J. C.SHIEHAND P. A. LYONS
3258 aliphatic rest are connected with the cyclic system of associated hydroxyl groups. I n the series heptanol-1, -2, -3, and -4, the carbon atoms are bound increasingly rigidly to the system of hydroxyl groups, on the average, so that the probability that neighboring multimers must reorientate at the same moment will increase in the same way. Therefore, in this series the activation enthalpy and entropy also increase, as has been demonstrated experimentally. 'The relaxation behavior of the mixtures of heptanol-1 and heptanol-4 can be explained qualitatively with this model; in these mixtures the relaxation is also caused by the activation of an area in the liquid, and this area is larger the more heptanol-4 the mixture contains. The problem of why the monoalcohols show a principal relaxation range characterized by one relaxation
time is reduced in this way to the same problem as that of why compounds like bromobenzene show one relaxation time. According to Anderson and Ullman,2esuch relaxation behavior must be expected if the environment fluctuates rapidly as compared to the reorientation. The reason for this difference between the various movements in the liquid is not clear, however. Nonetheless, we can explain the most important aspects of the dielectric relaxation of the monoalcohols by assuming that these compounds associate to dimers with a low dipole moment and to cyclic tetramers with a high dipole moment, the latter being retained during the reorientation.
(29) J. E.Anderson and R. Ullman, J. Chem. Phys., 47,2178 (1967).
Transport Properties of Liquid n-Alkanes by J. C. Shiehl and P. A. Lyons Department of chemistry, Yale University, New Haven, Connecticut
06680 (Received February 19, 1969)
+
Mutual and tracer diffusion coefficients supplementing existing data are presented for the systems n-C6Hlr n-ClzH26, n-C&6 n'C16H34, n-CsHl8 n-CleHar,and n-CloHzz n-Cl6H34 deriving from Gouy interferometric and diaphragm cell measurements. Based upon these and other reported data, the transport behavior of n-alkanes can be summarized as follows. (1) The Darken equation holds; Le., D12 = (xlDZ* x2D1* d In fIxl/d In x1 (This is consistent with Van Geet and Adamson's finding for the system n-CsH18 n-Cl~H26.~) (2) The activation energy for the tracer diffusion of any n-alkane is the same in any n-alkane medium a t a given density. I n a medium of a given density, the size of the moving segment is independent of the chain length. (3) For all binary n-alkane mixtures, Dlz/(d lnflxl/d In xl) is a linear function of density, p , All these lines extrapolate to zero mobility a t p = 0.84, corresponding to a supercooled melt of a n n-paraffin of very high molecular weight. The slopes of these lines are linear functions of 1/G2, where nl, n2 are the numbers of carbon atoms in the two components. (4) The tracer diffusion coefficient of any linear alkane C, in any n-alkane medium (either pure liquid or mixture) is determined only by n and the density of the medium a t a given temperature. ( 5 ) Deviation from linearity of plots of DI2against p can be used to determine the thermodynamic terms, d In flsl/d In xl, hence also activity coefficients and excess free energies. (6) Viscosities of n-alkanes (pure liquids or mixtures) are simple monotonic functions of density. These rules describe accurately the transport behavior of those n-alkanes which have been studied and should define those properties for any liquid n-alkane system or melt. Rules 2 and 4 are slightly modified versions of the application of the principle of congruence first used in this fashion by Van Geet and Adamson.2
+
+
+
+
Introduction This study was started to supplement the meager information on transport phenomena in systems with negative deviations from Raoult's law. As the work developed, the aim reduced to an attempt to answer a few specific questions. Is it possible to completely describe transport phenomena for simple n-alkane systems? Seen as a class, can their transport properties be rationalized? The Journal of Physical Chemistry
+
Experimental Section Mutual diffusion coefficients were measured over the entire range of concentrations for the system n-C6H14 n-CizHz6 a t 25 and 35" and for the system n-CloHzz n-CieHad a t 25". The Gouy results (with an expected
+ +
(1) Chemistry Department, Wesleyan University, Middletown, Conn. 06467. (2) A. L. Van Geet and A. W. Adamson, J. Phys. Chem., 68, 238 (1964).
