This niethod of analyzing ruthenium in alloys has been mainly applied to tungsten alloys containing 40 t o 80% of ruthenium. It should be capable of extension to other alloys whose components are soluble in alkali solutions, because the electrolyte or electrolysis conditions can be varied to suit the particular alloy and the distillation procedure separates ruthenium from most other elements. I t is even unnecessary for the electrolyte to be alkaline. For example, ruthenium metal can be dissolved anodically in dilute sulfuric acid, al-
though a t a slower rate. However, the simplicity of the method is then lost, a closed electrolysis cell being needed to prevent loss of ruthenium as the tetroxide (4). ACKNOWLEDGMENT
We are indebted to A. Velschou for the data shown in Figure 3 and J. A. James for the mass spectrographic analysis.
(2) Bircumshaw, B. L., Riddiford, A. C., Quart. Rev. (London) 6, 157 (1952). (3) Geach, G. A., Knapton, A. G., Woolf, A. A., “Plansee Proceedings 1961,” Springer-Verlag, Vienna, (in press). (4) Guebeley, M. A., Haissinsky, M., J . Chim. Phys. 51, 290, (1952). (5).Hansen, M., Anderky: K., “Constitution of Binary Alloys, p. 1160, Mc-
Graw-Hill. New York. 1958. (6) Haupt, G. W., J. Opt. SOC.Am. 42, 441 (1952). (7) Larsen, R. F., Ross, E., ANAL.CHEM. 31, 176 (1959). (8) Woodhead, J. L., Fletcher, J. M., J . Chem. SOC.1961, 5039.
LITERATURE CITED
(1) Anderson, E., Hume-Rothery, W., J . Less-Common MPtals 2, 443 (1960).
RECEIVEDJanuary 4, 1962. Accepted June 22, 1962.
Anion Exchange Separation of Thorium Using Nitric Acid JAMES 5. FRITZ and BARBARA B. GARRALDA Institute for Atomic Research and Deparfment of Chemistry, lowa State Universify, Ames, lowa
b Thorium is quantitatively retained b y an anion exchange column from aqueous 6M nitric acid solution. Most other metal ions are completely eluted from the column with 75 to 100 ml. of 6M nitric acid, Following the separation, thorium is stripped from the column with 0.5M nitric acid and titrated with EDTA.
S
AUTHORS have separated thorium using a n anion exchange column and nitric acid. Some of the most comprehensive work is by Korkisch and Tera (7, 9 ) . These authors separated thorium on an anion exchange column in the nitrate form from a solution consisting of 90% methanol and 10% of aqueous 5 X nitric acid. They separated thorium from a long list of other elements but reported that barium, lead, bismuth, lanthanum, and rare earths are also taken up by the column. Danon (2, 3) reported distribution coefficients for thorium and certain rare earths using an anion exchange resin a t various concentrations of nitric acid. Using a column, he was able to separate quantitatively thorium from lanthanum, neodymium, samarium, europium, and yttrium using 5J1 to 8111 nitric acid. Carswell (1) successfully separated thorium and uranium using an anion exchange resin and aqueous 4.M nitric acid as the eluting agent. This separation was carried out a t 77” C. Ichikawa (5) reported distribution coefficients of various elements between nitric acid and anion exchange resin. Distribution eoeffiEVERAL
cients reported by Nelson and Kraus (8) showed that thorium, bismuth, and lead are taken up by anion exchange resins from strong aqueous solutions of nitric acid. This paper studies in a more comprehensive manner the analytical separation and determination of thorium using nitric acid eluent with anion exchange columns. Although the method of Korkisch and Tera is excellent for the separation of thorium from some elements, the method does not work well for mixtures containing macro amounts of thorium and rare earths. The distribution coefficients of rare earths (6) (Dy = 25.4; Gd = 31.0) are such that on a macro scale these elements break through early but are difficult to elute completely. Using aqueous 6 M nitric acid, we obtained excellent separation of thorium from aluminum, rare earths, iron, zirconium, and other elements. The nonaqueous nitric acid separations required larger volumes of eluent for quantitative elution, and a slower flow rate had to be employed. Furthermore, 6-11 aqueous nitric acid solutions caused less deterioration of the resin than methanol-water solutions that were more dilute in nitric acid. EXPERIMENTAL
Ion Exchange Columns. Conventional glass columns of 12 mm. i.d. are used. T h e column is filled with a slurry of resin, in nitric acid of the concentration to be used as the eluent, to a bed height of 16 cm. T h e eluent is added to the column dropwise
