Noms
378
sidered as a displacement reaction l a or as a combination reaction l b 10’ (Id)
Vol. 61 TABLEI Conon.,
Aoid
PAA PAG PAA PAA PAA PAA Glutaric
N
Neutral salt
0.01 -01
None 0.2MNaNOs 2 M NsNOa 1 M KCl 1 M KCI 1 MKCI None
.01 .01
Bo(2c) x 108
&(ab) x 10’
420 460
1050 28 23
420 460
1050 28 138 398 0.174
.06 Both of these constants are well defined because the .1 40 concentrations of all the substances entering these .01 0.174 equations are readily determinable by experiment. The same is not true for binding of cop er to a poly- cause chloride ion forms a strong complex with ciielectrolyte such as polyacrylic acid. Thpis is because pric ion in aqueous solution. The striking disparity there is no direct way of measuring the number of between the values of Bz for PAA and glutaric acid7 adjacent ionized carboxylate sites. This has been emphasizes the need for a more comprehensive aprecognized by H. Morawetz, et for the special proach to this problem in which the electrostatic case of maleic anhydride copolymers. The general terms would be evaluated directly. result is that for polyelectrolytes we may only make The author wishes to thank Joseph Eigner, Eda rigorous test of equation la. ward Chun and Professor Paul Doty for construcGregor, et u L , ~employed equation la in the ex- tive criticism. pectation that it might lead to a formation constant (7) A statistical faotor of 2 favors the Br for PAA metal binding over that would be independent of the net charge carried glutaric acid metal binding. by the polymer since the reaction involves no net change in charge. They considered the displacement reaction of copper with polyacrylic acid to THE ACID DISSOCIATION QUOTIENT OF take place in two steps giving equations‘ 3-HYDROXYL-1 ,%DIPHENYLTRIAZINE
BY R. W. RAMETTE~ AND T. R. RLACKBURN Contribution from Laiuhton Hall of Chsmislry, Carleton Collsos, Norlhfield, Mmn. Received Bsptrmbar 17, 1066
Sogani and Bhattacharya’ reported that 3-hydroxyl-l,3-diphenyltriazine forms an insoluble chewith the over-all competitive complexation constant late with palladium, the latter forming’bonds with the oxygen of the hydroxyl group and the nitrogen farthest removed from this group. The present This procedure is in error because the second step research was concerned with the determination of in the formation of the Cu-PAA complex is not the quotient governing the ionization of the comcorrectly represented by (2b). If the Cu++ in pound as an acid. The quotient is defined as CuAl+ reacts further to form CuAz it is most likely K = (H+)(T-)/(HT) that it will react with an adjacent carboxyl group’ where T- represents the anion and HT the undis, and since the number of adjacent carboxyl groups is sociated molecular form which has the formula two (or less depending on the degree of complexaOH tion) reaction (2b) is independent of (HA). Indeed ~ - N - NI = N / this is the essence of the chelate effect. Thus (2b) should be replaced by (2b)
0
c ~ A ~ C+
+
~ A Ir~+
(38)
leading to The original values of Bz and the corrected values for Cu-PAA are given in Table I and compared with Bz for glutaric acid, the corresponding monomeric analog. The internal consistency between the competitive complexation constants in pure water and NaNOasolution is good, The values in KCl are lower and show a steady increase with increasing PAA concentration. The latter values; are suspect be(3) H. Morawete, A. M. Kotliar and 11. Maik. THte JOURNAL, 68, 619 (1954). (4) H.P.Grepor, e t n l . . ibid., 60, 34 (1955); 69,360 (1855); 69,559 (1955); 60, 990 (1965). (5) See reference 4 for an explanation of the symbolism. (6) Experimental evidence has been oited for thia by F. T. Wall and 8. J. Gill, THIEJOURNAL, 18, 1128 (1864).
.
Apparatus.-Absorbances were measured using silica 1-cm. cells in a Beckman DU s ectrophotometer. The temperature was controlled at 25” gy means of a circulating water-bath and dual thermospacers in the spectrophotometer. Reagents.-The triazine was prepared as described by Sogani and Bhattacharya,’ and waa recrystallized twice from ethanol. Stock solutions were prepared by dissolving weighed amounts in ethanol. Other reagents were of analytical reagent grade.
Experimental A series of solutions containing sodium hydroxide and potassium chloride were repared in 100-ml. volumetric flasks and were auspendecf in a water-bath at 25’. The concentrations were such that upon dilution to the mark the pH ranged from 10.85 to 11.60 (assuming pKw = 13.85) with an ionic strength of 0.050. I n each case, a 2-ml. portion of the stock trianine solution (freshly prepared, about. 1 X 10-8 M in most cases) was added with a pipet, the solution diluted to the mark immediately and mixed, and the absorbance was measured as soon as possible at 300 mp. Instability of the solutions mRde it desirable to take successive readings at known times (every three minutes) (1) N. C. Sogani and 8. C. Bhattsoharya, Anal. Chrm., PS, 81 (1966).
