Rapid Combustion Method for the Determination of Sulfur in Nickel-, Iron-, and Copper-Base Alloys Keith E. Burke Paul D. Merica Research Laboratory, International Nickel Co., Inc., Sterling Forest, Suffern, N . Y. 10901
The use of treated vanadium(V) oxide, as an accelerator flux, greatly improves the combustion-separation technique for the routine determination of sulfur in a variety of metallurgical systems. Sulfur, at the 0.001 to Oml% level, is separated from ferrous and nonferrous systems by combustion in a stream of oxygen and subsequently determined as sulfur dioxide by a photometric potassium iodate titration. The materials being analyzed are heated by a high frequency induction furnace. Replacement of the standard accelerator fluxes with vanadium(V) oxide decreases the time required for the separation from between 5 and 15 minutes to less than 2 minutes, increases the recovery of sulfur, and improves the precision of the analysis. Recoveries of sulfur using the standard combustion techniques are known to vary from 60 to nearly 100%. The use of treated vanadium(V) oxide improves the yield so that 90 i 10% of the sulfur is recovered in a variety of standard samples. Treated vanadium(V) oxide is prepared by heating the oxide under a stream of air at 670° & loo C to remove sulfur and eliminate the high blank. The precision of the method on a maraging steel is within 0.0006% at the 0.0120% level and within 0.0005% at the 0.005% level on a nickel-base standard.
N o SINGLE METHOD has been completely successful for the separation of sulfur from metallurgical systems. The combustion technique is generally regarded as convenient for the separation of sulfur from all types of steels, irons, copper- and nickel-base alloys, and other materials which can be burned in a stream of oxygen. After the separation, sulfur can be determined spectrophotometrically ( l - j ) , coulometrically ( 4 , 5), or titrated with potassium iodate or sodium borate (6, 7). The photometric iodate titration method is widely used, particularly in the steel industry, because of its simplicity and wide applicability. The main disadvantage of the combined combustion-titration technique is the incomplete and variable recovery of sulfur due to combustion problems. Failure to compensate for the incomplete recovery could produce an error of 40%, because recoveries as low as 60% have been reported. Combustion accelerators are added to materials being analyzed for sulfur to improve the combustion process. Normal fluxing agents are copper and tin. Copper is added to reduce the melting point of the sample and tin to start the combustion process; how(1) K. E. Burke and C. M. Davis, ANAL.CHEM., 34, 1747 (1962). (2) S.Barabas and J. Kaminski, Ibid., 35, 1702 (1963). (3) H. Goto, Y. Kakita, and K. Makabe, Bunseki Kagaku, 14, 244 (1965); Chem. Abstr., 63, 17142b (1965). (4) . _W. R. Bandi. E. G. Buvok. and W. A. Straub. ANAL.CHEM.. 38, 1485 (1966). ( 5 ) K. Hoshino, T. G. Ihara, and Y . Nakai, “Apparatus for the Determination of Microamounts of Sulfur in Iron and Steel by Applying the Coulometric Titration,” Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, March 1967. (6) P. deGelis, Chim. Anal. (Paris),47,468 (1965); Chem. Absrr., 64, 1348 (1966). (7) R. F. Jones, P. Gale, P. Hopkins, and L. N. Powell, J. Iron Steel Inst., 1966, 505. ~
ever, tin may have the disadvantage of retaining part of the sulfur (4, 8). A variety of other materials have been used as fluxing agents-e.g., zinc, bismuth, copper(I1) oxide, cobalt(I1) oxide, chromium(II1) oxide, and vanadium(V) oxide. Vanadium(V) oxide has been used as a flux in the analysis of various materials for sulfur, but there has not been an evaluation on the recovery of sulfur or of a decrease in required combustion time for methods using this material. A disagreement exists concerning the oxidation state of sulfur produced when vanadium@) oxide is used as an accelerator flux. Investigators have attributed low results of the combustion-separation method to the presence of sulfur trioxide, probably because the commercial process for the manufacture of sulfuric acid uses vanadium(V) oxide, at 428 ” to 444”C, for the