The corrected magnesium titration multiplied by the magnesium titer (1 ml. = 0.0004032 gm. MgO) equals mg. of MgO present. RESULTS A N D DISCUSSION
The Kational Bureau of Standards Sample Yo. 103, chrome refractory was analyzed to check the new system against classical procedures. The results of these analyses are shown in Table I. I n 1961, this laboratory participated in a round-robin analytical program requested by Eusner ( 7 ) . Six different laboratories were asked to analyze a number of basic refractory brick samples. In Table IC1 the averages of the results obtained on sample D-2 by the six laboratories using different methods are compared with the results obtained by this laboratory using the new rapid analysis scheme. Values obtained here were expressed to two decimal places; however, all roundrobin values of 1% or higher were reported to the nearest 0.1% by Eusner. Titania interferes with the alizarin red S procedure for alumina causing small plus errors. If appreciable titania is expected it may be determined on the ammonium hydroxide precipitate separated in the procedure for calcium and magnesium. An empirically derived table can be made to correct for the titania found as suggested by Shapiro and Brannock (16). For example, the alizarin red S value for alumina found on the N.B.S. chrome refractory would be reduced by 0.05%.
I n the determination of high percentages of chromium, alumina, and iron considerable care is necessary in all steps of procedure to obtain satisfactory precision and accuracy. The many precautions to be taken have been neatly summarized by Bennett, et al. (3). The rapid analysis methods presented have been applied successfully to samples of refractory grade chrome ore from the Philippine Islands, South Africa, Cuba, India, Turkey, Greece, Mexico, Montana, Oregon, and California. Moreover, the basic refractory products, consisting of chrome ore or combinations of chrome ore and magnesite, of many of the major domestic and foreign manufacturers have been analyzed using this new system of analysis. LITERATURE CITED
( 1 ) Am. Soc. Testing Materials, Phila-
delphia, Pa., “Manual of A.S.T.M. Standards on Refractory Materials,” p. 124, 1957. ( 2 ) Beckman Scientific and Process Instruments Division, Fullerton, Calif., Application Data Sheet UV-8070C. (1960). ( 3 ) Bennett, H., Eardley, R . P., Hawley, W. G., Thwaites, I., Trans. Brit. Ceram. Soc. 61,636 (1962). ( 4 ) Bunting, W. E., IND.ENG. CHEY., ANAL.ED. 16, 612 (1944). ( 5 ) Corey, R. B., Jackson, M. I,., ANAL. CHEM.25, 624 (1953). ( 6 ) Dinnin, J. I., U.S . Geol. Survey Bull. 1084-B (1959). ( 7 ) Eusner, G. R., Applied Research
Laboratory, I‘nited States Steel Corp., Monroeville, Pa., private communication, 1961. (8) Fortune, W. B., Mellon, M. G., IND. ENG.CHEM.,ANAL.ED. 10,60 (1938).
Table 111. Analysis of Chrome-Bearing Basic Refractory Brick Sample D-2 by Six Different Laboratories
Averages of Rapid Compound round-robin method determined values values Si02 3.20 3.17 FeQO.(total &on ‘as) 6.00 5.96 CrnOs 12.60 12.55 AhOs 11.50 11.45 CaO 1.00 1.09 MgO 65.50 65.40 (One magnesium and one chromium result were outside the average deviation and were not included in the round-robin averages. )
-
(9) Goetz, C. A,, Debbrecht, F. J., ASAL. CHEM.27, 1972 (1955). (10) Hazel, W. M., Ibid., 24,196 (1952). ( 1 1 ) Hedin, R., “Colorimetric Methods for Rapid Analysis of Silicate Materials,” Swedish Cement and Concrete Research Institute, Royal Institute of Technology, Stockholm, 1947. (12) Parker, C. A,, Chddard, A. P., Anal. Chim. Acta 4, 517 (1950). (13) Sandell, E. B., “Colorimetric Determination of Traces of lTetals,” Vol. 111, 3rd ed., p. 392, Interscience, New York, 1959. (14) Schwarzenbach!, G . , “Complexometric Titrations, p. 62, Interscience, New Yqrk, 1957. (15) Shapiro, L., Brannock, W. I%‘., c‘. S . Geol. Survey C‘irc. 165 (1952). (16) Ibid., U . S . Geol. Suroey Bull. 1144-A il962). \ - - - - ,
(17) Silverman,
I>., Hawley, D. W., ANAL.CHEM.28, 806 (1956). (18) Urone, P. F., Ibid., 27, 1354 (1955). RECEIVEDfor review XTarch 2, 1964. Accepted May 4, 1964.
