28 gage) sealed into cup inserts of borosilicate glass for the sample and reference differential thermocouple, and 10-mil platinum-platinum, 10% rhodium for the base temperature thermocouple. The recording system consists of an x-y recorder with a direct current amplifier of multiple range in the differential thermocouple system. The available amplification ranges in six steps from =kt25 to = t l O O O ~ v . DISCUSSION
A plot of base temperature against time is essentially linear, using a silver bar and saniple holder and 10% wattage control. A maximum deviation of 5’ C. has been observed which is related t o the on-off cycle of the control heater. The heating and cooling curves are identical. Figures 3 and 4 contain representative heating and cooling curves for single salt systems. Ferrous sulfate and ammonium nitrate illustrate the behavior of the DTA apparatus, but the curves do not represent investigations of the compounds themselves. The ordinates
are intentionally shonn as relative units, because the sensitivity of any given run \\-ill depend on many factors: sample size, thermocouple material, amplification, etc. Each relative ordinate unit is equal to about 2.5’ C. and was recorded with a ChronielAlumel differential thermocouple feeding the +5OO-pv. range of the preamplifier. The abscissas are in millivolts to emphasize the use of different thermocouple materials to extend or conipress the base temperature range. The reference material in all runs was prefired aluminum oxide. The described method possesses many features not inherent t o present apparatus. Foremost is its ability t o record cooling data under the exact reverse gradient used for heating. The gradient is varied by changing the control temperature of the hot zone; the rate of change of sample heating is varied by the same method or by changing the size of the take-up drum. Consecutive runs may be made immediately by changing sample holders or by cooling the same holder. Replacing the cooling
coil with a controlled heater extends small temperature zones to full tube range for minute scrutiny. Raising or lowering of the holder redraws a sample through any desired zone. A slow constant-rate purge of the tube with inert gas controls the atmosphere. Improved, but more complicated, control is obtained by modifying the tube t o prevent back diffusion or entrainment of air. LITERATURE CITED
(1) Brace, P. H., U. S. Patent 1,558,828 (Oct. 27, 1925). (2) Evans, R. M.,Fromm, E. O., Jaffee, R. I., J . M.etals Trans. 4, 74 (1932). (3) Norton, F. H., J . Am. Ceram. SOC.22, 54-63 (1939). (4) Rosenhain, IT., J . Inst. Xetals 13, 160 (1915). (5) Smothers, IT. J., Chiang, Y., Wilson, A., “Bibliography of Differential Thermal Analysis,” Research Series KO. 21, University of Arkansas, Fayetteville, Ark., 1951. RECEIVEDfor review July 5, 1937. Accepted December 7 , 1957.
S pect rochemicaI An a Iys is of Nonmeta IIic Sa mpIes Pellet-Spark Technique with a Multicha n ne1 Photoelectric Spectrometer W. H. TINGLE and C. K. MATOCHA Alcoa Research laboratories, New Kensington, Pa.
