be linear over a range of 2-10 ppm Ag. This corresponds t o a sulfide concentration range of 1.9-9.2 pmol/mL. Reaction Conditions and Concentrations. The concentration of reagent periodate and sulfide sample is not critical in this procedure, since quantitative oxidation of the sulfide to the sulfoxide can be accomplished over a large range of concentrations without the production of higher oxidized species, such as sulfones. It is, however, necessary t h a t periodate b e in excess, and it should be remembered that more dilute concentrations require longer reaction times. In this procedure, the final concentration of sulfide, after the addition of reagent to sample, was 0.5-2.5 pmol/mL while t h e final concentration of periodate was approximately 7.5 bmol/mL. These concentrations were found to give satisfactory results for some selected thioethers as reported in Table I. The reaction time required a t these concentrations was found to be approximately 15 h. Longer reaction times do not result in higher recoveries, because of the ability of t h e reagent to
Micromoles Found Taken 4.7455 4.8879
Recovery, %a 1 0 3 i 1.1 ( 6 )
4.081
99.7
4.069
*
3.4 ( 6 )
stop oxidation a t t h e sulfoxide stage. Effect of Other Functionalities. Compounds listed in Table I show that the substitution of other functional groups on the molecule have no effect on the theoretical recovery of silver iodate. The aromatic ring in both phenyl and benzyl sulfide shows stability to the periodate reagent. Methionine, both pure and mixed isomers, gave excellent results, showing no interference from its carboxyl or amino group. These results demonstrate the selectivity of the periodate reagent toward the sulfide group. However, all attempts made to quantitate N-acetyl-DL-methionine failed. The high recoveries of silver from this compound cannot be explained with certainty. I t may be possible t h a t the oxidized acid product is precipitated upon the addition of silver ion, unlike methionine, whose amino group promotes solubility under acid conditions. In addition to precipitation of the acid, inclusion of silver ion seemed t o be indicated from the poor precision of the 12 determinations. Interference. T h e ability of periodate to react with adjacent hydroxy functions has been known for some time and has been used as the basis for the quantitation of these groups. A comprehensive review of these methods is given by Kolthoff and Belcher (28). Older methods measured excess periodate by adding an excess of sodium arsenite followed by back titration with standard iodine solution. HIO,
+ Na,AsO,
+
Na,AsO,
+
HIO,
This method has been used to estimate adjacent hydroxy functions in both glycols and carbohydrates. Pesez has quantitated 1,2-dihydroxyacidsby fluorimetry using sodium metaperiodate to form the oxidized product which is then coupled with resorcinol (29,30). However, interference from diols presents little problem since they are rarely found in the presence of organic sulfides. Other functional groups which have been reported (31-34) to reduce periodate are a-hydroxy aldehydes, a-hydroxy ketones, 1,2-diketones, a-hydroxy acids, and a-amino alcohols. Iodate Precipitation. T h e ability to precipitate iodate in the presence of periodate with silver under acid conditions has made it possible to determine iodate directly. This separation was the basis of a method developed by Oles (35) for the determination of adjacent hydroxyl groups. Prior to this, no accurate method existed to determine the quantity of iodate in the presence of periodate. Thus, older methods
ANALYTICAL CHEMISTRY, VOL. 50, NO. 2, FEBRUARY 1978 Table
111. Quantitation of
Sulfide
Method Direct Standard addition
in
Shale
329
Oil
Equiv Sulfide S/g oil 2.77 x i 9.8% * 8.5% 2.58 x
measured excess periodate as discussed in the previous section. The solubility of silver iodate, and factors which affect its solubility, can be found in ref. 35. The important feature here is the decrease of silver iodate solubility due to the high concentration of silver ion, the low temperature of the wash solution (0 "C), and the high acidity of the reaction solution. Blank Value. A study on the source of the blank for this system is reported in detail in ref. 35. It was found that a wash solution consisting of equal volumes of water and acetone containing H N 0 3 (0.2% v/v) resulted in a small reproducible blank value of 0.354.44 ppm Ag+ in a 50.0-mL volume. This paper is in agreement with the present work, in which an average blank value of 0.2 ppm Ag+ was found in a 100.0-mL volume. Determination of Total Sulfide. The determination of total sulfide in mixtures has been accomplished. The results of this study for two mixtures of sulfides are reported in Table 11. Recovery Study. A column identical to that used in the separation of sulfur concentrate from the oil was used in this study. Butyl sulfide and phenyl sulfide in hexane were introduced onto the column and eluted with benzene. The collected benzene eluent was studied for its content of both standard sulfides by gas chromatography using a '/8-inch X 6 f t , 8% OV-7 on ABS (mesh size 70/80) column equipped with a flame ionization detector. The recovery of each sulfide from the column using this procedure was 95 f 2%. Determination of Total Sulfide in Shale Oil. The results from direct and standard addition measurements of sulfides in shale oil are reported in Table 111. From the percent sulfur in the shale oil, as determined by microanalysis, the total sulfur in the form of sulfides may be calculated. The good agreement between the two methods indicates t h a t the benzene eluent matrix does not significantly affect the quantitative reaction of sulfides with NaI04 under these conditions. In order to determine if interfering reactions were occurring in the oxidation of the sulfides, the reaction of a standard disulfide and thiol with N a I 0 4 was studied, since disulfides and thiols will also be present in the sulfur concentrate from the oil sample. The reaction of butyl disulfide did not proceed to any measureable extent while hexane thiol reacted to an extent of approximately 30% under the conditions used for sulfide reaction. This interference is negligible when applied to shale oil since thiols are present only at about 1% of the total sulfur in the oil (36). In cases where thiol interference is important, it may be desirable to perform a separate analysis for thiols by a selective method such as silver reaction to form mercaptides. This has been accomplished using amperometric (37) and atomic absorption techniques (38). Quantitative estimation of sulfur compounds in the naphtha cut (IBP to 200 "C) of N-T-U shale oil has put sulfides a t approximately 15-20% of the total sulfur in this fraction (18, 20). This is difficult to correlate with the levels of sulfides found in the crude shale oil because the naphtha comprises only about 18% of the total crude (15). No other data from past work are available concerning the levels of sulfides in
% Sulfide S in oil % total S in oil
0.089 0.083
0.85 0.85
% of total S as Sulfide S
10.4
9.7
shale oil and shale oil distillates. In the present study, the sulfides have been found to be about 10% of the total sulfur in crude TOSCO I1 shale oil. Because of the limitations of the adsorption method in separating the sulfur compounds, this analysis is applicable only to the "neutral" sulfides in the oil. Any sulfide groups in compounds containing nitrogen and oxygen are not analyzed by this method because of their strong adsorption on silica.
