Mar., 1955 will meet with the proper orientation and favorable distribution of the activation energy at the moment of collision to allow the union of the two species to occur. On the other hand the abstraction of a hydrogen atom by oxygen here should not require a highly unusual set of conditions if the requisite activation energy is available, and Pz is probably of normal magnitude. Two interesting observations proceed from the above. (1) It is remarkable how closely this large group of experimental studies agree with one another when analyzed in this fashion, as shown on the figure, particularly in view of the complex nature of hydrocarbon oxidation mechanisms. (2) The probability factor deduced for reaction 1 by this method of analysis has the abnormally low value frequently found in similar bimolecular reactions where a more complicated structure is formed by combination of reactants. These results lend additional support to the hypothesis that reactions 1, 2 and 3 are the predominating reactions of the propyl radical in the oxidation of propane.
NOTES
285
40”. These showed the tie lines a t all temperatures to be essentially the same.
50% Acetic acid
Fig. 1.-0, 25”; 0 , 15”; A, 40”. Experiments were carried out a t 15, 25 and 40”. Data are given in the graph. Because of the small temperature coefficient of solubility over this range one point was determined a t 80” and also is given on the graph.
ACTIVATION ENERGY AND ENTROPY FOR ADSORPTION BY TARAO KWAN~ The ReWarCh Institute f o r Catalysis. Hokkaido University, Sapporo, Japan Received October 16. 1964
It is well known that there is a regular relationship between the activation energy and the frequency factor of the Arrhenius equation, IC = A e - E / R T expressed , by log A = c bE (c and b are A COntr%‘butiO?ifrom the Chemistry Department, Lebanon Valleu College, constants),2 when a chemical reaction takes place Annville, Penna. over a series of catalysts of a similar type. This Received September 66, 1964 means that the rate constant does not change as During a study of the oxidation of certain alco- much as might be expected from the change of E hols being carried out in this Laboratory, it became because the term A acts simultaneously in a comnecessary to determine the distribution of benzalde- pensating manner. hyde in an acetic acid-water system. Since a There are many other examples of this phenomesearch of the literature revealed no data on this non. The Richardson formula for electron emissystem, a study of the three-component system sion, i = AT2e-eq/kT, is subject to a compensatory benzaldehyde-water-acetic acid was made. effect between the work function (o and the constant A when the metal surface is covered by various Experimental gases.3 The specific conductivity of a semiconBenzaldehyde exposed to the atmosphere for a short time was found to contain about 2% benzoic acid. Eastman Ko- ductor which has the form u = ae-e/kT, and subdak white label benzaldehyde was distilled a t a pressure of 3 stitution reactions in organic chemistry sometimes to 7 mm. of mercury under a nitrogen atmosphere. The show a similar trend.4s5 benzaldehyde purified in this way had a refractive index of This effect also has been observed for the adsorp1.5443 at 20” (lit. value corrected to 20” is 1.5456).’ Titrations of aliquots of this benzaldehyde in water showed that it tion of gases on solid catalysts. Here we shall instill contained 0.1% acid. This content was considered vestigate the effect for the adsorption of nitrogen satisfactory for this study and benzaldehyde was used with- on a promoted iron catalyst. The rate of the adsorpout further purification. It was stored in a nitrogen atmos- tion of nitrogen on the catalyst can be expressed phere and all transfers were made in a nitrogen atmosphere. Glacial acetic acid and distilled water were used throughout. by6v7 THE THREE-COMPONENT SYSTEM BENZALDEHYDE-WATER-ACETIC ACID BY ALEXANDER R. AMELLA N D TnoMAs TEATES
Temperatures of all reactions were held constant to within 0.5”. Known weights of benzaldehyde and acetic acid were buretted into a flask and titrated with water to the appearance of the second phase. I n the titrations in which the water concentration was very high, benzaldehyde was titrated into known weights of acetic acid and water to improve the sharpness of the end-points. Various known mixtures in the two-phase region of the three components were thoroughly mixed and the layers separated. The densities of the layers were determined and each layer titrated with standard sodium hydroxide. From these data the tie lines were determined a t each temperature by standard procedures.2 At 25” a number of tie lines were determined but only one t,ie line each a t 15 and
(1) N . A. Lange, “Handbook of Chemistry,” Handbook Publishers, Inc., Sandusky, Ohio, 1952, p. 1313. (2) Daniels, Metliews and Williams, “Expcriiiiental Physical Uhemintry,” McGraw-Hill Book C o . , Inc., New York, N . Y.,1949, 1,p. 117-120.
+
where p is the pressure of nitrogen at time t, 8 the fraction of surface covered, and a,k. are constants. As shown in Fig. 1 a varies linearly with the reciprocal of absolute temperature within a range ( 1 ) Fulbright scholar, now visiting lecturer, University of Washington, Seattle, Washington. (2) G . M. Sohwab, H . 8. Taylor and R . Spence, “Catalysis,” Van Nostrand Co., New York, N . Y., 1937, p. 286. (3) J . H. de Boer, “Electron Emission and Adsorption Phenomena,” Cambridge Press. New York, N . Y . , 1935, p. 152. (4) W. Meyer and H. Neldel, Physik. 2..38, 114 (1937). ( 5 ) For example see I. Meloche and K. J. Laidler, J . A m . Chem. Soc.. 73, 1712 (1953). ( G ) T. Kwan, J . Res. Inst. Catalysis, 3, 16 (1953). (7) T. Kwan and I
