31UTUA4LFRICTIONAL COEFFICIENTS O F
AMIXO,4CIDS
403
-
The Mutual Frictional Coefficients of Several Amino Acids in Aqueous Solution at 25”
by H. David Ellerton, Gundega Reinfelds, Dennis E. Mulcahy, and Peter J. Dunlop Department of Physical and Inorganic Chemistry. University of gdelaide, Adelatde, South Australia (Received August 12, 1983)
Diffusion and refractive index data a t 25’ are reported for the binary systems glycirieH20, glycylglycine-HZO, a-amino-n-butyric acid--H20, and dl-valine-HaO. The diff usjon data are combined with other available thermodynamic data t o compute mutual frictional coefficients for these systems. These mutual frictional coefficients are compared with those for other binary systems which have been calculated from the data in the literature. A relationship between relative frictional coefficients and relative viscosity is tested.
in steel supports on tlop of three concrete pillars which 35any papers in recent years have reported diffusion were isolated from the floor of the room and set 1.8 rn. coefficients for both binary and 1,ernary isothermal into the earth. diffusion. For binary diffusion these coefficients, which are defined by Fick’s first law,’ relate the (1) A. Fick, Pogg. Ann., 94, 59 (1855). flow of a given component to the corresponding (2) J. G. Kirkwood, R. L. Baldwin, I-’. J. Dunlop, L. J. Gosting, concentration gradient when relative motion of the and G. Kegeles, J . Chem. PILUS., 33, 1505 (1960). components is taking place. It has been emphasi.ied (3) R. P. Wendt and L. J. Gosting, J . Phys. Chem., 63, 1287 (1959). that, when reporting diffusion coefficients, the frame of (4) P. J. Dunlop and L. J. Gosting, J . Am. Chem. Soc., 77, 5238 reference should be specified”3 and coefiaients for (1955). several frames of reference have been given in the (5) I. J. O’Donnell and L. J. Gosting,”The Structure of Electrolytic Solutions,” W.J. Hamer, Ed., John Wiley and Sons, I n r , , New literature, both for binary3 and ternary d i f f ~ s i o n . ~ - ’ ~ York, N. Y . , Chapman and Hall, London, 1959. However, as has been previously indicated, it is possible ( 6 ) P. J. Dunlop, J . Phys. Chem., 61, ‘994 (1957). to define niutual frictional independent (7) P. J. Dunlop, ihid., 61, 1619 (1957). of the frame of reference, which may be computed from (8) P. J. Dunlop, ibid., 63, 612 (1959). the measured diffusion coefficients and certain cor(9) L. A. Woolf, D. G. Miller, and L. J. Gosting, J. Am. Chem. Soc., 84, 317 (196%). responding thermodynamic data. It is the purpose of (10) R. P. Wendt, J . Phys. Chem., 66, 1279 (1962). this paper to report frictional and diffusion coefficients (11) P. J. Dunlop and L. J. Gosting, ibid., 63, 86 (1959). for the systems glycine-H20, glycylglycine-1320, CYD. G. Miller, ibid., 63, 570 (1959). (12) amino-n-butyric acid-HzO, and dZ-valine-HzO and to (13) L. A. Wolf, ibid., 67, 273 (1963). compare these frictional coefficients with others which (14) 0. Lnmm, Acta Chem. Scand., 11, 362 (1957). may be computed from the diffusion and thermody(15) 9. Ljunggren. l’mns. Royal Inst. Technol., Stockholm, No. 172 namic data in the literature. (1961).
