V O L U M E 25, NO. 2, F E B R U A R Y 1 9 5 3 free batches and others containing acid in order to test the utility of the methods. LITERATURE CITED
(1) Am. Sac. Testing Materials, Designation D 871-48. (2) Am. SOC.Testing Materials, Designation D 914-47T, “Tentative Methods of Testing Ethylcellulose,” Sections 13-16. (3) Bogin. H. H., U. S.Patent 2,491,475 (Dec. 20, 1949). (4) Eastman Kodak Co., unpublished data. (5) Fiedler, S. O., Bjorksten, J., and Yaeger, L. L., U. 8. Patent 2,578,683 (Dec. 18, 1951). (6) Fordyce, C. R., Ibid., 2,000,587 (May 7, 1935). (7) I b i d . , 2,338,580 (Jan. 4, 1944). (8) Fordyce, C. R., Genung, L. B., and Pile, M. A., IND.ENG. CHEM., ANAL.ED., 18,547-50 (1946). (9) Fox, S. H., and Opferman, L. P., U. S. Patent 2,390,088 (Dec. 4,1945). (10) Genung, L. B., and Mallatt, R. C., IND.ENQ.CHEM., ANAL.ED., 13.369-74 11941) (11) Hart; J. A. H., and Lee, E. W.,Brit. Patent 585,760 (accepted Feb. 24,1947). (12) Hiatt, G. D., U. S. Patent 2,196,768 (April 3, 1940). (13) Malm. C. J.. Ibid., 1.884.035 (Oct. 25. 1932). (14) Malm, C. J., Emerson, J., and Hiatt, G. D., J . Am. Pharm. A s SOC., XL,520-5 (1951). (15) Malm, C. J., and Fordyce, C . R., I n d . E’ng. Chem., 32, 405-8 (1940). (16) Malm, C. J., and Fordyce, C. R., U.S. Patent 2,023,485 (Dee. 10, 1935).
249
(17) SIaim. C. J., Genung, L. B., and Williams, R. F., IND.ENG. ( ’ H E M . , -4x.k~. ED.,14, 935-40 (1942). (18) Malm, C . .J., Genung, L. B., Williams, R. F., and Pile, hl. A , , Ibid.. IS, 501-4 (1944). (19) Ihid., 5 3 7 pxticularly groupII, p. 502. (20) S h i ~ i i(’. , J., and Hiatt, G. D., U. S. Patent 2,455,790 (Dec. 7, 1948). (21) Slalm, C. J., and Waring, C. E.,
(22) (73) (24) (25) (26) (27) (28) (29) (30) (31) (32)
Ibid., 2,093,462, 2,093,464 (Sept. 21, 1937); Brit. Patent 410,118 (May 10, 1934). Nadeau, G. F., U. S. Patents, 2,211,346, 2,211,347 (Aug. 13, 1940), 2,289,799 (July 14, 1942), 2,326,056 (Aug. 3, 1943), 2,326,067, 2,333,809 (Nov.9, 1943), 2,376,175 (May 15, 1915). Xadeau, G. F., and Starck, C. B., Ibid., 2,131,747 (Oct. 4, 1938). Salo, ?J., Ibid., 2,276,685 (March 10, 1942). Samsel, E. P., and McHard, J. A , , ISD. ESG. CHEM.,ANAL.ED., 14,75&4 (1942). Schulre, F., U. S.patent 2,069,974 (Feb. 9, 1937). Shrew, 0. D., and Heether, M. R., ANAL.CHEY.,23, 441-5 (1951). Simmons, N. L., U. S. Patent 2,327,828 (Aug. 24, 1943). Staud, C. J., Ibid., 1,954,337 (April 10, 1934), 2,271,234 (Jan. 27, 1942). Stone, H. G., and Malm, C . J., Ibid.,2,108,455 (Feb. 15, 1938). Subcommittee on Acyl Analysis, ANAL. CHEY., 24, 4OC-3 (1952). Talbot, R. H., U. S.Patent 2,331,746 (Oct. 12, 1943).
