Fluorenols. Constituent 74 has ultraviolet absorption bands very similar t o those for 8-methyl-2-fluorenol (9). However, the longest wave length band in the region around 31 1 mp is held in common b y other methyl-2fluorenols and methyl-3(and 4)-fluorenols. The longest wave length bands for methyl-1-fluorenols are a t wave lengths a t least 10 mp lower. Thus, constituent 74 is a methyl-2-, -3-. or -4fluorenol. ACKNOWLEDGMENT
Special thanks are due Joseph R. Comberiati for perforniing the spinning band distillation and Edward E. Childers for assistance in performing the
countercurrent distribution fractionations. REFERENCES
(1) Anchel, M., Blatt, A. H., J . Am. Chem.
SOC. 63, 1918-52 (1941). (2) Bader, A. R., Ibid., 78, 1709-13 (1956). (3) Elsner, B. B., Parker, K. J., J . Chem. SOC. 1957, 592-600. (4) Friedel, R. A,, J . Am. Chem. SOC.73, 2881-84 (1951). (5) .Friedel, R. A., Orchin, M., “Ultrs;; violet Spectra of Aromatic Compounds, Wiley, New York, 1951; spectra 47,
51, 78, 79. (6) Golumbic, C., Woolfolk, E. O., Friedel, R. A., Orchin, M., J. Am. Chem. SOC. 72,1939-42 (1950). (7) Irvine, L., Mitchell, T. J., J . A p p l . Chem. 8, 425-32 (1958). (8) Karr, C., Jr., Brown, P. M., Estep,
P. A., Humphrey, G. L., Fuel 37,227-35 -
I
(1958). (9) Morrison. A., Mulholland, T. P. C., J . Chem. SOC.1958,2702-5. (10) Post, H. O., Scientific Instrument Co., Inc., 6822 60th Road, Maspeth 78. N,Y.. ‘LPriceLists & Prints, Glass
Countercurrent Distribution Instruments,” 1955, et. seq. ( 1 1 ) Sadtler, S. P. & Son, Inc., “The Sadtler Standard Spectra,” Sadtler Research Laboratories, Philadelphia,
1958. (12) Silverman, M., Bogert, M. T., J. Org. Chem. 11, 34-9 (1946). (13) Williamson, B., Craig, L. C., J . Bid. Chem. 168, 687-97 (1947). (14) .Woolfolk, E. O., Golumbic, C.,
Friedel, R. A,, Orchin, M., Storch H. H., U. S. Bur. Mines Bull. 487 (1950).
RECEIVEDfor review October 13, 1959. Accepted January 8, 1960.
Cocrystallization of Ultramicro Quantities of Alkaline Earth Elements with Potassium Rhodizonate Determination of Radiobarium in Sea Water HERBERT V. WEISS and MlNG G. LA1 U. S. Naval Radiological Defense laboratory, Sun Francisco, Calif. The feasibility of the cocrystallization of ultramicro quantities of elements from solution with organic reagents was studied with the alkaline earth-potassium rhodizonate system. Results indicated that crystallized rhodizonate was enriched with t h e alkaline earth microcomponent and that the distribution approximated the Doerner-Hoskinstype of equilibrium. These elements were quantitatively recovered with ease at concentrations of 1G - I 4 to 1 0-I6M. The cocrystallization process was applied to the determination of radiobarium in sea water. The cocrystallization step separated barium from sulfate ion, which interferes with its determination in radiochemical analysis by the carrier technique. The crystallized material was readily incorporated into a conventional radiochemical procedure, and reliable results were obtained.
