azeotrope failed to produce the same concordance in benzene as in the other two solvents. Acknowledgment.-The author wishes t o expresb his thanks to Mr. Jack Cazes, Department of Chemistry, New York University, for the purification of all reagents and for taking the infrared spectr:L used in this investigation.
THE EFFICIEXCY OF STREAMIKG POTESTIAL GEXEELiTION1 BY :iRMA?;n
F.LEWIS*AND
RAYMOND
R.
l\IYERS
Lehioh Cn'niverszty, Bethlehem, Pa. Received March 19, 1960
Experiments were conduct,ed to determine the efficiency of electric power generation in the electrokinetic streaming process. The electrokinetic streaming efficiency has been defined as the rat,io of electrical power, EI (streaming potential times streaming current) to the mechanical power, A P Q (pressure difference times volume flow rat,e through the diaphragm) . 3 Basically, the st,reaming potential phenomenon can be shown to consist, of an interaction between two apparent charge density funct'ions; the electrokinetic charge density, APIE, and the streaming charge density, I / Q . The electrokinetic charge densitmyhas been described in a previous paper4 where it, is defined as the apparent ionic charge concentrat.ion, e . ~ . u . / c m . ~within , t'he electrokinetically sensitive portion of the double layer. On t'he other hand, t8hestreaming charge density represent,s tzheratio of current I (e.s.u. per second) to flow rate Q (~111.~ per second); t,hus from a st,rict definition of terms, I / & represenh t,he number of ionic charges moved (or distorted at the double layer) by each of streaming liquid. The efficiency function t,herefore can be regarded as a ratio of these two charge density parameters, I / Q divided by AP/E.
sponge decreased a t higher temperature, while with quartz wool, the opposite trend was found. Of greater potential significance is the behavior of the charge density parameters. The streaming charge density I / Q rose with increased temperature for quartz wool, but dropped in the case of isoryanate. The electrokinetic charge density A P / E followed a reverse behavior with the two surfaces. A€'/& therefore augmented the temperature dependence of efficiency, since AP/X is inverted in the efficiency computation. TABLE I TEMPERATURE DEPENDENCE OF STREAMIIXG EFFICIEXCY OF QUARTZKOOL ASD ISOCYANATE SPONGE IS KATER
Quart7 n 001
25 27 30 40 49 57 67 25 Isoci anate 29 sponge 38 (nt, 1 5g 40 62 a Both diaphragms 3 9 (ntO4g)
1 54 0 73 0 63 2 10 1 71 8 3 66 2 06 1 71 94 1 82 70 2 23 1 54 1 45 88 3 58 2 12 1 06 1 22 3 20 1 07 % 42 1 10 3 48 3 25 1 -37 1 07 0 12 1 82 5 46 3 00 4 54 2 28 .14 1 99 4 56 2 24 2 03 17 4 62 2 20 20 2 04 Z 80 1 03 1 76 2-1 ern long and 1 1 ( m. in diameter.