b A comprehensive spectrochemical method uses a multichannel photoelectric spectrometer for the quantitative analysis of nonmetallic samples unlike in origin, physical structure, and chemical composition. For the determination of the major constituents the method provides for precision to 1 to 2% of the amount present. Quantitative accuracy may be obtained with either synthetic or chemically analyzed standards. A fusion technique reduces all materials to a common form. The fused sample is pulverized, mixed with graphite, and pelleted. A low-inductance spark discharge is used for excitation. Limits of detection are given for 21 oxides. spectrochemical methods have been developed for the analysis of nonmetallic samples, but there has been a need for a single method that simultaneously satisfies the requirements of routine, control, and general analytical laboratories. Although any universal method has
n/ll
.41i~
494
0
ANALYTICAL CHEMISTRY
compromises and limitations, the following method furnishes accurate analysis for major constituents and also limits of detection significant to the geologist or chemical engineer. It is universal in that the procedure is independent of sample origin or physical form, yet it may be applied to routine analysis of a specific product. Through the use of synthetic standards, it can be an absolute method independent of chemically analyzed samples for reference. Simplicity and speed are achieved through mechanical equipment, which can be used by relatively inexperienced personnel. The method is economically acceptable to the routine laboratory n-here man-hours per sample are a concern, and it also provides for an elapsed time per sample which is compatiblr with the requirements of a control laboratory. To analyze a variety of materials without excessive standardization, all samples must be reduced to a common form. This may be accomplished by disqolving the sample in a n appropriate solvent. All samples are then similar
in chemical state, and by dilution all elements are placed in a coninion environment. Aqueous solution methods, such as the porous-cup and spray techniques, are impractical because of the insolubility of many samples in acid or alkaline solutions. Fusion of the sample Ivith a fluying agent provides the most practical method. The advantages of a fusion technique have been adequately set forth by Price and others (4-6, 8-11). Price ( I O . I I ) investigated the use of sodium carbonate and borax as flusing agents and found that samples fused 11-ith borax produced clear, glasslike fusions. For analysis of miscellaneous materials, the determination of sodium is often required and borax cannot be used as a flus. Another fluxing agent which has also been used is a niisture of lithium carbonate and boric oxide (4-6.8, 9 ) . During development of this method, it n-as found that n hen used in proper proportions, this mixture produces clear, glasslike fusions with a wide variety of materials. As this fusion does not wet graphite, the bead formed is
-
i
i t
i
! I
I
easily removed from the bottom of a graphite crucible. This flux also serves as a buffer and provides lithium as an internal standard element. It has been established that for the analysis of samples obtainable in a metallic form, multichannel photoelectric spectrometers reduce man-hours and e1apst.d time per sample and provide high precision with resultant high accuracy [S,S). Thcy have also hem successfully applied t o the analysis of nonmetallics (1, 4,5, 12). For samples received in powdered form, efficient use of these instruments is mainly a problcm in sample preparation. In this method, the fused ljcad is ground and mixed lvith graphite in ordm to obhiri a conducting matcrial. For easc of handling, the resulting mixture in formed into a pellet. The rrquirement of uniformity within and among pellets is mct by mrchanization of grinding, mixing, and pcllrt-surfacing operations. This mechanization and associated assrmhly line systcm also result in a low sample preparation time. A spark discharge is used to ohtain the most repeatahle type of spectral rxcitation. As all samples are in a common form, synthrtic samples may be used for standardization. PROCEDURE
The samplc used for spectrochemical analysis should he representative of the material to be analyzed, no coarser than 100-mesh, and drird under conditions accepted as standard. The sample nerd not be calcined. Volatile matter is lost during the fusion and does not affect the dptcrminatioii of othcr constituents. A 0.2500-gram portion of this sample, 1.000 pram of lithium carbonatr, and 1.500 grams of boric oxide are mixrd in an agate mortar until no unmixed sample is evident, although a homogrnrorrs mixture is not required. As tho analysis depends upon the wriglit ratio of analytical rlrment to lithium, hoth the sample and lithium carbonate should he weighed to the nrarrst 0.2 mg. Because of thc hygroscopic naturc of boric oxide, it is not previously mised with the lithium carhonate. The absorption of moisture hy the boric oxide in a prcmixed flux rrould destroy the establishrd weight ratio of analytical element to lithium. The mixture of sample and flux is transferred to a graphite crumble. The crucihle may he preparrd by drilling a hole 1 inch in diamrter and inch deep xith a standard twist drill in a graphite rod l1I4inchrs in diameter and 1 inch long. Homvcr, yrrformed crucibles are now commcrrially available at such a cost that they may he considered expendable. C p to sis crucibles are loaded into a Nichrome wire tray, (Figure 1,A) and placrd in an electric furnace a t 1000" C. for 8 minutes. The crucible tray is removed from the furnace and cooled until the beads solidify.
Figure I .