T
DIRECT PRECIPITATION of a n element from solution is precluded when the quantity of substance t o be separated is less than the amount required to exceed the solubility product. Under such circumstances a nonisotopic carrier map be used; separation by this mechanism is known as coprecipitation. Details of the coprecipitation process HE
and the method of determining the Doerner-Hoskins logarithmic distribution coefficient (A) and the homogeneous distribution coefficient (D)are comprehensively reviewed by Hahn (4). Nearly all the coprecipitation reactions described involve the use of inorganic carriers (8). However, Kuznetsov (6) pointed t o the advantages of the coprecipitation of elements with organic reagents and reported a number of schemes in which minute quantities of a variety of elements were quantitatively recovered rrith such reagents. The method requires binding the trace elcment Rith ttn organic reagent and then precipitating the added agent M ith still another organic compound. If the compound formed upon the addition of the first agent is slightly soluble or only slightly ionized, then the element is usually carried efficiently. Kuznctsov emphasized the requirement for large molecular weight compounds to effect efficient coprecipitation and used combinations of organic reagents such as methyl violet and a n azo compound or tannins . The current study explores the possibility of isolating trace quantities of a n element by the direct crystallization of a n organic reagent from solution. Such a crystallization process simplifies the operating procedure. Furthermore, a
wide variety of reagents is available since the conditions required to crystallize organic reagents are usually easily achieved. If the trace element and the organic reagent combine to form a compound whose insolubility is greater t h a n that of the reagent, then according to Fajans’ rule ( I ) , the crj stallized reagent should be enriched with trace element. T o examine this premise as well as the feasibility of isolation of ultramicro quantities of an element by this process, the alkaline earth-potassium rhodizonate system was studied. This system was selected because the varying solubilities of the alkaline earth rhodizonates provide a basis for verification of the applicability of Fajans’ rule. The solubilities of the alkaline earth rhodizonates decrease with increasing molecular weight for calcium, strontium, and barium (2, 9). Although the radium rhodizonate salt has not been described, Iresumably it forms the most insoluble complex of this chemical group. The cocrystallization of elements of the alkaline earth group with rhodizonate upon crystallization of fractions of carrier with ammonium chloride or alcohol was studied. To measure ultramicro quantities of alkaline earth elements accurately, appropriate radioactive tracers were used. The informaVOL. 32, NO. 4, APRIL 1960
475
I
I I
I _.
53
130
2CO 2-0 300 350 A K V G Y Uh' C H L O R l D E ADDED I K G l
150
400
450
500
EXPERIMENTAL
Reagents. Amnioniuiii chloride, reagent grade; 0.2 gram per ml. of distilled water. Potassium rhodizonate solution; prepared at various concentrations with distilled water just prior to use. Other chemicals used were of reagent grade. Tracers. Strontium-85, calcium-45, and barium-lanthanum-140 rt-ere obtained in carrier-free form. Radium-223 was separated from actinium-227 by a solvent estraction procedure (5). The purity of separation was established by decay measurements. Radioactivity Measurements. Strontium-85, radium-223, and barium-lanthanum-140 gamma measurements were made in a well sciiitillation counter after solubilization of the rhodizonate in nitric acid and dilution to a standard volume. Barium-lanthanuni1-10 was counted after equilibrium was attained. The recovery of calcium-45 n-as determined by beta measurement. Samples were prepared for analysis as follows : The crystallized rhodizonate n-as solubilized with fuming nitric acid, and calcium carrier was introduced. After mixing, sulfuric acid was added to precipitate the calcium. Calcium sulfate was solubilized and reprecipitated with osalate, dried, weighed, and mounted. The beta activity was measured in a gas flow proportional counter. Appropriate corrections iTere made for carrier loss and self-absorption. Cocrystallization Experiments. Two series of experiments were p ~ r formed in iThich solutions of potassium rhodizonate vihich contained an alkaline earth element were crystallized with either ammonium chloride or absolute ethyl alcohol. KITH AMMONIUM CHLORIDE.-4 series of 37.2mM potassium rhodizonate solutions, 11 ml. in volume, was prepared to contain about lo4 disintegrations per minute (d.p.m.) of a carrier-free tracer. From 0.1 to 2 ml. of ammonium chloride solution was added dropn-ise to these 476
ANALYTICAL CHEMISTRY
C
20
3C
40
50
6C
O E C O i E R Y OF 3 0 T 4 S S U W R I I C 2 1 Z O U A T E
Figure 1. Cocrystallization of alkaline earth elements with potassium rhodizonate using ammonium chloride as crystallizing agent
tion gained from these experiments was applied to the isolation of radiobarium from sea water.