TRANSPORT PROPERTIES OF LIQUIDALKANES
+ n-Cl2H26 a t 25 and 35"
Table I: Gouy Data for n-C6H14 Axz
zany
Jma
3259 Table 111: Tracer Diffusion Data for ?&6HL4 at 25 and 35"
Dia X los, cmZ/sec
At (sec)
28
Di* X 106, cmz/sec 25*
0.0000
Traced n-Hexane 4.131
25°C 0.0116 0.0127 0.0682 0.1587 0.3251 0.4177 0.5773 0.7307 0.8687 0.9632 0.9676
0.0232 0.0253 0.0202 0.0298 0.0301 0.0288 0.0464 0.0589 0.0558 0.0737 0.0649
94.160 101.547 72.907 62.913 73.063 62.247 82.967 89.777 73.247 88.553 77.933
34 17 37 14 22 15 19 19 27 25 24
2.683 2.690 2.571 2.396 2.141 2.024 1.829 1.658 1.522 1.433 1.430
Limiting values a t 2 2 = 0: Dlz0 = 2.715 a t z 2 = 1: D12' = 1.395 35°C 0.0127 0.0129 0.0136 0.1139 0.1954 0.4277 0,5243 0.7552 0.9129 0.9642 0.9642 0.9673
0.0252 0.0257 0.0272 0,0248 0.0274 0.0395 0.0494 0.0504 0.0433 0.0717 0.0717 0.0655
105.847 107.667 114.413 87.147 84.363 86.787 96.213 73.047 56.287 87.707 87.440 79 * 547
Limiting values:
55 29 33 8 13 11 16 1 37 20 19 28
3.021 3.014 3.005 2.766 2.607 2.260 2.133 1.887 1.728 1.715 1.708 1.708
0.1032 0.1117 0.1162 0.3056 0.3140 0.5030 0.5079 0.6900 0.7045 0.8927
J,: total number of fringes.
3.137 2.243 2.531 1.902 2.117
xz
Da* X 106, cml//sec 25'
0.0000
Traced n-Dodecane 2.715
+ n-Cl6H84 a t 25"
0.8997
DIZ X 10'
ma"
0.0209 0.0278 0.0799 0.3198 0.5200 0.7166 0.9278 0.9698 0.9775
Am
JM
At(sec)
cmg/sec
0.0417 0.0278 0.0259 0,0457 0.0746 0.0610 0.0543 0,0604 0.0450
66.207 43.707 38.673 53.587 75.003 51.600 38.960 42.400 31.580
34 43 80 30 31 30 56 43 35
0.941 0.938 0.921 0 * 802 0.715 0.652 0.590 0.577 0.576
Limiting values:" D~ZO= 0.950 0 1 2 ' = 0.570 The limiting mutual diffusion coefficients for the system n-CaHI8 n-CleHacat 25" are DIZO= 1.426 and DIZ'= 0.675.
+
-
error of kO.1 0.2%) are listed in Tables I and 11. Limiting mutual diffusion coefficients for the system nCSHIB n-Cl6H34 at 25" are also included in Table 11. The Gouy experiment has been well described elsewhere. Limiting mutual diffusion coefficients were
+
DZ* x 106, cma/sec 350
3.0545 2.579
2,009 1.380 1.571 1,112 1.113 1.302 1.308 0.944 0.920
0.9025 1.0000
1.6674
2.344 1.760 1,761
0.7028
Table I1 : Gouy Data for n-C12Hzz
4.660
3.537 3.468 2.831
1.0000
0.3106 0.4964 0.5048 0.7014
DIP = 3.055 D I ~ '= 1.668
Di* X 106, cm*/sec 350
3.942 3.947
1,524 1.546 1.394
0.1032 0.1043 0.3091
+ n-ClaH24
0.837
1.087 1.096 0.998
obtained by extrapolation in the way described by Sandquist and Lyons.4 Tracer diffusion coefficients for the system n-CeH14 n-ClzHzO are compiled in Table 111. The general stirred diaphragm cell procedure employed and minor changes in technique used in this laboratory have been f6 discussed previ~usly.~ Densities and viscosities for the system n-CeH1, n-ClzH26 were determined and are listed in Table IV.
