V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
2015 t h a t coprecipitation may be controlled so as to compensate for the solubility error if desired. This could be accomplished by adding the ethyl alcohol before the complete neutralization of the periodic acid with lithium acetate. This measure may be of the greatest advantage, should the method be adapted t o microtechniques. Although this possibility is noted here in the light of experience with the method, there is no real need to use such a technique in macro work. T h e solubility error may be corrected for by means of the experimental curves, in which case the uncertainty in the results will be of the order of z t O . l % for amounts of potassium greater than 3 mg. Even if no correction is applied, the uncertainty in this range would probably not e\ceed -0.3y0 and in most cases would appear to be less than this
- 3 131
-0151 01
I
1
,
95
/
,
I
I
80
MG
OF
5 POTASSIUM
0 TAKEN
50
J
Figure 2. Analysis of results on potassium nitrate sample with cobaltinitrite and metaperiodate precipitations
bility error for small amounts of potassium is probably due t o this. Since the precipitation of small amounts of potassium as thc metaperiodate is slow and incomplete in aqueous solution, most of it precipitates upon addition of the ethyl alcohol, with resultant coprecipitation of periodate. The faster rate of precipitation inherent with t h e largest amounts of potassium taken for analysis noald also he likely t o cause some coprecipitation of periodate. The results for both sets of data diverge from the curves in Figure$ 1 and 2 for 25-mg. amounts of potassium. TI is is probably due t o practically no compensation by coprecipitation for this amount, because the rate of precipitation t~:isrelatively slower than for the largest amounts. Although it was recognized t h a t there x a s a h a y s somr coprecipitat ion, efforts were directed t o mininizing it in order to evaluate the real magnitude of the solubility error as nearly :IS possible. On the othrr hnnd, there is good reason t o believe
LITERATURE CITED
Burkhart, L., Plant Physiol. 16, 411 (1941). Crouthamel, C. E., Hayes, A. AI., Martin, D. S . , J . Am. C h e w . SOC.73, 82 (1951). Drude, P., 2.physik. Chem. 23, 267 (1897). “Gmelins Handbuch der anorganiachen Chemie. Kobalt,” Pdi t A, Sect. 2, 8th ed., pp. 405, 420, 422, Verlag Chemie G. i n b. H., Berlin, 1932. Jentoft, R. E., “Study of Determination of Potassium as t h e Rletaperiodate,” thesis, University of Washington, 1952. Jentoft, R. E., Robinson, R. J., ANAL.CHEJI.26, 1156 (1954). Jentoft, R. E., Robinson, R. J., J . -4m. Chem. SOC.75, 4083 (1953). Jones, J . H., I b i d . , 68,240 (1946). Jones, J. H., Heckman, N., Ibad., 69, 536 (1947). Kolthoff, I. M.,Sandell, E. B., “Textbook of Quantitative Inorganic -4nalysis,” 3rd ed., pp. 594, 606, Rlacmillan, Ken York. 1952. (11) Platow,’ -1.M., Chemist-Analyst 28, 30 (1939). (12) Scott, W.W., “Standard Alethods of Chemical Analysis,” 5 t h ed., pp. 1200, 1209, Van Nostrand, S e w York, 1939. (13) Willard, H. H., Boyle, 9.J., IND. ENG.CHEM.,ANAL.ED. 13, 137 (1941). RECEIVED for review February 3, 1956. Accepted August 6. 1886. Work 5 8 onr-BYO/III with t h e U n i v r s i t y of Washington.
supported b y Office of Naval Research Contract
Coprecipitation of Rare Earth Iodates with Thorium Iodate Precipitated from Homogeneous Solution KENNETH J. SHAVER’ M o u n d Laboratory, Monsanto Chemical Co., Miamisburg, O h i o
T h e separation of thoriuni from rare earths by piecipitation of thorinm iodate from homogeneous solrition is evaluated. The extent of coprecipitation is given when thorium is precipitated in the presence of the rare earths; lanthanum, praseodyiniuni, promethium, and europiuni; and the related elements, yttrium and scandium. The extent of coprecipitation is determined by the use of radioactive tracers of these elements. The distribution of rare earths with thorium follows the logarithmic or heterogeneous distribution law. I t is concluded that trivalent rare earths coprecipitate with thorium iodate by a type of isomorphous replacement within the thorium iodate lattice. A correlation is given between ionic radii and extent of coprecipitation.