March, 1957
NOTES
and to extrapolate the absorbances back to the values they presumably would have been before any decomposition occurred. It is felt that the uncertainty in this procedure is well under one per cent. Solutions of pH e ual to 6 and 14, containing the triazine virtually completdy converted to the molecular and anion forms, respectively, were prepared and measured in a similar manner. The absorptivity of the molecular form is about 3.3 X lo8 liter mole-' cm.-1 and the corresponding value for the anion is about 2.7 X 10' at 390 mp. It was found that the addition of small amounts of sodium sulfite to the solutions before adding the triazine resulted in improved stability, robably due to the reduction of oxygen, and t8hatthis dignot significantly affect the observed values of K . The absor tion s ectra (approximate, because of instability) of tffe two Lrms are shown in Fig. 1.
Acknowledgments.--It is a pleasure to acknowledge that this research wm supported through the partial use of grants from the Research Corporation and from E. I. du Pont de Nemours and Co. We are indebted to Mr. Herbert Richardson for the preparation of the triazine.
0.G
0.2
350 370 390 Wave length, mp. Fig. 1.-Absorption spectra of the two forms of 3hydroxyl - 1,3 - diphenyltriazine: concentration about 2.5-lo-' M . Curve 1, pH 6,all triazine as molecular form; curve 2,pH 14,all triazine present as anion form.
Results Table I gives the values of K found a t various pH values. The quotient was calculated by means of the formula K = (H+)(A - A&)/(Ab - A ) where A is the observed absorbance of the solution containing both forms, A , is the absorbance of the solution containing the triazine completely in the molecular form, and A b is the absorbance of the solution containing the triazine completely in the anion form, all solutions having the same total concentration,
379
THE SOLUBILITY OF SODIUM HYDRIDE IN SODIUM BY D. D. WILLIAMS,J. A. GRANDA N D R. R. MILLER Chsmislru Diuieion, Naval Rsaearch Laboratory, Waahinglon. D. C. Recaivcd August SO, 1986
As a continuation of the study of impurities in alkali metals' the solubility of sodium hydride in sodium has been determined. This system has implications bearing upon corrosion data interpretation from the standpoint of both direct reaction and apparent oxide content correlation. This impurity in a sodium system can come from two principal sources, hydrogen-sodium reaction (impure cover gas), and as a product of the reaction between sodium and sodium hydr~xide.~J Previous work at NRL2 established two facts pertinent to this study: that sodium hydride resulted from the Na-NaOH reaction a t temperatures above 325", and that the hydride so produced was stable when in solution in an excess of either primary reactant. Stability in NaOH has been shown by Gilbert,4 and mutual solubility of sodium-aodium hydride has been reported by Banus, et al.' The stability in solution results in a lowering of the dissociation pressure of the sodium hydride. Thus, if a sodium system is heated, under other than high vacuum conditions, in order to rid it of any contained h y d r o ~ i d e , ~sodium .~ hydride is introduced as an impurity. A sample drawn from such a system for oxygen analysis, without accounting for the contained hydride would result in erroneous values. The solubility of sodium hydride in sodium was, of necessity, determined by an indirect method, based upon the lowering of the dissociation pressure2s4 of this normally unstable material.2b7.8 Thus, a t a given temperature, a mixture of sodium and sodium hydride will exhibit a true dissociation pressure only so long as the condensed portion of the system consists of two phases: saturated sodium and solid sodium hydride. During stepwise temperature increases the first incremental increase in temperature which failed to exhibit a corresponding increase in pressure indicated the temperature of saturation as the lower of the two temperatures.
TABLE I Experimental DISSOCIATION QUOTIENTO F ~-HYDROXY-~,~-DIPHENYIATRIThree techniques, with different apparatus, were used to AZINE establish the curve for the solubility of sodium hydride in PH K x 1019 PK sodium. Low temperature (240-300") runs were made by 11.30 2.63 11.58 (1) D. D. Williams, J. A. Grand and R. R. Miller, in preparation. 11.40 2.79,2.51 11.55,11.60 (2) D. D. William8, NRL Memorandum Report f33, 1952. 11.45 2.80,2.89 11.55,11.54 (3) A. Klemenc and E. Rvetlik, 2 anorg. Chem.. 269, 153 (1958). (4) H. N. Gilbert, U. 5. Patent 2,377,876 (June 1045). 11.50 2.94,2.85 11.53,11.55 (5) M. D. Banus, J. J. McSharry and E. A. Sullivan, J . A m . Chem. 11.55 2.83 11.55 Soc., 7'7, 2007 (1955). 11 .49,11.52 11.60 3 .23,3.05 (6) J. D. Noden and K. Q. Bagley, Culcheth Laboratories, Tech.
These results give an average value of K = 2.85 (10.14)X 1O-I2.
Note #80,1954. (7) F. 0 . Keyes, J . Am. Chem. Soc., 94, 779 (1912). (8) A. Herold. Compl. rend., 228, 686 (1049).
