NOTES
750 TABLE I1 DIPOLEMOMENTS AT 1 Mc. Condition of
Form
prep.
A. Amine Sulfate Bisulfate
[HzSOal/ [ZRI
[ygI\/
P X
10'8
I-(3-ei,hylperityl)-4-ethyloctylamine dry (No H2S04)0.1 t o > I 5.07, 4.08 wet 0.500 4 4.05 wet .BO8 3 3.50
Amine Sulfate Sulfate Bisulfate
B. Di-n-decylamine dry (No H2S04) 1 wet ,500 1.5 wet . G74 no analysis
Amine Sulfate Bisulfate
C. Tri-n-octylamine dry ( N o H2SO4) < I 2.5 wet 0.494 wet .943 0.94
2.05 4.4,3.67 4.G7 5.13 0.277 6.77 5.40
deviations from linearity in the measurement of dielectric constants of various tri- and tetraalkylammonium picrates and bromides in benzene. They attributed this effect to an increase in aggregation with concentration, and noted that very symmetrical molecules showed little deviation from linearity, while very unsymmetrical ones showed large deviations. For the present solutes, the light scattering measurements indicated monodisperse aggregates; in addition, there is apparently little or no correlation between the non-linearity observed here and molecular symmetry. It seems likely that some other effect is responsible for the deviations observed. It is to be noted that the magnitude of the dipole moments in Table 11 are in a reasonable range for such compounds, although all are somewhat lower than the picrate, acetate and halide salts of some tertiary amines recorded by Geddes and Kraus. Corn pound
Tri-n-butylammonium Tri-isoamylammonium Tri-n-butylammonium Tri-n-butylammonium Tri-n-butylammonium
p
picrate picrate iodide bromide chloride
x
10'8
13.1 13.3 8.09 7.61 7.17
These differences are to be.expected from the more symmetrical arrangement of two alkyl ammonium groups associated with the sulfate radical. Of the compounds investigated here the dipole moments of the free amines show the expected t'rend, Le., primary > secondary > tertiary. I n the case of the amine sulfates, however, the tertiary amine shows a higher dipole moment than either the primary or secondary amine. Since the latter amine sulfates are known to be aggregated, while tri-n-octylamine sulfate is monomeric, this suggests that the moments due to the primary and secondary amine sulfate monomers in the aggregates are partially cancelled by their spatial arrangement. The bisulfates of these amines are likewise out of the expected order. Tri-n-octylamine bisulfate, which is known to be dimeric, shows a sharp decrease in po(8) G. S. Hooper and C . A. Kraus, J . Am. Chem. Soe., 66, 2265
(1934).
Faladay Soc., 3 2 , 585 (9) J. A. Geddes and C. A. Rraus, !!'Tans. (1936); C. A . Iiraus, THISJOURNAL,60, 129 (1956).
Vol. 63
larity from the sulfate, again in qualitative accord with masking due to the molecular grouping. Understanding of the dielectric behavior of these solutes is, of course, far from complete. Among the questions remaining to be answered is the role of water in the apparent dipole moment and in the degree of aggregation of the amine salts in organic diluents. In this connection the behavior shown by a relatively dry sample of di-n-decylamine sulfate is interesting (see Fig. 5 ) . The solution contained a small amount of water (ca. 0.06 mg./ml.), and a change in slope of the dielectric constant curve for this solute occurs in the region of two waters per mole of amine sulfute.10 This suggests the possibility of a stoichiometric hydrate, which may be of importance in controlling the extent and/or the stability of the aggregation. (10) Since the initially dry amine sulfate was dissolved in and successively diluted with benzene containing ca. 0.00 nig./ml., as t h e concentration of amine sulfate was reduced tlie ratio [ H r O l l [Amine sulfate] increased.
ELECTROLYTIC JUNCTIONS WITH RECTIFYING PROPERTIES BY B. L O Y R E ~ EA. R ,DESPI@ ~ AND J. O'RI. BOCKRIS John Harrison Laboratory o f Chemistry, Uniucisity of Pennsylvania, Philadelphia, P a . Received September 8, 1968
Reiss3 and Fuller4 have pointed out that the excess and decess of electroiis in, e.g., Si and Ge, containing impurities, corresponding to n- and p-type semiconductors, respectively, have a strong analogy to the excess and deficiency of protons in water, corresponding to acid and alkaline solutions. It follows that there should be a possibility of achieving, utilizing only aqueous electrolytes, the well known rectification of alternating electric current which occurs a t a junction of n- and p-type semiconductors. The purpose of this communication is to report that this has been achieved. The idealized electrolytic analogy to the p-n junction would consist of an electrolytic solution (A) containing an excess of highly mobile protons, together with corresponding anions so large as to be entirely immobile; and in coiitact with this a second solution (B), containing an excess of highly mobile hydroxyl groups, together with corresponding cations so large as to be entirely immobile. Suppose that inert electrodes are introduced into A and B and an alternating current applied across them. During the phase in which A is positive and B negative, the current carrying Hfand OH- ions will be impelled toward each other, meet a t the interface, and, in principle, form water. For this phase. therefore, curreiit flow will be easy. In the reverse phase, the mobile current carriers cannot flow freely in the opposite direction to that cocsidered in the first case, because they would have to be supplied by the dissociation of water at the interface between the two liquids, and this is slow (rate constant Kd = 2.6 X 10-5).6 Consequently, rectification should occur. (1) University of Zag1 eb, Zagreb, Yugoslavia. ( 2 ) University OI Belgrade, Belgrade, Yugoslavia. (3) H. Reiss, J . Cham. P h y s . . 21, 1509 (1953). (4) C. E. Fuller, Ree. Chem. Proyr., I T , 75 (105G).