T
HE precipitation of thorium iodate from a nitric acid sohtion has long been used for the qualitative separation of thoiium from rare earths This separation depends on the solubility of rare earth iodates in a moderately concentrated nitric
acid solution. As a quantitative method, hoxever, the separation is riot satisfactory because rare earths are coprecipitated to an appreciable extent. Recently, this situation has been improved through the application of the technique of precipitation from homogeneous solution. Stine and Gordon (8) a t Syracuse University applied this technique to the precipitation of iodates in a unique manner. I n this method, iodate ion is produced in solution from the reduction of periodic acid with ethylene glycol. The rate-controlling reaction is the production of glycol from the hydrolysis of 0-hydroxj-ethyl acetate. Thorium iodate slon-ly precipitatra as iodate ion is produced homogeneously throughout the solution. The degree of separation of thorium from rare earth 11-as determined by Stine and Gordon by precipitation of thorium iodate in the presence of trivalent cerium. The present work is a detailed investigation of this separation. The separation efficiency is given in terms of the degree of coprecipitation of a number of rare earths and related elements. 1 Present address, Inorganic Chemicals Division, hlonsanto Chemical Co., Everett Station, Boston 49, Mass.
ANALYTICAL CHEMISTRY
2016 For simplicity of discussion these related elements are generally included under the term "rare earth&." Coprecipitation data obtained in this evaluation are further interpreted t o gain information concerning the nature of this coprecipitation. From t h e standpoint of coprecipitation theory this is a particularly interesting sjstem, for t n o reasons. The extent of coprecipitation is extremely small and does not become significant until the extent of precipitation of thorium approaches 100%. This is a typical case of a separation which is nearly quantitative. Coprecipitation theory is more generally applied to the opposite extreme, where t a o more similar elements are involved and where coprecipitation is appreciable regardless of the extent of precipitation of the major components. The other factor 1% hich makes the thorium-rare earth iodate system of particular interest is the difference in charge betn-een the two cations involved. If these coprecipitate by a t j p e of isomorphous replacement, one must assume the likelihood of vacancies within the lattice and a corresponding degree of lattiw distortion. THEORETICAL DISCUSSIOY
K h e n one material copreripitates v i t h another, there ale ti\ o systematic ways in which the minor constituent may be distributed throughout the main component of the precipitate. It may be distributed homogeneouslj- throughout each individual particle of the precipitate, or it may be distributed in a logarithmic manner such t h a t the concentration is zero a t the center of each particle and increases layer by layer to a maximum a t the outermost l a j er. The opposite direction of increase in concentration would exist in an enrichment system. The first type of distribution has been expi essed mathematically in terms of a direct proportionality between the extent of precipitation of the major constituent and the extent of coprecipitation of the minor constituent. This relationship, mhich is usually referred t o as the homogeneous distribution law, is generally associated l\ith the investigations reported by Henderson and Kracek (3) dealing n i t h the radium-barium chromate s j stem. These authors did not derive the mathematical expression but similar relationships have been derived before and since this I\ ork based in some cases on the Berthelot-Sernst distribution laF ( I O ) and in other cases on simple equilibrium solubility relationships ( 2 ) . This mathematical expression 1%-asderived for and has previously been employed n i t h systems nhere the two ions are of like charge. This expression is used in the present nork t o interpret data obtained with a system where the two cations do not have the same charge. I t has been tacitly assumed that the expression used by Henderson and Kracek is sufficiently valid for the interpretation of data in the thorium-rare earth iodate system. Rare earth in precipitate Rare earth in solution -
thorium in precipitate -~ thorium in solution
The proportionalit- constant D is the homogeneous distiibution coefficient. .4s this law expresses homogmeity in the crj eta], it assumes equilibrium bet\%een the entire solid phase and the liquid phase. The other type of distribution is represented by the logarithmic distribution law derived by lloerner and Hoskins ( 1 ) . This law may be expressed in terms of the thorium-rare earth system as follon-s: total rare earth Log rare earth in solution