0
-C E0 i t 9 CENT)
90
100
Figure 2. Cocrystallization of alkaline earth elements with potassium rhodizonate using absolute ethyl alcohol as cryst a l k i n g agent
solutions to crystallize various amounts of rhodizonate. After standing 5 minutes the crystals were separated, washed with absolute alcohol, dried overnight in vacuo, and weighed, and the quantity of tracer recovered was determined. The recovery of rhodizonate was calculated on the basis of transformation from the potassium to the ammonium salt. KITHETHYL ALCOHOL. Aqueous solutions of potassium rhodizonate (29.5mLV),11 ml. in volume, which contained IO4 d.p.m. of an alkaline earth tracer were crystallized a t room temperature with 0.25 to 4 ml. of alcohol. Several minutes after crystallization the crystals were collected, dried, weighed, and counted as before. RESULTS A N D DISCUSSION
The recovery of the alkaline earth flrments and of rhodizonate upon crystallization with ammonium chloride is shonn in Figure 1. The recovery of these rlements reached maximum values of 87, 96,97, and 99% for calcium, strontium, barium, and radium, respectirely. (The error of measurement was about 370 for calcium and 1% for the other elements.) These maxima coincided with the point a t ahich incremental quantities of the crystallizing agent caused essentially no further crystallization. As the ammonium chloride concentration was raised beyond this quantity. the recovery of the microcomponents diminished perceptibly. Apparently the distribution of the trace elements was shifted tomard lesser recovery n hen the ammonium ion increased to a concentration a t which it displaced the tracer combined with reagent i n the crystalline phase. L-nder the experimental conditions used, rhodizonate salt crystallized instantaneously upon addition of ammonium chloride, and this obscured the true competitive aspects of the system. Since the diffusion of ions in crystalline matter is slow, crystallizing agent added beyond 1.50 mg. (Figure 1) acted only on the surface of the already formed crystals. However, when crystals remained in contact with the mother
liquor over an interval in n hich diffusion effects and recrj stallization nssumrd importance, progressire loss of the cocrystallized microcomponent n as manifest. Moreover, this effect was related to the concentration of salting agent in solution. For esaniple. a sample treated with 2.5 times the quantity of ammonium chloride required to yield optimum cocrystallization of strontium lost 34y0 of the tracer n lien the crystals were stirred in the mother liquor for 16 hours, 1%-hileanother treated n i t h the optimum concentration of salting agent lost only 8% of the tracer over the same interval. The delayed amnioiiiuiii chloride effect indicates that the microcomponents n ere internally incorporated rather than surface adsorbed. Analysis of the crystal pattern of alkali metal and alkaline earth rhodizonates b) x-ray diffraction shon ed that isomorphism \vas nonexistent between these chemical groups. The crystal lattice incorporation of minute quantities of alkaline earth metals by rhodizonate, therefore, represents another case of anoiiialou. mixed crystal formation (4). The results of the cocrystallization of tracers upon crystallization of rhodizonate with alcohol appear in Figure 2. These data are characteristic of the results obtained in the p H range of 5 to 7 . Below p H 4 rhodizonate is noncrystallizable, while betneen p H 4 and 5 crystallization is inconiplete and tracer recovery is accordingly reduced. I n contrast n ith crystallization by ammonium chloride, the quantity of tracer carried increased the more the rhodizonate n as removed from solution up to the point of quantitative recovery. Furthermore, because of the abqence of any competitive effect, the solid phase was more markedly enriched with tracer. The degree of enrichment n-as related to the insolubility of the respective alkaline earth rhodizonates and points t o the value of Fajans' rule in the selection of an organic compound for the purpose described. Distribution coFfficients were calculated a t various reagent recovery levels
with data taken from the smooth curves (Figure 2). These values are shonn in Table I. D n a s inconstant n-hile X ranged about a mean. The logarithmic type of distribution should be favored in view of the fact that the procedure did not provide for recrystallization. The variations in A are probably attributable to the inhomogeneous method of crystallization. When alcohol was added to the more or less concentrated rhodizonate solutions, crystallization was fairly rapid. Such cirrumstances created concentration gradients and randomnessn hich do not engender the exact conditions for the Doerner-Hoskins equilibrium. Sonetheless, rt is clear that the alkaline earth elemwts n-ere carried cfficiently by alcohol-crystallized rhodizonate. Even for calcium, n-here enrichment n as relatively less pronounced, the crystallization of less than 50% of t h. rhodizonate removed essentiallv all of this element from solution. The method does not provide for the separation of alkaline earth elements from one another. .Rather, it affords the separation of the whole group from solution by a process nhich is both d i c i e n t and rapid.
Table I.
