COMMUNICATIONS TO T H E EDITOR T H E DECOMPOSITION O F OZONE BY ALPHA PARTICLES AND BY THERMAL MEANS'
I should like t o report the results of experiments carried out one and a half years ago with W. Feitknecht in this laboratory on the decomposition of pure ozone by alpha particles from radon a t room temperatures. The M / N ratio, the number of molecules decomposed per ion pair, was found to be high, varying from about 4,500 a t 50 mm. ozone to about 15,000 a t 300 mm. ozone. The rate of decomposition followed the equation
where for a series of runs n was found to be 1.5. Very good constants were obtained throughout a given run and the constant was the same for different pressures. The rate was independent of the presence of oxygen. The M / N ratio was found to be proportional to [03]2'3. Since ionization by alpha particles is practically proportional to the pressure in the range investigated, this makes the rate of decomposition proportional t o [03]1.67, in substantial agreement with the rate found. It is thus seen that rather long chains are possible in ozone decomposing a t room temperatures. These facts provide evidence in favor of the viewpoint of Riesenfeld and Wassmuth (Z. physik. Chem. 8B, 314 (1930)), but not that of Schumacher and Sprenger (Z. physik. Chem. 6B, 446 (1930)). These experiments are to be extended and will be reported on later. More recently, during a study of the kinetics of the explosion of ozone induced by hydrogen, a rather complete series of experiments on the thermal decomposition of pure ozone was made a t 85°C. between initial ozone pressures of 40 to 200 mm. and in different glass and quartz vessels. The rate of decomposition is represented by the equation
K remains constant down to 80 per cent decomposition, which is as far as the reaction was carried usually. K seems to depend on theinitial concentration, for it increases somewhat as the latter is raised. I n a 'Published by permission of the Director, U. 5. Bureau of Mines. to copyright.) 533
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COMMUNICATIONS T O T H E EDITOR
given run the rate is independent of the oxygen concentration, but K is higher for an initial mixture containing ozone plus oxygen than for a similar amount of ozone alone. On investigating the published results on this subject of Schumacher and Sprenger (loc. cit.), who employed a 5-liter cylindrical vessel, Riesenfeld and Wassmuth (Z. physik. Chem. 143,408 (1929)), and Riesenfeld and Bonholtzer (Z. physik. Chem. 130, 255 (1927)), it is found that their experiments also are represented very well by the same relationship. When corrections are made for the temperature, using the known temperature coefficient, and when allowance is made for the initial pressure, the rate constants of their experiments derived from the above relationship agree quite well with the present ones. These authors have explained their rates by supposing that a monomolecular and bimolecular reaction are occurring simultaneously despite the fact that their corrected “true” monomolecular and bimolecular constants change with initial pressure (particularly the monomolecular constants, see Z. Physik. Chem. 143,408 (1929)). All the experiments are now in agreement and may be assumed to be correct. The interpretation yet remains. It seems more natural for the reaction to be represented by a simple formula rather than t o introduce unnecessary complications of simultaneously occurring monomolecular and bimolecular reactions. The 1.5 power indicates that the reaction is to be explained by a chain mechanism, just as in the alpha ray experiments. What this mechanism is will be left for a future publication. BERNARD LEWIS. U. S. Bureau of Mines Pittsburgh Experiment Station, Pittsburgh, Pa. THE ADSORPTION OF RADON BY SILICA GEL
I n view of the work of Francis (Kolloid-Z. 69,292 (1932)) on the adsorption of radon by silica gel, certain measurements of ours, made under widely different conditions, should be of interest. Our measurements were made by a static method, using comparatively large amounts of radon; the pressure of the other gases present was very low, not more than four or five times that of the radon itself, The silica gel used in these experiments was a clear glassy gel which had been purified by treatment with concentrated nitric acid. It was then dried in a stream of air at about 3OO0C., and finally electrodialyzed for a long period of time. Before use it was dried once more a t 300°C. The gel contained about 5 per cent of water. I n one experiment, 34 millicuries of radon were left in a glass tube, which contained 1 g. of silica gel, for twenty-four hours. The portion of the tube containing the silica gel was then sealed off from the rest, and the