+
+
(3) (a) L. G. Longsworth, J. Amer. Chem. SOC.,69,2510 (1947); (b) L. J. Gosting, E. Hanson, G. Kegeles, and M. S. Morris, Rev. Sei. Instrum., 20,209 (1949). (4) C.L. Sandquist and P. A. Lyons, J. Amer. Chem. SOC.,76, 4641 (1954). (5) R.H.Stokes, J. Amer. Chem. Soc., 7 2 , 7 6 3 (1950). (6) M. V. Kulkami, G. F. Allen, and P. A. Lyons, J.Phgs. Chem., 69, 2491 (1965).
Volume 79, Number 10
October 1969
J. C. SHIEHAND P. A. LYONS
3260
I
1.0
I
I
I
I
0.2
I
I
I
I
n. 8
n. 6
0.4
Mole Frsctlon,
1.9
Xz
Figure 2. Activation energies for n-Ce*, n-Clz*in n-Ca (A,O) and n-C,*, n-C16* in n-C7 n-Cl6 (0,X ).
+
+ n-cia
nents 1 and 2, f1 = activity coefficient of component 1, q = 1 d lnflld In $1, thermodynamic term. The maximum deviation of this equation for the above system is 2.3% a t 25" and 1.701, a t 35". The activation energy for tracer diffusion for each component given by
+
I
0.0
0 ;2
I
I I 0.4 Mole Fraction
I
"I
0.6
I 0.8
I
AEl*
Xa
Dz*) diffusion Figure 1. Mutual (&) and tracer (Dl*, coefficients for n-CsHl4 n-ClZH28 a t 25': 0, 0 1 2 , mutual diffusion coefficient, ==! 0.3%; 0, DI*, Dz*, tracer diffusion coefficient, 3~1.0%.
+
Phillips Petroleum Research grade n-hexane and noctane (99.99 mol % purity) were used without further purification in the Gouy experiments. Phillips Petroleum Pure grade n-hexane (99 mol % purity) was used in the diaphragm cell method. Humphrey Chemical Co. n-decane, n-dodecane, and n-hexadecane were used. CI4-labeled n-hexane and n-dodecane were obtained from Nuclear Research Chemicals Co.
+
Discussion Figure 1 presents the mutual and tracer diffusion ren-ClzHz6 a t 25". I n sults for the system n-C6H14 accordance with earlier findings of Van Geet and Adamson,' these results can be nicely fit by the Darken equation
+
+x&*)q
(1)
where D12 = mutual diffusion coefficient, D1*, Dz* = tracer diffusion coefficients of components 1 (lower molecular weight) and 2 (higher molecular weight) in the binary mixture; xl,xz = mole fractions of compoThe Journal of Physical Chemistry
RTiTz DTz*Ti In T~ - T~ DT'*T~' ~
where i = component 1or 2, is plotted against the mole fraction of "2" in Figure 2. Data for the system, nC&f.lS n-ClEHa4,7are also included in this figure. Within experimental error (k0.5% in D*)AEi* is the same for each species a t a given concentration. This confirms the suggestion of Van Geet and Adamson limited by their estimated error of 12.401, in D*. This point seems now to be very well established. Using the language of "The Theory of Rate Processes" by Eyring and coworkers,* one may assume that the
+
A twin-armed pycnometer was used for density measurements (estimated error & 0,0101,).