The important yariable of conductivity was studied by adding various amounts of KCl to the itreaming mater. As shown in Table 11, the presence of the electrolyte drastically reduces the streaming efficiency of both materials These data conform to the expected trend wherein the increase in streaniing liquid conductance impresses an internal shunt on the voltage produced Furtherthis analysis more, the I 'Q parameter is shown t o maintain a remarkable constancy 111 the face of \ride changes 111 ionic strength. ('onsequently, all of the efficiency drop with increased conductivity can be attributed to the increase 111 c~ectrokinetlc charge density
Experimental Quartz wool4 and isocyanate plastic sponge were used in this study. These materials were chosen because of their ease of packing into a diaphragm of reproducible permeability, and because they represent tn-o different types of surT A B L E 11 face. The isocyanate sponge> was similar to that manufactured by the Hudson Cnsh-?;-Foam Corporation. This 1 ~ I , P L \ l ) L \ ( F 0 1 ' SI'RE-\\II\(r C t F I C I h \ C l O\ 1 H L material was leached with water until free of ionic impurity 111 ( T I V I P Y OF TILE STRhA\IIh(. IAQC 11) ( 2 5 " I as determined by the conductivity of the leaching water. The sponge was t u t into i t vylindrical shape so that it ~ v o n l t l fit firmly into the sample holder of the itpparatiie.l The resistance of the plug R xi-as determinrd iising the technique of Iieale and Peters. l,/Q was calculated from a combination product of the tqerimental parameters ( EI'AP) Quai,tz wool 0 14 2.10 ( l P / Q ) (1 / R ) . Various plug permeahilities xere obt:tined 17 2 0 2 84 Q,/'AP: 0.W by compressing the sample int,o the holder by a thin-wdllrd 5 7 (i.81) r n ~ . ~ , ' w r . - X3 glass tube retainer. Thil diaphragm thiis i w s held a t :t 50 8 5 12.46 1.m. particular comprrssion during the mcmurcmc.nt with t h e minimum possihlr obstruction. 70 12.8 24.88
Results and Discussion Results of temperature studies on bot,h quartz wool and isocyanate sponge are given in Table I. I n general, the streaming efficiency of isocyanate ( I ) Based in p a r t on t h e Pl1.1). dissertation ot Armand F. Lewis, Lehigh University, October, 1938. ( 2 ) -4merican C y a n a m i d C o m p a n y , S t a m f o r d , Conn. (3) H. B. Bull a n d L. 8. Jloyer. THIS . I o I - R s ~ I . , 40, 9 (1936). (4) R. R. Myeis a n d -4. F. Lewis, t b t d . , 64, l9tj ( I Y G O ) .
100
li.R
cO\-
28.46
1 4 1 82 Isocyariatt, 0 sponge 25 4.6 5 69 Q / A I ' : 0.15 42 7 2 8 87 18 0 18 10 cm.3/ser. fm. 100 Same diaphragms as used in Table 1.
The influence of hydrodynamic permeability of the diaphragm on efficiency was studied by stream-
1339
SOTES
iiig water through quartz wool and isocyanate sponge held at various compressions. In Table 111, the permeability changes are represented by two factors, t'he solids density and the flow rate per TABLE I11 E F F E C T O F 'k'ERMESBILITY t
IF
QuAwrz
T.i.rli.t
h,"
('III.
6.3 5.5 4.8 8 I) 2.3 I
O S THE STRE.4ILIIXG
?';
Quartz wool 0.92 1.21 .82 2.15 .6i 2.29 .66 2.05 .49 2.13
Isocyanate sponge .33 1.22 ,26 .20 1.35 4. .2i .1R 1.40 3.9 ,:31 .I6 1.47 3.8 .32 .14 1.51 2.6 .47 .04 2.01 2.4 .5l .03 2.32 2.0 .61 .O1 2.46 3.0 ,05 1 .OO 1.48 3.0 .08 1.(io 1.23 3 .0 .0u 1.30 1.11 3 .0 .13 0.47 0.95 3.0 .38 .19 1.42 3 .0 .47 .ll 1.59 3.0 .53 .04 2.21 3.0 .B1 .01 2.84 01 Diameter of all diaphragms, 1.1em. ,i 2 4.i
EFFICIEXCY
\T-OOL AXTI ISOCYAS.4TE S P O S G E DIAPHRAGILIS .Solids ()/At'. AP/E I/(J Efii'm.3/ X lo-?, X 10-2. ciencs set'.-cm. e . s . i i . / c i i i . 3 e.s.ii./ciri.a x 10s
0.06 .07 .08 .10 .17 ,%
Acknowledgment.-The authors are pleased t o ncknowledge the support of the Armstrong Cork Company whose interest in electrokinetics made this work possible. In addition, the authors wish to thank Mr. M. Z. Nammari for obtaining some of the quartz wool data for this study.