Apparatus for sample preparation
The bcxds are about 9/16 inch in diameter. 1':ach bead is then loaded into a tungsten carbide capsule along with a tungsten carhide hall (Figure 1,B). The capsule is attached to a highspeed vihratory grinder, (Fignre 1,C). The grinder uses a '/Jip. motor and is a large version of the standard Kig-LBug amalgamator, manufaeturrd according to the requirrmcnts of this method by the Crescrnt Dental Manufacturing Go., Chicago, Ill. After grinding for 45 seconds, the rrsulting powder is emptied into a No. 325 sieve 3 inches in diameter, and screened for 1 minute on an automatic sieve shaker (Figure 1,D). I t has been shown experimrntally that hecause of the homogeneity of the fused head, complete pulverization to -325 mesh is unnecessary. Thrrc-trnths gram of the -325 mesh matrrial is transferred to a plastic capsule along with 0.600 gram of SP-IC graphite (National Carbon Co., Inc.) arid thrre plastic balls 3/,a inch in diamrter. The capsule is shaken for 3 minutrs on a Wig-L-Bug amalgamator [Figure 2,A), modified ta hold the intprlorking, plastic capsule 11/4 inchrs long and a/4 inch in diameter. At a cost of less than 2 cents per mix, thc capsulc and heads are considered cxpcndahlc and are not reused; however, the capsule is marked with the sample number and retained for storage of the pellet before and after analysis. After the plastic halls have heen removed, the mixturc is formed into a pellet '1% inch in diameter a t a pressure of 44,000 pounds per square inch. The pellet dors not disintrgrate upon handling, is easily resurfaced for repeated sparkings, and allom ample penetration by the spark. The specially developed pellet holders (Figure 2,B) have chamfered spring jaws that uniformly grip the periphery of the pellet and provide efficient electrical contact, thus avoiding interfacial
sparking. Pellets are simply pressed into numhercd holders, which are then handled like conventional rod or pin electrodes (Fieure 2.C). Before ea& spaiking, the pellet is surfaced by placing the loaded holder in a pellet surfacing ]ig (Figure 2,D), and rubbing the prllct Gross~filterpaper to prepare a new sparking surface. The jig m s designed t o align the pellet surface perpcndicular to the axis of the holder, thus ensuring repratahle surface geometry. After surfacing, the pellet holder is placed in an upper electrode clamp which is connected as the anode. The counter electrode, a high-purity graphite rod, '/4 inch in diameter, sharpenrd to a 20-degree cone that culminates in a hemisphere 0.06 inch in diameter, is spaced 3 mm. from the pellet. Excitation and exposure conditions are listed in Table I . A &second prespark period is folloned by an exposure of approximately 20 seconds as monitored by the integrated intensity of the
Table
I.
Excitation and Conditions
Exposure
Source. Applied Research Laboratories High-Precision Source, Model 4700, highvolt,age spark section Capacit,ance,pf. 0 .O O i a Inductance, Fh. 20.00 Resistance in series with EZD None added DGchargc current,, amperes 5.0 Discharge trains per cycle 4.0 Spectrometer. Applied Research Lahoratorips ll/,meter emission Quantometer Grating, lincs/ineh 24,400 Primary slit p Secondary siits, p a Residual valu e not included.
I
VOL. 30,
NO. 4,
APRIL 1958
50
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.
