Determination of Indium in Aluminum Bronze Alloys by Flame Photometry VlLLlERS W. MELOCHE, JOHN B. RAMSAY, DAVID J. MACK,
and
T. V. PHILIP
Department o f Chemistry and Department o f Metallurgy, University o f Wisconsin, Madison 6, W i s .
I
S T H E course of an investigation of the physical properties of indium-aluminum-copper alloys, it was necessary to determine the amount of indium in the alloy. The range of concentration was 0.5 to 2.5%. A review of the literature indicates that, whereas indium may be weighed as In203after ignition of the hydroside a t l l O O o to 1200’ C., the separation of interfering elements may be tedious and difficult. Saltman and Sachtrieb (4)and Hauser ( 2 ) mentioned that indium could be .tidyzed spectrographically, and as another laboratory had reported difficulty in the analysis of the above-mentioned alloys by classical wet methods, i t appeared that analysis by flame photometric procedure might result in a saving of time and yet J ield adequate results. The flame spectrum of indium has two strong lines, 451.1 and 410.2 mp, and i t was believed that one of these lines might prove sensitive enough for flame photometric malysis. This paper describes the application of a flame-photometric procedure to the analysis of a series of alloys for indium. In the vourse of this work the various possible interferences by elements n hich might be present in the alloy M-ere studied. APPARATUS AND MATERIALS
The instrument used in this study was a modified Beckman flame photometer equipped with a Model 4300 photomultiplier attachment and a Model 4020 hydrogen burner. The amplifier Iias been modified to include a fine adjustment on the dark current and a “bucking” circuit for opposing the potential caused by the flame background ( 1 , 3). Using this bucking circuit, it was possible to eliminate the unwanted background potential from the total potential, thereby leaving the full scale for measurement of the analytical radiation. Stock solutions of indium were prepared by dissolving 1000 gram of indium metal in a small amount of nitric acid, boiling to expel the oxides of nitrogen, and diluting to 1 liter. This gave a solution of 1000 p p.m. of indium. The metal used was indium shot obtained from the Indium Co. of America. The indium was checked by the spectrograph and found to contain only traces of aluminum and nickel. A stock solution of copper containing 10 mg. per ml. was prepared by dissolving 10.0 grams of analytical grade copper foil in nitric acid, boiling, and diluting to 1 liter. A 1000-p.p m. aluminum solution was prepared by
dissolving 13.9 grams of aluminum nitrate nonahydrate in water and diluting to 1 lit,er. EXPERIRI ENTA L
An examination of the flame spectrum of indium showed the 481.1 mp line to be approsimately twice as intense as the one a t 410.2 mp. It was therefore decided to use the 451.1 mp line. Interferences. The study of various possible interferences was carried out by preparing a working curve from a standard m-ies in the range 0 to 100 p.p.m. of indium and no other added elements. Two other series of solutions were prepared containing 10 and 50 p.p.m. of indium and various concentrations of the contaminants studied. The apparent concentration of the indium in these solutions was determined from the working curve and this concentration was compared to the amount added. The difference betveen these two values was a measure of the interference. COPPER. Copper imparts n green color t o the flame which affects the flame background intensity a t 451.1 my. This effect was found to be constant above 800 p.p.m. (equivalent to 80% of copper in the alloy). Because all the samples to be analyzed were greater than 85% copper, the effect of this interference could be nullified by adding copper to the standard series; therefore 900 p.p.m. of copper were added to all standard solutions. ALUMINUM.While aluminum has no flame spectrum in this region its presence does degrade the indium 451.1 my intensity. This effect became constant a t 30 p.p.m. and remained so up to 500 p,p.m. I t was not investigated a t higher concentrations. The alloys studied contained approximately 11% of aluminum: therefore 50 p.p.m. of aluminum were added to the standards. ZINC. The presence of zinc in the solution showed no effect in the range 0 to 100 p.p.m. of zinc. NITRICACID. The possibility that varying amounts of nitric acid used in dissolving the sample might affect the emission was studied. The emission of a I N nitric acid solution containing 900 p.p.m. of copper, 50 p.p.m. of aluminum, and 50 p.p.m. of indium was not appreciably different from that of a similar solution containing no excess nitric acid. HYDROCHLORIC A N D SULFURIC ACID. Up to 1N hydrochloric acid does not effect the radiation, but 1N sulfuric acid does degrade the flame. However neither acid is necessary for the solution of the sample. RECOMRIENDED PROCEDURE FOR DETERMINATION OF INDIUM IN ALURIINUM BRONZE ALLOYS IN RANGE 0.1 TO 10.0%
Instrumental Procedure.
The instrument is allowed to warm
up for 1 hour and the oxy-hydrogen flame is allowed to burn for 10 minutes. The slit is set a t 0.04 mni. and the wave length
Figure 1. Relative Intensity (451.1 mp) us. Concentration of Indium
dial is adjusted to the maximum emission for the 451.1 mp line. The gas pressure for maximum emission must be determined for each individual burner. The sensitivity and the bucking circuit arp adjusted so that the span of the slide wire represents 100 p.p,m. of indium. The 0.0 p.p.m. of indium solution should read higher than 0.0 on the instrument scale. It is then possible to determine whether drift has taken place. Preparation of Standards. The standard series is prepared by adding the required amount of indium stock solution (0.0 to 10.0 ml.) together with 9 ml. of the copper stock solution and 5 ml. of the aluminum stock solution and diluting to 100 ml. The emission of these solutions is determined on the flame photometer and the readings are plotted against concentration. The results obtained from these solutions are given in Table I and Figure 1. Although the above data indicate that the radiation is a linear
1387
ANALYTICAL CHEMISTRY
1388 Table I.
0,1000-gram sample has been dissolved and diluted t o 100 ml., as 1 p.p.m. is then equivalent t o 0.1% of indium in the alloy.
