Table 111. Effect of Anionic Substances on Determination of Lanthanum
(Lanthanum present, 20
Figure 4. Effect of acetate ion concentration on extraction of lanthanum into 0.1 M TTA in hexone
Concn., ?/Ml.
Anion
so,-c1c104-
PO,--F-
is not made, larger amounts of 2thenoyltrifluoroacetone must be added in order to ensure the complete extraction of lanthanum at p H 5. However, concentrations of chelating agent in excess of 0.1M are to be avoided because unsteady flame conditions often are encountered. Interference Studies. T h e degree t o which other substances interfere n i t h lanthanum extraction a t a p H of 5 from a n aqueous solution 1M in acetate ion is given in Table 11. Barium, chroniium(T’I), lithium, magnesium, potassium, rubidium, and sodium are either not extracted or extracted only in negligible quantities (11). hiilligram quantities of thorium and uranium accompany the lanthanum in the extract; however, a t the concentrations studied, neither thorium nor uranium interfere with the determination of lanthanum in the organic phase. Interference by aluminum and titanium is noted a t all wave lengths, although only relatively high concentrations of these elements and zirconium interfere a t 743 nip. Many interferences are found a t 560 mp; a t this wave length, results are low if aluminum, copper, lithium, neodymium, titanium, or zirconium are present. Of the anionic substances that were tested, phosphate and fluoride interfere seriously by preventing the extraction of lanthanum (Table 111). Application. T h e validity of t h e proccdure was tested by determining t h e lanthanum content in t h e rare earth oxide fraction of a monazite sand from
South Africa a n d in a mixture of residual rare earth oxides designated “didymium oxide.” Both samples were obtained from the Lindsay Chemical Co. Their compositions were reported as follows: Rare Earth Oside Fraction of Monazite Sand
Didymium Oside
22 47 5 16 3.5 -3 -2 -1.5
44 1 9.5 32 5.5 -3 -3 -2
The value obtained for lanthanum oxide in the monazite sand vias 22.2%, rrhich is in essential agreement with the value furnished by Lindsay Chemical Co. For the didymium oxide, an average value of 46.6% lanthanum oxide was obtained, which is somewhat greater than the value reported by the supplier. For both determinations the relative standard deviation !vas approximately 3%. ACKNOWLEDGMENT
The authors acknowledge the assistance of H. P. House and M. A. hiarler in the preparation of this report. LITERATURE CITED (1) Albinati, J. F. de, Anales asoc. quim. arg. 43, 106 (1955). ( 2 ) Bryan, H. A, Dean, J. A,, ANAL. CHEM.29, 1289 (1957). (3) Hillebrand, W. E ., Lundell, G. E. F.,
y
per ml.) Lanthanum Eound, %I at 743 hfcc
960 9600 350 3500 1000 10000
100 Si
950 9500 19 190
83 0 10 0
97 97 99 93
Bright, H. .I.,Hoffman, J. I., “Applied Inorganic Analysis,” 2nd ed., pp. 54958, Wiley, New York, 1953. (4) Ishida, R., J . Chem. Soc. J a p a n , Pure Chem. Sect. 76, 60 (1955). (5) Kelley, &I. T., Fisher, D. J., Jones, H. C., ANAL.CHEM.31, 178 (1959). ( G ) Mavrodineanu,
R., Boiteu.;, H., “L’halyse Spectrale Quantitative par la Flamme.” u. 196. Masson e t Cie. Paris, 1954.’ ( 7 ) Menis, O., Rains, T. C., Dean, J. A,, A
A n a l . C h i m Acta 19, 179 (1958). (8) Moeller, T., Record Chem. Prog. 14, 69 (1953). 19) Piccardi. G.. Gam. chim. ital. 63, 127 ‘ (1938). (10) Rodden, C. J., Plantinga, 0. S., I N D . EXG.CIIE?!I., ANAL. ED. 8, 232 (1936). (11) Suttle, J. F., U. S. Atomic Energy Comm. LAM-936 (AECD-2800)(1950). (12) Willard. H. H.. Gordon. I,.. .4XAL. ‘ CHEX.20,’1G5 (1948). I
,
RECEIVED for review February 15, 1958. Accepted September 22, 1958. Division of Analytical Chemistry, 132nd Meeting, A4CS,New York, N. T., September 1957.
Direct Photometric Determination of Aluminum in Iron Ores-Correction I n the article on “Direct Photometric Determination of Aluminum in Iron Ores” [ANAL.CHEM.28, 1419 (1956)l the last line of the fourth paragraph in the second column should read: T o 8 nil. of this solution add 10 ml. of hydrochloric acid and dilute to 1 liter. 1 nil. = 8 of A.1203. T i . T. HILL
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