495
Table II. Analytical Lines c Concentration Ranges Investigate[ Concn. Flang Analvtical Line. A. of Oxides.. ., (Internal st< Li 6103.6 A1 3961.5 0.1-70.0 Si 2R81.6 0.1-70.0 0.140.0 Fe 2395.6 nn-.5n Ti 3372.8 0.1-15.0 Na 5890.0 0.2-50.0 Ca 3158.9
internal standard. Relative intensi of the analytical lines are measured i recorded by an Applied Resea Laboratories Quantometer. Table I1 lists the spectral lines i concentration ranges of the mi elements investigated. The met1 is not restricted t o the elements or c centrations listed. Analytical curves may be deri from either natural or synthetic sta ards. As the measuring and recording system is linear with respect t o spectral intensity, analytical curves are plotted on linear coordinates. If the excitation and exposure conditions are held reasonably constant, the curvature of an analytical curve does not change. Thus, the periodic sparking of two selected standards, one high and low in the concentration of each element, furnishes criteria for maintaining the established calibration. Analysis is obtained from the average of two sparkings on the sample pellet. As additional sparkings may be obtained on the pellet, it is stored in its mixing capsule for subsequent analysis. DEVELOPMENT OF EQUIPMENT
A rapid method for mechanically mixing graphite with a powdered sample in a dental amalgamator is described by Hele and Scribner (7). For rapid routine analysis large, expendable, plastic capsules requiring no cleaning are more practical than the plastic-enclosed glass vial used by Hels and Scribner or other eapsulcs now marketed for mixing purposes. The plastic balls eliminate agglomeration. Microscopic examination of samples mixed in a plastic capsule with plastic balls s h o w
Figure 2.
Apparatus for mixer and pellet handling
uniform disperfiion of particles after shaking for 30 seconds. Continued shaking reduces the graphite particle size and results in improved sensitivity. This was verified by analyzing prllets made from the fractions obtained from a screen separation of National Carbon Co., Inc., Grade SP-1 graphite. For Si 2881.6 A,, Table I11 presents line-tobackground ratios obtained under various mixing conditions by using grades of graphite subsequently made available by National Carbon Co., Inc. The other spectral lines listed in Table I1 follow the same pattern. The gain in sensitivity is associated with increased line intensity. Spectral hackground remains relatively constant under all mixing conditions. With an initially fine graphite powder, such as SP-lC, a mixing time of 3 minutes was sufficient. Pellets made with graphite finer than SP-IC, 90% through 200 mesh, tend t o laminate. Conventional methods of hand grinding the bead t o -325 mesh were tedious and too lengthy for rapid analysis. Consideration wits thus given t o taking advantage of the grinding ability of
Table Ill. Line-to-Background Ratios a s Influenced by Graphite and Mixing Time Analytical Line. Si 2881.6 A. Concentration. SiOl = 6.01% Method of Mixing Hand,n Wig-L-Bug Tme 2 min. 1 5min. 3 min. 6 min. ". of GraDhite 1 . 9 2.4 SP-1(100% -100mesh) 1.2 1.4 3.1 3.5 SP-3 (90% -200mesh)b 2.3 2.7 2.3 3.0 3.4 3.7 SP-4(100% -325mesh) Agate mortar and pestle 6 Later designated SP-1C.
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496
ANALYTICAL CHEMISTRY
the amalgamator as observed in the mixing operation. Tests with a small steel capsule and steel pellet indicated that the Wig-LBug principle was practical for grinding. The manufacturer furnished the enlarged Wig-GBug and provided arms to hold the large, tungsten carbide capsule. This capsule, manufactured by Kennametal, Inc., is large enough t o accept the fused bead and is able t o withstand the rigorous action. Owing t o the hardness of tungsten carbide, its low spectral response, and its relative unimportance in samples, contamination from the capsule is no problem. With the capsule and ball in present use, a sufficient quantity of bead is ground in 45 seconds. With respect to grinding time, a point is reached after which no further grinding is practical; thereafter, packing occurs a t the ends of the capsule. The present '/rhp. model operates at 3600 r.p.m. The minimum grinding time rapidly increases as the motor speed is reduced below 2503 r.p.m., while speeds greater than 36M) r.p.m. produce intolerable strains on the hearings and arms of the grinder. I n order t o take full advantage of the reduced grinding time, an automatic screening operation was desired. The bench-model vibrating shaker, developed by Derrick Manufacturing Co., Buffalo, N. Y., was modified by attaching a clamping arrangement t o permit simple and rapid loading and unloading of sieves. While the shaker is equipped to provide vibrations from 200 to 10,000 per second, the rate of vibration for this operation bas little effect on the t i e required t o obtain sufficient - 325-mesh powder.