Separation of Lead by Anion Exchanae JOHANN KORKISCH and FRANZ FElK Analytical Institute, University o f Vienna, Wahringerstrasse 38, Vienna, Austria
b A method for the anion exchange separation of lead from various elements employs the strongly basic onion exchange resin Dowex 1 , X8. As a medium for this separation, a mixture consisting of 90% tetrahydrofuran and 10% 5N nitric acid was selected. From this solution lead is adsorbed much more strongly on the resin than most other elements, so that an ion exchange separation by column chromatography b y using the mixture as the eluent is easily possible. Uranium, thorium, bismuth, thallium, the lanthanides from1 samarium to lutetium, iron, magnesium, calcium, and other elements pass quantitatively into the eluate, whereas the rare earth elements lanthanum to neodymium are
retained on the resin with lead. Lead is subsequently eluted with a mixture of 8OY0 tetrahydrofuran and 20% 2.5N nitric acid. The distribution coefficients were measured for numerous elements as a function of varying concentrations of nitric acid and tetrahydrofuran.
P
investigations have shown that lead cannot be adsorbed on strongly basic anion exchange resins from pure aqueous nitric acid media (1) because of the low tendency of the lead ions to form negatively charged nitrate complexes in such solutions. However, in partially nonaqueous media containing nitric acid the adsorption of lead is greatly enhanced by increasing REVIOUS
the nonaqueous component of the mixtures, so that high distribution values can be obtained. Fritz and coworkers ( 2 ) have shown that all that is required in the solution is a neutral complex, the anionic complex then being formed in the resin phase. For instance, Korkisch and hrrhenius (4) have measured a distribution coefficient of 261 for lead in an acetic acidnitric acid mixture. Fritz and Greene (S), on the other hand, found a value of 1100 in a 2-propanol-nitric acid mixture. I n methanol-nitric acid medium high adsorption of lead was earlier observed by Korkisch and Tera (6). A comparison of these lead values with those found for bismuth, thorium, and uranium under the same exlmiVOL. 36, NO. 9, AUGUST 1964
1793
mental conditions shows that in all the nitric acid-organic solvent mixtures mentioned above not only lead but also bismuth and thorium are preferentially adsorbed on the resin, so that lead cannot be easily separated from these elements. Equilibrium studies in nitric acidtetrahydrofuran media have shown that from such mixtures only lead is strongly retained on the resin, whereas the adsorption of uranium, thorium, bismuth, and many other elements is negligible or rather low, so that milligram amounts of lead can be quantitatively separated. The present paper therefore deals with tetrahydrofuran-nitric acid systems and especially stresses the adsorption and separation characteristics of lead, uranium, thorium, bismuth, and thallium because of their simultaneous occurrence in the natural radioactive series.
3
i
2
I
U
Y
w 0 I
C
EXPERIMENTAL -1
The resin used for the equilibrium studies and separation experiments was Dowex 1, X8 (100- to 200-mesh, nit'rate form). T h e eluting solution is prepared by mixing tetrahydrofuran with 5A' nitric acid in the ratio of 9 to 1. For column experiment's the air-dried resin was soaked in the eluting solution prior t o its addition to the column. T h e ion exchange column was prepared by adding t,he resin to the column from such a solution and then passing from 30 to 50 ml. of this elut'ing solution through the column (pretreatment of resin bed). St'ock solutions of lead, uranium, bismuth, and many other elements were made by dissolving reagent grade niReagents.
Table I.
