different effects. The stability of the 8-quinolinol complex is apparently unaffected ab evidenced by a negligible change in the absorbance of the solution at 365 mp. There is, however, a 25% decrease in emittance from the solution, but this is to be expected and is in keeping with the general effect of an increase in the polarity of a solvent on the quantum yield of fluorescence ( I d ) . Addition of the water to absolute ethyl alcohol solutions of the 2-methyl complex produces a rapid decrease in both the absorbance a t 365 mp and in the fluorescence intensity; within about eight minutes these spectral quantities are reduced to almost zero. Complete destruction of the aluminum-(2-methyl8-quinolinol) complex and replacement of the ligand by water or perhaps by the hydroxide ion is indicated. Further kinetic studies are in progress.
fluorometer used in this study (Figure 4). Solutions of the complex were essentially stable if stored in the dark for up to 13 days, but decomposed in less than 3 days if exposed to normal room radiation. When the apparent-pH was above 8 the rates of the formation and decomposition reactions were quite different. As shown in Figure 4 the time required to reach maximum fluorescence intensity was now much longer, 60 minutes, and there was also noticeable decomposition within 90 minutes, although the maximum fluorescence intensity was about the same as that observed from equivalent solutions a t slightly lower apparent-pH values. This acidity effect on the formation and photolytic decomposition was not evident with the aluminum-8-quinolinol complex. Effect of H20. The addition of enough water to absolute ethyl alcohol solutions of aluminum complexes with 8-quinolinol and with 2-methyl-8quinolinol t o make the solution 95% in ethyl alcohol produces strikingly
LITERATURE CITED
(1) Bailar, J. C., Jr., “Chenfitstry of the Coordmation Compounds, pp. 238, 239, Reinhold, New York, 1956.
(2) Irving, H., Butler, E. J., Ring, M. F., J. Chem. SOC.1949, 1489. (3) Kolthoff, I. M., Sandell, E. B., “Textbook of Quantitative Inorganic Analysis,” 3rd ed., p. 321, Macmillan, New York, 1955. (4) Merritt, L. L., Jr., Walker, J. K., IND.ENG.CHEM.,ANAL. ED. 16, 387
_ .
Ibid., 41. (9) Phillips, J. P., Emery, J. F., Price, H. P., ANAL.CHEM.24, 1033 (1952). (10) Phillips, J. P., Huber, W. H., Chung, J. W., Merritt, L. L., Jr., J. Am. Chem. SOC.73,630 (1951). (11) Phillips, J. P., Price, H. P., Ibid., 4414 (1951). (12) Pringsheim, P., “FIuoreaence and Phosphoresence,” Interscience, Kew York, 1949.
RECEIVEDfor review March 15, 1962. Accepted June 13, 1962. Work was supported in part by the Research Corporation.
Temperature Effect on the Polarographic Oxygen Electrode ROBERT B. RAYMENT U. S. Navy Electronics laboratory, San Diego 52, Cafif.
The constants A and B depend on the permeability of plaatic through which oxygen must diffuse before being reduced a t the platinum electrode. Differentiation of the equation showed that the permeability of 1-mil Teflon increases by 2.3 times that of 1-mil polyethylene per degree rise in temperature; also, the platinum electrode displayed a photoelectric effect. To establish clearly the behavior of. the oxygen electrode when affected by temperature, it was necessary to find an analytical equation relating oxygen concentration in sea water, temperature, and current.
,The improved polarographic electrode was studied to determine its behavior under temperature effects, an empirical differential equation was formulated, and the relative permeabilities were compared. The study also revealed that light appreciably affects the electrode by increasing the current.
D
ETERMINATION of
the oxygen electrode temperature dependence showed that di/dc = AT+eBT where i is the current, c is the sea-water oxygen concentration, and T is the absolute temperature.
:
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Figure 1
.
A double-sized model of the CarrittKanwisher ( I ) dissolved-oxygen analyzer was made a t the U. $. Navy Electronics Laboratory, San Diego, in early 1960. A tank was also available in which the temperature of sea water could be maintained within ~ 0 . 0 0 2 ”C. The temperature of water in the tank was raised to about 30” C. A 1foot layer of carbon dioxide was allowed to settle above the water to displace dissolved air, the water thus freeing a considerable amount of dissolved oxygen in accordance with Henry’s law. The temperature was next lowered to 25” C. and water
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PROCEDURE
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Oxygen-current isotherms, polyethylene
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Oxygen-current isotherms, Teflon VOL 34, NO. 9, AUGUST 1962
1089
samples were taken, their oxygen content being determined by the Winkler method. The current was observed at the same time. This was repeated at 5" intervals until 10' C. was reached. At this point the carbon dioxide layer was removed and the water allowed to become air saturated. While the equilibrium waa being established, samples for oxygen analysis were taken a t every 5" until the temperature reached 25" C.