must be integrated over the period of crystal gros-th to obtain the logarithmic relationship. From a common initial value of the distribution coefficient, a precipitation may be carried out in such a manner that either U or X Fvill remain constant. If the method of precipitation result? in a homogeneous distribution of rare earths, calculated values of D will remain constant while values of X n-ill increase continuously as thorium is precipitated. Conversely, if conditions of precipitation lead to a logarithmic distribution, calculated values of A will remain constant, Lvhile values of D ill decrease continuously. This is a general relationship ivhich is always true Tvhere D and X are less than 1. In any case, hovever, for a given initial value of the distribution coefficients the extent of coprecipitation will be less if the method of precipitation is such that A remains constant rather than D. This is illustrated graphically in Figure 1, 1%-hich s h o w how coprecipitation increases as precipitation occurs and approaches completion for tJvo casee where D and X have the same numerical value. For any degree of precipitation, the corresponding extent of coprecipitation is less when X is constant rather than D. K i t h any proposed separation procedure, then, a logarithmic distribution must be demonstrated to ensure that this procedure will give a maximum separation. The technique of precipitation from homogeneous solution generally tends toward this result. Also shown in Figure 1 is the same relationship between extent of precipitation and extent of coprecipitation for a verj- much smaller value of the distribution coefficient where h is 5 X 10-4. This is the situation which would exist in the case of a separation vihich is nearly quantitative. Searly complet,e precipitation is accompanied bj- only slight coprecipitation. However, a t some point. prior to complete precipitation, coprecipitation d l start to increase sharply, as is shown by an enlargement of the corner of t h e graph. If information is available in this extreme range, it is possible t o control the extent of precipit,ation to obtain any desired degree of purity of the precipitate and to avoid the sharp increase in coprecipitation.
total thorium log thorium in solution
The logarithmic distribution Ian assumes only that equilibrium exists betxeen the solution and each nen-ly formed infinitesimal surface layer of the solid phase. At the start of precipitation, it is evident that the two Ian s are equivalent and that D is equal to A. As precipitation occurs, however, the simple distribution lam
Figure 1. Relative rate of increase of coprecipitation as precipitation occurs for different values of the distribution coefficient
The separation of thorium iodate from rare earth iodates is a separation \\-hich is nearly complete and most of the coprecipitation data in the present work fall within this extreme range. EXPERIMENTAL
The method of precipitation of thorium iodate which was employed for the present n-ark was essentially that of Stine and Gordon, with two modifications. First, the concentration of nitric
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6 acid was increased slightly to 4s. The greater rare earth solubility at this concentration avoids the possibility of direct precipitation of rare earth iodates, because the concentration of rare earth was greater in most cases t h a n that specified in the method of Stine and Gordon. Secondly, ethylene diacetate was the soiirce of ethylene glycol rather than the monoacetate ester, so that all of the ester could be added at the start and t o achieve a slower rate of precipitation. The amounts of ester and periodic acid added a t the start n-ere adjusted so t h a t t,he final concentratioii of iodate would be 5Yc as in the method of Stine and Gordon. After the ester and periodic acid were added to the mixture of thorium and rare earth nitrates in 4 5 nitric acid, the solution \Tas allowed t o stand a t room temperature with stirring for 1.5 hours. At the end of this time, the ester was completely hydrolyzed and the periodic acid was reduced t o iodate by the ethylene glj-col. T h e precipitate, which in most cases consisted of approximately 10 mg. of thorium, was filtered on a I-em. glass frit and m s h e d with a minimum volume of dilute iodic acid n-ash solution, The washing procedure was standardized at four 1-nil. washes and all roprecipitation data were determined on the basis of this washed prwipit:it e. In deteriiiiuing distriiiution data for a system of this type where the extent of coprecipitation is very low, t,he problem of analysis becomes considerable. It can be greatly simplified, however, by the use of radioactive tracers as a means of analysis. I n the present work, radioactive rare earth tracers were added t o the mixture of thorium and rare earth nitrates before precipitation. The fraction of