from a cylindrical separatory funnel fitted into the column through a onehole stopper a t a flow rate of about 2 ml. per minute. Ion Exchange Resin. Dowex I X 8, 100- to 200-mesh, anion resin in the nitric form is used. The analyzed reagent grade resin is in the chloride form and must be converted to the nitrate form before use. This is done by placing the resin in a large column and backwashing to remove fine particles. The resin is then washed with 5 M nitric acid until the effluent gives a negative chloride test with silver nitrate. The excess nitric acid is rinsed off with distilled water, the water is removed by suction filtration, and the resin is air-dried. Metal Salts. Solutions (O.05M) of the salts are made using reagent grade nitrate salts of the metals and nitric acid of the concentration to be used a? the eluent. PROCEDURE
Distribution Coefficients. Air-dried anion exchange resin is weighed into a 125-ml. glass-stoppered Erlenmeyer flask. The desired amount of metal ion in nitric acid solution is pipetted into the flask, and nitric acid of the desired concentration is added to bring the total solution volume to 50 ml. The flask is stoppered and shaken for 24 hours. An aliquot is pipetted from the flask and the metal ion content is determined with (ethylenedinitri1o)tetraacetic acid (EDTA) titration. The water content of the airdried resin is determined by oven drying a sample of known weight. The distribution coefficient is then determined on a dry resin basis. The relationship used is: VOL 34, NO. 1 1 , OCTOBER 1962
1387
=
Kd
mmolcs of metal ion on resin per grams dry resin ninioies of metal ion in solution per total volume of solution
Column Elutions. For experiments with single metal ions, t h e column is loaded with 0.25 mmole of metal ion in a solution containing nitric acid of t h e concentration t o be used for elution. The volume of sample solution is indicated in Table I. Kitric acid concentrations greater t h a n about 7 M cause decomposition of the resin. ~
~
Table 1. Elution of 0.25 mmoles of Individual Ions from 1.2 x 16 cm. Anion Exchange Columns with 6.OM "03 Using a 10-ml. Sample Solution
Breakthrough, nil."
Ion
0 0
AI-3
Ba-2 Bi + 3 CaT2 Cd - 2 Ce - 4
40
0 0
150
co-2
0 0 0 0
Cr - 3 cu-2
Dy -3
Elution complete, m1.b 75 30
210 25 50 >200 50 50 20 100
Er + 3
0 0
20
Ga - 3 1n - 3 La - 3 LU- 3
0 0 0 0
25
Fe+3
hIg - 2 hln - 2 RIo Kd - 3
50
25 50
0
50
50
0
150
>200
75 50 50 ppt. on the column 0 0 15
Ii1-2
Pb + 2 Sb+3
Sn1-3
0 0
Sr-2 Th 14 EO?12 S'
15
>zoo
50
50 *20 ...
100 50 ppt. on the column 0 100
-4
0
w y-3 1-b t S Zn +z Zr --4
0
0 0
50 25 50
0 nieans that breakthrough occurred in effluent from sample solution. S'alue given is the elu,ent required in addition to the smiple sc lition.
Table II.
Anaiytical EDTA Titration Methods
Direct, S A S indicator ( d ) , pyridine buffer, pH 6: Cd-2, Ce-4, CoT2, CuT2,Dy+3, Er+3, Luf3, Yd-3, S i A 2 ,Pb-2, Sm+3, v+4.y t 3 .
1
yb-3. Zn-2 -
B(CU-~); N A G indicator ( 4 ) , pyridine buffer, pH 5 5 : A l - 3 , Fe-3, Ga'3, In'3. RTn-6
Di&t, Eriochrome Black T indicator, pH 10: Ca'2, %1g72.Mn-2 Direct, Rletalphthalein indicator, pH 10: BaT2. Sr+2 Direct, Xylenol Orange indicator, pH 1-3: Bi+3. T h t 4 . La-3 B(Bi*;),* Xi-lenol Orange indicator, pH 3-4.5: Cr-3, Z r - 4 Redox: L O 2 - ? a Back-titration Kith the ion in parentheses.
1388
The effluent from t h e sample solution is collected and tested qualitatively for the metal ion present in the sample. The column is then eluted with aqueous nitric acid; 10-ml. fractions are collected and tested qualitatively for the metal ion. The breakthrough volume and the volume required for complete elution are recorded. For quantitative separation of mixtures containing thorium, a sample containing 0.25 mmole of thorium plus 0.25 mmole of another metal ion is diluted t o 15 ml. and the nitric acid concentration is adjusted to 6/14, The sample solution is added t o a 1.2 X 16 cm. Dowex 1 x 8 column (100- t o 200-mesh) which has previously been washed with 6M nitric acid. The other metal ion is then eluted from the column with 75 to 100 ml. of 6M nitric acid at a flow rate of approximately 2 ml. per minute. The effluent is evaporated nearly to dryness, then is diluted, neutralized, and titrated as outlined in Table 11. Thorium is stripped from the column by elution with 150 ml. of 0.5M nitric acid at a flow rate of approximately 2 ml. per minute. The pH of the thorium effluent is adjusted to 2.0 to 3.0 with solid sodium acetate, and the thorium is titrated with 0.05Af EDTA using Xylenol Orange indicator.
