NOTES
3358
Foundation, Grant GP-4274. This work will constitute a part of the thesis of S. R. which will be submitted to the Graduate School of Kansas State University in partial fulfillment of the requirements for the degree of Master of Science.
Pulse Radiolysis of Anhydrous Amines by Larry R. Dalton, James L. Dye, Department of Chemistry, Michigan State University, East Lansing, Michigan
E. R4. Fielden, and Edwin J . Hart Chemistry Division, Argonne Katwnal Laboratory, Argonne, Illinois (Received May 2, f966)
In their original studies, Hart and Boag' demonstrated that the hydrated electron absorption band is altered considerably in 12.2 M aqueous ammonia and in 12.5 Ai' methylamine solutions. In each case the transient absorption peak formed during pulse radiolysis lies beyond 9000 A, the limit of sensitivity of their photographic plates. From the time of these first spectrophotographic observations of the hydrated electron,' it has been assumed that solvated electrons produced by the radiolysis of water and other solvents are analogous to those formed when alkali metals are dissolved in liquid ammonia and amines. Comparison of the spectra of metal solutions with those of the transients formed during pulse radiolysis of the same solvent should form a good test of this assumption. Compton and co-workers2 have shown the spectrum obtained by pulse radiolysis of anhydrous ammonia to be similar to that of metal-ammonia solutions. On the other hand, Anbar and Hart3 reported an absorption maximum a t 9200 A for the transient produced by pulse radiolysis of anhydrous ethylenediamine. They attributed this band to the solvated electron in disagreement with the assignment of Dewald and Dye4 based upon the spectra of alkali metals in et,hylenediamine. The latter investigators found no peak NnnmOn to the various alkali metals in this region and assigned an absorption maximum a t 12,800 A to the solvated electron and loosely bound aggregates of the electron with cations. This disagreement, and the observation of an anomaly in the hydrated electron absorption spectrum in the regon of solvent (water) absorption bands5 (7500 A), prompt,ed US to reexamine the spectra of the transients produced by puke radiolysis of anhydrous The J O U Tof~Physical Chemistry
amines. I n the case of the hydrated electron in water, the anomaly had been shown to be an artifact essentially produced by the effect of scattered radiation on the particular photomultiplier used, complicated by effects due to different illumination intensities. Although an apparent decrease in the radiation-induced absorbance occurs near the ethylenediamine solvent absorption band (10,500 A), by minimizing stray radiation and operating the photomultiplier under constant illumination conditions in a range of proven linearity, the previous results3 were shown to be incorrect. For each of the amines tested, the absorbance continued to increase up to the cutoff wavelength of the photomultiplier used (11,200 A). The band shape is similar to that attributed to the solvated electron in metal solutions in eth~lenediamine,~ although the comparison suffers from our inability to search far enough into the infrared to locate the absorption maxima in the radiolysis studies.
Experimental Section Anhydrous ethylenediamine (Matheson Coleman and Bell) was first purified by fractional freezing and . ~ was distillation as described by Feldman, et ~ 1 This followed by two distillations in vucuo into a quartz bulb attached to the quartz irradiation cell. The first of these final distillations was from a sodium mirror and the second was from an intermediate vessel containing no metal. I n this way, the carry-over of ions by the spray can be avoided. A second sample of ethylenediamine was prepared using a potassium mirror in place of the mirror of sodium. A similar purification procedure was used to prepare the sample of 1,3-propanediamine ("Itheson Coleman and Bell). Ethylamine (Eastman Organic Chemicals) and n-propylamine (Matheson Coleman and Bell) were purified by two distillations in a nitrogen stream followed by two distillations in vacuo as described above. The absorption spectrum of the solvated electron in these amine solvents was determined by examining the decay of absorbance of the transients produced by a 0.4-psec pulse of 15-34ev electrons. The pulse intensity was estimated by determining the absorbance (at 7000 (1) E. J. Hart and J. W. Boag, J. AWL Chem. Sac., 84, 4090 (1962). (2) D. hf. J. Compte;: J. F. Bryant, R. A. Cesena, and B. L. Gehman in "Pulse Radiolysis, M. Ebert, J. P. Keene, A. J. Swallow, and J. H. Baxendale, Ed., Academic Press, London and New York, N. Y.. 1965, D 43. (3) hl. Anba; and E. J. Hart, J. Phys. C h a . , 69, 1244 (1965). (4) R. R. Dewald and J. L. Dye, ibid., 68, 121 (1964). (5) E. M. Fielden and E. J. Hart, unpublished results. (6) L. H. Feldman, R. R. Dewald, and J. L. Dye, Advances in Chemistry Series, No. 50, American Chemical Society, Washington, D. c.,1965, 163.
NOTES
3359
Table I: Initial Absorbance" Produced by Pulse Radiolysis of Amines Wavelength, A
Ethylenediamin-
l,3-Propanediamine
from Na
from K
0.0347 0.0392 0.0426 0.0533 0.0531 0.0622 0.0702
0.0344 0.0405 0.0458 0.0538 0.0601 0.0663 0.0660 0.0755
0.0817
...
7,000 7,500 8,000 8,500 9,000 9,500 10,000 10,900 11,000 11,200
...
0.0841
Ethylamine
n-Propylamine
... .*.
...
...
0.0195 0.0244 0.0270 0.0294 0.0350 0.0388 0.0404
...
0.0086
0.0068 0.0106 0.0109 0.0127
0.0104 0.0117 0.0119
...
... ...
...
...
... 0.0142
...
Corrected to a pulse intensity which gives A = 0.148 a t 7000 A for the hydrated electron from HzO saturated with HSat pH 11.
r
1
0.08
it was necessary to operate a t nearly the same photomultiplier voltage and current (lo)at the different wave lengths. To do this, neutral density filters were used to vary the light intensity.