conversion of sulfur dioxide to sulfur trioxide. Rittner and Culmo (9) used this reaction in the determination of sulfur in organosulfur compounds. Sulfur dioxide formed on the oxidation of the organosulfur compounds was converted into sulfur trioxide at 450’ to 500°C and retained by technical but not chemical grade vanadiurn(V) oxide. Several other authors report, but do not prove, that sulfur is converted to sulfur trioxide when vanadium(V) oxide is used as a flux at temperatures of 900” to 950°C, and they subsequently used heated copper to convert sulfur trioxide into sulfur dioxide (10-14). Green (15) tried vanadium(V) oxide as a flux for cast irons at 1350’ to 1500°C and found a decrease in the recovery of sulfur dioxide which he attributed to the catalytic action of the flux to produce sulfur trioxide. The procedure reported in this work proves that very little sulfur trioxide is formed and agrees with others (3,16,17) who used vanadium(V) oxide as a combustion aid and determined the resulting sulfur dioxide either spectrophotometrically or titrimetrically. EXPERIMENTAL Apparatus and Reagents. HIGH FREQUENCY INDUCTION FURNACE. The induction furnace used (Model 523, Laboratory Equipment Corp., LECO, St. Joseph, Mich.) was equipped with an adjustable transformer to regulate the plate current and control the rate of combustion. Porous crucible (8) A. I. Ponomarev and A. A. Astanina, Metallurgiya Metallooed., Fiz-Khhn. Met. Issled., Trudy Insf. Met. A. A. Baikoua, 1962,
231. (9) R. C. Rittner and R. Culmo, Microchem. J., 11,269 (1966). (10) J. Dokladaloua, Z . Anal. Chem. 208,92 (1965); Anal. Absrr., 13, 2320 (1966). (11) R. P. Larson, L. E. Ross, and N. M. Ingler, ANAL.CHEM., 31, 1696-7 (1959). (12) D. B. Hagerman and R. A. Faust, Ibid., 27, 1970 (1955). (13) C. Bloomfield, Analyst, 87, 586 (1962). (14) L. F. Lust and B. P. Van der Cook, “Sulfur Determination Supporting the Waste Solidification Program,” BNWL-265 (1966); Nucl. Sei. Abstr., 20, 38795 (1966). (15) H. Green, Mefallurgica, 60, 229 (1959). 38,777 (1966). (16) H. Ray and S. Banerjee, ANAL.CHEM., (17) W. Fischer, H. Bastius, and R. Mehlhorn, N e w Hiitte, 8, 35 (1963); Chem. Abstr. 59, 2155e (1963). VOL. 39, NO. 14, DECEMBER 1967
0
1727
I
I
I
I
I
I
I
I
0 0
A X
I
I I , I l l
I
I
I
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I 1
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,
I
ALIQUOTS OF No2 SO3 COMBUSTION OF NH4SCN STANDARDS WITH V 2 0 5 COMBUSTION OF N B S STANDARDS WITH Sn AND Cu COMBUSTION OF NES STANDARDS WITH V ~ O L ,
NO ACCELERATORS
SULFUR PRESENT, %
Figure 2. Recovery of sulfur from standards after combustion VZOSor Sn-Cu accelerators
No. 532-000) reads directly in one tenth or one hundredth of 1 % sulfur, with a 1-gram sample. T I M E , MINUTES
Figure 1. Recovery of sulfur from NBS 1156 (O.O12%S) as a function of time
covers (Leco No. 528-41) were placed between the crucible (Leco No. 528-120) and pedestal (Leco No. 550-124), as well as on the crucible. Only induction heating was used. The effect of vanadium(V) oxide in a resistance-type furnace was not evaluated. COMBUSTION ACCESSORIES.A silica combustion tube (Leco No. 550-120), attached with silicone tubing (Leco No. 521-112) to a right-angle connecting tube (fitted with a glass wool plug), was used to join the combustion section to an automatic titrator (Leco No. 532-0001. PURIFICATION TRAIN. Tank oxygen was passed through sulfuric acid, Ascarite (Arthur H. Thomas Co.), and magnesium perchlorate traps, and a flowmeter (Leco No. 516-100). TREATED VANADIUM(V) OXIDE,Vz06. To reduce the sulfur blank in this material, add several hundred grams of reagent grade vanadium(V) oxide to a boat made of nickel-chromium alloy 600, place the boat in a tube furnace at 670" 10' C, and allow air to pass over the oxide at 1 liter per minute for 16 to 20 hours. Higher temperatures produced some undesirable sintering and should not be used. POTASSIUM IODATESOLUTIONS, 0.4440 and 0.0444 gram per liter. No attempt was made to standardize these solutions; however, at these concentrations the buret (Leco Table I. Comparison of Accelerators on the Recovery of Sulfur from Standards Sulfur, awn Accelerator
NBS No.
