93
V O L U M E 2 8 , N O . 1, J A N U A R Y 1 9 5 6 Table VI.
Effect of Oxygen on Determination of Cobalt
(Rate of huhhling, 2 nil. per minute) Cohalt Found," Time, Cobalt Present, Rlg. 31g. Minutes 11.80
11.78 11.75 11.55
1 20 120
No. of
Expts. 2 2 2
standard iodine solution were added and the excess iodine was determined potentiometrically in the usual way. The results of these experiments, recorded in Table VI, indicate that decammine M-peroxo dicobalt(II1) ion is very stsablein the dilute cobalt and ammonia solutions present in the proposed analytical procedure.
a Iodine solutions added after oxygen was bubbled through ammoniacal solutions of cobalt.
If, on the ot,her hand, decanimine p-peroxo dicobalt(II1) v-ere formed by the air oxidat,ion of cobalt(I1) ammines and subsequently x a s converted, perhaps catalytically, int,o hydroxopent,amminecobalt( 111) or hexamminecobalt(II1) by some react.ion other than that of Equation 2, then low cobalt results would be served. A series of experiments was carried out in order to study the stability of decammine M-peroxo dicobalt(II1) using the following procedure: Oxygen, which had previously been passed through a solution of ammonium hydroxide, was bubbled through 25 ml. of a solution of cobalt sulfate containing 25 grams of ammonium nitrate and 5 ml. of concentrated ammonia a t the rate of 2 ml. per minute. After a predetermined length of time, 25 ml. of a
4CKYOW LEDGlRI ENT
The author \Tishes to thank Allan Fischlowitz and Delmrah Edelman for making marly of the cobalt analyses. LITERATURE CITED
(1) (2) (3) (4)
Dickens. P., a n d M a a s s e n , G . . A r c h . Eisenhiittenzo. 9, 487 (1935). Diehl, H., a n d Butler. J . P., bsa~. C H E X 27, 777 (1955). LIc.ilpine, R. IC.,J . Chem. Educ. 26, 362 (1919). Qureshi, lI.,a n d Veeraiah, K., Current Sei. (India) 15, 132
(1946). (5) Smith, J. D . hI., Chern. In&. 44,5391 (1925). (6) Tomicek. 0..a n d Freiberner. F.. J . A m . Chem. Soc. 5 7 . 8 0 1 11936). ( 7 ) T e r n e r , d.,Ann. 375, 1 (7910) ( 8 ) Y a l m a n , R. G., J . Am. Chem. Soe. 75, 1842 (1953). (9) Y a l m a n , R. G., Ibid.,77, 3219 (1955).
RECEIVED for review July
21, 1955.
Accepted Octoher 6, 1955.
Interaction of Platinum Group Elements with 1,2,3-Benzotriazole RAY
F. WILSON
and LOUBERTA E. WILSON
D e p a r t m e n t o f Chemistry, Texas Southern University, Houston, T e x .
This paper is part of a general study of the interactions of the platinum metals with 1,2,3-benzotriazole. Methods for the prai irrietric and for the amperometric determination of palladium(I1) chloride, in acetic acid-sodium acetate buffer, have been developed using 1,2,3-benzotriaaole as a precipitant. From 3 to 60 mg. of palladium u ere determined gravimetrically with an average error of less than 0.1 mg. The amperometric method has been applied to 0.2 to 6 mg. of palladium. When the concentration of palladium is greater than 0.2 mM, the a\erage relative analytical error is within &0.3%. The methods are recommended primarily for the accurate determination of chloride solutions of palladium containing only traces of other platinum elements.