RECEIVED for review September 5 , 1952. Accepted November 13, 1952. Presented before t h e Division of Cellulose Chemistry a t the 122nd Meeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, S . J.
Spectrophotometric Determination of Aluminum in Thorium Extraction of Aluminum with 8-Quinolinol in Chloroform D. W. MARGERUM, WILBUR SPRAIN, AND CHARLES V. BANKS Iowa S t a t e College, Ames, Iowa The preparation of highly pure thorium metal has necessitated accurate methods for the determination of trace impurities of common metals such as aluminum. While this may often be accomplished spectrographically, wet chemical methods are advantageous because of their greater accuracy and i n some cases their simplicity. A rapid and sensitive chemical procedure has been devised for the determination of trace quantities of aluminum in thorium. This procedure utilizes a spectrophotometric determination of aluminum following an extraction with a solution of 8-quinolinol in chloro-
T
H E determination of microgram quantities of aluminum following a chloroform-&quinolinol extraction has proved highly satisfactory (1, 3, 5, 8, 11). I n these procedures aluminum is determined spectrophotometrically subsequent to its extraction into chloroform as tris(8-quinolinolo)aluminuminum(III). In the present investigation this method was applied t o the separation and determination of aluminum in thorium metal, for which no previous chemical method has been reported. Because chloroform-&quinolinol solution readily extracts thorium and other metals as well as aluminum, selective masking agents and accurate p H adjustment are essential to the method. Arsonic acids are noted for their selectivity for quadrivalent cations (10). A sulfonated arsonic acid was sought which would form a soluble thorium complex. The preparation of the sodium salt of 4-sulfobenxenearsonic acid had been reported ( 7 ) and it was therefore chosen as a masking agent for thorium. I n this application the thorium masking agent must prevent not only t h e precipitation of thorium hydroxide a t a p H of nearly 5 but
form. Extraction of thorium is prevented by the use of either 4-sulfobenzenearsonic acid or concentrated acetate buffer as the masking agent. From 2 to 120 micrograms of aluminum may be determined to within 3 ~ 0 . 5 microgram. The method can easily be extended for greater amounts of aluminum. Extraction with 8-quinolinol in chloroform from an acetate-acetic acid buffer results in removal of acetic acid into the chloroform phase, causing partial ionization of the 8-quinolinol. The absorption spectrum for a 1% solution of 8-quinolinol in chloroform containing acetic acid is given.
also the extraction of any thorium by the chIoroform-8-quinlinol phase. By itself the sodium salt of 4-sulfobenzenearsonic acid is peculiarly unfitted as a masking agent because its thorium salt has a low solubility and it will not prevent the precipitation of thorium hydroxide above a pH of 3. However, when this compound is used in conjunction with a dilute ammonium acetate-acetic acid buffer it meets all the requirements of a proper masking agent. Although the sodium salt of 4sulfobenzenearsonic acid forms a soluble complex with zirconium a t pH 5, it cannot be used to mask this element for an gquinolinol extraction. Strong emulsions form along with extensive zirconium extraction upon shaking with a chloroform-8-quinolinol solution. Small quantities of other sulfonated arsonic acids such as 2sulfoethanearsonic acid have been prepared in this laboratory. Preliminary tests have indicated that 2-sulfoethanearsonic acid is a better masking agent for thorium than is 4-sulfobenzenearsonic acid.