Distribution Coefficients for Alkaline Earth Elements Cocrystallized with Potassium Rhodizonate Using Alcohol as Crystallizing Agent
Rhodizonate Recovered,
%
x
10
3.0
18
a
Calcium
2.8
D 3.3
3.4
Distribution Coefficients" Strontium Barium
Radium
A
D
x
D
x
9.4 7.2 6.9 8.1
15 16 18 60
12 9.3 8.9 9.1 ...
22
14 11 9.8 9.7
24 35 90
D 33 46 47
25 2.9 3.8 35 3.2 5.7 120 45 4.5 16 ... .. .. ... ... D and A represent the homogeneous and logarithmic distribution coefficients, respec-
tively.
conium-niobium-95; rutheniuni-rhodiuni-103, 106; and cesium-137. QualiTable II. Cocrystallization from Sea tative gamma-ray pulse height disWater of Various Radionuclides with tribution analyses of fission products Potassium Rhodizonate a t various stages of the analytical proRecovery and cedure were performed with a 256Radionuclide Standard Deviation, % channel analyzer of the Argonne National Laboratory type. Ba-La140 98.8h0.5 Pu237 100.0 i 0 . 3 The cocrystallization of the individual Ce-Pr144 96.1 k 0 . 1 fission products as well as antimonyZr-?;bgs 8 8 . 4 f0 . 8 125, molybdenum-technetium-99, co74.6 f 0 . 1 ZnB5 balt-60, manganese-54, iron-59, zinc-65, Fe69 70.8 f 1 . 4 and plutonium-237, was determined 66.5 f 1 . 5 NnK4 quantitatively by gamma count. The 47.1 i1.8 C0 6 0 tracers used were of sufficiently high Mo-Tcs8 14.3 f0.1 1 3 . 4 f0 . 4 qpecific activity t h a t only submicroRu-Rh'o' 4.1 4 ~ 0 . 5 Cs'37 gram quantities of the element were 2.8f0.1 Sblz6 introduced into the system. SEPARATION OF BARIUM FROM SEA WATER COCRYSTALLIZATIOK OF BARIGMAXD OTHER ELEMENTS WITH POTASSIEM The determination of barium radioRHODIZOSATE. TO 1 volume Of sea isotopes in sea n a t e r using the convenwater (20 to 400 ml.) nhich contained this stage revealed, as expected from tional carrier technique is complicated a single radioelement were added 2 the results reported in Table 11, that by the interference of sulfate ion, the volumes of potassium rhodizonate soluthe majority of the fission product acaverage sulfate content of sea water betion. The introduction of rhodizonate tivity also cocrystallized. T o remove ing 0.26% by neight ( 7 ) . Upon the into sea water by this method \\as rethese contaminants from radiobarium, additionof bariumcarrier to thismedium, quired because the salts of this medium conventional decontamination reacinhibit direct dissolution of the reagent. insoluble barium sulfate precipitates tions (6) were performed after the addiT h e solutions were mixed and a quanimmediately. T o achieve radiochemical tion of barium carrier to the solubilized tity of absolute ethyl alcohol equivalent rhodizonate. The introduction of barpurity, thc bariuni precipitate must be to 30% of the total volume was slo~vly ium carrier a t this stage was necessary dissolved t o pcrniit decontamination added to effect crystallization. (These because the purification steps were from other 1ntc.rfering radioactivities. conditions yielded quantitative recovpredicated on bariuni precipitations. Since the sulfate is not so amenable t o ery of barium from distilled nater.) The rhodizonate crystals were dissolubilization as are other barium salts, The crystals were separated from the solved in 2 N nitric acid, and 70 mg. of it is not the compound of choice for the mother liquor by filtration, solubilized, barium ion and 10 mg. of zirconium and initial precipitation. and diluted t o a standard volume for cerium hold-back carriers mere added. This problem was solved by the coradioactivity counting. The results, The nitrate, chloride, and chromate \T hich were independent of the volume of crystallization of barium with potassium salts of bariuni were precipitated in that sea water used, together with the standorder. The chromate was then disrhodizonate directly from sea m-ater. ard deviation of duplicate analyses are solved, diluted t o standard volume, Procedure. REACIEKTS.