Experimental Apparatus. Almost all the diffusion measurements were made with a Gouy diffusiometerZ1which was supported and aligned on a 9-m. lathe bed. This optical bench was mounted kinematically on three stainless steel ball bearings, 7.6 em. in diameter, which rested
(16) (17) (18) (19) (20) (21)
A. Klemrn, 2. Nnturforsch., 8a, 397 (1953). R. W.Laity, J . P h y s . Chem,. 63, 80 (1959). R. J. Bearman. ibid., 6 5 , 1961 (1961). L. Onsager, Ann. iV. Y . Acad. Sci., 46, 241 (1945). P. J. Dunlop, J . Phys. Chem., 68, 26 (1964)
This apparatus gave diffusion coefficients and refrartive index increments for sucrose which agreed t o better than 0.1% with those of Gosting and Akeley (see ref. 24).
Volume 68, A-umber 9
February, 1964
H. D. ELLERTON, G. REINFELDS, D. E. MULCAHY, BND P. J. DUNLOP
404
h Wratten 7711 filter was used to isolate the green mercury line, X = 5460.7 A., of a n AH-4 mercury vapor lamp which was supported in a water-cooled housing. Light from the lamp was focused onto a Gaertner bilateral slit which was then focused, by means of a high quality lens,22through the water bath and cell onto the photographic plate. The optical distance, b, from the center of the diffusion cell to the photographic plate was measured and found to be 304.82 cm 2 3 The two quartz ceIls A and B, which were used for the diffusion measurements, had thicknesses, a, along the optic axis equal to 2.5032 and 2.4950 cm., respectively. The values of the diffusion and refractometer corrections, 6 and 6 ' , were approximately 18 p and appeared to be essentially independent of the concentration of the diffusing material. Calculations. h paper from another laboratoryz4 has adequately described the methods used for computing the differential diffusion coefficients, D ,and the refractive increments, An 'A(?. The values of the relative fringe deviations for each Gouy experiment, for each f22,,24were generally 111 the range + 2 X value of the reduced Cringe number f({).'* The bath temperature, which a t all times was within a hundredth of a degree of 25', remained constant to =tOo.OO5" during the course of each diffusion experiment. Observed diffusion coefficients, D , at each temperature, I',were corrected to 25 000' using the Stokes-Einstein where 4 is the visrelation ( D ~ / ! P ) W= (Dq//T)exDtl, cosity of water. Frictional coefficients for binary were computed from the measured diffusion, Rol = Rlo,20 coefficients, the corresponding partial molar volumes of the solvent, F0,the values of the osmotic coefficients, and the solution densities, d. These calculations are described in more detail below. The value of the gas constant used was 8.3144 X lo7 ergs deg.-l mole-' and the absolute zero was taken as being -273.16". Materials and Solutions. All solutes were of Analar grade, wherever possible, and were recrystallized from distilled water before use. Further details of the materials used in this work can be found in a companion paper.26 All solutions were made up by weight using doubly distilled water as solvent. The weights were convcrted to weights in vacuo before calculating the solute concentrations, in moles/1000 cc. The molecular weights of glycine, glycylglycine, a-aminon-butyric acid, and dl-valine mere taken as 75.068, 132.120, 103 122, and 117.149, respectively. Densities, d , and relative viscosities, qr, mere measured for several of the above systems and have been reported previously 26 ~
.