Table IV. SO.
la 70 99 i6 i7 75 88 91 9i 95 104 69
693,
Limestone Feldspar Soda feldspar Burnt refractory Burnt refractory Burnt refractory Dolomite Opal glass Flint clay Plastic clay Burned magnesite Bauxite Bauxite
Compatibility of Various Nonmetallics
SiOp, %
S-Cb, 70
14.1 66.7 65.7 54.7 32.4 20.7 0.3 67.5 12.9 59.1 2.5 6.3 6.0
-0.2 -1.9 -1.2 0.7 0.3 0.2 0.1 -0.3 0.2 0.4 0.1 -0.1 0.0
T i 0 ~% ~,
S-Cb, %
0.3 0.1 0.0 0.0 0.1 0.0 0.1 0.1 0.0 0.1 -0.2 0.0 0.0
0.2 0.0 0.0 2.2 2.9 3.4 0.0 0.0 2.4 1.4 0.0 3.1 2.5
0.1 0.0 0.0 -0.1 -0.1 -0.2 0.0 0.0 0.1 0.0 0.0 0.0
0.0
2.0 2.5 2.6 1 1 3 9 2 7 4 8
0.0 0.0 0.0
Fe203a,% S-Cb, 70 XBS Standards 1.6 0.0 0.1 2.4 0.9 0.5 0.1 0.1 1.o 2.0 7.1 5.7 5.8
0.1
4.2 15.0 19.1 37.7 59.4 70.0 0.1 6.0 35.8 25.5
-0.8 0.1 0.1 -0.4 0.5 0.4 -0.9 0.4 0.1 -0.2 0.1
0.8 55.1 55.0
0.0
0.4
Alcoa Standard Bauxite Bauxite Bauxite Schist Bayer mud Sinter feed Sinter mud Chemical analysis.
12.3 2.4 8.5 56 2 23.0 13 0 24 8
0.6 0.3 0.0 0 0 -0 5 -0 2 -1 1
5.3 9.3 20.8
0.2 ...
si
0 -0 0 O
4 4 2 9 5 5
0 3 2 R
0.0' 0.0 -0.4 1.0 0.1 -0.2 -0.2
51.0 55.7 47.1 22.6 26.1 15.7 3.6
0 .i
-0.1 0.4 0.3
Difference between spectrochemical and chemical analysis.
INTERELEMENT EFFECT
IThile dilution and buffering by the flux and the graphite tend to reduce the interelement effects, it was found that the aluminum spectral intensity is affected by the silicon content of the sample. This was measured quantitatively by adding silica to a number of samples. The effect can be considered proportional to the alumina content and related curvilinearly to the silica content as follows:
Table V.
Compound
Assigned, yo
ALOs
55.0 6 01 5.82 2.78
Si02
Fen03 Ti02
A = =
A - AA A
- Af(s)
Spectrochemical, 70 XBS Bauxite 69a 54.72 5.97 5.76 2.76
51.0 12.32 5.30 1.95
50.85 12.40 5.24 1.99 Table VI.
Concn., 70
Compound
AR
Interval for Spec. Results, %
-0.28 -0.04 -0 06 -0.02
h0.30 f0 . 0 7 f 0 . 05 f0.02
-0.15 0.08 -0.06 0.01
f0.42 f0 . 0 9 f0.04 f0.02
Precision
vlo, % 1.0
54.0 9.0 5.6 2.4
1.5 2.0 1.4 60
v,,
%
va,
1.1 0.9 1.2 1.1 20
%
1.8 1.9 2.6 2.1
(2) A-
A R
= -
(5)
and plotting relative intensity ratios against for containing any silica concentrations.