the rare earth which coprecipitated with s recovered and determined by comparing the thorium ~ n then iictivity in the fraction with t h a t remaining in solution. The coprecipitated rare earth n-as recovered by dissolving the washed thorium iodate precipitate in hydrobromic acid. The resulting bromide solution n-as converted to nitrate by evaporating the solution to near dryness with nitric acid. Finally, the concentration of nitric acid v a s adjusted to 4 S and thorium n-as reprecipitated by the direct addition of iodic acid. When this procedure was used, no more than 15; of the rare earth which had initially coprecipitated n-as coprecipitated again n-ith the second thorium precipitate. The major portion of the rare earth lvhich rrniains in the filtrate from this second thorium precipitate can then be determined by a counting procedure. An aliquot of this solution JTRS mounted on a 2-inch stainless steel disk and evaporated t o dryness. The total amount of solids on the disk was negligible. The @-activityof the tracer was then determined in a Suclear Measurements Corp., 1Iodel PC-1 proportional counter. The use of tracers as an analytical tool generally results in three significant figures. Coprecipitation d a t a are given in terms of only two figures, however, as this more nearly expresses the degree of reproducibility of the results. T h e tracers employed t o obtain coprecipitation data were lanthaniim-140, praseodymium-143, promethium-147, europium152, 154, yttrium-90, and scandium-46. I n the case of lanthanum, promethium, and yttrium, it v a s possible t o obtain tracers which were carrier-free, so t h a t the coprecipitation of tracer alone with thorium could be determined. Lant,hanum-140 and yttrium-90 were obtained from the parent materials, barium-140 and strontium-90, by a chemical separation according t o the method of Salutsky and Kirby (6, 6). These parent materials and all of the other tracers were obtained from the Isotopes Division, Oak Ridge Kational Laboratory. The small quantity of thorium remaining in solution due t o the normal solubility of thorium iodate was determined by an cycounting technique using thorium-228 which was available from bIound Laboratory stocks. Data are given in Table I for the coprecipitation of various rare earths, yttrium and scandium, when 10 mg. of thorium is precipitated from homogeneous solution as the iodate in the presence of about 15 mg. of stable rare earth and 10 microcuries of radioactive tracer. The extent of precipitation of thorium is 99.96C;.
2017 Table I. Extent of Coprecipitation of Rare Earths, Yttrium and Scandium w-ith Thorium" Extent of Coprecipitation, % Rare Earth or Related ~ l Homogeneous ~ ~ Precipitation ~ ~ Heterogenet ous preRare earth Rare earth Present during Precipitation carrier present carrier absent cipitation Lanthanum 0.49 0.61 1,13,0.97 Praseodymium 0 . 4 4 (0 44) h ... Promethium ... 0.53 Europium 0.19 Yttrium 0,079 0 088 Scandium 0.48 a Thorium precipitation of 99.967,. 5 Mixed carrier present.
:
when this quantity of thorium is precipitated in a volume of 0 ml. Data are also given in some cases where the same quantity of thorium was precipitated but no rare earth carrier was present. I n addition, the coprecipitation of praseodymium TTas determined in the presence of a mixed carrier consisting of 10 mg. each of lanthanum and praseodymium. I n order t o show the advantage of the procedure for precipitation from homogeneous solution, thorium iodate n-as also precipitated in the presence of lanthanum by a comparable het'erogeneous procedure. Iodic acid was added dropwise n.ith stirring to a hot nitric acid solution containing 10 mg. of thorium, 20 mg. of lanthanum, and 10 microcuries of lanthanum-140. The final and the final iodic acid volume was 6 ml.; the final acidity, 4\-; concentration, 5yc. The solution was then cooled, filtered, and washed as described. The extent of coprecipitation of lanthanum is given in Table I. I n order to calculate distribution coefticieiits, additional coprecipitation data were needed. Those shown in Table I correspond t o 99.96y0 precipitation of thorium. Additional data are shown in Figure 2 where different amounts of thorium are precipitated. Incomplete precipitation of thorium for t'his purpose was readily achieved by precipitation in a greater volume of soliition. -1s the volume of solution during precipitation is increased from 3 t o 30 ml. the extent of precipitation of thorium decreases from 99.98 to 99.8:;. The extent of coprecipitation of the various rare earths, lanthanum, praseodymium, eruopium, and yttrium, was determined, and the data are plotted in Figure 2 opposite the corresponding extent of precipitation of thorium. The single value for ceriuni was taken from the ryork of Stine arid Gordon (9). It falls, as n-oiild he expected, betneen lanthanum and pr:iseodymium.