z
~
i
z
6
e,
The Journal of Physical Chemistry
Results Values of the experimental diffusion coefficients, D obtained a t mean solute concentrations = f, (?B)/2] and solute increments = - 6.4, are tabulated for each of the systems studied in column 5 of Table I. Here h and B denote the upper and
e, [(e, ~e (e,
Table I : Experimental Diffusion Data a t 25" (A~/A?) x 103
A8
Cm
D
x
J
106
( A ) Glycine& 0 0 0 0 0
049990h lOOOO~ 2499gc 49960~ 80712 1 24982 1 99858
0 0 0 0
0 0 0 0 0
022680 036434 24442 24443 47962 1 00043
0 0 0 0 0 0
0 0 0 0 0 0 0 0
031044d 048620" 062380~ 2464~~ 48234d 4989$ 81540~ 99912"
099990 20000 14999 14911 o 22247 0 13954 0 13891
13 568 13 540 13 444 13 290 13 126 12 884 12 567
61 123 92 91 133 82
77 29 55 01
1 0504 10411
I 0128
80 02
0 9696 0 9293 o 8767 0 8130
52 55 84 31 88 57 88 55 89 85 92 74
0 0 0 0 0 0
7863 7815 7112 7117 6647 5810
(C) a-Amino-n-butyric acid 0 062088 17 9,58 101 89 0 097240 17 981 80 15 0 12476 17 967 204 84 0 057370 17 936 94 03 0 057710 93 (i7 0 10056 17 843 82 25 0 062530 17 745 101 40 0 099770 17 702 80 96
0 0 0 0 0 0
8258 8230 8220 7922 7586 7587
( B ) Glycylglycineu 25 273
045359 072868 077440 077440 079430 083750
25 24 24 24 24
240 950 945 674 157
86 41
0 6962
( D ) dl-'v'alinea 20 596 52 32 0 7682 0 055416 027708 0 090470 20 612 85 48 0 7657 045235 74 31 0 7538 0 078715 20 594 12666 0 095770 20 582 90 36 0 7190 36638 a Cell A was used for all experiments, except where otherwise See ref. 9. These experiments indicated. 5 See ref. 28. were performed with the Spinco electrophoresis-diffusion apparatus (see ref. 27) in which the light passed through the cell twice. Cell B was used for these experiments. e Cell A was used for these experiments.
0 0 0 0
(22) Supplied by the Perkin-Elmer Corp., U. S. A. (23) This distance was measured by the Standards Laboratory of (24)
the South Australian Government Railways. L. J. Gosting and D. F. Akeley, J . Am. Chem. Soc., 75, 5685 (1953).
R. A. Robinson and R. H. Stokes, "Electrolyte Solutions," Butterworths Scientific Publications, London, 1959, p. 29. (26) H. D. Ellerton, G. Reinfelds, D. E. Mulcahy, and P. J . Dunlop, J . Phys. Chem., 68, 398 (1964). (25)
MUTUAI,FRICTIONAL COEFFICIENTS OF AMIXO ACID^
Table I1 : Constants for the Least-Squared Equations of D us.
Glycine Glycylglycine a-Amino-n-butyric acid &Valine
405
8 a t 25"
DO
Ai X 10
Az X 10
A3 X 10
A4 X 10
% dev.
1,0609 0.7963 0.8305
- 2.1097 -4.708 -1.545
0.7248 6,581 0.2127
-0.2151 -6.411
0,0352 2.399
, . .
...
10.06 f 0 11 10.09
0.7722
-1.454
, . .
, . .
*0. 01
lower solutions, respectively, used in each diffusion experiment. .As previously stated, almost all the diffusion measurements were performed with the Gou,y diff usiometer ; however, several measurements were performed for the system a-amino-n-butyric acid witlh a modified Spinco electrophoresis-diffusion apparatus which has been described p r e v i o ~ s l y . ~The ~ agreement between the two types of apparatus was quite satiefactory. By rneans of a 7090 IBI4 electronic computer the experimental diffusion coefficients were fitted by the method of lleast squares to polynomials of the form
where Do is the value of the diffusion coefficient a t infinite dilution. The constants A , for all materials together with the average. deviations of the experimental points from the smooth cuirves are given in Table 11. Soime of the diffusion data for glycine in Table I have been reported p r e v i o ~ s l y28. ~ Refractive index increments per mole were calculated using the relationship ( A n / A e ) = ( X J / a A e ) , where J is the total number of fringes in a Gouy or an integral fringe pattern and X is the wave length of the green mercury line. The refractive increments for all systems are given in column 3 of Table I and are referred to the refractive index of air as unity. These increments may be represented by equations of the> form
+
( A T L / A ~ )x 103 = ( A T L / A ~ ) O
3
B,@ (2) 2.=1
where (An/Ae)O is the value of the refractive increment at infinite dilution. Values for the constants B , foi all materials, together with the average deviations of the experimental points from the srnooth curves, are given in Table 111.