(2102*
=
Table IV : Viscosities and Densities for n-C6Hl4 n-ClZH2ea t 25 and 35' XP 22
0.0000 0.0232 0 0783 0.1736 0.3100 0.4033 0.6005 0.7012 0.8401 0.9351 1.0000 I
p,
250
0.6550 0.6590 0.6674 0.6805 0.6961 0.7054 0.7216 0.7286 0.7371 0.7422 0.7454
p,
+
7,25' CP,
0.6459 0.6500 0.6587 0.6719 0.6881 0.6976 0.7140 0.7211 0.7298 0.7381
OP, 86"
350
0.0000 0.0232 0.0783 0.1736 0.3209 0.4110 0,6005 0.6932 0.8557 0.9271 0.1615 1* 0000
0.2979 0.3154 0.3506 0.4183 0.5387 0.6213 0.8244 0.9294 1.1368 1.2408 0.4067 1* 3793
0,2709 0.2875 0.3133 0.3742 0.4799 0.5504 0.7191 0.9709 1,0543 0.3656 1.1652
(7) Y . T. Tan, Thesis, Yale University, 1966, University Microfilm, Ann Arbor, Mich.
3261
TRANSPORT PROPERTIES OF LIQUIDn-ALKANES Table V : Comparison of Diffusion Data with Theory
-----
Dln X I@, oml/seo-------
7
P
P
22
Calod from eq 2
+ n-CizHzs, K = -14.61,
(A) n-C~Hir
1.0000 1.0130 1.0285 1.0318 1,0249 1.0100 1.0000
0.0 0.1 0.3 0.5 0.7 0.9 1.0
0.6550 0.6705 0.6951 0.7136 0.7283 0.7403 0.7454
0.0 0.1 0.3 0.5 0.7 0.9 1.0
(B) n-C?Hle 0.6792 0.6964 0.7222 0.7407 0.7545 0.7653 0.7698
0.0 0.1 0.3 0.5 0.7 0.9 1.0
(C) n-CsHis 0.6985 0,7047 0.7158 0.7255 0.7342 0.7418 0.7454
0.0 0.1 0.3 0.5 0.7 0.9 1.0
(D) n-CeHlr 0.6550 0.6822 0.7160 0.7382 0.7545 0.7656 0.7698
+ n-C~eHar,~K = -11.33, I.0000 1.0166 1.0386 1,0460 1,0386 1.0166 1.0000
2,715 2.509 2.180 1.918 1.691 1 484 1.395
0.00 0.48 0.50 0.00 0.30 0.00 0.00
b = 9.476, z / n x = 10.59 1.781 1.781 1,612 1.600 1,343 1.334 1.134 1,135 1.964 0.966 0.819 0.815 0.755 0.755
0.00 0.75 0.67 0.09 0.21 0.49 0.00
I
+ n-ClzHza,’ K = - 12.27, b = 10.288, d n y z = 9.80 1.0000 1.0032 1.0075 1.0089 1.0075 1.0032 1.0000
1.718 1.647 1.516 1,398 1,290 1.190 1,143
0.00 0.24 0.99 2.04 1.18 0.00 0.00
1.718 1.643 1.501 1.370 1,275 1* 190 1,143
+ T Z - C ~ BKH ~=~-, ~12.64, b = 10.48, dnyz = 9.80 1.0000 1.0231 1.0501 1.0553 1.0427 1.0167 1.0000
2.206 1.925 1.600 1.365 1.150 0.950 0.854
2,206 1.917 1.600 1.319 1.084 0.925
0.00 0.42 0.00 3.36 5.74 2.63 0.00
0.854
+ n-CiaH34,‘K -10.50, b 8.760, z/n>z = 11.31 + n-CleH,r are obtained from D. L. Bidlack and D. K. Anderson, J. Phys. Chem., 68, 206, =
a Dl2for n-CTH16 n-Cl&r and n-C&4 3790 (1964). * DI2for n-CsH18 n-ClzHzsare obtained from Adamson.2 systems because the p terms are not available.