ANALYTICAL CHEMISTRY
RESULTS A N D DISCUSSION
Preliminary work with methanolaqueous nitric acid eluents (8) indicated that aqueous nitric acid is preferable for separations of thorium from other metal ions. Data for elution of individual metal ions are given in Table I. These elutions are for a 1.2 X 16 cm. anion exchange column (nitrate form) with several different concentrations of nitric acid. The effluent was collected in 10-ml. fractions and each fraction tested for the presence of the metal ion. Most metal ions are completely eluted by 100 ml. of 6 X nitric acid. Profile curves for the elutions indicate that there is little tailing of the bands. Because the thorium ion does not break through until more than 300 ml. of effiuent has been collected, separation of thorium from most metal ions should be feasible. Cerium(IV), molybdenum (VI), antimony(III), and tungsten(V1) are likely interferences. Mixtures containing thorium(1V) and another metal ion were separated by anion exchange and the individual metal ions titrated with EDTA. The quantitative data for 62 separations are reported in Table 111. Elution of the first metal ion requires 75 to 100 ml. of 6M nitric acid, thus giving a large safety margin before breakthrough of thorium. illthough most of the mivtures analyzed contained thorium and another metal ion in approximately equal molar
I
I
100 -
90-
80-
2 70W
0 V
z 60-
E 503 m a k
240301 2ot
'$
1
01 0 2 5
050
0.75
LOA0 IN MMOLES
Figure 1. Effect of loading on batch distribution coefficients Conditions: 1.3 grams of anion exchange resin (nitrate form), metal ion a d d e d to the resin in 50 ml. of 6 M nitric acid
amounts, mixtures containing thorium (IV) - uranium(VI), thorium(1V)yttrium(IIT), and thorium(1V)-zirconium(1V) in 10: 1 and 1 : 10 molar ratios were successfully analyzed. It thus appears that sample mixtures of widely varying ratios can be separated providing the column is not overloaded. Although bismuth and lead are quantitatively eluted with 6 M nitric acid, bismuth (and to a lesser extent lead) is retained by the column from 2M nitric acid solutions. Elution with 2M nitric acid is a practical method for separating bismuth from other metal ions including lead.
Table 111. Quantitative Separaticns of 0.25 mmole of a Metal Ion from 0.25 mmole of Thorium on 1.2 X 1 6 cm. Anion Exchange Columns Ion separated Eluent A l + 3 ,CaA2,C d t 2 , Cof2, Load 75 rnl. Ert3, Fe +?, G d 3 , 6 O M HSO, Lat3, L u * ~ , l \ I g f 2 , A h A 2 , Pb+2, Nd+3, Sr+2, U02+2.V+',Y+3, Yb-3. Zn+2. Zr"Bi T 3 Load 200 rnl. 6 O M "0% Cu t2, Pb + Z Load 100 mi. 6 O M HN03 Average recovery": Th t4, l O O . O ~ , ; other ion, 1 0 0 . l ~ o Standard deviation": Th+4,0.197&; other ions, 0.22Vc.
+
+ +
a
Sixty-tvio separations.
I n Figurc 1, the distribution coefficients of several metal ions are plotted as a function of loading using 6JI nitric acid. The distribution coefficients show large variations with loading for thorium but only minor changes for yttrium and lead. I n column separations with 10-nil. samples containing 0.25 mmole of thorium plus 0.25 mmole of another metal ion, brmkthrough of the thorium was premature. By increasing the sample volume to 15 ml., this difficulty was avoided. If samples are used which cont.a.iii more than 0.25 mmole of thorium, the volume of loading solution should bc increased accordingly. However, excessive dilution of the sample solution ca,uses tailing of some elements separated from thorium and requires more fluent for their complete elution. The effect of common anions n-as in-
vestigated briefly. Addition of 2 ml. of concentrated sulfuric acid t o a sample containing 0.25 mmole each of thorium(1V) and uranium(V1) in 15 ml. of 6M nitric acid causes no interference in the quantitative separation and determination of thorium and uranium. Perchloric acid added to a thorium sample causes the thorium to break through too early unless most of the perchloric acid is removed by evaporating the sample almost to dryness. Chloride can be removed by evaporation; fluoride interference can be avoided by evaporation t o fumes of sulfuric or perchloric acid. Concentrated phosphoric acid added t o a thorium sample results in very incomplete removal of thorium from the anion exchange column by the usual 0.5M nitric acid stripping solution.