...
(i
=
O , l , . . ., q )
(3)
for a system of g solutes in a solvent 0. The X, are the gradients of chemical potential causing diffusion
xi =
(4)
-(bP,/bz)T,P
and here the CrZ9are the solute concentrations in moleel/ cc., the p, are the chemical potentials of the various components, and the ( u , ) ~are diffusion velocities with respect to the volume frame of reference defined by2
9
i = o
B,(J,)v
=
E
i = o
B,C,(u,)v
=
0
(5)
where the 7, are the partial molar volumes of the components and the (JOY are flows in the .T direction. For a binary system consisting of a solute, 1, and a solvent, 0, it has been that eq. 3 become~~~
+ C b In y / b C ) / D ] [ R T v o ( l+ e b In y / b e ) / D ]
Rol = [ R T v o ( l =
(6)
where Rolis the mutual frictional coefficient for binar,y diffusion, R is the gas constant, y is the solute activitiy coefficient on the volume concentration scale, and 13 is the experimentally measurable mutual diffusion coefficient. It is clear from eq. 3 that, even though the mutual diffusion coefficients depend on the frame of reference used for measurement, the Ro, values are independent of such reference frames since velocity differences appear in the above equations. Equation 6 has been used to compute frictional coefficients, ROI,for the systems reported in this paper (27)
J. M. Creeth, L. W. Nicol, and D. J. Winzor, J . Phvs. Chem., 62, 1546 (1958).
(28) P. J. Dunlop, J . Am. Chem. SOC.,77, 2994 (1955).
Discussion (29) It should be noted that this ctncytration variable C differs fzom the concentration variable C ( C = IOOOC). The variable One formal method of defining a sat of mutual fricC is more useful for experimental purposes. tional coefficients, Rik, for isothermal diffu~ionl7-~~ (30) Here and in the following discussion we choose t o delete the provides the equations subscript 1 from all concentrations and activity coefficients. Volume 68, .Yumber 2
F e b r u a r y , 1.964
H. D. ELLERTON, G. REINFELDS, D. E. lfULCAHY,
406
~~
Table I11 : Constants for the Least-Squared Equations of (An/A?) us.
Glycine Glycylglycine a-Amino-n-butyric acid &Valine
0.2 0.4
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
1 000 0 973 0 953 0 939 0 930 0 925 0 924 0 926 0 930 0 936 0 943
0 0 0 0 0 0 0
0.0 0.2' 0.4 0 6 0.8 1.0
1.000 1.027 1.057 1 090 1.126 1.166
1 0 0 0
000 962 933 912 898 889 885 884 887 892 899
Ba
% dev.
Concn liniit
13.603 25,305 17.985
-0,6561 - 1.6125 -0,286
0.0685 0,749
... -0.287
...
...
f0.02 fO.O1 f0.05
2.0 1. 0 1. 0
20.59j
, . .
, .