Certified
125a 32a 19e 8h 20e
130 210
1728
0
300 500 780
Tin (19) KIOa NaOH
108 181 262 424
703
ANALYTICAL CHEMISTRY
118 192 277 459 710
VZOG
KIOs
126 195
302 501 800
ABSORBENT SOLUTION.Dilute 30 ml of hydrochloric acid to 1 liter with distilled water. STARCH. To 9 grams of soluble starch in a 50-ml beaker add 5 to 10 ml of water, and stir until a smooth paste is obtained. Pour the mixture slowly into 500 ml of boiling water. Cool the solution, add 15 grams of potassium iodide, stir until the salt is dissolved, and dilute to 1 liter. Store this solution in a refrigerator. Discard this solution when it begins to darken. PROCEDURE
Equilibrate the combustion system by two ignitions with 1 f: 0.2 gram of treated vanadium(V) oxide and an ironbase material which contains approximately 0.03 % sulfur. After equilibration, select appropriate standards and the proper iodate solution to calibrate the system. Burn 1 f 0.2 gram of treated vanadium(V) oxide with 1 st 0.2 gram of low-sulfur iron powder (Leco No. 501-78) to determine the blank. Weigh the sample and calibration standards to the nearest 0.1 mg and transfer to separate crucibles. Add a scoop (1 & 0.2 gram) of treated vanadium(V) oxide to the crucible and if the sample or standard is not ferromagnetic or if the sample weight is less than 0.5 gram add 1 zt 0.2 gram of low-sulfur iron powder before covering the crucible and placing it on the preignited combustion pedestal. (Add low-sulfur nickel powder as required instead of iron, for the analysis of nickel.) Raise the crucible into the center of the combustion zone, close the tube, and adjust the flow of oxygen to 1.5 liters per minute. Fill the absorption vessel to an appropriate level with hydrochloric acid absorbent solution, add 5 ml of starch-iodide indicator, and titrate to the end point, photometrically. Turn on the power to the induction furnace and titrate the evolved sulfur dioxide continuously. Discontinue the combustion after a total combustion time of 2 minutes (Figure 1). The suggested combustion period includes a 30-second safety factor. Calculate the sulfur content of the sample using a factor determined by the analysis of a standard similar in composition to the sample. If a standard of similar composition is not available, select a material from Table 11 which gives a 90 % recovery.
Table 11. Determination of Sulfur by Iodate Titration after Combustion in the Presence of Vanadium(V) Oxide
Values in parentheses are provisional Sulfur,
Standard No.
Material
INCO 74 NBS 123 BCS 322 N B S 121c BCS 328 NBS 135 NBS 101e NBS 55e NBS 1156 NBS 339 NBS l l l b NBS 13f NBS 36a BCS 337 NBS 100 NBS 32a NBS 21e NBS 73 BCS 169 NBS 115 BCS 206/2 BCS 23612 BCS 17212 BCS 17012 NBS 8% NBS 5k NBS 6f NBS 129
Maraging steel Cr 18-Ni 11 steel Mild steel Cr 18-Ni 10-Ti steel Mild steel Cr-Mo steel Cr 18-Ni 9 steel Ingot iron Maraging steel Cr-17 Ni 9 steel Ni-Mo steel B.O.H. steel Cr 2-Mo 1 steel Austenitic stainless steel Mn rail steel Ni-Cr steel A. 0. H. steel Stainless steel Hematite cast iron B Ni Resist High Si and P cast iron Hematite iron Low alloy cast iron Foundry iron Bessemer steel Cast iron Cast iron High sulfur steel
NBS 169 HT 6308ev HT 7051ev N 4379a HF 0459 NX 1476 NBS 161 NBS 1203
77 Ni-20 Cr alloy Ni-Cr Alloy 718 Ni-Cr Alloy 718 Nickel 200 Ni-Cu Alloy K500 Ni-Cr Alloy 600 Ni-base alloy High temp. aIloy (Alloy 713-A) Ni-Cr Alloy 600 Ni-Cr Alloy 600 Ni-Cr Alloy 600 Ni-Cr Alloy 751 Ni 64-Cu 31 High temp. alloy (Alloy 713-C) High temp. alloy (A286) High temp. alloy (D24) Ni-Cu Alloy K500 High temp. alloy (Alloy 713-B) Ni-Cr Alloy 751 Ni-Cr Alloy 751 Ni-Cu Alloy K500 High temp. alloy (U 500)
B 5789 B 5967 B 5968 INCO 5936 NBS 162a NBS 1205 NBS 1194 NBS 1195 HF 0460 NBS 1204 INCO 5937 INCO 5938 HF 0461 NBS 1190
Found" i u
Recovery,
0.0015 f 0.0002 0.005
...
