DAVID T. PETERSON AND R. ICONTRIMAS
362
8 mole % of added et,hylene however seems improbably high if they are formed by a different mechanism .in the presence of et'hylene than in its absence. If their formation does not involve t,he ethylene then it would appear t'hat the tritium incorporation step must be a hot reaction on CHI (or C2H6or CSHJ followed by a rapid srries of chain lengthening and termination steps not irit'crfwed wit,h by the ethylene. (By contrast to the insensitive yields it may be noted that the yield of isobutane is complet'ely eliminat'ed by ethylene). The reduction in chain lengthened yields by added H, st,rongly suggests that part, of these yields is due to reaction of chain carriers with HT. From a knowledge of the average amount of H2 in t,he system (calculated from the G-value of 5.7 for Hz formation in CITJ, and from the fraction of the tritium found as chain lengthened hydrocarbons compared to that as HT, it may be estimat,ed that if all incorporation of chain lengthened products occurred by R or It+ €IT the C: lor chain lengthening is about unity. This is a reasonable value and t herefore does not exclude t'his mechanism. 'l'hc ohserved effects of int,ensity of radiat,ion indiwtc: that chain lengthened products map possihly be formcd by hot,h intei1sit.y dependent and intcrisity iiidcpcndent reactions. Results on the radiolysis of mixtures of H T and CH, indicate that a midi:~iiiam involving reactions of chainlengthenetl >.pecieswith H T may he important, i n the systems reported here.'5,1fi -1 ,
+
( l j ) R . \V. Alirens. If. (-. Sxiicr, . I r , , ani1 .J. I:. \VilIanl, .I. A m . Chem. S o c . . 79. 3289 (l!l,:7).
Yol. 61
extensive study of the radiation chemistry of HThydrocarbon mixtures with varying amounts of €12 a t varying radiation intensit,ies will be required to understand the observed effects. In considering the observed chain lengthening it should be noted that chain lengthening has been observed in systems which do not contain ions. I, molecules act,ivated by 1849 A. radiation in methane lead to the production of C2He,CIHR, C2HJ, C3H91, etc., as well as CH31 and HI," and chain lengthening has been observed in various other photochemically activated systems where CH2 radicals may be produced.'8-'9 Halogen atoms activated by t'he ( n , r j nuclear reaction undergo hot replacement reactions2U-22 similar to those observed for recoil tritium atoms and also initiate chain lengthening.23 Acknowledgment.-This work has been supported in part by the United States Atomic Energy Commission and in part by the University Research Committee with funds made available by the Wisconsin Alumni Research Foundation. (IO) R. W. Ahrens, Ph.D. thesis, University of Wisconsin, 1959, available froin Vniversity Microfilms, Ann Arbor, Michigan. (17) T. A. Gover and J. E. Willard, J . A m . Ciiem. SOC.,in press. (18) (a) W. E. Doering, R. G. Battery, R. G. Laughlin and N. Cliaudhiiri, J . A m . Chem. Soc., 78, 3224 (IY5t3); (b) H. hl. Frey and (;. 13. IGstinkowsky. zbid., 79, ( 3 7 3 (19.57). (10) W.11. Vrry and J. R. Eiszner, i b i d . , 73,2377 (1951). (201 . I . 1:. IIornig, 0 . 1,evcy and J. E. TVillard J . Chem. P h y s . , 90, ( 2 1 ) (;. I,r\.cy and J. E . Willard, i h i d . . 26, 901 (1958:. (22) A . Gorillis anhcrouiitiiig rate for the three precipitates wis usu:illy 0.45; and always less tlmn 1 5 , .
Reisults and Discussion The distribution coefficient Kd is the atom fraction silver in zinc over the atom fraction silver in liquid lead. The concentration of silver in the zinc phase mas known from the amounts of material charged into the melt and \vas checked by analysis a t concentmtions above 0.5 wt. 70. The concentration of silver in the lead phase was calculated from the concen.tration in the zinc phase and the ratio of the counting rates per gram of each phase. (3) F. Feigl, 2 . anal. Chem., 74, 380 (1928). (4) G , Prierllnndrr rind J. W. Kennedy, "Introrliiction to Rsrliochcmistry," J o l i n Wile,. and Sons, Inc.. Kcw York. N. Y.. IP40.
LEADAND ZIXC
LIQUID
3G3
7 7 -
0 0
438.C 508.C
A 548.C
1 2 3
5
1
,
7 I X i Q ' Z
3
,
# , / / # I
M O L E FHACTION Ag
Fig. 1.-Distribution
I
3 n
I 1 , I I l
,
I
5 7
2
3
ll!ll 5
7
Zn
coefficients of several tenipcr:itures and concentrations.
I
I
I
I2
of log
Kd
I
I
1
13
+x
Fig. P.-V:triatiori
,
1
5 71X103 2
14
10-3
with reciprocal tcmpcrature.
The solubilities of lead in zinc and of zinc in lead, which were needed to calculate the atom fractions, were assumed to be the same as t'he binary solubilities. These were estimated from the data reported by Rosenthal, Mills and Ilunkerley.5 The values used are given in Table I. COMPOSITION O F
Temp., OC.
TABLE I EQUILIBRIUM PHASES SYSTEM n'pb
in Z n
IS THE
.Vzn i n Pb
438 0.0052 0.055 508 ,0082 ,090 548 ,010 ,120 Solubility of zinc in liquid lead whirh present investigation.