2.10 1.41 1.30 1.74 1.62
1.74 0.65
:3,55 4.34 3.91
2.91 3.22 2.80 3.04 3.35 6.55 7.36 9.07 0.26 0.49 0.60 2.13 2.12 3.10 3.69
4.47
5.07 13.16 17.04 22.30 0.38 .62 .67 2.02 3.00 4.95 8.16 20.50
.57 .85 .76
7.23
unit pressure across the diphragm, Q l A P . A wide range of permeability could not be attained with quartmawool plugs; hence the effect of permeability on efficiency x a s not clearly defined. On the other hand, the permeability of isocyanate sponge was varied in two ways. First, t'he amount of sample was held constant and then compressed t'o various lengt'hs; second, the sample was held at const'ant, length ( 3 em.) and the permeability was varied by changing the packing. Under both conditions the efficiency increased at decreased permeability. The data present'ed show that permeability drast,ically influences the streaming efficiency below a Q,!AP of about. 0.1 ~m.~/sec.-crn.Since this behavior is not predicted by classical theory of streaming potential, much doubt is cast on existing literature which reports streaming data at lorn permeabilities. A similar conclusion has been made by Biefer and In general, streaming potential generation is a very inefficient process with efficiency values in the order of low5, depending upon experimental conditions. The results presented illustrat'e that t8hestreaming potential phenomenon can be a useful tool for studying the solid-liquid interface without employing t'he classical approach. Furthermore, this analysis gives a broad picture of the streaming potential effect which may serve as a basis for future studies in the field. ( 5 ) G . J. 13iefi:r and S. G. AIason, Trans. Faraday Sac., 5 5 , 1239 (19.59).
T H E HEATS OF FUSIOK O F THE CADMIUJI €IAT,IDES, MERCURIC CHLORIDE *IXD BISMUTH BROMIDE BY L. E. TOPOL A X D L. D.
R.4sso~
Atomics International, A Division o f Y o r l h A m e r i c a n Aviation, I n c . Canoga Park, California Reremed March 81, 1960
In the course of invest'igations of molten metalmet'al salt syst'ems in this Laboratory, cryoscopic measurements in CdCl2, CdBrz, CdIz, HgClz arid BiBra solutions have been carried out. Interpretation of these results required an accurate value for the heat of fusion of t'he salt solvent. As the literature values for the heats of fusion of the above salts were all based on cryoscopic measurements and thus, as has been shown in recent calorimetric studies with other s a l t , ~ may , ~ . ~be of doubtful accuracy, a calorimetric study was made to determine these values. Experimental Materials.-CdC12, CdBrn and Cd12 were prepared and purified as described elsewhere.4 BiBra was synthesized from the elements in a similar manner to CdBr2. HgC12, Rlallinckrodt analytical reagent grade, was dried overnight a t 140" i n vucuo. Apparatus and Procedure.-The drop-calorimeter and procedure were identical to those used earlier.* A minimum of six drops over a 60 to 100' range both above and below the melting point of each salt was made. The salt samples, 10 t o 20 g. in weight, mere contained in platinum and were always melted before the measurements were carried out t o ensure intimate contact between the salt and container. In the case of HgClz the possibility of reaction between the salt and container was checked by X-ray fluorescence techniques. Within the sensitivity of the method (0.5% by weight) no platinum was found in the salt phase.
Results and Discussion The calorimet'ric results for CdCl2, CdBr2, CdIz, HgClz and BiBr3 found in this study together with the literature values for the heats of fusion5f6 are listed in Table I. The heat capacities of the salts were assumed to be constant for the limited temperature ranges of the measurements. It is interesting to note that the heats of fusion report'ed in the literat'ure were determined cryoscopically and are lower in every case than the calorimetrically measured values. These lower results might be expect'ed when solute concentrations are not sufficiently dilute to permit accurat,e use of the Raoult-van't Hoff relation. (1) This work was supported by t h e Research Division of the Atomic Energy Commission, ( 2 ) L. E. Topol, S . W. 3Iayer and L. D. Ransom, THIEJOURS.AL, in press. (3) 4 . S. D a o r k i n and AI. A . Bredig, THIS JOVRSAL,6 4 , 269 (1960). (4) L. E. Topol and A. L. Landis, t o be published. ( 5 ) K. K. Kelley, U. S. Bur. Mines Bull. 393, 1936. ( 8 ) L. Brewer, et al., "The Chemistry and Metallurgy of Miscellaneous ,Materials: Tlierniodynaniics," ed. by L. L. Q ~ i i I l ,3IcGraw-Hill Book Go., S e w T o r k , S . Y.,1950.