0,005 (0.008)
0.008
...
0.009 (0.010) 0.010 0.010
0.009 0.009 0.010 0.010 0.0120 f 0.0004 0.0117 =t0.0006
...
0.012
0.012 0.013 0.015 0.016 0.016 0.018 0.021 0.022 0.030 0.031 0.031 0.032 0.039 0.041 0.043 0.053 0.063 0.100 0.106 0.172 Nickel-Base 0.002 0.003 0.003
(0.0035) 0.004 0.004 0,005
(0.005) (0.005) (0.005) (0.005) 0.0050 0.007
0.013
0.014 0.016 0.015
93 95
...
86 74 78 100 87 80
77 94 96 85 93
0.018 0.021 0.021 0.030 0.030 0.031 0,036 0.040 0.041 0.040 0.054 0.062 0.093 i 0.009 0.10 0.17
100
0.002 0.003 0.003 0.004 0.004
87 83 92
87 80
94 94 97 90 98 97 93 94 86 80
0.005
80 100
0.0045 i 0.0005 0.002
.. .
0,004 0.003 0.005
... ... ...
0.005
94
(0.008)
0.008
96 96 87
0.008 0.008 0.008 (0.010)
0.008 0.008 0.008 0.010
92 100 94 100
0.0121 0.0125 0.017 (0.028)
0.012 0.012 0.018 0,028
98 98 94 85
0.0022 f 0.0004 0.010
100 97
Copper-Base Cast bronze 0.002 Cupro-nickel 0.010 Factor discussed under Experimental used to obtain these values.
NBS 52c BCS 18011 a
Certified Iron-Base
0.007
VOL. 39, NO. 14, DECEMBER 1967 e
1729
RESULTS AND DISCUSSION
Several investigators have made the recovery of sulfur the object of their studies. Rooney and Scott (18) reported the recovery of sulfur dioxide varies from 61 to 83 % as the combustion temperature of a resistance-type furnace was increased from 1200" to 1400°C and the oxygen flow rate increased from 1 to 2 liters per minute. Their radiochemical investigation shows that when the sulfur present in the cast iron was evolved and titrated as sulfur dioxide, approximately 4 % was not caught by the absorbent and 12 % remained behind in the boat or combustion tube. They did not use accelerators. Fulton and Fryxell (19) studied the recovery of sulfur dioxide after combustion in an induction furnace and found an average recovery of 85% sulfur as sulfurous acid or 92% as sulfuric acid-i.e., by the iodate or sodium hydroxide titrations, respectively. In the present study, a few of these same standards are analyzed by the iodate method using vanadium(V) oxide as the accelerator flux (Table I>. The data show an average recovery of sulfur as sulfur dioxide of 99%; vanadium(V) oxide increases the recovery of sulfur from these standards by approximately 14%. The combustion conditions are of course not exactly the same. The discussion and data which follow verify an increased recovery. First a comparison was made of the sulfur recovery from a maraging steel in the presence of no accelerator, copper and tin, and vanadium(V) oxide. The data in Figure 1 show complete recovery of sulfur in the presence of vanadium(V) oxide, whereas only 80% of the sulfur is removed when the standard accelerators are used, and 75 % when no accelerator is present. Others ( 4 ) report 80 % recovery with copper and iron accelerators. This difference in per cent recovery points out a major problem in the analysis of metallurgical materials for sulfur. The data in Figure 2 are a graphical representation of sulfur recovery; they are plotted on a log-log scale because of the wide range of sulfur concentrations. The 45 O line in Figure 2 represents complete recovery of sulfur as sulfur dioxide. The five open circles along this theoretical recovery line were obtained by titrating measured amounts of a sodium sulfite solution (standarized gravimetrically as barium sulfate). The closed circles represent the recovery of sulfur from the combustion of 1 gram of iron with 20, 50, and 150 pg of sulfur as an inorganic salt (Leco No. 501-201). The points marked by X show the results obtained when various standards were burned with vanadium(V) oxide. The proximity of these points to the 45 O line indicates that very little sulfur is lost either through retention of sulfur in the combustion system or sulfur trioxide formation. For the standards shown in Figure 2, the average sulfur recovery in the presence of vanadium(V) oxide is 90 i 10%. On the other hand, the broken line in Figure 2 is the locus of points obtained by burning some of the same standards with copper and tin accelerators. The recovery with these accelerators i s much lower than obtained with vanadium (V) oxide. The rate of sulfur evolution from various samples is much faster in the presence of vanadium(V) oxide. Figure 1 shows that separation is complete after 1.5 minutes for a maraging steel. This short combustion period is a n improvement in the method, because combustion and preheat periods of 5 to 15 minutes have been reported and recommended using standard accelerators (4). If all operations including weighing require 3
(18) R. C . Rooney and F. Scott, J . Iron Steel Inst., 1960, 417. (19) J. W. Fulton and R. E. Fryxell, ANAL.CHEM., 31,401 (1959).