-4 1.27, jhorvn in Table IT. The recovery of pulse height analyzed, and gamma solution of purified potassium rhodibarium was uninfluenced by the salts counted. The spectrum obtained from zonate was prepared in distilled n-ater of sea water. The other radioelements pulse height analysis after equilibrium and used JTithin 1 hour after preparacocrystallized in varying amounts and reproduced that of a n authentic sample tion. the results indicated that the determiof barium-lanthanum-140 and there Carrier solutions of barium and holdnation of radiobarium in a radioactivewas no evidence of any other radiation. back carriers of zirconium and lancontaminated medium would require Correction of the chromate gamma thanum were prepared from analytical decontamination steps to achieve purity. count for the carrier recovery (78%) reagent grade salts to contain 10 mg. Crystallized rhodizonate also contained accounted for 99 i 1% of the total of ion per ml. Barium carrier was macro quantities of calcium whose requantity of barium tracer introduced standardized gravimetrically by chromoral was desirable. initially. mate precipitation. RADIOBARIChI DETCRMINATIOS IK S E A RADIOACTIVITIES AUD THEIR ~ I E A S - WATER SOLUTIONOF FISSION PRODDiscussion. The preliminary sepaUREMENT. Barium-lanthanum-140, as UCTS. To a 50-ml. sample of sea water ration of barium tracer from salt water described above. which contained lo4 d.p.m. of bariummedium b y t h e technique described is The fission products used to study the lanthanum-140 and 5 x lo5 c.p.m. of easily controlled t o give essentially a decontamination of radiobarium from other fission products was added 100 quantitative tracer recovery. The isoother radioactivities were formed from nil. of the rhodizonate solution. The lated crystals which carry the tracer irradiation of enriched uranium and were rhodizonate was crystallized with 45 incorporate easily into the conventional 6 months old. The principal gamma nil. of absolute ethyl alcohol, and the barium radiochemical procedure. The emitters present at this time were crystals were collected after 5 minutes cerium-praseodymium-141, 144; zircrystallized material is soluble in acid, of standing. Pulse height analysis at VOL. 32, NO. 4, APRIL 1960
477
a treatment tvhich simultaneously strips barium from rhodizonate. Under these conditions a homogeneous distribution within the solution occurs between the tracer and carrier introduced at this stage and the analysis then proceeds as usual. The crystallization step of the analysis does not decontaminate certain gammaemitting fission products from the barium tracer. On the other hand, some of the radioactivities cocrystallize quantitatively, or at least very nearly so, and this technique, which in essence is carrier-free, may be useful in their separation as well. The cocrystallizationof tracer amounts
of the elements with a variety of organic compounds will be studied to provide for wider application of the general met hod. ACKNOWLEDGMENT
The authors
Jack Quan of this laboratory FI ho performed the x-ray diffraction analyses, the Paul B. Elder Co., Bryan, Ohio, for its contribution of potassium rhodizonate, and the Mound Laboratory, Miamisburg, Ohio, which kindly furnished actinium-227. LITERATURE CITED
(1) Fajans, K., Berr, P., Ber. deut. chem. Ges. 46, 3486 (1913).
( 2 ) Feigl, F., Xikrochemze 2, 187 (1924) Chem. 5’OC. 72, (3) Hagemann, F., J . 768 (1950). (4)Hahn, 0 , ttAippliedRadiochemistry,l, Cornel1 University Press, Ithaca, N. Y., 1936. (5) Kuanetsov, V. I., Zhur. Anal. Khim. 9,199 (1954) (6) Sunderman, D, S , , hIeinke, W, R,, ANAL.CHEW29, 1578 (1957). (7) Svedrup, H. V., Johnson, 11. W., Fleming, R. H., “The Oceans,” Prentice Hall, Englewood, X. J., 1942. (8) Jvahl, A. c., B ~ K. A.,~ ctRadio~ ~ activity Applied to Chemistry,” Table 6B, Wiley, New York, 1951. (9) Weiss, H. V., Shipman, W.H., ANAL. CHEM.29,1764 (1957). for review September 8, 1959. RECEIVED Accepted January 7, 1960.