8
NOTES
May, 1959 I n practice, rectification of alternating currents has been observed with the following practical approximations t o the above idealized system. (1) One electrolyte is an aqueous solution of a strong polyacid; the other is an aqueous solution of a strong polybase. The polyacid and polybase should both be of the highest practical molecular weight. The two electrolytes are separated by a thin dialyzing membrane and one electrode is immersed in each. I
I+I
I
1-1
Fig. 1 .
(2) The electrolytes are a cation-exchange membrane in H + form and an anion exchange membrane in OH- form. The membranes are pressed against each other. T o make the electrical contacts, each membrane has ail adjacent electrode compartment filled with a suitable electrolyte in which ail inert electrolyte is immersed. Both types ( 1 ) and (2) were constructed and the rectification effects detected. For type ( l ) , solutions of polyvinyltoluenesulfonic acid and polyvinyltrimethylbenzylammonium hydroxide (kindly supplied by the Dow Chemical Co.) were used. Dialyzing parchment was used as a membrane. A rectifying element of type (2) was constructed of NeptonCR-6lAD and Nepton AR-111AD membranes in H + and OH- form, respectively. A thin perforated Teflon sheet (0.02 mm. thick) was placed between the membranes to reduce the active surface of the rectifier in respect to outer surfaces in contact with electrolytes. In most experiments the electrolytes were pure water. Platinum gauze electrodes were used. A.c. voltage (60 c.P.s.) was applied across the electrodes and the resulting current-voltage relation was observed directly on a CRO screen. A typical rectification curve obtained is shown in Fig. 1. A multi-element device was also composed by connecting a number of single elements of type (2) in series. Each “sandwich” was separated from the next by a thicker Teflon spacer, the free space being filled wit,h water. Electrode compartments were added to the end elements on both sides. Rectification efficiencies up to 85 % were observed. It is known that certain biological systems also exhibit rectification properties.6 The above described model of a rectifying electrolytic junction may possibly be applicable also to these systems. (5) M . Eigen and L. De Rlaeyer, Z . Eleklrochem., 69, 986 (1955). (6) T:Teorell, Z . physik. Chem. Neue Folge, 16, 385 (1958).
75 1
PORE STRUCTURE OF SINTERED GLASS FROM DIFFUSION AND RESISTANCE MEASUREMENTS BY I. FATT D?uis?on of Mineral Technology. Universzly o f California, Berkpleu 4 > California Received September 1, 105s
Barrerl recently has proposed the use of transient diffusion measurements in porous media to determine the tortuosity factor of these media. He also called attention to the suggestion of Wyllie and Rose2 that tortuosity can be derived from the ratio of the specific electrical resistance of a porous medium saturated with a conducting fluid to the specific resistance of the fluid itself. The purpose of this note is to show that for a given sintered glass body the tortuosity calculated from precise transient diffusion measurements is exactly equal to thc tortuosity calculated from the specific resistnnce. Furthermore, this equality of the tortuosities iiidicates that the sintered glass has no “dead end” pore space or at least none which can influence the transient diffusion. (Dead end pore space is considered to be pore space which is connected to the main pore space but through which there is no diffusion or electrical flux when a diffusion or electrical potential is applied across the porous body.) Dr. E(. J. Mysels has very kindly made available to the aufhor, for the purpose of making resistivity measurements, the sintered Pyres discs used by Mysels and Stigtera in their development of a transient diffusion method for measuring the self-diffusion coefficient of micelles. Mysels and Stigter had previously measured the transport of sodium chloride in these discs. The tortuosity factor was calculated from the pore volume and length of the discs, and the slope of the transport ratio versus square root of time curves published by Mysels and Stigter.4 The transport equation for transient diffusion across an interface between two solutions was given by Mysels and Stigter as
for their experimental arrangement and in the range 0 < R t < 0.6 Rt is the transport ratio, t is time, q is the cross-sectional area open for diffusion, V Land Vu are the pore volume of the lower and upper chambers, respectively, and D is the diffusion coefficient. When the chambers are replaced by porous discs the open area, q, of the upper disc, into which diffusion is taking place, can be obtained from q = V,/L, where L, is the bulk length of the upper disc. Equation 1 then becomes
Mysels and Stigter used sodium chloride solution in the range 0.2 to 0.7 N as the diffusing material. (1) R. M. Bsrrer, THISJOURNAL, 57, 35 (1953). (2) &I. R . J. Wyllie and W. Rose, Nature, 166, 972 (1950). 67, , 104 (1983). (3) I