Pb
-
% TETRAHYDROFURAN
~~
100
00
60
40
20
0
C% WATER
Figure 1. Influence of tetrahydrofuran concentration a t nitric acid concentration of 0.5N
trates in 5 N nitric acid. Chemically pure tetrahydrofuran was also used. Apparatus. The columns were of the type and dimensions described earlier (6); their length was 10 cm. and the inner diameter, 0.6 em. Procedure. For the determination ot batch distribution coefficients ( K d )
Column Loading Experiments Using 90% Tetrahydrofuran-1 0%
5N
"03
Pb 0.5 0.5 0.5
u
Element, mg. Th Bi
0.5
1 .o 1.0 1 .o
1.0 1. 0 5 0 5 0 .j 0 3 0 .jO 10 0 IO 0 10 0 10 0
in o
1794
Elution volumes, ml. I! Th Bi T1 40 70
0.5
0.5
n. 5_ 0.5
T1
0.5
1.0
1.0
5 0
0.5
1.0 1.0
0.5
1.0 1.0
0.5 0.5
40
45
70 80
1.0
1. o
45 50
80 90
5 0
5 0 5 0 10 0
5 0
10 0
io o
io o
5 0
10 0
io o
ANALYTICAL CHEMISTRY
5 0 5 0
50
70
90
100
10 0
io o
70
100
100 100 110 110
35 35
40 40
120 120 130 130
50 50
60 60
Breakthrough volumes of lead, ml. 90% tetrahvdrofuran:lo% 5 ) nitric ~ acid 180 180 180 180 180 160 160 160 160 160 150 150 150
in each case 2 ml. of a stock solution containing 5 mg. of the metal ion were diluted to 20 ml. with tetrahydrofuran. T o this solution 1 gram of the resin was added and the mixture was agitated for 12 hours to ensure complete attainment of equilibrium. Thereafter the resin was filtered off and the element determined quantitatively in an aliquot portion of the filtrate by a suitable method. All Kd values shown in Figures 1 and 2 were obtained by this procedure. Since tetrahydrofurannitric acid mixtures tend to explode easily when heated (there is no danger of explosion a t room temperature), all the quantitative determinations were carried out in the presence of this solvent, which did not interfere a i t h the conventional chelatometric methods used for the E D T l titration of the elements investigated. The indicator used for the determination of lead was xylenol orange in a medium buffered with hexamethylenetetramine. In both the distribution and column experiments all elements, except uranium which was determined fluorometrically ( 7 ) , were determined with 0.001 to 0.01M EDTA, depending on the amount of metal present. I n the column experiments 0.5- to 10-mg. amounts of the elements were used. After pretreatment of the resin bed the sorption solution consisting of 18 ml. of tetrahydrofuran and 2 ml. of 5 N nitric acid with known amounts of the elements investigated was passed through the column at a flow rate of 0.25 to 0.3 ml. per minute. Each 5-ml. fraction of the effluent was collected and the element in question was determined quantitatively. Thereafter the eluting solution having the same composition as the sorption solution was passed through the resin bed a t the same flow rate and each 5-ml. fraction was also collected and its metal content determined. (In the case of the loading experiments shown in Table I each milliliter of the effluent was collected separately and analyzed for the element in question.) Thereafter the very strongly adsorbed elements lead, lanthanum, cerium, and praseodymium were eluted with a mixture consisting of 80% tetrahydrofuran and 20y0 water with an over-all nitric acid concentration of 0.5N. Five-milliliter fractions of this eluate were collected and their metal content was determined. Loading experiments were carried out by determining the batch distribution coefficients of lead as a function of the amount present and also determining the breakthrough point on the column using different quantities of this metal ion. The breakthrough point was taken as the place in the elution where a t least 0.1% of the total metal ion present had appeared in the effluent ( 3 ) .
150
150 140 140 140 140 140
RESULTS A N D DISCUSSION
I n Table I1 it is seen that of all the elements investigated only lead, lanthanum, cerium, and praseodymium are strongly retained by the resin. Neo-
c
5 3
> a
W
Y
U
a
w
0
k
-I
m
-a a
2
0 Ia a
+ Zi w
0
2
0 0
1
a + W
I MOLARITY OF NITRIC ACID
Figure 2. Variation of distribution coefficient with concentration of nitric acid iln 90% tetrahydrofuran-1 0% nitric acid r
l
0
Table II. Distribution {Coefficients and Elution Volumes in 90% Tetrahydrofuran-1 0% 5N Nitric Acid on Dowex 1 ,
X8
R;Ietal ion Pb(I1) UO*(!I ) Th( 11 ) Bi(II1) 1) NdII) Ca(I1) Sc(111) Y(II1) La(II1) Ce(II1) Pr(II1) Yd( I11j Sm(II1) Eu(II1) Gd(II1) Tb + Lu( I1I ) Fe(II1) Co(I1) Ni(I1) Zn(I1) Cd(I1) Cu(I1) Mn(I I ) Al( I11 j
Ga( I11j In( 111) ri(I V ) Zr( IV)
Distribution coefficient,., 5 mg./20-m.l. load 250 11.0 27 42 25 17 38.8 1.0 10 306 146 134 80 35 22.2 17.5 9 . 0 --c 6 . 2 18 17.5 17.5 18.5 16.5 6.8 15.7 18.0
16.5 15.0 30 15.3 14.8
Elution volume, ml., on
l
l
40
l
80
l
l
120
l
l
l
l
160 0 IO
l
l
30
l
l
)
50
Effluent volume, MI.