-
_c LANTHWUM PRASEODYMIUM -EUROPIUM -YTTRIUM
0 '
;o
b
4;
$1
VOLUME I
9978
I
9980
l
I
9982
9984
/
;1
DURING
;I
PRECIPITbTION
,
d
A
ML i
I
9986 9988 -90 9992 % THORIUM PREClPITATED
9994
9396
9998
IC4
Figure 2. Rate of increase of rare earth coprecipitation as precipitation of thorium approaches completion
ANALYTICAL CHEMISTRY
2018 I n addition t o the data shown in Figure 2, some coprecipitation data were obtained for lanthanum and praseodymium where less than 99.8% of the thorium was precipitated. Incomplete precipitation of thorium in this case was achieved by adding a quantity of ester insufficient for complete reduction of the pericdate present. As the iodic acid concentration is then less than 5(:, there is an increase in the thorium solubility. The single low value for praseodymium was obtained by precipitating 10 mg. of thorium in a volume of 24 ml. and adding half the normal quantity of ester. The three values for lanthanum were obtained by precipitating 10 mg. of thorium in a volume of 12 ml. and adding one half, one third, and one fourth the normal quantity of ester. These data are given in Table 11.
also listed opposite the proper rare earth. There is a general trend of relationship b e h e e n decreasing ionic radii and decreasing extent of coprecipitation.
Table 111. Correlation between Ionic Radii and Extent of Coprecipitation Ionic Extent of Radii, Coprecipitation, Element A. % La3 1.04 0.49 (0.61)a 1.02 Ce3+ Pr3'++ 1 00 0.44 Th 0.99 ... Pm3+ (0.98)b (0.53)a Sm3+ 0 97 ... n 96 Eu3 0.19 y 3+ 0.88 0.079 (0.088)a &3 + 0 68 0.48 * Coprecipitation in absence of rare earth carrier. * Interpolated value. +
+
Table 11. Calculated Distribution Coefficients Thorium Rare Earth Precipitated, Coprecipitated,
%
88.2 96.2
99 967 99 987
%
Lanthanum
0.15 0.24 0.33 0.32 0.35 0.38 0.41 0.46 0.49 0 51
7.0
7.3 7.2 5.2 5.5 5 6 5.9 6.4 6.3 6 4
0 60
x
D
lo-'
6 7
Av.
98.810 99.840 99,880 99.920 m ..-960 .~.. 99.980
x
200
95 33 6.4 5.8 4.6 4.1 3.7 2.0 1 6
x 10-6
0 8
6 4 X 10-4
Praseodymium 0.26 5 . 9 X 10-4 0.32 5.0 0.35 5.2 0.38 5,3 0.44 4.9 0.53 6.2 ~ v .5 . 4 x 10-4
31.6 X 10-6 4.9 4.0 2.9 1.7 1.0
The apparent irregularity of scandium may be due t o the fact that scandium is somen-hat removed from the rare earths in its chemistry, and such a direct comparison n-ith rare earths may not be valid. The effective ionic radius-that is, the hydrated radius for scandium-may be similar to lanthanum. It appears from the data in Table I for lanthanum t h a t precipitation from homogeneous solution is approximately ta ice as effective as heterogeneous precipitation with regard t o rare earth contamination in thorium iodate.