+
z/nx= 8.49
2.715 2.521 2.191 1.918 1.686 1.484 1.395
(F) n-CsHis
+
b = 12.285,
Dev, %
Exptl
rate-determining step in tracer diffusion is the creation of a space into which the moving segment moves. If the size of the moving segment in the diffusion process were independent of the length of the molecule, one would also anticipate that activation energy for this process would be the same for either component a t a given density of the surroundings. McCall and coworkersghave estimated the volumes of activation (the extra volumes required to form the activated state)8 of n-alkanes; they were found to be about 16-20 ml/mol, effectively independent of chain length. This observation is consistent with moving segment sizes being nearly the same and also with the size of the moving segment being quite small. Their finding obviously supports our findings and Eyring’s model. Figure 3 is a plot of D12/q against density at 25” for
Calculations of DLZfrom eq 2 cannot be carried out for these
all systems for which data are available (see Table V). D12/q is a linear function of density in all cases. The equation D12/q= K p b, with K = - 14.61, b = 12.285 for the present system n-CaHlr wC12H26, gives a maximum deviation of only 0.591, from experimental D12’s, far better than that given by eq 1. Several features of these curves should be noted. First, they all intersect a t a common point p = 0.84, Dlz/q = 0. This is entirely reasonable if one expects these systems to exhibit vanishingly small mobilities a t a density corresponding to a supercooled melt of very high molecular weight. The experimental specification
+
+
(8) S. Glasstone, K. J. Laidler, and H. Eyring, “The Theory of Rate
Processes,” McGraw-Hill Book Co., Inc., New York, N. Y., 1941.
(9) D. W. McCall, D. C. Douglass, and E. W. Anderson, Phys. Fluids,
2, 87 (1959).
Volume 78, Number 10 October 1960
3262
J. C. SHIEHAND P. A. LYONS
0.70
n. 80
0.75
Density ( q I c c I
Figure 3. Linear relationship between n-alkane binary systems at 25'.
Dll/q
0.81
and density in
* E 0.65
0.. 70
0. 7 5
Density I g l c c )
5
10
Figure 4. Relationship between the slope K and the average number of carbon atoms in several n-alkane binary mixtures.
of this extrapolated value ( p = 0.84) may be compared with the value for n-CboHloz ( p = 0.842) calculated from the data of Sakurada and Nakajima1° a t 25" (ie., 1 / p = 1.143 + 0.00089t 1/(0.500 - 0.0011t)n, where n is the number of carbon atoms and t is the temperature in "C) and from the extrapolation of p vs. l / n to n = which gives p = 0.848. The slopes, K , of the various curves in Figure 3 are, within experimental error, directly proportional to dG2, or (n1n2)-1/2,in keeping with Dlz/q being a measure of the mean mobility of the two components. Figure 4 shows these slopes plotted against d n X 2 , The values can be found in Table V. For any binary system with a known value of the corresponding value of K can be interpolated in Figure 4. As a consequence, mutual diffusion coefficients can be predicted at a given composition of known density by use of eq 2, since b = -0.84 K . A plot of K against (n1n2)-'/* would be appropriate for purposes of extrapolation. A logical consequence of the striking linear dependence of the average mobility on density is an expectation that a given n-alkane C, would have the same tracer diffusion coefficient D,* in any n-alkane mixture
+
l/x,
The Journal of Physical Chemistry
Figure 5. Tracer diffusion coefficient os. density a t 25': 0 , n-Ce n-Cls; X, n-C7 n-C16; 0, n-Cs Ciz; A, llrcu n-Clz with n-C18*.