90% tetrahydrofuran10% 5 N nitric acid
Figure 3. ions
80% tetrahydrofuron2070 2.5N nitric acid
Typical elution curves for several metal
10-cm.
column, 5-mg. loada 400 (200) 50 (15) 90 (40) 120 (60) 50 (35) 55 (25) 90 (40) 30 (10) 50 (25) 600 (250) 300 (180) 200 ( 130) 170 (100) 80 (35) 50 (30) 50 (20) 50 (20) 55 (20) 55 (20) 55 (20) 55 (20) 55 (20) 50 (20) 55 (25) 55 (20) 50 (20) 50 (20) 70 (35) 50 (20) 50 (20)
Hf(1V) a 1-olumes of eluent in which element concentration reaches a ,maximum, shown in parentheses.
dymium, bismuth, and calcium have distribution coefficients in between those of the elements with the highest and lowest Kd values. Uranium, thallium, and all other elements listed in Table I1 are adsorbed to an extent which ensures their quantitative chromatographic separation from lead. When mixtures of the elements listed in Table I1 are passed through the column under the experimental conditions described, the first 50 to 55 ml. of eluent quantitatively contain all elements except those with Kd values higher than 30, whereas the next 70 ml. of eluent will remove all the other elements except lead and the “light” rare earths which are retained by the resin. I n Table I1 the elution volumes required for the complete elution of the metal ions are listed, as well as the volumes of eluent in which the concentration of the element reaches a maximum, the elution peaks. T o demonstrate the effectiveness of the separation of lead from other elements, typical elution curves are shown in Figure 3 ; separations are quantitative in all cases. For com-
parison, elution curves of lanthanum are included. Because of the peroside content of tetrahydrofuran, a sorption solution containing titanium develops a strong yellow color. This means that titanium forms a peroxide comples which possibly prevents to a great extent the adsorption of this element as a nitrate complex. Figure 1 shows the influence of variations of tetrahydrofuran concentration on the distribution coefficients of lead, uranium, thorium, bismuth, and thallium under identical experimental conditions of element and acid concentration. I n all cases increase of adsorption with increasing percentage of tetrahydrofuran was strictly linear. A similar linear relationship between log Kd a t a constant tetrahydrofuran concentration of 90% and varying concentrations of nitric acid was shown by increase of the molarity of this acid from 0.25 to 1.055 (Figure 2 ) . Investigations of the effect of concentration of lead on its distribution coefficient in 90% tetrahydrofuran10% 5A7 nitric acid have shown that the Kd value of lead does not change VOL. 36, NO. 9, AUGUST 1964
1795
Table 111. Application of Method to Analysis of Sediment Standard (4)
Lead, mg. Added to sorption solution containing 0 25 gram of sediment sample Found in eluate 0.0
0.01
0.5
0.52 1.02 2.51 5.02 7.52 10.01
1 0 2.5 5 0 7.5
10.0
within the whole region of concentrations used (0.5 to 10 mg. of P b per 20 ml. of mixture). The solubility of lead nitrate in the mixture applied was 1.0 mg. of lead per ml., whereas that for strontium nitrate is only 0.05 mg. per ml. Barium nitrate is even less soluble. Investigations of the influence of concentration of lead, uranium, thorium, bismuth, and thallium on column separation have shown that a quantitative separation is possible in the range of concentrations shown in Table I. From these loading esperiments it is seen that the breakthrough volume of lead decreases with increasing con-
centration. Since the elution volumes of bismuth increase with an increase of concentrations, an overlapping of the elution curves with the breakthrough volume of lead is expected when more than 10 mg. of lead and 10 mg. of bismuth are present simultaneou.ly in the sorption solution. This effect can be eliminated by employing larger columns. Analogous esperiments performed by using microgram amounts of lead and milligram quantities of the other elements showed that the lead could be recovered quantitatively in all cases, which means that this separation method can wxesqfully be applied on a micro scale. I n Table I11 are shown results of the application of this method to a standard sediment sample (4) to which known amounts of lead were added. I t is seen that lead can be recovered quantitatively with only a small error. Comparison with other procedures based on the anion exhange separation of lead, which have hitherto been developed in pure aqueous hydrochloric acid media, s h o w that the present chromatographic technique could be employed for the assay of lead in a variety of materials such as marine sediments, leaded steels, copper-base alloys, high purity metals such as uranium, optical glass, rubber products, canned food, wines, and body fluids.