Si mu1ta neous Extraction and Spectrophotometric Determination of Cerium with 2-Thenoylfluoroacetone SHRIPAD M. KHOPKAR and ANlL K. DE Department o f Chemistry, Jadavpur University, Calcutta A colorimetric method has been developed for milligram amounts of cerium(lV) on the basis of color reaction with 2-thenoyltrifluoroacetone in benzene. The bright orange-red cerium(lV)-TTA chelate solution (in benzene) follows Beer’s law at 450 mp over the range of 3 to 40 y of cerium (IV) per ml. At pH 4.0 to 6.0 80% or more of cerium(lV) i s removed from an aqueous solution of TTA-benzene in a single extraction. The colored system is stable for 2.5 hours. It can tolerate equal amounts of silver, manganese, copper, and cobalt, whereas nickel, bismuth, aluminum, thorium, uranium(VI), citrate, tartrate, and EDTA seriously interfere. The method i s accurate and reproducible to within f2% and offers a simple procedure for simultaneous extraction and determination of cerium(1V).
T
HE chelating agent, 2-thenoyltrifluoroacetone, commonly known as TTA, has been used in this laboratory (1-3) for extraction and colorimetric determination of metals such as iron (111), copper(II), and uranium(V1). From a slightly acidic solution cerium (IV) gives a deep orange-red chelate with TTA, which is extractable into solvents such as benzene, giving a brilliant orange-red solution. I n its simplest form, the over-all chelate .formation can be expressed as:
Ce.’
4
+ 4 HT, e CeT,* + 4 H.C
where HT is the enol form of TTA, and subscripts a and b refer to aqueous and
478
ANALYTICAL CHEMISTRY
32, India
benzene phases, respectively. T T A and cerium chelate have very little solubility in aqueous acid solutions but are soluble in benzene. Smith and Moore (6) described a method for fast extraction of radiocerium (with or without carrier) with TTB. Cerium(II1) is extracted into 0.5X TTA-xylene from a 1N sulfuric acid solution containing potassium dichromate and sodium bromate, with about 80% yield and thus separated from many other elements. They observed a dark reddish brown color in the organic phase, but so far no spectrophotometric studies have been reported. I n this paper systematic investigations on the liquid-liquid extraction behavior of cerium(1V)-TTA chelate a t different pH’s and spectrophotometric studies of the chelate are described. This offers a simple and rapid procedure for simultaneous extraction and spectrophotometric determination of cerium(1V) a t the milligram level. The method requires simple equipment and only moderate amounts of time, is suitable for small amounts of samples, and is adaptable to automatic or semiautomatic manipulation with the minimal introduction of chemical reagents and solvents. APPARATUS
Absorbance measurements were carried out with a Hilger quartz spectrophotometer, using matched 1-cm. quartz cells, and p H measurements with a Cambridge p H indicator. All chemicals were chemically pure or reagent grade materials, unless otherwise mentioned.
TTA (Columbia Organic Chemicals, Columbia, S. C.) solutions in benzene, about 0.15M, were used. A stock solution of ceric sulfate was prepared by dissolving about 3.5 grams of ceric oxide in 1 liter of 1N sulfuric acid. The solution, standardized gravimetrically as ceric oxide after oxalate precipitation and ignition, contained 2.79 mg. of cerium per ml. For spectrophotometric studies the stock solution was diluted tenfold (1% in sulfuric acid), so that the cerium content was 279 y of cerium per ml. A buffer solution of p H 5.4 was prepared by dissolving 77 grams of ammonium acetate in water, acidifying with acetic acid t o p H 5.4, and diluting to 1liter. GENERAL PROCEDURE
i i n aliquot (2 ml.) of the ceric sulfate solution, containing 279 y of eerium(1V) per ml., was adlusted to the desired p H with 0.01N sulfuric acid and 0.01N sodium hydroxide, using a pH-meter. Hydrochloric acid was avoided for p H adjustment, because chloride ion is known to accelerate the reduction of cerium(1V) (6). For the study of diverse ions, the solution containing the ion under investigation was added prior to pH control. The aqueous solution, unless otherwise mentioned, was adjusted to p H -5.4, treated with 10 ml. of buffer solution (pH 5.4), and made u p t o 25 ml. with water. It was introduced into a separatory funnel (250 ml.) and shaken for 15 minutes with 10 ml. of 0.15M TTA-benzene. The lower aqueous layer was transferred to a beaker and the upper benzene layer to a 25-ml. volumetric flask. The aqueous layer was rinsed once with 5 ml. of benzene and the benzene solution
~