+
6
+
+
+
a t a given density regardless of molecular composition. This is in keeping with the application of the "principle of congruence'' to tracer diffusion proposed by Van Geet and Adamson.2 As is shown in Figure 5 , tracer diffusion coefficients of n-ClzHz6 in a system studied in this work (n-CeH14 n-ClzHz6) and another studied by Adamso9 (n-CsH18f n-Cldh) fall on the same curve of D12* VS. density. Generalizing, it is possible to plot a surface of D,*, n, p (or n = xlnl xzn2,where n, is the number of carbon atoms for component i) by assembling all the data available in the literature and from the present work, ranging from n = 6 ( p i 3 0.65) to n = 18 ( p E 0.77). By use of this surface, tracer diffusion COefficients for any n-alkane in any n-alkane mixture, binary or multicomponent, can be determined7 at a given density. Since Dlz/q = K p b represents the binary diffusion data very precisely, this equation can be used to calculate the q terms if D12and p are available over the entire range of compositions. For example, using both limiting mutual diffusion coefficients, DlZoand D d , and
+
+
+
(10) S. Sakurada and K. Nakajima, High Polymers (Japan), 3 , 91 (1946).
TRANSPORT PROPERTIES OF LIQUIDALKANES
3263
Table VI: Calculation of Thermodynamic Properties at 25" by Use of Eq 2 -In fi (integrated) area
-In fz, (integrated) area
22
0
01 02 03 04 05 06 07 08 09
0.6705 0.6837 0.6951 0.7050 0.7136 0.7213 0.7283 0.7347 0.7403
0.00060 0.00192 0.00466 0.00892 0.01436 0.02146 0.03010 0.04018 0.05076
0.04648 0.03830 0.03050 0.02298 0.01656 0.01082 0.00610 0.00260 0.00060
01 02 03 04 05 06 07 08 09
0.7324 0.7381 0,7433 0.7481 0.7526 0.7466 0.7603 0.7636 0.7668
0.00088 0.00178 0.00358 0.00573 0.00828 0.01140 0.01420 0.01728 0.01990
0.02700 0.01880 0.01365 0.00948 0.00620 0.00360 0.00175 0.00065 0 * 00020
- GE1, cal/mol
-In fa, exptl
Celcd
Exptl
0.05315 0.04105 0.03069 0.02202 0.01490 0.00928 0.00506 0.00214 0.00045
3.08 5.45 7.36 8.62 9.16 8.94 7.88 6.20 3.33
3.55 6.23 8.08 9.13 9.22 8.92 7.78 5.81 3.23
-1nf1,
exptl
Dev, cal/mol
+
n-CeH14 n-ClZHZ6 0.00073 0.00286 0.00631 0.01098 0.01681 0.02367 0.03185 0.04036 0.05034 n-CioHzz
-0.47 -0.78 -0.72
-0.51 -0.06 +0.02
+0.16 +0.39 +0.10
+ n-CiaHsr 2.07 3.07 3.92 4.28 4.29 3.98 3.25 2.36 1.29
lated and Dlz/p = p=1+-
- 14.61 p
+ 12.285.
Since
d lnf1 = I + - - d In f 2 d In x1 d In x2 Diz/( - 14.61 p
=
. f ~ ~ ~ ~]
+ 12.285)
[12.285 D12 - 14.61 -p - 1 d In x1
and
By graphical integration of the areas of the plots of [&,/ (12.855- 14.61 p ) - 11 os. In x1 and In XZ,respectively, lnfl and In f2 can be calculated and hence the excess free x2 In f a ) , can be obtained. energy, GE = RT(x1 in f1 The results are shown in Table VI. Experimental values obtained by Bronsted and Koefoedll from vapor pressure measurements are also listed for comparison. The agreement is well within the experimental error claimed for the thermodynamic work. This gives us confidence that GE for any binary n-alkane system may be calculated by this procedure. As an example, In f ~ , In f2, and GE for the system n-CloHzz n-C16Ha4 for which thermodynamic values are not yet determined experimentally, are estimated from the diffusion data in Table V. An interesting and related aspect of transport phenomena in n-alkanes is the variation of viscosity with
+
+
the corresponding densities po, p1 for each component of the system n-C6& n-ClzH26, K and b can be calcu-
+
(11) J. D. Bronsted and J. Koefoed, Kgl. Danske Videnskab. Selskab, Mat-FysMedd., 2 2 , No. 17,1 (1984).