ANALYTICAL CHEMISTRY
250 -4dditional work by the authors has shown that very concentrated acetate solutions alone will mask thorium sufficiently to allow the separation of aluminum, but multiple estractions are required. APPARATUS
Absorbance measurenient,s were made with a Beckman Model DU quartz spectrophotometer and a Cary Model 12 recording spectrophotometer. Matched 1-, 2-, and 5-cm. Cores and silica cuvettes were used throughout the study. A Beckman Model G p H meter was used for all pII measurements. A f3urrell shaker, 250-ml. Squibb-type spparatory funnels, equipped with Teflon stopcock stoppers, and 25-nil. glass-stop pered Erlenmeyer flasks were used for the estractions. The Teflon stoppers were obtained from Kontes Glma Co., Vineland, S . J. A Sargent Model T' oscillometer was used for the high frequency titrations. REAGENTS
Standard Aluminum Solution. h stock solution of aluminum sulfate was prepared from very pure aluminum metal, kindly supplied by J. R. Churchill of the Aluminum Co. of America. Thorium Solution. stock solut'ion was prepared from especially purified thorium nitrate tetrahydrate. 4-Sulfobenzenearsonic Acid Solution. The sodium salt of 4-sulfobenzenearsonic acid was prepared and purified in this laboratory by a modification of Oneto's procedure ( 7 ) . 0.24 151 Eolution w&s made and analyzed by potentiometric titration with sodium hydroxide. 1,lO-Phenanthroline Solution. h 0.1% aqueous solution was prepared from reagent' grade 1,lO-phenant'hroline monohydrate. Hydroxylammonium Chloride Solution. 1 10'To aqueous solution was prepared from reagent grade hydrosylammonium chloride. Dilute Acetate Solution. Two hundred grams of ammonium acetate and 100 nil. of glacial acetic acid were dissolved and diluted t,o 1 liter. Concentrated Acetate Solution. Six hundred grams of ammonium acetate and 600 ml. of glacial acetic acid were dissolved and diluted t o 2 liters. This solution was then purified by three estractions with 100-ml. portions of a 1% solution of 8-quinolinol in chloroform, followed by washing with 100-nil. portions of chloroforni until all 8-quinolinol had been removed from the aqueous layer. 8-Quinolinoi Solution. A 1% solution was prepared by dissolving the proper amount of reagent grade 8-quinolinol in reagent grade chloroform. Fluosilicic Acid Solution. One milliliter of a 30% solution of fluosilicic acid waa diluted t o 2 liters. Alkaline Cyanide Solution. A cyanide wash solution was prepared by dissolving 40 grams of ammonium nitrate, 20 grams of pot,assium cyanide, and 10 ml. of concentrated ammonium hydroxide so1ut)ion in enough dist,illed water t o make 1 liter. \A
on the absorbance of the chloroform phase due to this decrease in 8-quinolinol concentration is negligible. Even a 10% decrease in 8-quinolinol concentration would alter the absorbance by only 0.006 unit. pH Range of Extraction. The incompleteness of the aluminum extraction below p H 4.6 and the formation of strong thorium emulsions above pH 7 fix the pH of the extraction between these limits. The optimum range lies betneen pH 4.7 and 5.0, in which complete aluminum removal is assured and thorium extraction is negligible. Range and Accuracy. From 2 t o 120 micrograms of aluminum may be determined to within + 0 . 5 ~ . I n the concentration range used (a maximum of 6 y of aluminum per ml. of chloroform) the absorbance conforms to Beer's law a t a wave length of 383 mfi Extraction Time. T h r time of extraction after 3 minutes has no measurable effect on either the amount of aluminum or thorium taken into the chloroform-%quinolinol phase. Sunlight. Exposure of the chloroform-8-quinolinol extract to sunlight causes darkening of the solutions and a great deal o! error in the absorbance measurements (6). Unesposed solutions may be kept for a day or more without change of absorbance. Stopcock Grease. Stopcock grease in the separatory funnel can be a source of considerable error. owing to its solubility i n chloroform. Greases may be prepared ( 4 ) to avoid this error. hut the authors recommend the uye of Teflon stopcock stoppei s.