1730
e
ANALYTICAL CHEMISTRY
Table 111. Removal of Sulfur from Vanadium(V) Oxide by Heating at 670" 10°C for 15 Hours in a Stream of Air Sulfur, ppm Batch No. As receivedAfter treatment
*
32208 21467 37361 30372 30372
35
58 26 21
21
minutes per run, one operator should be capable of analyzing at least 140 samples per day using this rapid combustion process, compared with approximately half that number by the established practices. The data in Table I1 are a measure of the accuracy obtained by the iodate titration after combustion in the presence of vanadium(V) oxide. The values for the per cent sulfur found are based on factors obtained from initial analyses of a limited number of similar standards for which sulfur recoveries were 90 =t10%. The per cent recovery values are not factored but calculated from corrected buret readings and the certified sulfur content. The precision data (sigma values) given for several samples represent 20 determinations per standard over a period of several months with no more than four determinations in a single day. At least two factors must be considered in any possible accelerator mechanism: melting point and chemical behavior. For sulfur to be evolved from its matrix, it must first combine with another element to produce a volatile gas. It is generally accepted that sulfur is present as the sulfide; Luke (20) proves this point for nickel, so it can be evolved in an oxidizing atmosphere as sulfur dioxide or sulfur trioxide, depending on the temperature, etc. Sulfur is present in nearly all metallurgical systems as a minor constituent; therefore, it is necessary to oxidize the entire sample to ensure the oxidation and subsequent removal of sulfur. The presence of an oxide accelerator makes this an easier process. An ideal oxide accelerator does not necessarily have an abundance of oxygen, but it must produce a low melting mixture with the oxidized metals comprising any sample. Vanadium(V) oxide exerts such a desirable fluxing action in the presence of oxides of nickel, iron, copper, or chromium. The low solubility of sulfur dioxide in the low melting vanadium(V) oxide-alloy system is also important in the mechanism, because it causes very little gas entrappment. The amount of vanadium(V) oxide added to the sample is not critical. Studies with 1 gram of iron-base standards and increasing amounts of vanadium(\') oxide show that at least 0.6 gram of the accelerator-flux is required to increase the recovery to near theoretical. Amounts of vanadium(V) oxide up to 3 grams do not affect the recovery of sulfur. Certain materials may require longer burn periods or additional vanadium(V) oxide. The presence of sulfur in one batch of reagent grade vanadium(V) oxide was found, by a gravimetric analysis, to be 40 ppm. Table 111shows that the sulfur level in different batches varies between 20 and 60 ppm. The blank is reduced to between 0 and 9 ppm by the roasting process. Reagent grade vanadium(V) oxide has a chlorine content between 0.05 and 0.2 . _ which is also lowered by the roasting process. Unless many precautions are taken, a combustion procedure for the determination of sulfur will generally be empirical.
z,
(20) C. L. Luke, ANAL.CHEW, 29, 1227(1957).
Some sulfur may be retained in the melt, some sulfur trioxide is formed, and there is certainly some retention of sulfur dioxide on the walls of the combustion system. The routine combustion conditions used for this work may or may not have been optimum for each of the various alloys systems. However, under these conditions vanadium(V) oxide shows an increase in the recovery of sulfur as well as the rate of sulfur evolution. Contrary to prior reports, the main product is sulfur dioxide rather than sulfur trioxide.
ACKNOWLEDGMENT
The author thanks Thomas Ruppert and Bruce Dod for obtaining many of the analytical data.
RECEIVED for review May 16, 1967. Accepted September 11, 1967. Division of Analytical Chemistry, 153rd Meeting, ACS, Miami Beach Fla., April 1967.