Volume 76,Number 10 October 1969
C. CAPELLOS AND A. 0. ALLEN
3264 density. It was observed that, for all pure alkanes and binary mixtures, a plot of viscosity against density gives one smooth curve (Figure 6). Again the principle of congruence applies, in this instance to the viscosity of nalkane systems. Together with earlier work, this study permits a very good and quite complete description of the transport properties of linear alkane mixtures. Much of the behavior of these systems is readily interpretable in terms of a simple model. However, it must be pointed out that while Dlz/q might be expected to decrease with den-
sity and approach zero a t p = 0.84, the exact linear dependence is both unexpected and unexplained. Acknowledgment. The authors wish to thank Dr. Y. T. Tan for the use of the data for the system nCTH16 n-CleH34 before publication, as well as for his stimulating discussions. They are also grateful for thoughtful comments from Professors L. Onsager and M. Fixman, This work was supported by the Atomic Energy Commission, Contract AT (30-1) 1375 and the American Chemical Society Petroleum Research Fund, Grant 3854-A5.
+
Ionization of Liquids by Radiation Studied by the Method of Pulse Radiolysis. 11.
Solutions of Triphenylmethyl Chloride' by C. Capellos Explosives Laboratory, F . R.L., Picatinny Arsenal, Dover, N e w Jersey
07801
and A. 0. Allen Chemistry Department, Brookhaven National Laboratory, Upton, N e w York 11978 (Received February 20,1969)
Solutions of triphenylmethyl chloride in five solvents (n-hexane, cyclohexane, 2,2,4-trimethylpentane,carbon tetrachloride, and carbon disulfide) subjected to pulse radiolysis gave yields of triphenylmethyl carbonium ion equal within experimentalerror to the total yield of free ions in these solventsover the solute concentration range 10-8 to IO+ M . The ion does not form in the presence of substances like alcohol which possess basic character. Kinetics of formation and decay of the ion were determined. Knowledge of the yield of ion pairs produced by irradiation of various liquids is essential to the understanding of the mechanism of the chemical reactions produced by radiation in these liquids. Determination of this yield is best made by electrical measurements,2 but these methods are difficult or impossible to apply in liquids which have appreciable spontaneous conductivity. We therefore turn to the use of charge scavengers-compounds which readily react with almost any ion in a solution to form charged transients of distinctive absorption spectrum which can be determined by the methods of pulse radiolysis. In previous publications we have described attempts to use tetramethyl-pphenylenediamine (TRIIPD) and triphenyl~arbinol~ for this purpose. The former compound gave results which were confused by the simultaneous formation of a triplet state having optical absorption properties very similar to those of the ion being looked for. The carbinol did give triphenylmethyl ions which were easy to determine, but the yields occurred only to a fraction of the total T h e Journal of Physical Chemistry
yield of ions known to form in the solvents tried. I n the present paper we describe results obtained with triphenylmethyl chloride as a positive-charge scavenger.
Experimental Section Many of the irradiations reported here used the Van de Graaff generator, employing the techniques previously de~cribed.~In order to study the kinetic processes occurring in times of 1psec or less, we also used as radiation source a Febetron model 705 electron generator, which delivers an intense pulse of 2 MeV electrons in a total time interval of less than 0.1 psec. The chief difficulty in using this machine for pulse radiolysis is the emission along with the electron pulse of intense hertzian waves, pickup of which in the circuitry results (1) Research performed under the auspices of the U. S. Atomio Energy Commission. (2) W. F. Schmidt and A. 0. Allen, J . Phys. Chem., 72,3730 (1968). (3) C. Capellos and A. 0. Allen, ibid., 72,4265 (1968). (4) C. Capellos and A. 0. Allen, Science, 160,302 (1968).