W
studying the interaction of palladium (11) and 1 2 3-benzotriazole (15)i t was observed that palladium r a s HI? precipitated quantihtively in this reaction. 1,2,3-Benzotriazole has been studied as a precipitant for silver by Remington and \Toyer (11), Tar:isevich ( I Z ) , and Cheng ( 2 ) . Curtis (4)has ex;%minedthis reagent :is :L precipitant for copper. These studies indicate t,hat iron(I1 j , nirkel(IT), cobalt(II), zinc, and cadmium :ire also previpitated l)j, this reagent. When an excess of 1,2,3-benzotriazole is added to an acetic acid-sodium acetittc huffer solution containing palladium(I1) c.hloride in the ahsencc or presence of sodium dihydrogen (ethylenedinitri1o)tetraacetic acid. a white colored coordination compound is formed, which, n-hcn dried, corresponds to the formula Pd(C6H4NHNl)pCI? (151. In excess palladium, 1,2,3-benzotriazole forms a reddish-hron-n colored coordination compound; its formula is Pd(C,H,SHS,)Cl? ( 1 5 ) . GRAVIIUETRIC DETERJIINATION OF PALL.IDIUM The gravimet'ric determination of palladium has been t h e subject of several investigations during the past few decades. Pal-
ladium has been determiiirtl gravimetrically xith salicylaldosime ( 7 ) ) with p-furaldoxime ( ~ 7 ) n-ith ~ 1,2-cyclohexanedione ( l e ) , with dimet,hylglyosime (Io),and with phenylthiourea, thiophenol, and thiobarbituric acid ( 3 ) . Of these gravimetric methods, the dimethylglyosinie procedure has been used very widely. I t was the purpose of this investigation to ascertain the possibility of obtaining reproducible and sufficiently accurate stoichiometric results in the direct gravimetric determination of palladium(I1) xith l ,2,3-benzotriazole in acetic acid-sodium acetate buffer, and to determine the estent of interferences from certain diverse ions on the determiriation of palladium. EXPERIIIENTAL
Reagents and Solutions. A 5-gram sample of palladiuni(I1) chloride, obtained from Coleman and Bell Co., was dissolved in 10 ml. of concentrated hydrochloric acid and diluted t o 1 liter with distilled water. This solution was standardized gravimetrically, using modifications of the Gilchrist-\Tichers procedure (6). Reagent grade rhodium( III), iridium( IV), platinum( IV), ruthenium( III), iron( I11 chromium( 111), aluminum( 111), zinc, magnesium, nickel(II), and cobalt(I1) chlorides \\-ere used to prepare solutions of these elements. Osmium(VII1) solution was prepared from osmium tetroxide, using the procedure of A y e s and Wells ( 1 ) . Platinum(I1) solut'ion was prepared from potassium tetrachloroplatinate(I1). Gold(II1) solution was prepared from chloroauric acid trihydrate. 1,2,3-Benzotriazole, East,man Kodak Chemical KO.2759, was recrystallized tn-ice from chloroform and dried a t room temperahre. A n-eighed amount n-as dissolved in 125 ml. of glacial acetic acid and diluted to 250 ml. with distilled water. The concentration of this solution was checked by modifying the method of Cheng ( 2 ) ; the results obtained hy this method agree closely with the calculated concentration of 1,2,3-benzotriazole. (Ethylenedinitrilo jtetrnacetic acid (Versenate) solution n-as prepared by dissolving 10 grams of the disodium salt of (ethylenedinitri1o)tetraacetic acid, analytical reagent grade from T'ersenes, Inc., in 1 liter of distilled water. -4buffer solution was prepared, which was 251 in acetic acid and in sodium acetate.