Results and Conclusions 0.06 d
I
e m 2
0.04
0.02
I
tu
I
,
I
1
1
I
I
A) of the hydrated electron produced by radiolysis of an Hz-saturated aqueous solution at p H 11. Individual pulse intensities were monitored by measuring the charge developed on a capacitor placed in the electron beam. The optical arrangement used has been preA path length of 8.0 cm was viously used. I n order to avoid radiation-induced anomalous absorption measurements in the region of strong solvent absorbance and low photomultiplier sensitivity,
Decay of absorbance for all of the amines was first order with half-times between 2.5 and 3.0 psec. The absorbance a t zero time was obtained from a leastsquares fit of the data. The results, corrected to a common pulse intensity, are shown in Figure 1. For comparison purposes, the spectrum of the infrared band of dilute cesium-ethylenediamine solutions is also shown.4 The absorbance of the metal solution has been adjusted to agree with the present resultsfor ethylenediamine at 9500 A. Within experimental error, all of the amines gave the same spectral shape. The absorbance data are given in Table I. Since it is to be expected that the molar extinction coefficient of the solvated electron will not vary greatly from one amine solvent to another, the electron yields apparently drop by a factor of about 6 from ethylenediamine to n-propylamine. It would be highly desirable to extend these measurements using fast infrared detectors far enough into the infrared to locate the absorption maxima. This would permit direct comparison with the results obtained with metal-amine solutions. Even without this extension, however, the present results show that there is certainly no disagreement between the spectral assignments made on the basis of radiolysis and from the spectra of metal solutions in the same solvent. (7) S. Gordon, E. J. Hart, and J. K. Thomas, J. Phys. Chem., 68, 1262 (1964). (8) J. K. Thomas, S. Gordon, and E. J. H a r t , ibid., 68, 1524 (1964).
Volume 70, Number 10 October 1966
NOTES
3360
Acknowledgments. We gratefully acknowledge the assistance of Larry Feldman, Earl Hansen, and Jay Rynbrandt in solution preparation and data treatment.
I 1000
I
I
900
The System Potassium 8 00
Carbonate-Magnesium Carbonate
-Y 7
by S. E. Ragone, R. K. Datta, Della M. Roy, and 0. F. Tuttle
W
700
a 3
I-
Department of Geochemistry and Mineralogli and Materials Research Labbratory, The Pennsylvania State U n h m a y , UniversBy Park, Pennsylvania (Received June 88,1966)
As a part of an investigation of glass-forming carbonate systems,1 phase equilibria have been determined for the K2COs-MgC0a join of the MgO-K20-C02 system. Starting materials were Fisher certified reagent grade chemicals (see Table I). The usual hydrothermal equipment2 with cold-seal pressure vessels was used, enabling an over-all temperature control of h lo", with a pressure control of +500 psi. Initially, samples were K2C03-iClgC03 mixtures held in sealed Au capsules, but better results were obtained with KzCOr MgO mixtures in unsealed Au capsules open to COZ pressure so that complete carbonation could take place.
;600 W
a I
E
500
n + . +
+
+
+
460' t
* IO
t
400
K2C0,
t MgC03
t I:I
I
300
K,C03 20 K2C03
I : I + MgCO,
40
M 0L
60
E
80
/'e
Figure 1. Temperature-composition projection of the pseudobinary system K&03-MgC03 in equilibrium with 15,000 psi of COZ. Because of experimental difficulty, the melting point of K&03 at this pressure has not been checked. Lower part of diagram represents equilibria a t about 500 psi, where the 1:1 compound,EKzC03.hfgCOs is stable.
Table I : Analysis of Reagents KzCOs
MIZO
Ba, Not, Ca, K, Na, Sr Iron (Fe) Chloride (Cl) Sulfate/sulfite (aS
sod
Heavy metals m (Pb)
P.T. 0.002% 0.005% 0.002%
0.002%
Chloride/chlorate C1) Sodium (Na) Heavy metals &s (Pb 1 Sulfur compounds (as sod
P.T. P.T. 0.0001% 0.0003%
The quenching method was used, in which a charge is held at the desired temperature and pressure for a period of time, quenched rapidly in water to room temperature under the pressure of the run,and examined under a petrographic microscope and by X-ray diffraction. Glass-forming compositions are particularly suited to the quenching method, as they yield a homogeneous glass when quenched from above the liquidus. In borderline cases, it is frequently possible to distinguish between primary phase and quench phase crystal^,^ the latter usually appearing brownish and The Journal of Physical Chemistry
slightly birefringent under the polarizing microscope, or having dendritic and spherulitic growths. Failure to distinguish between primary and secondary (quench) magnesite (MgC03) crystals in preliminary work caused the dissociation temperature to be placed about 100" too high. Distinction can be made on the basis of microscopic form and birefringence. Quench magnesite appears as rhombohedral cleavage fragments formed in preparing slides, the quench mass breaking along cleavage planes when ground. Primary magnesite displays no such cleavage, forming subhedral single crystals instead. Proper high order white birefringence is observed in all primary crystals while secondary crystals are usually high first to second order. Wavy, irregular isochromes provide another indication of secondary quench growth. All compositions near the 1 :1 ratio KZC03-MgC03 (1) R. K. Datta, D. M. Roy, S. P. Faile, and 0. F. Tuttle, J . A m . Ceram. SOC.,47 (3), 153 (1964). (2) R. Roy and 0. F. Tuttle, "Physics and Chemistry of the Earth," Vol. I, Pergamon Press, London, 1956, Chapter VI, pp 138-180. (3) P. J. Wyllie and 0. F. Tuttle, J. Petrol., 1 , 1 (1960).