. . ,
10.05
0 36
( A ) Glycine 1 0609 4 222 1 0214 4 269 0 9868 4 32; 0 9562 4 398 0 9289 4 481 0 9044 4 576 0 8822 4 682 0 8620 4 798 0 8438 4 920 0 8274 5 045 0 8130 5 169
1 ,000 1,029 1.060 1,093 1.127 1.163 1.202 I . 242 1.284 1 329 1.376
1 000 1 014 1 027 1 039 1 054 1 072 1 095 1 122 1 154 1 190 1 228
1 000 1 032 1 067 1 104 1 141 1 180 1 220 1 262 1 307 1 356 1 409
7.488
1.000 1.065 1.137 1 214 1 298 1.388
1.000 1.073 1.150 1.234 1.329 1.437
( D ) &Valine 18 068 0.7722 5 , 8 0 1 18,068 0 7577 6.013 18 068 0.7432 6.239 18.068 0.7286 6.479 18.067 0.7141 6.734
1.000 1.037 1.076 1 117 1.161
1.000 1.042 1 087 1.137 1 191
18 18 18 18 18 18 18 18 18 18 18
068 06; 066 065 082 059 056 052 048 043 038
0 0 0 0 0 0 0 0 0 0 0
7963 7552 7237 6989 6784 6603 6433 6269 6109 5957 5824
5 5 5 5 5 6 6 6 6 6 6
625 706 776 846 92; 029 157 312 493 695 906
(C) a-Amino-n-butyric Acid
0 . 0 1.000 0 . 1 1.017 0 . 3 * 1.035 0 3 1.054 0.4 1 074
18.068 18.068 18.067 18.065 18.063 18.060
0.8305 0.8004 0.7721 0.7454 0 7204 0.6972
5.394 5.746 6.131 6 550 7 002
a The partial molar volumes, Voj have units of cm.a mole-I. The The diffuaion Coefficients, D , have units of em.$ sec.-l. frictional coefficients, Rol, have units of ergs cm. sec. molec2.
b
~~
~
The Journal of Physical Chemistry
~
Bz
(B) Glycylglycine 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 10
~~
8 a t 25"
Bl
1 000 1 011 1 025 1 042 1 061 1 084 1 109 1 136 1 165 1 195 1 224
18 068 18 06; 18 065 18 061 18 055 18 047 18 03; 18 025 18 010 17 993 17 973
P. J. DUNLOP
(AdA?)Q
Table IV : Summary of Frictional Coefficient and Relative Viscosity Data a t 25"
0.0
AND
and the results are tabulated in column 5 of Table IV. The values of Po were calculated from the density equations reported in a companion paper26 and the thermodynamic factor was computed from the equations for the osmotic coefficients given in the same paper. The constants in Table I1 were used to compute the D values a t round values of All computations were performed with the aid of an IBM 1620 electronic computer. Inspection of Table IV shows that the frictional coefficients so obtained show a much larger concentration dependence than do the corresponding diffusion coefficients. Frictional coefficients were also computed from the thermodynamic and diffusion data in the literature3,26,81 for the systems a-alanine-HzO, lactamideHzO, P-alanine-HzO, glycolamide-Hz0, sucrose-HzO, raffinose-H20, urea-HzO, and biphenyl-benzene. Table V gives values of the frictional ratio R, = (BOJBo?) for these systems a t round values of the concentration, f?. Here Role is the value of the frictional coefficient which is found by extrapolating the experimental values to infinite dilution. Table IV includes values of R, and also 7, a t round concentrations for the systems glycine-H20, glycylglycine-H20, a-amino-n-butyric acid-H20, and dl-valine-H2O. Xow if we assume that Stokes' law can be used to predict the variation of the frictional coefficients with concentration and if we also assume that the shape of
e.
(31)
(a) L. J. Gost,ing and M. S . Morris, J . Am. Chem. SOC.,71, 1998 (1949); (b) L. J. Gosting and D. F. Akeley, ibid., 74, 2058 (1952): ( c ) P. J. Dunlop and L. J. Costing, ibid., 75, 5073 (1953): (d) P. J. Dunlop, J . Phys. Chem., 60, 1464 (1956); (e) F. J. Gutter and G. Kegeles, J. Am. Chem. Soc., 75, 3893 (1953): (f) C. L. Sandquist and P. A. Lyons, ibid., 76, 4641 (1954); (9) H. C. Donoian and G. Kepeles. ibid., 83, 255 (1961); (h) L. S. Mason, P. M . Karnpmeyer, and A. L. Robinson, ibid., 74, 1287 (1952): (i) F. T. Gucker, Jr., F. W. Gage, and C. E. Moser, ibid., 60, 2582 (1938); (j) F. T. Gucker, Jr., and T. W. Allen, ibid.. 64, 191 (1942); (k) R. H. Stokes, Trans. Faraday Soc., 50, 565 (1954): (1) F. T. Gucker, Jr., and W. L. Ford, J . Phys. Chem., 45, 309 (1941): (rn) R . A. Robinson, J . B i d . Chem., 199, 71 (1952); (n) D. H. Everett and M. F. Penney, Proc. Roy. Soe. (London), AZ12, 1 6 4 (1952); (0)H. T. Briscoe and W. T. Rinehart, J . Phys. Chem., 46,387 (1942); (p) E. R. B. Smith and P. K. Smith, J . Biol. Chem., 132, 47 (1940): (9) G. Scatchard. W. J. Hamer, and 9. E. Wood, J . A m . Chem. SOC., 60, 3061 (1938).