20001
I
The isotherms for polyethylene and Teflon (Figures 1 and 2) show that the current, i, in microamperes bears a linear relationship to the concentration of dissolved oxygen. However, if the logarithmic product of the current derivative with reference to concentration (dildc) and the absolute temperature, T, are plotted as a temperature function, a linear curve results (Figure 3). The respective differential equations of polyethylene and Teflon are: di/& = 7.57 X l O - T - W Q a 7 T (1) di/& = 5.37 x 10-9T-1e0.~7T(2)
The diffusion coefficient of most substances in water solution increases by about 2.5% per degree. This is the coefficient of decrease of viscosity ( 2 ) . But by differentiating the above equations with reference to temperature,
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Figure 3. curves
RESULTS
I
Permeability-temperature
the per cent increase in current, per degree per unit change in the oxygen concentration, is 3.97 - 100/T for polyethylene and 8.67 - 1OO/T for Teflon. The inference is that these values are greater because of the increased permeability of the membranes aa the temperature increases. Teflon's permeability i n c r w e per degree is approximately 2.3 times that of polyethylene. Both membranes should be identically permeable at 28.3' C., shown by the intersection of the extrapolated curves (Figure 3). Photoelectric Effect. During the calibration of a temperature-compensated oxygen electrode, sunlight directed through water and onto the platinum electrode by a mirror in-
stantly increased the current by 15%The current returned to ita former level instantly each time the light waa removed. No change in the current mas detected when the light waa directed on the silver-silver oxide electrode. The work function of platinum is too high for photoelectric emission unless the presence of oxygen on ita surface is sufficient to decrease ita work function. This effect could also be due to photosynthesis, but in this example the water contained no living matter. ACKNOWLEDGMENT
The program of research was made possible by the U. S. Navy Electronics Laboratory, under whose authority i t was conducted. Thanks are due to Graham Marks and Albert Hudimac for a critical review of the paper, to Palle Hansen and Charles Curtis for helpful suggestions, and to William Armstrong and Joseph Thompson for making the electrode. LITERATURE CITED
(1) Carritt, D. E., Kanwisher, J. W., ANAL.CHEM.31,5 (1959).
(2) Glasstone, Samuel, "Introduction to Electrochemistry," p. 452, Van NWtrand, New York, 1946.
RECEIVED for review March 20, 1962. Accepted June 4, 1962.
Potentiometric Investigation of the Metal Complexes of 1-(2-PyridyIazo)-Znaphthol and 4-(2-Pyridy1azo)- resorcin01 ALFIO CORSINI, INGRID MAI-LING YIH,' QUINTUS FERNANDO, and HENRY FREISER Deparfmenf of Chemisfry, University of Arizona, Tucson, Ariz.
b The acid dissociation constants of 1-(2-pyridylaro)-2-naphthol and 4(2-pyridylazo)-resorcinol and the formation constants of the metal chelates formed by these reagents with Mn(ll), Co(ll), Ni(ll), and Zn(ll) have been determined potentiometrically at 25' C. in 50 volume yo dioxane-water. The chelates of both PAN and PAR, with these metal ions, have a metal-ligand ratio of 1 to 2. The order of decreasing stability for the PAN and PAR chelates was found to be Ni Co Zn Mn.
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dyes have assumed importance in analytical chemistry, particularly as metallochromic indicators. In recent years two such dyes, 1-(2=pyridylazo)-2naphthol RTHOHYDROXYAZO
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ANALYTICAL CHEMISTRY
(PAN) and ~(2-pyridylazo)-resorcinol (PAR), have received considerable attention in analytical determinations. PAN was first introduced by Cheng and Bray (2, 3) as a metallochromic indicator for the complexometric titration of Cu/II), Zn(II), and In(II1). Since then, it has been used both as a metallochromic indicator (4, 6-9) and a colorimetric reagent (11, lie), and for the solvent extraction and the subsequent colorimetric determination of a number of metal ions (19). In spite of the interest in PAN, little information is available on the formation constants of its chelates, even though a knowledge of these constants is essential for an understanding of complexometric titrations in which PAN is used. Recently, Pease and Williams (17) found that the formation constant of the 1
to 1 Cu(I1)-PAN chelate was lo1'. No other study on the stability of the PAN chelates has been published. Because PAR is more soluble in water than PAN, it has been suggested as a more useful indicator than PAN (N), and has been used in the titration of several metal ions (16, 21). PAR has also found use as a colorimetric reagent (18). The stoichiometry and stability of several PAR chelates have received some attention recently. Iwamoto (14) has examined the composition of several PAR chelates, using the method of continuous variation, and has reported
1 Present address, Department of Chemistry, University of Pittsburgh, Pittsburgh 13, Pa.