D a t a for Working Curve
Indium Concentration, P.P.M. 0.0 25.0 75.0
Intensity,
100.0
Average of 5 Readings
DISCUS S I 0 3
3 2 2R. 1 76 6 101 I
A series of samples containing various concentrations of indium and the other elements mentioned earlier in the paper was prepared. These solutions were then analyzed by this procedure. Table I1 gives the results obtained. I n order to calculate the precision of the procedure, the standard deviation of the readings used to obtain the working curve was calculated. A value of 0.33 p.p.m. was obtained using the readings from four working rurvea (approximately 100 readings). The samples all fall within the 3u limit indicating that the procedure is accurate to within = t O . l % indium. The sensitivity of the method may be increased by increasing the slit width; however, if this is done the effect of copper must be re-examined. The minimum detectable amount of indium for an oxy-hydrogen burner appears t o he approxim:ttely 0.2 p.p.m.
Tahle 11. Results on Prepared Samples
X U
1 2 3 4 5
Lj
& 9
10 11
Cu 822 935 850 930 820
AI
930
68 100 30 73 57 100
850 900 845 910 830
.iO
46 63
60 45
Added, Zn 25 27 30 0 $0 0 38 0 52 0 0
P.P.Al. Ph Fe 2 0 3 0.2 0 0 0 3
0 2 1 0
2 0
0
0.5 0 0 6
n
0 0 0
In 86.0 8 0 67.0 11.0 35.0 2.0 8.8 80.8 29.5 28.0 70.0
Re. ported, P.P.11 In 86 1 8.1 66.0 10.8 34.5 2.3 8.8 81.3 29.0 28.0 69.5
Error -0 +O --I -0
1 1
0 2 -0.5
+O.R
0 0 +0.5 -0.5
0.0
-0.3
LITERATURE CITED
(1) Boycks. E. C . , Ph.D. thesis, U n i v e r s i t y of Wisconsin, in prepara-
function of concentration from 0 to 100 p,p.m., it was found that the range for this relat,ionship was at least 0 to 1000 p.p.m. for an indium solution to 1vhic.h no other elements had been added. Analysis of Samples. Ai0.1000-gram sample of alloy is dissolved in a small amount of nitric acid, and the solution is boiled and diluted t,o 100 nil. The emission of this solution is determined on the flame photometer and the concentration of the indium in the alloy is determined by interpolation from the n-orking curve. The calculation of per cent indium is easy if a
tion.
R.,A p p l . Spectroscopy, 2, 11-13 (1952). (3) Jefferson. J. H., Ph.D. thesis, University of Wisconsin, 1961. (4) S a l t m a n , If-., and S a c h t r i e b , S . H., ;~K.LL. CHEY.,23, 1503-5 (1 9 5 1 ) .
(2) H a u a e r , H.
R E C E I ~ Efor O review February 27. 1954, Accepted N a y 5 , 1954. The work described was supported in part by the Research Committee of the Graduate School froin funds supplied by the Wisconsin Alumni Research Foundatioli.
Absorption Spectrum of Aqueous Yonochloramine Solutions JACOB KLEINBERGI, M E L V I N TECOTZKY, and L. F. AUDRIETH Department
ol Chemistry and
Chemical Engineering, University o f Illinois, Urbana,
OSOCHLOKBMISE, SH2C1, an intermediate in the formation of hydrazine in the Raschig synthesis, is commonly determined iodomet~rically. Inasmuch as i t is conceivable that aqueous chloramine solutions might, on standing, give deconipositioii products which would interfere wit,h iodometric analysis, the present study was undertaken to determine the fearibility of :rnalyris for monochloramine hy spectrophotometric‘ means. Xccordiiig to lletcxlf ( e ) ,aqueous solutions of nionochloramine give a maximum absorption a t 2450 -%. and have a molecular estinction, E, of 416 at this wave length. Moreover, on the assuniption that iodometric analysis gives a true measure of chloramine content, the molecular extinction (in solutions containing :iretate or phosphate buffer) remains essentially constant over an extended period of time. Hon-ever, Uetcalf states that when the titers of monochloraniine solutions fall to about one half their original values (no quantitative data are given), extinctioiis no longer correspond to the iodometric titers. The authors have definitely established the adherence to Beer’s law a t the wave length of inasimum absorption of buffered aqueous solutions of monochloramine in the concentration range of 5 X to 3 x 10-3x1, the concent,ration of the chloi~aniine tieing calculated by iodometric analysis. Conformity to I3ec.1,’~ lan. is observed even in solutions which had been permitted to stand for 136 hours. RIoreover, possible products of the decomposition of aqueous monochloramine solutions-e.g., hydrazine, hydroxylamine, nitrate, and nitrit,e ions-do not absorb to any extent a t the wave length of maximum absorption by monochloramine. The results, therefore, demonstrate that nioriochloramine may be determined spectrophotometrically. 1 Present address, Department of Chemistry, University of Kansas. Lan-wnce, Kian.
111. EXPERI\IESTA L
The Spectrophotometer. -4Cary recording spectrophotometer, Model 11, was employed for the spectrophotometric studies. The following instrument settings were used: slit control switch at 10, chart range 0 t o 2.4 and Hi-Lo knob at the Lo positio?; The chart drive gears were kept at “60 driving, 60 driven, which gave a chart speed of 10 seconds per division. The large scanning gear was employed and provided a scanning rate of 5 A. per second. One-centimeter cells of fused silica were used in all measurement*.
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