EXPERIMENTAL WORK
Wave Length. The absorption spectrum for tris(8-quino1inolo)-aluminum( 111) is shown in Figure 1. The aluminum was extracted from a dilute acetate-buffered aqueous solution into a 1% solution of 8-quinolinol in chloroform. A similar aqueous solution was prepared a t the same pH without aluminum and was also extracted with a 1% solution of Squinolinol in chloroform, to serve as the blank. The absorbance of the aluminum extract was then measured against the blank on the Cary recording spectrophotometer. In this manner compensation was made for any alteration of the absorbance of t h r chloroform-&quinolinol upon equilibration with the aqueous phase. These are the conditions of the actual analysis and under these conditions the absorbance maximum in the visible region occurs a t a wave length of 385 mp rather than 390 to 395 mp as previously reported (9, 6, 11). The absorption spectrum for the thorium 8-quinolate chelate is similar to that for aluminum, with the maximum absorbance peak occurring a t a wave length of 378 m p , A 1% solution of Squinolinol in chloroform has an appreciable absorbance itself a t a wave length of 385 mp. There is some loss of Squinolinol from the chloroform phase on eutraction due to it? slight solubility in a a t e r However, the effect
WAVELENGTH,
rnw
Figure 1. Absorption Spectra 2.
1. Tris (8-quinolinolo) aluminum( Ill) in chloroform Chloroform-8-quinolinol phase after equilibration with 1 ?f acetate buffer, pH 5
Volume. Accurate volume regulation of the aqueous phase is unnecessary, as one extraction quantitatively removes all nieas urable amounts of aluminum. Hqwever, to maintain constant acetic acid concentration the total volumes should be approsimately the same. Acetic Acid Interference. -4cetate buffer solutions have been used a great deal with chloroform-8-quinolinol eytractions. In the present instance the buffer serves as a compleving agent for thorium and stabilizes the pH as well. However, when a 1% solution of 8-quinolinol in chloroform is shaken with a 1-2.1 animonium acetate-acetic acid buffer, some acetic acid is taken into the chloroform phase. Thiq miall amount of acetic acid causes
V O L U M E 25, NO. 2, F E B R U A R Y 1 9 5 3 partial ionization (9) of the 8-quinolino1, which results in a strong absorption peak a t a wave length of 372 mp as seen in Figure 1. This absorption spectrum was obtained as folloivs: T\vent,ymilliliters of a ly0solution of 8-quinolinol in chloroform was shaken with 100 ml. of 1 Jf ammonium-acctic acid buffer a t pH 5 . after the chloroform phase had been dried ovrr sodiium sulfate the absorbance was measured in a 2-cm. cell n-ith the Cary spectrophotometer, using an unestracted 1% solution of 8-quinolinol in chloroform as a blank. This important interference from acetic acid h:ti not trc,?n reported tiy previous 11-orkers. It necessitates measuring all ahsorbances against an extracted blank and enlphaiizei t!lr i:nportance of accurate pH control. The observed absorbance is a function of the acetic acid concentration in the aqueous phase. When extracting from a 1 JI acetate buffer in the vicinity of pH 5 , there is an 0.008 absorbance unit increase measured a t 390 mp per 0.10 pH decrease of the aqueous phase. If the acetic acid is not removed from the chloroform i t is advisable to measure the absorptionof the tris(8-quino1inolo)aluminuminum(111)in chloroforni a t 390 mM rather than 385 mp to minimize possible error from the ahsorption of the ionized species of 8-quinolinol. K h e n extractions are performed from more concentrated acetate solutions. the absorbance caused by the acetic acid taken into the chloroform becomes too great to tolerate. This acetic acid interference may be readily removed simply by washing the chloroform phase '\\-it,h watcr. Chloroform-insoluble acids such