94
ANALYTICAL CHEMISTRY
Qualitative Study of Interaction of 1,2,3-Benzotriazole with Platinum Metals. Preliminary qualitative tests mere carried out using individual solutions of the platinum elements employing l,2,3-benzotriazole as a possible reagent for the qualitative or quantitative determination of these metallic ions. These esploratory tests were undertaken to determine the nature of these reactions and t o ascertain whether or not the properties of the systems might offer possibilities for further investigation. The interactions of the platinum elements, after the solutions had been diluted so that concentration of the ions was of the order of 1 X l O - 3 ; M , with 1,2,3-henzotriazole was studied in the absence and in the presence of disodium dihydrogen (ethylenedinitri1o)tetraacetic acid. At room temperature (about 25' C.) and in the absence of disodium dihydrogen (ethylenedinitril0)tetraacetic acid, 1,2,3-benzotriazole reacts with palladium(I1) to give a white precipitate which remains suspended in solution, for a t least several hours. -411 test solutions in which Versenate was employed contained about a five-fold molar excess of this reagent. I n the presence of disodium dihydrogen (ethylenedinitri1o)tetraacetic acid. palladium begins to precipitate only after the addition of nearly equal molar amounts of 1,2,3-benzotriazole. However, in the absence of disodium dihydrogen (ethylenedinitri1o)tetraaretic acid, palladium begins to precipitate immediately after the initial addition of a very small quantity of reagent. The fact that palladium(I1)-Versenate complex is more stable than the palladium(11)-chloride complex has been reported (IO). After being heated in a water bath a t 85' C. for 10 minutes, the palladium(II)-chloride-1,2,3-benzotriazole precipitate was slightly coagulated; however, the precipitate coagulated when disodium dihydrogen (ethylenedinitrilo)tetraacetic acid was present. I n the absence of disodium dihydrogen (ethylenedinitril0)tetraacetic acid a t room temperature, the ruthenium-l,2,3benzotriazole system gives an intense rose-red color, and the osmium-l,2,3-benzotriazole system gives a pale yellow color. These two elements gave no visible reaction with this reagent in the presence of disodium dihydrogen (ethy1enedinitrilo)tetra-
0
-0.3 -0.6 E.M.F VS. SATURATED
-0.9 -1.2 CALOMEL CELL, VOLTS
-1.5
F i g u r e 1. Typical polarograms 0.0865 X 10-241 palladium(I1) in 0.4.M acetic acid-sodium acetate buffer 2. 0.257 X 10-2.11 1,2,3-benzotriazole i n 0.4.M acetic acid-sodium acetate buffer 1.
Table I. Pd Taken, lfg. 2.97 2 97 2.97 8 91 8 91 8.91 14.85 14,85 14.85 29.70 29.70 29.70 44.55 44.55 24,j.j a9 40
Gravimetric D e t e r m i n a t i o n of Palladium Wt. of Ppt., Mg.
11.5 11.6 11.4 34.8 34.5 34.6 58.2 57.8 57.9 115.5 115.7 115.6 174.1 173.0 173,s 232,l
Pd Found, AIg. 2 95 2 98 2 92 8 93 8 85 8 89 14 93 14 83 14 86 29 64 29 69 29 66 44 67 44 39 44 60 59 56
Difference, llg.
-n. nz .+0.01 -0 05 + O 02 - 0 00 -0 02 + O 08 -0
02
+o.oi -0.oii
-0.01 -0.04
+ o . 12 -0.16
+0.05
+O.l6
Table 11. Gravimetric Determination of Palladium in Presence of Diverse Ions Pd Taken, Rlg.
14.8.5 14.85 14.85 14.85 14.85 14.85 14.85 14.85 14.85 14.85 14.85 14.85 14 85
Ion Added, AIg. 9.3 Pt(IV) 10.1 Ir(1V) 7.8 Rh(II1) 8.9 Os(VII1) 9.4 Ru(II1) 5.6 Fe(II1) 2.8 AI(II1) 6.5 Zn(I1) 2.4 Mg(I1) 5.9 Ni(I1) 6 . 0 Co(I1) 12.4 NOa19.2 SO1--
Pd Found, .Mg.