MUTUAL FRICTIOXAL COEFFICIEXTS OF AMISO ACIDS
407
-
-
Table V" : Valules of Relative Frictional Coefficients for Severrtl Two-Component Systems a t 25"
8
=-Alanine
Lactamide
p- Alanine
Glyoolamide
0 0 0 1 0 15 0 2 0 4 0 6 0 8 1 0 1 2 1 4 1 6 18 2 0 2 2 2 4 2 6 2 8 3 0 3 2 3 4 3 6 3 8 4 0
1,000
1.000
1 000
1 000
...
...
1 036 1 074 1 117 1 164 1 215 1 271 1 332 1 398 1 469 1 546 1 628 1 717 t 811 1 911 2 018 2 131 2 251 2 378 2 514 2 660
1 015 1 031 1 048 1 066 1 085 1 106 1 127 1 150 1 174 1 200 1 226 1 254 1 283 1 314 1 345 1 378 1 411 1 445 1 479 1 512
... 1.041 1.086 1.135 1.186 1.2421 1.304 1 ,375 1 ,4631 e
, . .
1.031 1.064 1,100 1.137 1.176 1.218 1,262 1.309 1.358 1,409 f
Sucrose
Raffinose
Urea
Biphenylb
1 000 1 093 1 144
1 000 1 150
1 000
1 000
004 009 014 019 025 1 031 1 038 1 045 1 052 1 059 1 067 1 076 1 086 1 097 1 108 1 119 1 131 1 143 1 156 1 169
1 032 1 065 1 101 1 138 1 179 1 222 1 269 1 318 1 372 1 428 1 489 1 550 1 625 1 701 1 783
d
1 1 1 1 1
h
0
3
a References t o the data used for computing the relative frictional coefficients and the corresponding relative viscosities are givcn See ref. 31a, q. See ref. 26 and 31d. e See a t the bottom of each column. * The solvent for biphenyl was benzene (see ref. 31f). See ref. 31g, h, and p. * See ref. 31i, c, k, and 1. ' See ref. See ref. 31f, n, snd o. ref. 31e, h, and mi. 'See ref. 3, 26, and 31j. 31b and q.
0 GLYCINE
T GLYCYLGLYCINE
0 a-AMINO-
0 dl-VALINE +a-ALANINE &)-ALANINE
n-BUTYRIC ACID
I
Figure 1. Valueci of log (R,) us. log ( q r ) for several uncharged solutes in water alt 25". The solvent for biphenyl is benzene.
the diffusing entity is independent of concentration. then we would expect that
Rr
(Rol/Rol0)=
(~r)"
(7)
I
.I
Figure 2. Values of log (R,) os. log (vr) for several amino acids in water a t 25".