as citric or tartaric cannot he used as they complex aluminum. Masking Agents. The dilute acetate solution will prevent thorium from precipitating as the hydroxide a t pH 5 and higher, but it does not prevent large quantities of thorium from being oxtracted by a solution of 8-quinolinol in chloroform. The sodium salt of 4-sulfobenzenearsonic acid serves as a soluble complexing agent for thorium under certain conditions, but it precipitates thorium a t medium concentrations in acid solution. Once this precipitate forms it cannot be readily redissolved by dilution. ;Zn analysis of this precipitate indicates the formula (SaSO3C6H,.4sOj),Th. Thorium hydroxide s l o ~ l y precipitates when the pH of a solution of thorium and 4-sulfcbenzenearsonic acid is raised from 3 to 4. I n the presence of the ammonium acetate-acetic acid solution the thorium complex with 4-sulfobenzenearsonic acid is more soluble. Thorium hydroxide \vi11 not precipitate and this mixture adequately masks thorium, preventing its extraction by a solution of 8-quinolinol in chloroform. As high as 0.5 gram of thorium may be held in 100 ml. of solution in this manner, but the stability of such a solution is low. These higher concentrations also occasionally lead to emulsification upon ,estraction. -4more practical limit. in this volume is 0.25 gram of t,horium per 100 ml. On standing for more than a day, a precipitate of the thorium salt of the arsonic acid may form in this mixture. A sodium acetate solution was substituted for the ammonium acetate solution, but the stability of the resulting mixture was much lower both on standing and during extraction. The stability of the thorium solution is also dependent on the order of addition of reagents. Precipitation is prevented by adding the thorium to the mixture of 4snlfobenzenearsonic acid and ammonium acetate solutions. The molar ratio of 4-sulfobenzenearsonic acid to thorium must be a t least 2 to 1 in order to prevent thorium from being extracted into the chloroform-8-quinolinol phase. Attempts tostudy the thorium-4-sulfobenzenearsonate-ammonium acetate complex spectrophotometrically in t'he ultraviolet region proved unsuccessful. .4high frequency titration also failed to give additional information concerning the nature of this complex. One gram of thorium is sufficiently masked in 150 ml. of 6 M acetate solution a t pH 5 so that less than 0.2% of the thorium is extracted by a 1% solution of 8-quinolinol in chloroform. Under these conditions the aluminum extraction is not affected. -4 second extraction of the chloroform phase with a 1 M acetate solution efiectively removes the extracted thorium as well as
25 1 most of the extracted acetic acid. The use of a concentrated acetate solution as a masking agent for thorium avoids the preparation and time-consuming purification of the sodiiim salt of 4-sulfo5enzenearsonic acid. I t also allows a larger thorium sample to be taken for analysis, as there is no longer the limitation of the solubility of the thorium-4-sulfobenzenearsonate complex. and hence gives greater sensitivity for aluminum This method has the disadvantage of necessitating multiple extractions. Concentrated formate solutions, like concentrated acetate solutions, complex thorium, but the weak aluminum formate complex prohibits the use of formate in this determination.
Table I.
Effect of Various Ions on Determination of Aluminum in Thorium
Ion Added Be(I1) Mg(11j Na(I) K(I) Pb(I1) Fe(1IIj Nd(II1) Si(IV) Ce(II1) hIn(I1) Ni(I1j Cr(II1) Bi(III1
Table 11.
Amount Added,
y
1000 100 100 100 100 100 100 20 20 100 100 100 100 100 100 100 100
Equivalent Positive Error, y A1 Segligible Xegligible Negligible Xegligible Negligible Negligible Negligible Segligible Negligible 0.5 1 1 2.5 8 11 29 32
Determination of .\luminum in Thorium Using .ilkaline Cyanide Wash"