14.81 14,78 14.88 14.93 14,99 14.86 14.83 14.88 14.86 14.65 14.83 14.86 14.83
Difference, RIg. -0.04 -0.07 +0.03 +0.08 +0.14 +0.01 -0.02 +0.03 +0.01 -0.20
-0.02 +0.01 -0.02
acetic acid; this probably indicates that the Versenate complexes of these ions, if they exist, are rather stable. On heating the solutions which contained no disodium dihydrogen (ethylenedinitri1o)tetraacetic acid, the ruthenium-l,2,3-benzotriazole system changed from rose-red to bluish green and the osmium1,2,3-benzotriazole system changed from pale yellow to orange. After digesting these solutions in the usual way with disodium dihydrogen (ethy1enedinitrilo)tetraacetic and excess 1,2,3-benzotriazole, osmium gave no visible reartion and ruthenium gave a brown precipitate which formed slowly on standing. Of the other platinum metals no visible reaction was obtained x-ith or without disodium dihydrogen (ethylenedinitri1o)tetraacetic acid a t room temperature. Rhodium(II1) and platinum( 11) during digestion reacted very slowly, in the absence of disodium dihydrogen (ethylenedinitri1o)tetraacetic acid, to form precipitates which remained suspended in solution; in the presence of disodium dihydrogen (ethy1enedinitrilo)tetraacetic acid, rhodium gave no visible reaction and platinum(I1) gave a small amount of turbidity which formed on standing. Further tests showed that a high concentration of acetate ion was ver>- effective in coagulating the palladium( 11) chloride1,2,3-henzotriazole precipitate. I t was found that this precipitate coagulates immediately when an acetic acid solution of this reagent is added to an acetic acid-sodium acetate buffer solution containing palladium, in either the presence or absence of Versenate. Properties of Palladium(I1) Chloride-1,2,3-Benzotriazole Precipitates. When palladium is precipitated by 1,2,3-benzotriazole in the presence of excess reagent, the ratio of reagent to palladium is 2 to 1; the precipitate exhibits a mhite color, both in solution and after drying. I n ewess palladium, the reagent t o palladium latio is 1 to 1 ( 1 5 ) . Careful observation shoms that in solution Tvhen palladium combines with 1,2,3-henzotriazole in the ratio of 1 to 1, the precipitate appears beige; however, after drying the precipitate appears reddish brown. Temperatures from 110' to 150" C. were safe for drying the precipitates. Constant weight was obtained for the precipitates after they had been heated a t 110' C. for 30 minutes. The pre-
95
V O L U M E 2 8 , N O . 1, J A N U A R Y 1 9 5 6 cipitates did not show sensitivity to diffuse light. The precipitates were practically insoluble in most concentrated inorganic acids and in most organic solvents. The precipitates are readily coagulated by acetic acid-sodium acetate buffer. Hoaever, when interfering ions that are complexed b? disodium dihydrogen (ethylenedinitri1o)tetraacetic ncid in acid media are present, it is desirable to carry out the precipitation i n disodium dihydrogen (ethylenedinitri1o)tetraacetic acid solution. Recommended Procedure. T o a solution containing from 2 to 50 mg. of palladium are added 10 ml. of 2.M acetic acidsodium acetate buffer, and 5 to 10 ml. of 4yo disodium dihydrogen (ethylenedinitri1o)tetraacetic acid, depending upon the amounts of interfering metals present. Then a slight excess of a 2.5Vo 1,2,3-benzotriazole (dissolved in 50% acetic acid) solution is added, and the solution is digested betn-een 60" and 90" C. for 10 minutes to coagulate the precipitate. The cooled, digested precipitate is then filtered using suction through a weighed, medium porosity, sintered-glass crucible or a weighed Gooch crucible which contains an asbestos mat. The precipitate is washed several times with dilute hydrochloric acid (1 to 100) and finally several times with distilled water. The precipitate is dried at 110" C. for 1 hour to constant weight. The theoretical factor for palladium, corresponding to the formula Pd( c6H4r\rHS,)2c12,is 0.2566, the value that is used to calculate the palladium content of the precipitate. Experimental data were in good agreement with the theoretical factor 0.2566. The data obtained from several determinations of palladium with 1,2,3-benzotriazole, in the absence of and in the presence of interfering ions, are shown in Tables I and 11.