- T H E O R E T I C A L CURVE, 1 . 6 4 D EXPERIMENTAL POINTS
2 06
x 104
8
Both the logarithmic and homogeneous distribution coefficients have been calculated in all cases for lanthanum and praseodymium and are given in Table 11. DISCUSSION
It is evident from the data in Table I that there is little change in the extent of coprecipitation, whether the quantity of rare earth is present a t the microgram level where tracer alone is present or a t the milligram level where rare earth carrier is added. It is probable, therefore, t h a t adsorption does not occur. Instead, a systematic replacement must occur within the crystal lattice of thorium iodate. This is further supported by the fact t h a t the coprecipitation figure for praseodymium alone was exactly duplicated when an equal quantity of lanthanum carrier was also present. The lattice replacement of one cation by another of different charge when a single species of anion is present is not without precedent i n nature. Examples of this are the replacement of potassium with divalent lead in feldspars and the replacement of trivalent yttrium with divalent calcium in yttrofluorite. Replacement by an ion of lesser charge probably results in a vacancy or defect in the lattice and perhaps even some degree of lattice distortion. The quantity of foreign ion that can be tolerated in such a situation may be related t o the difference in the ionic radii of the two cations ( 4 ) . Such a correlation betlveen ionic radii and extent of coprecipitation has been reported for the coprecipitation with lanthanum fluoride of various rare earths, ceric fluoride, and uranium fluoride ( 7 ) . A list of ionic radii are given in Table 111, mhich were taken from t h e work of Zachariasen (12). For convenience of comparison, coprecipitation data from Table I are
88
90
92
94
96
98
%liORIUMPPEC#?.TlTtO
Figure 3. Comparison between experimental rate of increase in coprecipitation and that calculated for an average value of X for lanthanum
The data shown in Table I1 indicate that this coprecipitation follows the logarithmic rather than the homogeneous distribution law. The calculated values of A are approximately constant, while the corresponding calculated values of D vary continuously. Over the range of precipitation of thorium between 88.2 and 99.9970, this variation for lanthanum is 200-fold. The single value for praseodymium and the three values for lanthanum corresponding t o an extent of precipitation of thorium less than 99.87, are in general agreement with the remaining values in each series in spite of the fact that, in these cases, a loTver final concentration of iodic acid was employed. It is evident from the data that the calculated values for X in these four cases are essentially equal t o the remaining values in each series, while the values of D continue the variable trend established by the other data. Therefore, all of these data have been listed in a single table and are treated as continuous. In order to illustrate further the constancy of X, curves have been plotted similar t o the enlarged portion of Figure 1 showing
V O L U M E 28, NO. 1 2 , D E C E M B E R 1 9 5 6
2019 i t will be successful to a predetermined extent. As an added advantage, it may be possible t o predict qualitatively or semiquantitatively the behavior of other similar contaminants without actual experimentation. The limiting factor with regard to general application, h o w ever, is the fact that in many cases the type of coprecipitation may be such that neither distribution law is followed, because coprecipitation is nonsystematic or the systematic distribution is something intermediate between logarithmic and homogeneous distribution. ACKNOWLEDGMENT
I 98 0
98 5
I
I
990
99 5
I00
%THORIUM P R E C I P I T A T E D
Figure 4. Comparision between experimental rate of increase in coprecipitation and that calculated for an average value of X for praseodymium