A1 Added, y
Other Ions Added. y
30.0 30.0 30.0
Kone Sone
100 Cu and Zn 100 Cu and Zn 30.0 1 gram of thorium present in each case.
A1 Found, y 30.0 30.2 30 7 30.2
Other Interferences. Trace quantities of iron, which are always present in the samples as well as reagents, seriously interfere with the aluminum determination. This interference may be completely and conveniently eliminated by complexing the iron with 1,lO-phenanthroline. Care must be taken when working in concentrated acetate solution to allow ample time for complete formation of the tris(1,lO-phenanthroline)iron(II) ion. Iron may also be determined by measuring the absorbance of this reddish-orange colored complex a t a wave length of 515 mw. The 1,IC-phenanthroline appears only slightly to decrease interferences from copper, zinc, cobalt, and nickel. Table I presents the results for a number of ions using the first of the recommended procedures. The interferences from copper, nickel, cobalt, and zinc are completely eliminated by mashing the chloroform-8-quinolinol extract with an alkaline cyanide solution (3) as given in the recommended procedure. h tinge of red frequently forms in the solutions when the bis(8-quinolinolo)copper(II) is removed with the cyanide solution. This has been used by Feigl (2) as a spot test for copper. The color does not interfere with the aluminum determination. Results showing the removal of copper and zinc interferences are presented in Table 11. The presence of trace quantities of fluoride ion is important in expediting the solution of thorium metal. I n the absence of thorium, the strong complex formed between fluoride and aluminum strongly interferes with the aluminum extraction. However, in this case the large amount of thorium allows limited quantities of fluoride ion to he tolerated so that it may be used to aid
252
ANALYTICAL CHEMISTRY
in dissolving the sample. The extent of the fluoride interference using the first of the recommended procedures is shown in Table 111. Perchlorate ion interferes, as it forms an insoluble salt with tris(1,lO-phenanthroline)iron(II) ion which extracts into the chloroform phase. RECOMMENDED PROCEDURES
Masking with 4-Sulfobenzenearsonic Acid. Keigh about 1 gram of thorium metal into a 100-ml. beaker and dissolve by warming with 50 ml. of 1 to 1 nitric acid and 1 t o 2 nil. of dilute fluosilicic acid solution. Evaporate the excess nitric acid and dilute to volume in a 100-ml. volumetric flask. Take an aliquot containing approximately 0.25 gram of thorium and transfer to a 150-ml. beaker containing 25 ml. of the dilute acetate solution, 20 ml. of the l,l0-phenanthroline solution, 1 ml. of the hydroxylammonium chloride solution, and 10 ml. of the 4-sulfobenzenearsonic acid solution. Dilute to approximately 100 ml. and accurately adjust the pH to 4.80. Allow 15 to 20 minutes for complete formation of the tris(1,lO-phenanthroline)iron(II)ion. Prepare a blarik containing all reagents in the same concentration and a t the same pH. Transfrr the solution to a 250-ml. separatory funnel and add exactly 20 nil. of the solution of 8-quinolinol in chloroform to both. Shake once, release the pressure, and then shake for 3 minutes. .Illow the phases t o settle for a few nunutes. Draw o f f the lower chloroform layer into a 25-1111. glassstoppered Erlenniever flask containing 1 to 2 grams of anhydrous sodium sulfate. Shake well and allow to stand for 15 minutes to ensure dryness of the chloroform before measuring the abeorbance on the spectrophotometer a t 390 nip.
A caliiiration curve is obtained by preparing a series of solutions containing about 0.25 gram of thorium and var!.ing known amounts of aluminum from 10 to 120y. These solutions are treated as was the aliquot above. In this case the blank solution must contain thorium as well as all other reagent,s, unless completely aluminum-free thorium has been prepared. The plot of absorbance against micrograms of aluminum per 20 ml. of chloroform-gquinolinol solution conforms to Beer’s law over the concentration range of 0 to 120y of aluminum per 20 ml. of chloroforn-8-quinolinol solution. Masking with Concentrated Acetate Solution. Prepare the thorium sample as before, using 2 t o 3 grams of thorium metal. Take an aliquot cothining approximately 1 gram of thorium and add to it 1 nil. of the hydroxylammonium chloride solution and 20 nil. of the 1,lO-phenanthroline solution. ;\fter allowing a few minutes for complete formation of tris( 1,lO-phenanthro1ine)iron(I1) ion, add 100 ml. of the concentrated acetate solution. .4djust the p H to 4.80. Prepare a blank containing all reagents in the same concentration and a t the same pH. Transfer to a 250-ml. separatory funnel and extract as before with 20 nil. of the chloroform-8-quinolinol solution. Transfer the chloroforn-8quinolinol extract to a 250-nil. separatory funnel contaiiiing 25 ml. of the dilute acetate solution, 20 ml. of the 1,lO-phenanthroline solution, 1 ml. of the hydroxylammoniuni chloride solution, and 50 nil. of water. Extract again, draw off the chloroform-8quinolinol phase, dry, and mcasure the absorbance of the tris(8quinolinolo)aluminum(III) at 390 mp. If zinc, copper, cobalt, and nickel interferences are to hr removed, transfer the chloroforni-8-quinolinol extract from the second extraction to another separatory funnd coiitaining 100 ml. of the alkaline cvanide solution. Extract as liefore, drain the chloroform-%quinohnol, dry, and measure thc absorbance of the tris(&quinolinolo)aluminum(III) at,385 nip. This wave lrngth is recommended here rather than 390 mp, as all acetic acid interference has been removed. Prepare a calibration curve by analyzing a series of solutions containing thorium and varying known amounts of aluminum by this procedure.