palladium used in the amperometric titrations were generally less concentrated than those employed for the gravimetric determination of palladium. The nitrogen, as obtained from the Houston Oxygen Co., was of 99.5% or greater purity. This gas was further purified for polarographic use by passing it through a copper-filled furnace tube, which was maintained a t an average temperature of 450' C. All other materials used in the preparation of solutions Tvere reagent grade chemicals. Amperometric Titration of Palladium(I1) Chloride with 1,2,3Benzotriazole. In Figure 1 are recorded typical polarograms of palladium and of 1,2,3-benzotriazole in acetic acid-sodium acetate buffer. These current-voltage curves indicate that the optimum voltage range for carrying out amperometric studies is from -0.3 to -0.9 volt. After a preliminary study of the palladium( 11) chloride-1,2,3-benzotriazolesystem, the following procedure was adapted for the amperometric determination of palladium.
5.0
I
DISCUSSIOY
A method for the gravimetric determination of palladium is presented, which involves the precipitation of palladium as palIadium(I1) chloride-1,2,3-benzotriazoleJPd( C6H4"N2)&1*. The method is primarily recommended for the accurate determination of chloride solutions of palladium containing only traces of other platinum elements. However, platinum(I1) and gold(III), in moderate amounts, interfere Fith the determination of palladium. Moderate amounts of sulfate and nitrate ions do not interfere with the determination of palladium(I1) chloride. This method is believed to offer certain advantages over the generally accepted dimethylglyoxime procedure. The precipitate has a larger formula weight and hence a smaller palladium content. The palladium(I1) chloride-1,2,3-benzotriaxole procedure, as compared to the dimethylglyoxime procedure, saves time and the precipitate is easier to handle.
AMPEROMETRIC DETERMINATION OF PALLADICllI Toropova and Yakovleva ( 1 3 ) have performed amperometric titrations of palladium with salicylaldoxime and with mercaptobenzenethiazole. Kolthoff and Langer (8),while investigating the amperometric titration of cobalt with 1-nitro-2-naphthol from a few experiments, observed that palladium could also be titrated with the same reagent. The present investigation is concerned with the amperometric titration of palladium(I1) chloride with 1,2,3-benzotriazole. EXPERIMER-TAL
Apparatus. A Sargent ;\lode1 XI1 photographic recording polarograph was used to carry out all amperometric titrations herein reported. Polarograms of palladium and of lJ2,3-benzotriazole, in acetic acid-sodium acetate buffer, were recorded employing a Sargent Model X X I visible recording polarograph. The titration cell contained a saturated calomel reference electrode in one compartment, as described by Kolthoff and Lingane (9). All current measurements were taken a t 25' =k 0.1" C., and potentials are expressed us. the saturated calomel electrode (S.C.E.). The characteristics of the capillary used were: m = 0.890 mg. see.-'; t = 8.15 see. (open circuit in distilled water); m z i J sec.1'6 = 1.313 m2/3sec.-1'2; and h = 40.4 cm. Reagents and Solutions. Preparation and standardization of the palladium(I1) chloride solution and of the 1,2,3-benzotriazole solution were described under Gravimetric Determination of Palladium. However, solutions of the reagent and of the
0
I
0 VOL.
0-T
1
0.2
0.4
0.6
1,2,3-BENZOTRIAZOLE
0.8
1.0
SOL.,ML.