the variation between extent of precipitation of thorium and extent of coprecipitation of rare earth for two theoretical cases which show a X type of distribution, with X equal to the average value of lanthanum (Figure 3) and praseodymium (Figure 4) as given in Table 11. Actual coprecipitation data have been superimposed on these theoretical curves t o illustrate the extent of agreement. The application of coprecipitation theory in general areas such as this can serve as a very useful tool. Where a separation is good but not quite good enough, it can tell first of all whether or not the contaminant carries bj- systematic replacement or by some nonsystematic means such as adsorptibn. If the coprecipitatiori is systematic, i t will tell whether the maximum possible separation is being achieved-i.e., whether the distribution is logarithmic Finally, once the nature of the systematic distribution has been established, the process of precipitation can be controlled to achieve any predetermined purity in the precipitate. A tm-0-step precipitation process (11) can be designed with assnrance that
The author is pleased to acknowledge the helpful suggestions and encouragement offered by Murre11 L. Salutsky during the course of this work and is also indebted to H. \Ir, Kirby for assistance with the radiochemical techniques employed. LITERATURE CITED
Doerner, H., Hoskins, W., J . Am. Chem. SOC.47, 662 (1925). Gordon, L., ANAL.CHEM.27, 1704 (1955). Henderson, L., Kracek, F., J . Am. Chem. Soc. 49, 738 (1927). Rankama, K. K., Sahama, T. G., “Geocheniistry,” pp. 103-28, University of Chicago Press, Chicago, Ill., 1950. Salutsky, M. L., Kirby, H. W.. ANAL.CHEM.26, 1140 (1954). Ibid., 27, 567 (1955). Schlyter, K., Arlziv Kemi 5, 61-71 (1952). Stine, C. R., Gordon, L., ANAL.CHEM.25, 1519 (1953). Stine, C. R., Gordon, L., U. S. Atomic Energy Comm., NYO3188 (1953). Wahl, A. C., Bonner, N. A., “Radioactivity Applied to Chemistry,” pp. 104-22, Wiley, New York, 1951. Willard, H. H., Sheldon, J. L., ANAL.CHEM.22, 1162 (1950). Zachariasen, W. H., “Crystal Chemistry of the 5f Elements.” Chap. 18, “The Actinide Elements,” Seaborg, G. T., Katz. J. J., Ed., NNES IV-l4A, pp. 775-6, LIcGraw-Hill, New York, 1954. RECEIVED for review December 9, 1955. Accepted July 6, 1956. Division of Physical and Inorganic Chemistry, 125th Meeting, ACS, Kansas City, March-April 1954. Mound Laboratory is operated b y Monsanto Chemical Co. for the U. S. Atomic Energy Commission under Contract Number AT-33-1-GEN-BR.
Determination of Zirconium and/or Hafnium Using 1-Naphthylglycolic Acid R. B. HAHN and P. T. JOSEPH’ Chemistry Department, W a y n e University, Detroit 2, Mich.
M
specific reagent for the precipitation of zirconium (or hafnium I because of the presence of the zirconium-binding - CH( OH)COOH group. Although glycolic acid contains this group, the reaction is not quantitative, because of the absence of the weighting effect of the phenyl group. It was expected, therefore, that the substitution of a group like naphthyl in place of the phenyl group of mandelic acid would produce an effective reagent for zirconium. Oesper and Klingenberg (7) prepared a number of such substituted compounds, including 2-naphthylglycolic acid, and studied their reactions with zirconyl ions. Because l-naphthylglycolic acid has not been studied previously, this investigation was undertaken.
1 Present address, Titanium Alloy Division, National Lead Co., Niagarn Falls, N. Y .
The acid was prepared by treating 1-naphthyl magnesium bromide with chloral and hydrolyzing the resulting product ( 6 ) . The acid was purified by steam distillation and recrystallization from water. The product was obtained as white needle-shaped
Bath zirconium and hafnium are precipitated quantitatively from dilute acid solution by 1-naphthylglycolic acid. No interference is caused by aluminum, ferric, lanthanum, stannic, thorium, titanium, and uran! 1 ions. The method was tested by the analysis of a zircon are. The results obtained using 1-naphthylglycolic acid compare favorably with those obtained with mandelic acid.
ANY organic compounds have been used for the determination of zirconium (8-10). The most specific reagents are phenylglycolic acid (mandelic acid) and other derivatives of glycolic acid. These reagents, however, do not differentiatr between zirconium and hafnium, both of which are precipitated quantitatively ( 2 ) . According to Feigl ( I ) , mandelic acid is :I
PREPARATIOK OF 1-NAPHTHYLGLYCOLIC ACID
