ACKNOWLEDGMENT
Table VII.
Metal Mn(11) co
Equilibrium Constants of Metal-PAN Complexes
Log K D X (It0.2)
No. of protons released on Metal: PAN complex ratio in formation complex
... 2.4c
Xi(I1)
...
Cu(1I)
3.6
Zn(I1)
4.0
2 2b
a
K H
1:2 1:2b
(15.3)“ 16.4b
1:2
...
...
1:2b
1
1:l 1:2b
26
Log
...
1 I*
2b 2 2b 2
Log K f (k0.5)
1:l 1:ld
1:2 1:2b
... ...
25.3b 12.6 16d 21.8 21. 7 b
We are grateful t o Giuliana Grassini of the University of Rome and t o Barry 1lcCoy for carrying out some preliminary extractions with P-IX, and t o Gordon Tollin for obtaining the electron spin resonance spectra.
...
LITERATURE CITED
...
... ...
_ _ 1 I.
-6.9
... ...
...
Assuming log K D X = 4. Yalues determined potentiometrically in 50% aqueous dioxane (6). CHCL used as organic phase. Values determined spectrophotometrically (6, 9).
complex, ZnR2(0H)-, is being formed, both of which would be insoluble in the organic phase; but in both cases an ion pair, possibly the sodium salt, could extract a t high pH. The data which show the dependence of extraction upon reagent concentration a t high p H indicate t h a t the formation of ZnRs- is unlikely. The application of Equation 4 shows that the species extracted at p H 11.6 is different from that extracted at p H 7. If the increase in the total metal concentration in the aqueous phase is due to the formation of the ionic species ZnRp(0H) -, between p H 7.5 and 9.0, it can be shown that the distribution ratio of the metal is given by :
p H 9.5 and 11.5. It can be shown that the extraction of ZnR2(0H)-; S a + would be independent of p H but dependent upon the sodium ion concentration. I n the experiments the sodium ion concentration n-as essentially constant. CONCLUSION
With the exception of the nickel(I1)PAN system, there is good agreement between these results and the results found in a parallel potentiometric and spectrophotometric study (6, 6). Very stable PAX complexes have been found, in accordance with PAN acting as a tridentate ligand. The equilibrium (61
If in the region between p H 7.5 and 9.0, Equation 6 applies, K f B is approximately However, the extraction of ZnR2(0H)-; S a + does not explain the rest of the distribution curve between
298
ANALYTICAL CHEMISTRY
(1) Berger, W.,Elvers, H., 2. m a l . Chem. 171. 255 11959). ( 2 ) Bisev, 14.. I.,’ Kiseleva, L. V., Vestn. Mosk. L-niv. 4 , 179 (1958); Anal. A h d r ., 6 -, 3174 (14.5Q) , - _”,.3) Cheng, K. L., ilsa~. CHEY.30, 1027 (1958). 4) Cheng, K. L., Bray, R. H., Ibid., 27, 782 (1955). 5) Corsini, A,, Fernando, Q., Freiser, H., Inorg. Chem., in press. (6) Corsini, .4.,Yih, I. X - L . , Fernando, 0.. Freiser. H.. ASAL. CHEM.34. 1090 (i962). (7) Geary, TI7. J., Kickless, G., Pollard, F. H., Anal. Chim. $eta 27, 71 (1962). (8) Goldstein, G., Manning, G. L., Menis, O., ANAL.CHEW31, 192 (1959). (9) Pease, B. F., Williams, 11.B., Ibid., 31. 1044 (1959). (10) ’Shibata, S.,’Anal. Chim. Acta 22,
constants obtained in this study are summarized in Tables VI and VII. rt70rk is in progress with similar azo compounds and it is hoped to elucidate some of the anomalies observed in the extraction of metal-PAN complexes.
--.1
479 I1 9601. \ - - - - I -
( i i j Ibid., 23, 367 (1960). (12) Ibid., 25, 348 (1961). (13) Snavely, F. H., “Investigations of the Coordinatinn Tendencies of o-Substituted Aryl-Azo Compounds.” Department of Chemistry, Pennsylvania State College, 1952. (14) Staten, F. W.,Huffman, E. W. D., ANAL.CHEY.31, 2003 (1959). RECEIVED for review September 7 , 1962. Accepted December 12, 1962. Financial assistance received from the U. S. Atomic Energy Commission.
Correction
A Mercury Derivative-Chromatographic Method for the Separation of Unsaturated Fatty Acid Esters I n this article by D. E’. Kuemmel 1003 (1962)] on page 1004, column 3 under the heading “Chromatography,” the flow rate should read “1.5 to 1.8 ml. per minute.” [ ~ A L CHEM. . 34,