A
RESULTS
=
%
Coefficient of Variation Among \Tithin pellets, pellet mgans, Of analysis,
Degrees of freedom
where d is the concentration as read from a n analytical curve made up from standards containing 0.0% silica. Equation 2 can be written as
Equation 3 becomes A
Difference,
Alcoa Standard Bauxite Alp03 Si02
Fe20t Ti02 where AA is the apparent change in alumina concentration resulting from the addition of s units of silica t o a sample containing 0.0% silica, A is the actual alumina present, and f(s) is a function of the silica added, as sholi-n in Figure 3. The actual alumina content of a sample is given by
Analysis of Bauxites Based upon Synthetic Standards 95y0 Confidence
(4)
The factor R is normally tabulated for each 0.5% silica and the correction becomes a simple multiplication. The requirement of a n alumina analytical curve for samples containing O.Oyo silica is satisfied by writing Equation 4 as
To test the universality of the method, the best-fitting analytical curves were drawn through points obtained from various Alcoa and National Bureau of Standards samples. Table IV lists, for each oxide investigated, the deviations of these points from a single best-fitting curve. hIatrix corrections were made only for the influence of
silica on alumina. Although a few discreDancies are amarent. the accuracy is believed to be sat^isfactory, considering the unlikeness of origin (natural and processed materials), physical nature, and chemical comDosition. The accuracy bf this method was also evaluated by comparing natural samples with corresponding synthetic samples. For this test, Kational Bureau of Standards bauxite KO.69a and a n Alcoa bauxite standard were chosen. A number of independent analyses furnished the results in Table V. The spectrochemical results agree with the assigned values within the errors attributable to chemical analysis and the precision of the method. VOL. 30, NO. 4, APRIL 1958
0
497
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lb-
,ai,-
22
-
o
r
- 0s-
--
>?I-
+
I
3c
100
03
*oo
103
PE“CEhT
,30
sco
51-1C4
Figure 3. Effect of silica on determination of alumina Apparent reduction in alumina content (70AIzOa) for each 170 alumina present in sample
--As)
Synthetic standards, in addition to eliminating dependency upon chemically analyzed standards for calibration, provide for a direct measurement of alumina rather than a difference measurement as is generally accepted in chemical analysis. The most repeatable results on synthetic samples are obtained !\-hen the total Tveight of the oxides or their equivalents is mixed with the flux and fused into a single bead. I n this case, the synthetic Constituents need not be rvell mixed before they are added to the flux. A synthetic mixture that has a total weight of about four times that of the corresponding natural sample reduces weighing errors to a satisfactory level, is conveniently handled in a large crucible, and furnishes material for about 24 pellets and over 100 exposures. The spectral response from pellets made from these large beads was found to be directly comparable to that from pellets made from the normal-sized beads. The procedure for
Table VII.