Figure 2. Titration of 20 ml. of 0.0865 X 10-2M palladium(I1) with 0.0642M 1,2,3benzotriazole An appropriate aliquot of the stock standard solution of palladium, to give the final concentration desired, mas added to a 25ml. volumetric flask, then 5 ml. of 2 X acetic acid-sodium acetate buffer and 1 ml. of 0.2'35 gelatin solution were added; the solution was then diluted to volume with distilled water. A 20-ml. aliquot of this solution was transferred to an H-type cell, and oxygen-free nitrogen, which had been conditioned by passage through a blank solution that contained all of the reagents in the usual concentration evcept palladium or the titrant, was passed through for 15 minutes. After the passage of nitrogen had been completed, the tip of a microhuret containing the 1,2,3-benzotriazole solution was pushed through a hole in the stopper of the titration cell. All current measurements r e i ? taken a t -0.5 volt and mere corrected for dilution effecte. After the expiration of a fen- minutes, the current became constant and the mean of the galvanometer deflections was recorded. A small quantity of the titrant m-as run into the cell; the solution was stirred with nitrogen for 1 minute, and the current was read 2 minutes thereafter. After each addition of titrant, about 1 minute was required for the current to become constant. This latter procedure was continued throughout the titration. The extrapolation method was employed in ascertaining the volume of titrant used in each titration. Figure 2 is a typical titration curve of palladium Kith 1,2,3-
96
ANALYTICAL CHEMISTRY
benzotriazole. The results for the amperometric titration of different concentrations of palladium are shovn in Table 111; each line in the table is the average of two closely agreeing results on samples of the concentration indicated. These data indicate that one palladium ion combines with one molecule of reagent. I n Figure 3, the data are recorded for the amperometric titration of 1,2,3-benzotriazole with palladium. When the 1,2,3benxotriazole is titrated with palladium the ratio of reagent to palladium is 2 to 1. Effect of Diverse Ions. For application of the method in the analysis of palladium in common compounds of this element, the possible interference from a number of positive and negative ions should be considered. The metallic ions selected for this study were platinum(IV), platinum(II), rhodium(III), iridium(IV), ruthenium(III), osmium(VIII), iron(III), chromium(III), gold(III), aluminum(III), cobalt(II), calcium(II), nickel(II), and magnesium( 11). Results of preliminary experiments showed that moderate changes in chloride ion concentration had no measurable effect on the amperometric titration of palladium; therefore, the only negative ions selected for this study were nitrate and sulfate. The interference effect of these ions on the amperometric titration of palladium(I1) was studied by adding selected molar concentrations of the diverse ions, individually, to 1 m M solutions of palladium (in the final concentration); these solutions m r e then made up in the usual way. Palladium could not be determined accurately in the presence of osmium(VIII), ruthenium(III), or nickel(II), because the diffusion current v-as not steady or reproducible when theee ions were present in moderate concentrations. When iron(II1) or gold(II1) were present, the amount of 1,2,3-benzotriazole required for the titration was too large as indicated by the data in Table IV. The presence of the remaining diverse ions produced no measurable effect on the end point for the determination of palladium. Palladium was determined accurately in the presence of trace amounts of cobalt or iridium, but large amounts of these two ions interfered with the titration.
An amperometric method for the accurate determination of small concentrations of palladium(I1) chloride has been described. The determination is rapid and involves only a few operations. Of the several diverse ions studied, only osmium( I T I I ) , ruthenium(III), iron(III), gold(III), and nickel(I1) interfered seriouslr with the determination of palladium; how-
Table 111. -4mperometric Titration of Palladium(I1) in Acetic ..lcid-Sodium Acetate Buffer at -0.5 Volt vs. S.C.E. 1,2,3Benzotriazole, Millimoles x 102 0 176 0.345 1.084 1.731 2 594 3 404 5 180
Pd Taken, 3Iillimoles X 101 0.173 0,346 1,081 1 730 2.594
3 459 .5 ,189
Mole Ratio Pd/Titrant 1:1.02 1:l.OO 1:l.OO 1:1.00 1:1.00 1:1.01 1:1.00
Table 11.. Effect of Some 1011son imperometric Titration of Palladium(I1) Pd Taken,
Ion Added,
Pd Found,
Ivlg.
Mg.
Ng.
Mg.