where (Y = 1. Hence a graph of log (R,) us. log (vr) would be a straight line with a slope of unity, and deviations from this slope would then be a measure of thle Volume 68, n'urnber 3
February, 1964
NOTES
408
deviations from Stokes’ law. Accordingly, in Fig. 1 and 2 graphs of log (R,) us. log (7,) have been made for the systems reported in this paper and for those systems selected from the literature (see Table V).3z It is estimated that the error in each frictional coefficient is d=0.3y0 and that the error in each value of the relative viscosity is =t0.2.%. Thus the error in the relative frictional coefficients is f0.6%. These limits have been clearly marked in Fig. 1and 2 . Inspection of Fig. 1 shows that of all the substances considered, sucrose is the only one which, in agreement with Stokes’ law, gives a value of a = 1. It is interesting to note that the a-values for all the other systems containing solutes with relatively small dipole moments, but excluding the system raffinose-Hz0, are approximately equal to 0.8. Figure 2 gives a similar graph for the amino acid-HzO systems. However, while some of the relative frictional coefficients for the amino acids
give a-values of approximately 0.8, dl-valine and aamino-n-butyric acid give values which lie between 0.8 and 1.0, while glycine and glycylglycine give avalues which are considerably less than 0.8, particularly a t low concentrations. The marked change in slope for glycine and glycylglycine is interesting in view of the fact that the other amino acids show an essentially linear dependence of log (R,) on log (vr). Acknowledgments. The authors wish to thank RIr. E. W. Gooden for performing some of the experiments with a-amino-n-butyric acid and Dr. B. J. Steel for many helpful discussions and his criticism of the manuscript. This work was supported in part by grants from the Colonial Sugar Refining Co. Ltd. of Australia and the United States Institutes of Health (ALI-06042-02). (32) The relative viscosity data are given in ref. 31.
NOTES
The Solubility of 3Iercury in Hydrocarbons by Robert R. Kuntz and Gilbert J. Mains Departmrnts of Chemistry, Uniuersity of Missouri, Columbia, Missouri, and Carnegie Institute of Technology, Pittsburgh 23, Pennsylvania (Receiaed August 21, 1965)
The solubility of mercury in hydrocarbon solvents is of interest to the solution thermodynamicist in his efforts to understand the nature and extent of solventsolute interactions1 and, more recently, to the photochemist in his studies of mercury photosensitization of liquid hydrocarbon^.^^^ Because the solubility is very low, of the order of micromoles per liter a t 2 3 O , earlier experimental measurements have involved the absorption of mercury from a large volume of saturated solution by gold foil4 or radioactive tracer technique^.^ A summary of these solubilities is given in the first column of Table I. The purpose of this note is to point out that the optical density at 2560 A.of a saturated solution of mercury in hydrocarbon is a reliable measure of the solubility and, furthermore, that it is possible to estimate these solubilities using the Hildebrand equation for “regular” solutions. The Journal of Phusical Chemistry
Experimental Phillips “pure grade” hydrocarbon solvents were made optically pure by passing through silica gel which had been previously baked and cooled in uacuo. Each solvent was degassed and distilled into a vessel which had been fused to a 100-mm. quartz absorption cell and contained a drop of mercury. Saturation was accomplished by vigorous shaking of the vessel for 20 min. a t the desired temperature. Absorption spectra were taken with a Beckman DU spectrophotometer.
Results and Discussion The absorption spectra of mercury in hydrocarbon solvents all exhibit a broad absorption in the 2537 A. region which can be resolved into two overlapping peaks on most spe~trographs.~’~,6 Maximum absorption -~~ ~
(1) J. H. Hildehrand and R. L. Scott, “The Solubility of Nonelectrolytes,” 3rd Ed., Reinhold Publishing Co., S e w York, N. Y . ,
1950. ( 2 ) M. K. Phibbs and B. deB. Darwent, J . Chem. Phys., 18, 679
(1950). R. Kuntz and G. J. Mains, J . Am. Chem. Soc., 8 5 , 2219 (1963). (4) H. Reichardt and K. F. Bonhoffer, Z. Physik, 67, 780 (1931). (5) H. C. Moser and A. Voigt, U.S.A4.E.C.Rept. ISC-892 (1957). (6) R. Kuntz, Ph.D. Thesis, Carnegie Institute of Technology, 1962. (3)
