Spectrophotometric Determination of Platin um with N,N ’-Bis( 3- dimethy Ia mino propy I)dithiooxa mid-e Simultaneous Determination * ‘. of Platinum and Palladium WILLIAM D. JACOBS Department of Chemistry, University of Georgia, Athens, Go.
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Platinum(1V)reacts slowly with N,N’dimethylaminopropy1)dithiooxamide in a strong hydrochloric acid solution. However, when platinum(lV) i s reduced to platinum(ll), the reaction proceeds rapidly a t room temperature. Factors affecting the analytical use of the reagent were studied. The rose-colored platinum complex has an absorption maximum a t 515 mp. Color i s developed rapidly in solutions approximately 4.8M in hydrochloric acid, where studies indicate that a complex i s formed between 1 mole of platinum and 2 moles of the reagent. Beer’s law i s obeyed over the range investigated, 0.30 and 12.0 p.p.m. The sensitivity of the reaction is 0.009 pg. per sq. cm. Relatively high concentrations of rhodium(lll), iridium(lV), iron(lll), cobalt(ll), nickel(ll), and gold (Ill) can b e tolerated as can smaller concentrations of ruthenium(lll), osmium (VI), palladium(ll), and copper(l1). Platinum and palladium may b e determined simultaneously b y measuring the absorbance of a sample a t 515 and 427 mp, respectively, and then b y calculating the concentrations of each element from spectrophotometric equations derived from known molar absorptivities of the two complexes.
bis(3
I
RECENT INVESTIGATIONS of the color reactions between N,N’-bis(3 dimethylaminopropy1)dithiooxamide and rhodium (3), palladium (2), and ruthenium (4, platinum formed a rose-colored solution with this reagent in the presence of high concentrations of hydrochloric acid. Color developed very slowly a t room temperature. In a boiling water bath color developed in approximately l / 2 hour. Color reaction in both cases is believed to be due to the reaction of quadrivalent platinum by excess reagent to the more reactive bivalent state. If this is true, reduction of the platinum prior to the addition of the reagent should cause rapid development of color. This paper describes a study of the reaction when platinum(1V) is reduced with sodium sulfite to plstinum(I1).
N
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0.6
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I
8
W
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2
100
%
Relative to
Platinum 107 507 1540 40
Ir( IV) Ru( 111) Os(V1) 20 ~. Cu(I1) 500 Co(11) 1330 Ni(I1) 1330 Fe(II1) 1550 ,414 111) 1670 Sulfate Nitrate a Simultaneous determination of palladium and platinum will allow greater concentrations of palladium. Table 111. Molar Absorptivities of Platinum and Palladium Complexes 427 Mp 515 Mp CP t 3,570 19,900 €Pd 13,300 800
Equations derived from above values: (Pt) x 106 = 5.07 A , 515 mp - 0.31 A , 427 m.u (Pd) X 106 = 7 . 6 0 A . 427 mp - 1 . 5 0 A , 515 mp
The author thanks the Mallinckrodt Chemical Works for their gift of the N ,N’-bis( 3 - dimethylaminopropyl) dithiooxamide used in this work. This investigation was supported by a research grant NSF-G13515 from the National Science Foundation. LITERATURE CITED
(1) Harvey, A. E., Manning, D. L., J. Am. Chem. SOC.72,4488 (1950). (2) Jacobs, W. D., ANAL.%EM. 32, 512 (1960). 13) Zbid.. D. 514. (4j Jacob;, W. D., Yoe, J. H., Talanta 2, 270 (1959). (5) Sandell, E. B., “Colorimetric,, D e termmation of Traces of Metals, 3rd ed., p. 83, Interscience, New York, 1959. (6) Ibzd.. D. 97. (7) Zbid.; b. 103. (8) Ibid., p. 726. (9) Vosburg, W. C., Cooper, G. R., J . Am. Chem. SOC.63,437 (1941). (10) Yoe, J. H., Jones, A. L., IND. ENQ. CHEM.,ANAL.ED. 16, 111 (1944).
RECEIVEDfor review March 9, 1961. Accepted May 1, 1961. Paper presented at Southeastern Regional Meeting of the American Chemical Society, Birmingham, Ala., November 3-5, 1960. VOL 33, NO. 9, AUGUST 1961
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