Ai further application would be in the field of petroleum research for the isolation of lead prior to its quantitative determination in petroleum productsfor instance, in gasoline. Because the “light” lanthanides are coadsorbed with lead, and uranium is practically not retained on the resin, this method could also be useful for the separation of uranium from fission products, which consist to a great degree of the radioactive isotopes of the “light” rare earth elements, LITERATURE CITED
(1) Buchanan, R. F., Faris, J. P., U. S. At. Energy Comm., R e p l . RICC/173 (1960). ( 2 ) Fritz, J. S.,Iowa State Cniversity of Science and Technology, Ames, Iowa, prim te communica tion, 1964, ( 3 ) Fritz, J. S.,Greene, R. G., A N A L CHEM.,36, 1095 (1964). (4) Korkisch, J., Arrhenius, G., Zbid., 36, 850 (1964).. ( 5 ) Korkisch, J., Farag, A . , Hecht, F., Mikrochim.Acta 1958, p. 415. (6) Korkisch, J., Tera, F., AISAL.CHEM. 33, 1264 (1961). ( 7 ) Schiinfeld, T., El Garhi, M., Friedmann, C., Yeselsky, J., Mikrochz’m. Acta 1960, p. 883. RECEIVED for review February 24, 1964. Accepted -4pril 10, 1964. Research supported by the Petroleum Research Fund, administered by the American Chemical Society ( P R F grant KO.1587-A3).
Solvent Extraction of Platinum and Palladium with Derivatives of Dithiocarbamic Acid JOHN T. PYLE and WILLIAM D. JACOBS Department o f Chemistry, University o f Georgia, Athens, Ga.
b The use of selected derivatives of dithiocarbamic acid as extractable chelating agents for platinum and palladium in acidic media is described, Factors and variables affecting the analytical application of these derivatives have been investigated. Although several dithiocarbamate derivatives are unstable in an acidic medium, others were found to exhibit sufficient stability to make practical their application as complexing agents for platinum and palladium in a medium in which some base metals and other platinum group metals do not react favorably. Three such derivatives are cited. One of these derivatives, the dibenzyl, was found to be the most promising chelating agent in the presence of certain diverse ions. This derivative was made the basis of an analytical 1796
ANALYTICAL CHEMISTRY
scheme for the simultaneous separation of platinum and palladium from certain other metals. Chloroform is used as an extractant.
S
of the work by Delepine (3, 4) concerning the analytical use of sodium diethyldithiocarbamate, techniques have been developed for the use of this derivat’ive and other disubst’ituted derivabives of dithiocarbamic acid, DC-1, as analytical reagents. Callan and Henderson ( 2 ) made a systematic study of the reactions of sodium diethyl DC.l with the more common metals, and proposed a colorimetric det,ermination of small amounts of copper with this reagent. Gleu and Schwab ( 5 ) investigated the behavior of several derivatives of IICA toward the more common metal* as well ax toward IKCE THE PUBLICATIONS
noble met’als and the platinum grouli metals. Malissa and Miller ( 8 ) studied t’he reactions of metals with still other DC-4 derivatives. In this work observations were made under varied experimental conditions to determine reaction sensitivities and to ascertain t’o what extent these derivatives might serve as the basis for quant,itative separation. Welcher (13) collected a number of analytical procedures using several DC;1 derivatives. These techniques deal with qualitative and precipitation studies, as well as with extraction phenomena. Reactions involving derivatives of DC-1 have been studied mainly in alkaline, ncutral, or weakly acidic media. This palier describes the reactions of certain derivatives with platinum and palladium in a highly aridir medium. Pollard (10) used tlicxthj.1