LITERATURE CITED
(1) Carswell, D. J., J . Inorg. AVucl,Chem. 3, 384 (1957). ( 2 ) Danon, J., J . Am. Chem. SOC.78, 5953 (1956). ( 3 ) Danon, J., J. Inorg. Nucl. Chem. 5, 237 (1958). ( 4 ) Fritz, J. S., Abbink, J. E., ANAL. CHEM.33, 1381 (1961). ( 5 ) Ichikawa. F.. Bull. Chem. SOC.JaDan ' 34,952 (196l).' ( 6 ) Korkisch, J., University of Vienna,
Austria, private communication, April
1962.
( 7 ) Korkisch, J., Tera, F., ANAL.CHEM. 33, 1264 (1961). ( 8 ) Nelson. F.. Kraus. K. A..J. Am. Chem. ' Boc. 76, $916 (i954j. ( 9 ) Tera, F., Korkisch, J., Hecht, F., J . Inorg. Nucl. Chem. 16, 345 (1961).
RECEIVEDfor review April 2, 1962. Accepted August 14, 1962. Contribution No. 1135 from the Ames Laboratory of the U. S. Atomic Energy Commission.
Spectrophotometric Determination of Trace Quantities of Alpha-Dicarbonyl- and Quinone-Type Conjugated Dicarbonyl Compounds D.
P.
JOHNSON, F. E. CRITCHFIELD, and J. E. RUCH
Research and Development Department, Union Carbide Chemicals Co., South Charleston, W. Vu.
b Microgram quantities of a- and conjugated dicarbonyl compounds are determined b y formation of the bis(2,4dinitrophenylhydrazones) and reaction of the latter with diethanolamine and pyridine to produce characteristic colors. The color due to excess 2,4dinitrophenylhydrazine reagent is eliminated b y treating the reaction mixture with 2,4-pentanedione which forms a colorless pyrozole. Monofunctional and nonconjugated difunctional carbonyl compounds do not produce colors under these conditions. Optimum reaction conditions and absorption maxima are presented for eight compounds.
I
(@, the authors described a method for determining low concentrations of lj4-benzoquinone by its reaction with 2,4-dinitrophenylhydrazine. The resulting bis-hydrazone was treated with a solution of diethanolamine in pyridine to produce a blue color which was measured spectrophotometrically. I n a continuation of that work, an investigation as made of the application of the same principle to t.he determination of other similar multifunctional carbonyl compounds. Of particular interest were 1,2naphthoquinone. lj4-naphthoquinone, anthraquinone. and other compounds N A PREVIOUS PUBLICATION
containing two or more carbonyl groups either adjacent or conjugated t o each other. The principle of bis(nitropheny1hydrazone) or osazone formation as a colorimetric means of analyzing a-dicarbonyl compounds has been covered rather extensively in the literature. Neuberg and Strauss (Sj reviewed the theoretical and practical aspects of the subject in 1945 and provided an excellent bibliography covering the period from 1874 to 1945. A year later the same authors (4) extended their discussion to quantitative formation of these products from various biological substances. Banks and associates (1) prepared the bis(2,4-dinitrophenylhydrazonejfor a colorimetric determination of glyoxal as an enzymatic oxidation product of carbohydrates. More recently, Sah-icki et al. reported the use of 4-nitrophenyll hydrazine and 2,4-dinitrophenylhydrazine for determining glyoxal by a similar principle (6). 2,4-Dinitrophenylhydrazine has been used by the present authors for some time for analyzing glyoxal ( 5 ) and other related dicarbonyl compounds ( 2 ) . I n their studies, Keuberg and Strauss used sodium ethylate as proton acceptor to produce the colored hydrazone species. Banks et al. employed alkaline acetone for the same purpose. I n both of these media, however, 2,4-dinitro-
phenylhydrazones of simple monocarbonyl compounds such as acetone, and in general, all polyfunctional carbonyl compounds except 8-dicarbonyls likewise produce color. While the colors differ somewhat from those formed by the products of a-dicarbonyl compounds, they interfere in precise 'measurements of the latter substances. I n the present application, specificity is gained by using a mildly basic solution of diethanolamine in pyridine as the color developing medium. Under these conditions, only the 2,4-dinitrophenylhydrazones of vicinal and conjugated polyfunctional carbonyl compounds produce colors. EXPERIMENTAL
Reagents. Diethanolamine, 2% (v./v.) solution i n pyridine. 2,4-Dinitrophenylhydrazine. Dissolve 0.1 gram in 50 ml. of methanol a n d add 4 ml. of concentrated hydrochloric acid. Dilute t o 100 ml. with water and mix. 2,4-PentanedioneJ Union Carbide Chemicals Co. Procedure. Prepare a solution of t h e compound in t h e solvent specified in Table I. Pipet a n appropriate aliquot, not exceeding 3 ml., into a 25-ml. glass-stoppered graduated cylinder a n d add 1 ml. of 10% (v./v.) sulfuric acid. Add 1 ml. of 2,4dinitrophenylhydrazine reagent and VOL. 34, NO. 1 1 , OCTOBER 1962
1389