1.846 1 846 1.84B 1.846 1,846 1 848 1.846
1 6 Pt(IV) 1 9 Pt(I1) 2 0 Rh(II1) 0 4 Ir(1V) 0 9 FeiIII) 1 1 Cr(II1) 1 6 Au(II1) 4 7 Co(I1) 0 7 AI(II1) 3 2 Ca(I1) 2 0 AIgiII) 7 5 so*--
1.848 1.846 1.844 1.845 1,902 1,846 1.879
+0.002 0.000
1,846 1.840 1 846 1,846 1.846
0
0.4 0.8 1.2 1.6 2.0 VOL. PALLADIUM SOL., ML.
2.0
Figure 3. Titration of 20 ml. of 0.257 X 10-2.M 1,2,3-benzotriazole with 0.0216.M palladium(I1) ever, these elements are separated easily from palladium according t o the standard procedure (6). The data obtained from the amperometric investigation of the palladium( 11) chloride1,2,3-benzotriaxole interaction were in agreement with the result,s obtained from the gravimetric study of the same interaction. ACKNOWLEDGMENT
DISCUSSION
1.846
3.01
5 0
?Jog-
1.850
1.845 1.847 1.848 1.846 1.846
Difference
-0,002
-0.001
+0.056 0.000
f0.039
The authors wish to express their sincere thanks to Research Corp. for a Frederick Cottrell grant, Jvhich supported the gravimetric study reported in this paper; the amperometric study was made possible by a grant from Sational Science Foundation. LITERATURE CITED
(1) Awes. G. H.. and Wells. W.N.. ASAL.CHEY.22..~ 317 (19501. i 2 j Cheng, K. L., Ibid.. 26, 1038 (1954). (3) Currah, J. E., IlcBride, W. .i. E., Cruikshank, A. J., and Beamish, F. E., ISD.ESG. CHEX.,A S ~ LED. 18, 120 (1946). (4) Curtis, J. A., Ibid. 13, 339-51 (1941). ( 5 ) Hayes, J. R., and Chandler, G. C., Ibid., 14, 491 (1942). (6) Hillebrand, W. F., Lundell, G. E. F., Bright, H. A,, and Hoffman, J. I., “Applied Inorganic Inalysis,” 2nd ed., pp. 3388 3 , \%ley, Kew York, 1953. (7) Holser, H., Z . anal. Chem. 95, 392 (1933). (8) Kolthoff, I. I I . , and Langer, .1.,J . -‘in%. C‘hem. SOC.62, 3172 (1940).
Kolthoff, I. M., and Lingane, J. J., “Polarography,” 2nd ed., vol. 2 , p. 903, Interscience, Xew Tork, 1952. (10) lIacSevin, W.AI., and Kriege, 0. H., -Ls.AL. CHEM.26, 1768 (9)
(1984).
Remington, W. J., and Moyer, H. V., Columbus, Ohio, Ohio State Univ. Press, Dissertation Abstr. 24, (1937). (12) Tarasevich, N. I., Vestnik Moskoa. l-niz.. 3, S o . 10, 161-8 (11)
(1948). (13)
Toropova, V. F., and Yakovleva, G. S..Z h ~ t r .Anal. Khim. 1,
(14)
Voter, R. C., Banks, C. V., and Diehl. Harvey, ANAL.CHEM.
290 (1946).
20, 652 (1948). (15) F l s o n , R . F., and Wilson, L. E., J . I m . Chem. Soc., in press. (16) \?under, H., and Thuring, V.,C h e m Ztg. 2, 550 (1912).
+0.004
-0.001
+0.001
-0.001
0.000 0.000
RECEIVED for review July 19, 1955. .4ccepted October 20, 1955. Presented in p a r t a t Southwest Regional Meeting. .icy, Houston, Tex., December 1055. Condensed from thesis by L . E . Wileon submitted t o Texas Southern University in partial fulfillrnmt of requirements for degree of hIaster of Science, 1955.