LITERATURE CITED J. R. Sampey, K. H. Stagle, and E. E. Reid, J . Am. Chem. SOC., 54, 340 (1932). S. Siggia and R. L. Edsberg, Anal. Chem., 20, 938 (1948). J. W. Sease, C. Nieman, and E. H. Swift, Anal. Chem., 19, 197 (1947). B. Gauthier and J. Maillard, C. R . H e w . Seances Acad. Sci., 236, 1178 (1953). R. Belcher, Y. A. Gawargious, and A. M. G. MacDonald, Mikrochim. Acta, 6, 1114 (1966). S. L. Leutch, J . Franklin Inst., 239, 334 (1945). L. N. Lewin, J . Prakt. Chem., 2, 118, 282 (1927). C. B. Puchalsky, Anal. Chem., 41, 843 (1969). J. Churacek, J . Chromatogr. Libr., 1975, 3 (Lig. Column Chromatogr.), 927-937. S. Siggia, "Instrumental Methods of Organic Functional Group Anavsis", Wiley-Interscience, New York, N.Y., 1972. S.H. Hastings, Anal. Chem., 25, 420 (1953). S. H. Hastings and B. H. Johnson, Anal. Chem., 27, 564 (1955). H. V. Drushel and J. F. Miller, Anal. Chem., 27, 495 (1955). G. P. Hinds, Proc. Am. Pet. Inst., 42, 18 (1962). M. T. Atwood, Chem. Tech., 3, 617 (1973). W. E. Cady and H. S. Seelig, Ind. Eng. Chem., 44, 2636 (1952). G. U. Dinneen, R. A. Van Meter, J. R. Smith, C. W . Bailey, G. L. Cook, C. S. Allbright, and J. S. Ball, U . S . Bur. Mines, Bull., 593 (1961). G. U. Dinneen, R. A. Van Meter, J. R. Smith, C. S. Allbright, and W. R. Anthoney, Anal. Chem., 27, 185 (1955). G. U. Dinneen, Proc. API 1962 Summer Sym., 42, 41 (1962). H. T. Rall, C. J. Thompson, H. J. Coleman. and R. L. Hopkins, U . S . Bur. Mines, Bull., 659, 60 (1972). S. F. Birch, T. V. Cullum, R. A. Dean, and R L. Denver. Ind. E m . Chem.. 47, 240 (1955). 119491 D. Haresnape, F. A Fidier, and R. A. Lowry, Ind. Eng Chem., 44, 2691 \
-
-,
R. A. Dean, Proc. Am. Pet. Inst., 42, 54 (1962). R. A. Dean and E. V. Whitehead, 7th WorldPet. Congr. Proc., 9, 165 (1967). N. J. Leonard and C. R. Johnson, J . Org. Chem., 27, 282 (1962). C. P. Parker, "Water Anatysis by Atomic Absorption Spectroscopy", Varian Techtron Pty. Ltd., Palo Alto, Calif., 1972. R. P. D'Alonzo, Ph.D. Dissertation, University of Massachusetts, Amherst, Mass., 1977. I.M. Kotthoff and R. Belcher, "Volumetric Analysis", Voi. 3, Interscience, New York, N.Y., 1957, p 475. M. Pesez, Bull. SOC. Chim. F r . , (5) 3,676,2072 (1936). M. Pesez, and J. Bartos. Talanta. 14, 1097 (1967). N. D. Cheronis and T. S. Ma, "Organic Functional Group Anatysis by Micro and Semimicro Methods", John Wiley & Sons, New York, N.Y., 1964, p 507. R. J. B. Reddaway, Analyst (London), 82, 506 (1957). R. L. Shriner, R. C. Fuson, and D. Y. Curtin, "The Systematic Identification of Organic Compounds", 5th ed., John Wiley & Sons, New York, N.Y., p 146. R. Adams, "Organic Reactions", Vol. 11, John Wiley & Sons, New York, N.Y., 1944. P. J. Oies and S. Siggia, Anal. Chem., 46, 2197 (1974). A. P. Carpenter, Jr., Ph.D. Dissertation, University of Massachusetts, Amherst, Mass., 1977. I . M. Kolthoff and W. E. Harris, Ind. Eng. Chem.. Anal. E d . , 18, 161 (1946). J. Marhevka, Ph.D. Dissertation, University of Massachusetts, Amherst, Mass., 1976.
RECEIVED for review September 2,1977. Accepted November 9, 1977. This work was supported by grants CHE76-07378 and CHE74-15244 from the National Science Foundation.
