0. E. WAGNERAND W. E. DEEDS
288 nesium perchlorate, probably by reaction of the oxide with HC104 from the ammonium perchlorate, and then a melt of ammonium perchlorate and magnesium perchlorate forms in which the oxide steadily dissolves as 0 2 -ions are removed by (14). This mechanism thus explains the long established use’ of ammonium perchlorate to form magnesium perchlorate from MgO and the fact that the formation of Zn(C104)2has been confirmed in the catalysis of the ammonium perchlorate decomposition by ZnO.l6 It is difficult to assess how essential to the reaction is the formation of a melt. There is, in fact, no real evidence from dta that melting occurs. However, this may be taken to imply that the whole mixture does not form a molten phase; partial melting at the interface between the two materials is not excluded by the dta evidence. The primary evidence would appear to be (i) the fact that the decomposition of Clod- occurs at a much faster rate in the mixture of magnesium perchlorate with ammonium perchlorate than it does in the
pure magnesium perchlorate and (ii) the fact that the addition of PbO, ZnO, or CdO to ammonium perchlorate promotes melting.16 Thus although total melting of the reactants evidently is not a prerequisite for reaction, partial melting at the magnesium perchlorate-ammonium perchlorate interface probably does occur and has the effect of greatly accelerating the decomposition of ammonium perchlorate, as outlined above. Barium perchlorate is not a catalyst for the ammonium perchlorate decomposition’ and this is also easily understood in terms of our mechanism, for barium perchlorate decomposes to form the chloride, not the oxide, and so does not form a proton acceptor.
Acknowledgment, We are indebted to the National Research Council of Canada for their support of this work. (15) A. V. Boldyreva and V. N. Mozzhova, Kinet. Katal. 7, 734 (1966).
Some Electronic Properties of Solutions in Solid Matrices by 0. E. Wagner and W. E. Deeds The University of Tennessee, Knoxville, Tennessee 97916
(Received July 8, 1969)
It has been found t h a t salts together with a little solvent imbedded in an insulating material provide some very interesting electrical characteristics as well as a promising method of obtaining molecular parameters. The slope of the log polarizability vs. 1/T curve over a limited temperature range was found to be proportional to the ionic dissociation energy of the included molecule. Similarly, the slope of the log resistivity vs. 1/T curve was found to be proportional to the ionization energy of either the cation or anion plus the ionic dissociation energy. Solving both of the above curves simultaneously gave very good values for the electron affinities of the radicals which became the anion. This provides a method for obtaining electron affinities of radicals which heretofore were considered intractable. With larger amounts of a proper solvent present the dielectric constant was found to be larger than lo7at room temperature. Thermoelectric and other measurements on the filled matrix indicated electrons and/or holes as carriers depending on the type of salt used.
Intd u c tion There is very little literature on the physics of electric conductivity and polarization phenomena manifested by salt-filled porous matrices. The thermodynamic properties of dispersed molecules have been studied quite extensively,’ but the electrical parameters such as dielectric constant and resistance have not. At present there are many molecules whose parameters are very difficult to study by conventional methods and thus a i y applicable new methods would be desirable. It is hypothesized here that if mo~ecu~es are dispersed in a matrix, the effects of other molecules and the matrix The Journal of Physical Chemistry
can be combined into an averaged dielectric constant. It will also be assumed here in general that chemical bonding to the matrix has not occurred. For the purposes of this paper, the matrix is defin.ed to be a porous substance where the pores are of molecular size or larger. The voids or pores are assumed to be interconnecting so that there is a continuous path through the matrix. The latter assumption is made be-
(1) D. H. Everett and F. S. Stone, “The Structure and Properties of Porous Materials,” Butterworth and Co., Ltd., London, 1958, pp 1-389.
289
ELECTRONIC PROPERTIES OF SOLUTIONS IN SOLID MATRICES cause as yet a method has not been found to seal the pores of the matrix on enclosed molecules. The matrices may be any molecular structure with pores larger than the specific molecule to be put into the pore. The matrices may be ceramics, organics, or combinations of compounds especially designed to achieve or eliminate certain observed effects. A typical matrix might be a metal oxide such as TiOz, MgO, A1203, Zr02, NbzOs, Vz05, or any other oxide that is inert to the included solution’s constituents. Matrices can also be made of cellulose or wood (which is mainly a combination of cellulose and lignin). Combinations of types of matrices may be used. In general it is desirable that the matrix provide an environment where the included molecule retains its identity. Further combinations of solids which do not include the above can be imagined. Wood together with porous ceramic are the chief matrices used in the present work. Wood was found to be most stable as a matrix for most of the molecules tested. Care was taken to remove the volatile substances from the wood by boiling the matrix material for several hours in distilled water. The data obtained from using wood matrices speaks for itself. Wood is very inert to many substances which react with other matrices. Chemical interaction of the matrix and the dispersed molecule was avoided in general, although some interactions were observed in a few cases. Since very large resistance changes were observed with changes in temperature, it was first assumed that a melting phenomenon was occurring. This was questioned, however, because the resistivity did not change abruptly but varied exponentially over a large temperature range. It was evident that the effect could be used to provide a very sensitive thermistor. From the start it was assumed that the slope of the resistivity vs. temperature curve would be a function of the dielectric constant. To test this hypothesis, the dielectric constant was measured. I n measuring the dielectric %onstant” it was observed that the dielectric constant was not constant. One of the first molecules studicd with respect to dielectric constant was NaC1. It was found that the slope of the log dielectric constant vs. 1/T curve a t the lower temperatures provided almost an exact measure of the known dissociat)ion energy, as did also the slope of the KCl curve. Other molecules also provided very close values. The first molecules studied were diatomic molecules. Since such good dissociation energies were found for diatomic molecules, other polyatomic molecules were tested with good results. The first three molecues studied (NaCl, KC1, and I