Oxide CUO SrO
MnO RIgO ZnO
?-io
BaO PbO BizOa Sn02 Be0 h’a.0
Limits of Detection
-4nalytical Line, A. 3274.0” 4215.5 2593.7 2852. l5 3345.0 3414.8 4934,l 4057,8
Limit of Detection, % 20,uh. 360 ph. 0 012 0.005 0.03 0.02 0.007 0.003 0.02 0.004 0.17 0.04 0.15 0.02 0.02 0.007 0.19 0.02 0.60 0.08 0.16 0.02 0 002 0.001 0.06b O . l O b 0.05 0.36 0.02 0.01 0.42 0.16 0 09 0.02
3067. 3178.0= 3130.4O 5890.0 4379.2, v 1 0 5 CaO 3933. I P“0, 2149.1 %fo& 3194.0a 0 08 0.005 Gaz03 2943 6 a Second order. High because of Na present in flux. ~~
498
~
determining the weights of components in the synthetic samples is explained by Price (10, 11). Table VI lists the repeatability within pellets and the reproducibility among independent pellets of the same sample. The coefficient of variation among pellet means does not include the variation within pellets. Assuming that the analysis is determined by the difference betn-een a standard and the sample, the expected coefficient of variation of analysis, V,, for two exposures each on standard and sample is
ANALYTICAL CHEMISTRY
and is listed in column 5 , Table 1‘1. K i t h only normal care rariations in crucible characteristics, cooling rate of beads, grinding and sieving times, briquetting pressure, and pellet thickness have no significant effects on the results. M I N O R ELEMENTS
Khile the method was designed to favor the determination of major constituents, it is also being used to determine minor impurities. Column 3 of Table J‘II lists the limits of detection for some oxides in aluminous ores using the standard conditions. On some samples, these limits of detection are not low enough to he significant to the geoIogist or chemical engineer. By increasing the inductance of the spark discharge circuit to 360 ph,] limits of detection are decreased to those shown in column 4. The limits of detection given in Table VI1 are for the average of trro sparkings and are three times the standard deviation of repeated exposures a t zero concentration. SUMMARY
I n general, this method is applicable to the determination of metallic elements present as major constituents in samples obtainable in a nonmetallic form. An exception is the determination of silicon in samples containing fluorides as major constituents. It is also applicable to the determination of many minor elements, some of which are listed in Tahle VII. Elements are customarily reported as oyides. TTben determination of lithium is required, strontium carbonate is used as a fluxing agent in place of lithium carbonate. Some lithium borates are satisfactory as unitized flusing agents. The use of lithium tetraborate anaits only commercial availability in proper physical form and nil1 further simplify the preparation of samples. At present, a batch process is used, requiring about 0.3 man-hour per sample. For control applications, a t
least six elements can be determined in a sample in from 30 to 40 minutes. The cost of expendable items, such a s chemicals, crucibles, graphite, plastic capsules, and filter paper is less than 29 cents per pellet. Although fusing and pelleting methods hare been applied to similar problems in the past, this successful application to rapid control and batch analysis is largely a result of the development and application of mechanical apparatus. These not only increase speed of analysis and simplify technique, but also provide greater precision and accuracy through the elimination of numerous variations attributable to operators. LITERATURE CITED
Black, R. H., Lemieux, P. E., ASAL. CHEW29, 1141 (1957). Callon, R. W., Charette, L. P., Ibid., 23, 960 (1951). Churchill, J. R., I r o n Age 168, 97 (19.51 ). \ - - - - I
Gillette, J. M., Boyd, B. R., Shurkus, A. A., -4ppl. Spectroscopy 8, 162 (1954). Hasler, 31. F., Spectrochim. A c t a 6, 69 (1953). Hasler, hl. F., Applied Research Laboratories, Glendale, Calif., unpublished work. Helz, A. W.,Scribner, B. F., J . Research S a t l . B u r . Standards 38,
439 (1947). Lnadermen. S.. Muld. IT.. Mikrochim.-Ach 2-3, 245 (1955). Lounamaa, N., Spectrochim. Acta 7, 358 (1956). Price, W.J., Brit. Cast I r o n Research Assoc. J . Research Deve1o.a. . 4., 315 (19521. Price, I\. J., Spectrochim. Acta 6 , 26 (1953). Turner, C., Jondro, A,, Forbes, T., “Determination of Sodium in illumina Using a Two-Line Direct Reading Spectrometer,” Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, 1954.
RECEIVED for review July 1, 1957. Accepted K’ovember 27, 1957.
Ultraviolet Spectrophotometric Determination of Sulfate, Chloride, and Fluoride with Chloranilic Acid-Corre ct ion I n the article on “Ultraviolet Spectrophotometric Determination of Sulfate, Chloride, and Fluoride with Chloranilic Acid” [Bertolacini, R. J., and Barney, J. E. 11, ASAL. CHEM. 30, 202 (195S)l in Figure 2 column 1 should have been headed “Ethyl Alcohol,” column 2 “Methyl Cellosolve,” and column 3 “Isopropyl Alcohol.”