LEAD-ZINC .Vzn in I'ba
0.056 ,093 ... W:IS
found in the
The distribution coefficient a t a given teniperature did not change as the silver concentration in the zinc phase was increased from 5.5 X to 4.8 x atom fraction. The values a t each temperature were fitted to an equation of the form Kd = A B N A , by a least squares treatment. The largest number of determinations was made
+
f R J F. D. Roscnthnl, 0 . J. >fills a n d 212. 153 (1958),
F..J.
D i i i i k f i l ~ y .Trans. A I J f E ,
P. A. HOWELL
364
a t 508', and for thcse pointls the value of B was so small th:Lt the iiidicatcd coliccntrat,ion dependence was much sm:Lller than the standard deviation. The concentration dependence a t 548' was also less than the standard deviation. The values of & arc plotted in l'ig. 1 against the logarithm of the silver concentration. The logarithmic ordinate wad; used to expand the concentration scale so that the coefficients a t low concentrations could be shown more clearly. The coefficients at 438' indicate a small concentration dependence of Kd, but this resulted largely from two low values a t the highest concentrations. The larger scatter and simall number of determinations a t this temperature reduce the significance of this variation. The mean distribution coefficient and the standard deviation of the mean were calculated a t each temperature. The values are given in Table I1 and the logarithm of & plotted ag:Linst reciprocal temperature in Fig. 2. The mean values a t each temperature were weighted as the reciprocal of the square of the standard deviation of the mean, and a least squares method was used to calculate the slope and intercept. The enthalpy of transfer of silver from liquid lead to liquid zinc, calculated from the slope, was -10.9 ked. with u standard deviation of 0.13 kcal. TABLE I1 I~TRIBIITIO (COEFFICIENTS N
OF
SILVERBETWEEN T m v m
LEADA N D ZINC Temp., "C.
Kd
438 508 548
55.7 f 2 . 1 2 7 . 5 f 0.5 20.1 f 1 . 1
If the part'ial molar enthalpy of silver in each liquid phase wcre unaffected by the small amount
VOl. 64
of the other component dissolved when the liquid phases were cquilil)r:ited, t,he enthalpy of transfer of silver would be equal to thc partid molar heat of silver in zinc minus the partial molar heat of silver in lead. The partial molnr heat of silver in dilute solutions in lend (reference state pure solid silver) is given by Kleppa6 a s +5.74 kcal. per mole. The partial molar enthalpy of silver in zinc was estimatcd from data compiled by Kubaschewski and Evans? to be between -3.2 and -6.0 kcal. per mole. A lack of data a t low silver concentrations prevented a closer determination of this value. The calculated enthalpy of transfer is -8.9 to 11.7 kcal. per mole of silver. The agreement between the calculated and observed enthalpies indicates that the partial molar enthalpy of silver in liquid lead and zinc is either not changed by saturation with the other liquid phase, or is changed in the same direction in both phases. This agreement also indicates that the enthalpy of transfer of +2.06 kcal. which was observed by Naish2 must be in error. The constancy of the distribution coefficient a t each temperature over a wide range of silver concentration shows that Henry's law is obeyed by silver in both liquid phases or that the deviations from Henry's law in each phase are so similar as to compensate. Considering the wide concentration range over which the distribution coefficient was constant, the considerable difference between the concentration in the zinc and lead phases, and the difference between Ag-Zn and Ag-Pb interactions, compensating deviations from Henry's law are very unlikely. The distribution in this system is governed by the interaction of silver with each liquid phase, and these seem to be identical to the interactions in the Ag-Zn and Ag-Pb binary systems. (6) 0. J. Kleppa, THISJOURNAL, 60, 440 (1956). (7) 0. Kubaschewski and E. L. Evans, " M e t a ~ l u r g i c a ~Therrnochemistry," 3rd mi., Pergarnon Press, New Pork, N. Y., 1958.
JAlM' ANGLE X-RAY SCATTERING FROM SYNTIIETIC ZEOLITES : ZEOLITES A, X AND Y BY P. A. HOWELL Contribution j r o m the Research Lnborntory of Linde Company, Division o j Union Carbide Corporntion, Tonnwanda, N . Y . Received October t9. 19.59
X-Ray scattering has been observed a t low diffraction angles for sevrrd synthetic rrystalline zcolitrs. For hydrous and anhydrous sodium and c:ilcium exchanged forms of zeolite type A, th(1 observed i n t c n ~ i t yin the range 2e = 1 to 5' depends on the cation rontent of the zeolite and the d(1grw of hydration. For hydrous and :mhydroiis sodirim zc~olitcstypes X and Y, the scattering rurves are ch:trackristic of n material possessing a distribution of scattering ol)jthctts of different sizes. The observed scattering probably arises because of the disorder of the cations within thcw crystal striivtrirrs.
Introduction The small tingle X-ray scattering tcchnique has found use in recent years for the characterization of inhomogeneities in various systems usually of an amorphous nature. I In this technique where the X-ray scattering given by a substance a t angles near the main beam is measured and int,erpreted, the magnitude of the scattered intensity and the (1) A. Guinier arid G. Fournet, "Small-Angle Scattering of X-Rays," John Wiley and S a m . Inc., New York, N. Y., Chapter G , p. 167.
angular dependencc of this intensity is determined. The angular dependence can be interpreted in terms of the size and shape of the inhomogeneities of the material while the intensity depends on the difference of electronic density between the inhomogeneity arid its surroundings. In this paper we will show that certain crystalline zeolite minerals scatter X-radiation a t low to moderate angles and that this scattering probably is due to cation disorder in their structures.