S o attempt was made to separate the phsses quantitatively. The accuracy of the procedure rest.s upon duplication of concentration of the tris(gquinolinolo)aluminum(III) in the chloroform -8-quinolinol phase. Quantitative separations may be made by simply washing each extracted solution with additional 1% solution of 8-quinolinol in chloroform and diluting the extract and washings to an exact volume. The slight increase in accuracy of the latter method is offset by the additional time required and hence is not recommended. Table I V shows the substantially good agreement between the
-_ Fluoride Interference in Determination of Aluminum in Thorium“
Table 111.
.41 Added, -I
48
30.0 30.0 30.0 30.0 30.0 30.0 30 0 30 0
Fluoride Added, y XaF As H?SiFe
.. io0
... ...
... ..
100 300 300
...
500 1000
, . .
..
A I Found, Y
30 0 30.2 30.1 30.5
27.7
80.4 30 5
29.6
0.25 gram of thorium present in each case. -
Table IV.
Comparison of Proposed Chemical and Spertrographic Procedures Average F.P AI. of .I1 Found Spectrographic ______
Sample
Chemical Laboratory 1 Thorium Metal
Laboratory 2
Thorium Oxalate’ 10 11 12
12 13 16
13 14 15
26 25 23
10 10 10
10 5 10
Thorium Oxidea 10 10 10
10 10 10
.411 samples converted to nitrate before analysis
extraction-spectrophotometric and the spectrographic procedures for determining aluminum in thorium. The thorium for these analyses was of such high purity that no attempt was made to remove the zinc, copper, nickel, and cobalt interferences. Slight interferences from these elements probably account for the greater amounts of aluminum found by the chemical analyses. OTHER APPLICATIONS
hluminum may be determined by the proposed method in a n y thorium sample which can be converted to the nitrate. In aiidition, trace amounts of other elements such as iron. copper. : i i i i i zinc could possibly be determined or a t least estimated by chloroform-8-quinolinol extraction. LITERATURE CITED
(1) *Uexander, J. W., “Summaries of Doctoral Dissertations, University of Wisconsin,” Vol. 6, p. 205, Madison, Wis., Unirer-
sity of Wisconsin Press, 1942. (2) Feigl, F., “Qualitative Analysis by Spot Tests,” p. 47, 2nd English edition, New York, Xordeman Publishing Co., 1939. (3) Gentry, C. H. R., and Yherrington, L. G., Anal2/st, 71, 432 (1946). (4) Herrington, B. L., and Ytarr, SI. P., IND.ENG.CHEM.,;\s.u.. ED.,14, 62 (1942). (5) Moeller, T., Ibid., 15,347 (1943). ( 6 ) Jloeller, T., and Cohen, A. J., J . Am. Chem. SOC.,72, 354F (1950). (7) Oneto, J . F., Ibid., 6 0 , 2058-9 (1938). (8) Sprain, W., and Banks, C. V., Anal. Chim. Acta, 6 , 363 (1952). (9) Stone, K. G., and Friedman, L., J . A m . Chem. Soc., 69, 209 (1947). (10) TYrlcher, F. J , “Organic Analytical Reagents,” Yol. 4 , pp. 54-5, Yew York, D. Van Nostrand Co., 1948. (11) Kiberley, S. E., and Bassett, L. G., ANAL.CHEM.,21, 609 (1949). RECEIVED for review September 17, 1952. Accepted Sovember 10, 1952. Contribution No. 206 from t h e Institute for Atomic Research and Department of Chemistry, Iowa State College, Ames, Iowa. This work was S U P ported in part by the -4tomic Energy Commission.