Emission Response of Some Hydrocarbon-Methanol Solutions in Hydrogen Flames Peter F. iMcCreal and Truman S. Light Research Center, The Foxboro Co., 38 Neponset Aue., Foxboro, Mass. 02035
A spectrometric study was made of air-hydrogen and oxyhydrogen flames containing hydrocarbons in methanol solutions. The technique of limited area flame spectrometry (LAFS) was utilized to study the prominent band-head of the CH emitter a t 431.5 mp and of Caat 516 mp. To study quantitatively the net emission due to various hydrocarbons, itwasnecessary to devisea technique of introducing controlled quantities of hydrocarbons into the flame. This was accomplished by aspirating dilute hydrocarbon solutionsof methanol into the total consumption burner. As great as a 20-fold enhancement of CH emission was found when oxygen was employed as an oxidizer instead of air. Increasing Cz and CH emission intensity was found for hydrocarbons in the following order: hexane, cyclohexane, benzene, toluene and o-xylene. Comparison was made of relative response of hydrocarbons with previous studies. Analytical curves for these hydrocarbons in methanol solutions were obtained for air-hydrogen and oxyhydrogen flames at the wavelengths of the CH and Cz bands. The analytical curves for hydrocarbons in methanol were linear over the concentration range utilized.
A CHARACTERISTIC SPECTRAL FEATURE of air-hydrogen and oxyhydrogen flames containing hydrocarbons is the strong CBand C H emission from the inner cone. Gaydon ( I ) mentions that CBand CH radiation from such flames is stronger for aromatics or unsaturates than for saturates, but found quantitative comparison of the various fuels difficult. A flame emission detector for chromatography was first described by Grant ( 2 ) whose data confirmed the above view and indicated the potential response selectivity of the device. More recently, Juvet and Durbin (3) and Braman (4) have studied the characteristics of such a detector. The use of chromatographic systems in flame emission studies introduces complexities such as differences in eluted Present address, Department of Chemistry, University College of Swansea, Singleton Park, Swansea, Glamorganshire, Great
Britain.
peak profiles, restricted sample size, and flame flicker associated with low flow rates, which may limit the interpretative value of the data. Although the use of transmission filters of the appropriate spectral band-pass can be employed to observe Cz and C H emission in flames, a flame emission spectrum obtained from a recording spectrometer has the advantage of selective viewing of CBand CH emission bands throughout the visible region. If peak height, as opposed to area response, is to be used as a measure of emitter concentration, sharply defined band-heads obtained through use of a recording spectrometer are necessary. Limited area flame spectrometry (LAFS), a technique in which only a selective region of the flame is observed at a given time, has been utilized by Buell(5-7) in various studies of spectral emission from combusting organic solvents. Carnes (8) has also used LAFS in his study of emission from the reaction zone of an oxyacetylene flame. Typically, LAFS has been applied to the analysis of elements which are not easily excited when used in conjunction with organic solvents. Not much attention has been placed on the utilization of this technique for the study or analysis of hydrocarbons in flames. Neither Juvet and Durbin nor Braman, in their works on the spectral emission of hydrocarbons in hydrogen flames, used LAFS to any great extent. Since the present investigation of emission response entailed changing the hydrogen and oxidizer flow rates as well as the oxidant used, LAFS studies were indicated, as opposed to viewing the entire flame, to determine the relative concentration of the excited CZand CH species in various regions of the reaction zone. This study of flame emission presents a new analytical method for studying hydrocarbons in solution, utilizing commercially available instrumentation with minor modifications. EXPERIMENTAL Apparatus. Spectral energy data were obtained with a Beckman DK-2 recording spectrophotometer and a modified flame photometry attachment. The flame source used was a
(1) A. G. Gaydon, “The Spectroscopy of Flames,” Wiley, New
York, 1957.
(2) D. W. Grant, in “Gas Chromatography,” D. H. Desty, Ed., Butterworths, London, 1958, pp. 153-64. (3) R. S. Juvet and R. P. Durbin, ANAL.CHEM., 38,565 (1966). (4) R. S. Braman, Zbid., 38,734 (1966).
( 5 ) B. E., Buell, ASTM Special Tech. Publ. No. 269, 1960, pp.
157-64. (6) B. E. Buell, ANAL.CHEM., 35, 372 (1963). (7) B. E. Buell, Zbid.,34, 635 (1962). (8) W. J. Carnes and J. A. Dean, Analyst, 87,748 (1962). VOL. 39, NO. 14, DECEMBER 1967
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