The History of Ozone. Vi. Ozone on Silica Gel (“dry Ozone”) (1)

As part of a general study of the interaction between gases and solids in the laboratory of Alfred Magnus (Fig. 1) at the University of Frankfurt, Magnus and Grähling (2) reported the adsorption of ozone on silica gel in 1929. These measurements were complicated by the thermal instability of ozone, which, as shown by Magnus and Grähling, was further catalyzed by silica gel. A second problem was the low concentration of ozone in oxygen obtained from conventional ozone generators. Nonetheless, Magnus and Grähling found that considerable amounts of ozone could be adsorbed on silica gel at low temperatures where decomposition was not a problem. The average heat of adsorption of ozone, measured by taking the difference between pure oxygen and ozone-oxygen mixtures was 5,600 cal/mole with a temperature coefficient of -175 cal/ deg. The corresponding values for oxygen were 3,200 cal/mole and -30 cal/deg. Thirty years later Cook et al (3) performed a similar study with results in agreement with those of the earlier work. They measured the adsorption isotherms (Fig. 2) for ozone on silica gel over the range -78.5o C to -140o C as a function of ozone THE HISTORY OF OZONE. VI. OZONE ON SILICA GEL (“DRY OZONE”) (1)