NOTES
July, 1960
pronounced in the activated complex. An analogy is D1 reactions. The differences in ground found in the Hz state energies for Hz and Dz account for the differences in their activation energy for hydrogenation.’
+
Summary 1. The experimental evidence points to a mechanism in which the attack of the methanol takes place a t the carbonyl carbon in both acetates studied. Steric hindrance is not a predominant factor. 2 . A suitable criterion for elucidation of reaction mechanism results in the evaluation of the entropy of activation as well as in the energy of activation. 3. Gas-liquid partition chromatography lends itself to studies in chemical kinetics. Acknowledgments.-The authors are indebted to members of the research staff of the Electrochemicals Department for their encouragement. The work of Mr. J. A. Love who conducted many of the experiments is also appreciated. (6) C. K.Ingold, Chem. Reus., 16, 225 (1934). (7) S. Glasstone, “Textbook of Physical Chemistry,” D. Van Nostrand Co., Inc., New York, N. Y.,1940,p. 1104.
T H E TWO CRYSTAL FORMS OF
(ETHYLENE-DINITRIL0)-TETRAACETIC ACID BY R. B. LEBLANC AND H. L. SPELL Teaad Division, The Dow Chemical Company, Freeport, Tezas Received February 11, 1060
A very great number of papers have appeared in the literature on (ethylene-dinitri1o)-tetraacetic acid (EDTA). Most of them concern the analytical applications of this compound and the chelation of it with metal ions.*J The properties, including acid-base constants, have been studied.sJ The infrared spectrum of this compound has been reported,’ but no mention was made that it has more than one form. During a routine infrared analysis of some EDTA precipitated by addition of acid to a solution of the sodium salt a spectrum was obtained which did not match the standard spectrum of EDTA. Chemical analysis proved the compound to be EDTA with a “different” spectrum. Further work was done to substantiate that there are two forms of EDTA. Experimental When EDTA is precipitated by acid addition to a 8 0 1 ~ tion of one of its sodium salts at room temperature, the low temperature form (a) is produced. Precipitation a t a temperaturc near the boiling point of water produces the high tt.mpernture form (6). Most commercially available EDTA is the 6-form since high temperature precipitation usually gives a purer product. The published infrared spectrum1 is for the pform. The a-form can be converted to the @-formby suspending some of the former in water and boiling for a short time. Attempts to convert the 8-form to the a-form by a similar (1) D. Chapman, J. Chem. Soc., 1766 (1955). ( 2 ) H. Flaschka, “EDTA Titrations,” Pergamon Press, New York, N. Y.,1959. (3) G. Schwaraenbach and H. Ackermann, Helo. C h i n . Acta, SO,
1798 (1947). (4) G. Schwarsenbach and H. Ackermann, ibid., 81, 1029 (1948). (6) F. J. Welcher, “The Analytical Uses of Ethylenediaminetetranoetic Aoid,” D. Van Nostrand Co., Princeton, N. J., 1958.
949
met,hod (stirring a suspension of the p-form in water a t room temperature for 24 hours) were unsuccessful. This conversion probably would take place by this method if sufficient time were allowed. The refractive indexes of the two forms were measured by microscopy. These values are a-form: 1.53-1.54 8-form: 1.576-1.620 The infrared spectrum of t8he a-form is shown in Table I. The infrared spectrum of the 6-form was determined by Chapman.’
TABLE I INFRARED SPECTRUM OF THE FORM OF EDT-4 The wave numbers in cm.-1 and the strengths of the bands are listed: vw = very weak, w = weak, m = medium, s = strong, vs = very strong. 670w 1059w shoulder 1380m 713s 1072w 1465m 814vw 1094m 1690vs 856m 1217m 2655w 910s 1235m 2860vw 933w 1260s 2995w 1040w shoulder 1282m 3020m 1348s The X-ray diffraction patterns for the two forms are shown in Table 11.
TABLE I1 X-RAYDIFFRACTION PATTERNS FOR
THE
Two FORMS OF
( ETHYLENEDINITRILO)-TETRAACETIC ACID
The diffraction data were obtained with a Norelco X-ray diffractometer using iron Ka radiation. dA. is listed followed by 1/11 in parentheses. 01 Form 6 Form 7.13( 16) 6.90( 62) 5.58(100) 5.03( 11) 4.68( 12) 4.10( 40) 3.QQ( Q) 3.84( 16) 3.65( 66)
3.61(39) 3.42(26) 3.17( 7) 3.02(28) 2.04( 8) 2.76(13) 2.75( 8) 2.58(12) 2 . 5 0 ( 7)
2.41(5) 2.35(3) 2.28(5) 2.22(71 2.14(5) 2.12(6) 2.02(3) 1.97(3) 1.83(3) 1.80(4)
8.0 ( 13) 6.65( 5) 5.41( 4) 5.14( 5) 4.96( 28) 4.42( 20) 4.01(100) 3.79( 8)
3.61(42) 3.45( 9) 3.32(13) 3.09( 9) 3.02(10) 2.95( 2) 2.79(16) 2.71( 4) 2.58( 4)
2.48( 4) 2.43(11) 2.39( 6) 2.21( 4) 2.14( 2) 2.10( 1) 2.07( 1) 1.97( 1) 1.93( 4)
Discussion
No difference in chemical properties was observed for the two forms of EDTA nor was any difference observed in the physical properties in solution. The difference in physical properties of the two forms can be attributed to two different crystalline structures. Acknowledgment.-The X-ray diffraction work and the refractive index work were done by Knud C. Poulsen and Dr. A. A. Levinson, respectively, both of The Dow Chemical Company. FLAME TERIPERBTURE AND COMPOSITION IN THE ALUMINUMPOTASSIUM NITRATE REACTION BY A. W. BEROER, D. GOLOMB AND J. 0. SULLIVAN Geophysics Corporation o f America, Boston 16,Massachuselta Received Februury 3, 1060
For the purpose of artificial electron cloud generation a t high altitudes,’ potassium vapors were re(1) F. F. Marmo, L. M. Aschenbrand and J. Presnman. Plan&. Space Sei., 1, 227 (1959),st eeq.
950
Vol. 64
SOTES
Plalrlr temp..
"K.
5500
2
2
v,= 11.
111;
0 . 0 0I
010
Pt = 770 atm. 3 2.66 P, = 500 atm. ,819 ,496 ... ,029 4 2 P, = 100atm. ,848 ,145 ... ,015 0 3 P, = 100 atm. , 733 745 ... ,044 6 3 Po = 1 ntm. ,717 ,783 ... ... In addition the Aame consists also of I mole K ( g ) and 0.5 mole 3Tz(g)per mole of KN03.
leased from rocket-borne canisters, by the reaction of aluminum powder with potassium nitrate. In order to estimate the number of free electrons in the flame, obtained by ionization of potassium, flame temperatures were ca1culat)edfor various conditions of release. The following reaction products are considered to be involved in simultaneous equilibria A1203(c), &O(g), AlO(g), Oz(g),and O(g), where c represents condensed and g gaseous phase. X2(g) and K(g) are assumed to act as inert diluents only. Minor products such as NO, N, K + and e- are neglected in estimating flame composition and t'emperat~re.~ Minimizing, thus, the number of products and assuming ideal gas behavior, desk calculation of equilibrium conditions is feasib1e.j Equilibrium concentrations are calculated in the usual way from the mass balance relations and equilibrium equations. The heat of reaction is then compared with the enthalpy change (from the initial t,emperature) of the assumed equilibrium products. The temperature at which heat balance is achieved is defined as the flame temperature. Equilibrium const'ants were calculated from tabulated free energy The heat of formation of the elements in their standard state at 298.16"K. is t'aken as zero. For A1203(c) and ,4120(g), AHro = -400.1 and -39.4 kcal.,/mole, respectively, were a d ~ p t ' e d .A10(g) ~ is usually present in negligible amounts. For E(N03(C) and O(g), AHfO = -117.9 and +59.16 kcal./mole were taken, respectively.* Since all alkali nitrates have similar heats of formation and the enthalpies of the gaseous alkalies are alike (except Li)-no great difference is expected in flame temperature and :?b3
(2) M. A. C O O K , "The Science of High Explosives," Reinhold Publ. Corp., X e w York, K. Y., 1956, p . 389. (3) "Preliminary Report on the Thermodynamic Properties of I& Be, h l g and 91," Natl. Bureau of Standards, Report 6297, 1959. (4) For instance in a 49OO0IC flame a t 500 atm. t h e equilibrium mole fraction of electrons is about 0.003. T h e heat of ionization will not alter substantially t h e flame temperature. On the other hand. such a n electron concentration is detected easily by radioradar techniques. (5) S.S. Penner, "Chemistry Problems in J e t Propulsion," Chapt. 13, Pergamon Press, New York, N. Y . , 1957. (13) E. A . hlickle, "Collected Thermodynamic Properties of 88 Possible Products of Reaction," General Electric Co., E\-andale, Ohio, DF58AGT 111, 1957. (7) R. Altman, "Thermodynamic Properties of Propellant Combustion Products," Rocketdyne Publication, R-669, 1959. (8) "Selected Values of Clhemical Thermodynamia Provertiea," Natl! Burmu Qf Gtandatds, OiMtilar 608, 1P62,
068
52(K)
,008 ,080 .002
4900
,024
4600 io00 3600
composition by substituting other alkalies for potassium. Table I gives the product composition and flame temperature in KN03-A1 mixtures a t constant volume (V,) or constant pressure (Pc). For the constant volume reactions the total pressure (Pt) in the vessel is also calculated. The volume of 165 rnl. in Row 1 is the capacity of the canister necessary to hold (without pressing) a mixture of 2 moles of aluminum powder ( ~ 2 0 0mesh) and 0 Row one mole of potassium nitrate ( ~ 2 mesh). 6 gives the equilibrium conditions at 1 atm. constant pressure. However, preliminary experiments have shown the reaction to be extinguished at atmospheric pressure. In sealed bombs explosioiir are p r o d ~ c e d . ~ According to Table I, the flame temperature increases with increased pressure in the vessel and decreases with increasing dl/KNO3 ratio. The highest (calculated) flame temperatures are obtained in the 2A1: 1KKo3 systems-which is the stoichiometric ratio. As a first approximation, equilibrium electron concentrations are calculated readily from a given flame temperature and the ionization potential of potassium by means of the Saha equation.lo The number thus calculated, however, is reduced during the expansion of the products, due t o recombination processes. An elementary treatment of this problem will be presented elsewhere. Acknowledgment.-This research was supported in part under U. S. Army Signal Corps C0ntrac.t DA4-36-039-SC-78971. (Y) A A ' Berger and L. Aschenbrand, G e o p h y w , Corp of i m r r i c a , Boston 15, M a s s , unpublished results (10) R H Fowler, "Statistical Mechanics," Cainbridar Press, London, 1936, 2nd edition, p 372
THE CALCULATION OF E Q U I L I B R I I X COSSTANTS FROM SPECTROPHOTOMETRIC DA4TA4 BY c. P. SASH Department
o/
Chemtstrg, Cneberszty of Calzfornza, Davis C d ~ j o , n ~ d Received Februarg 16, 1960
Very recently there has been a revival of interest in methods for treating visible and ultraviolet spectral data t o obtain equilibrium eonstants for
