Chemistry of Dissociated Water Vapor and Related Systems

Surface effects in the reactions of dissociated hydrogen–oxygen systems and the products condensed therefrom have been investigated. Water vapor at about 0.1 Torr was streamed at high velocity through an electrodeless discharge confined in tubes of different materials or with various surface coatings. In all cases the products trapped in liquid nitrogen evolved oxygen gas on warming, but the relative amounts varied considerably from one type of surface to another. In some cases there was clear evidence that the walls of discharge tube were attacked by hydrogen atom bombardment. The decomposition, both thermal and electrical, of pure hydrogen peroxide vapor was studied likewise. The pyrolysis products gave off very little oxygen on warming. By contrast the products from electrical decomposition, even at low power level, evolved much oxygen, most of it above the melting point.It is concluded that there is always some decomposition of hydrogen peroxide in the trapped products. However, this does not seem sufficient to account for all the evolved oxygen; at least not in the case of dissociated water vapor.

“…Varying the distance between the discharge zone and the cold trap altered the yield in the same fashion as reported before (3,13) acid surface (Fig. 1) for the reason already discussed.…”

Section: Miscellaneous Efsectssupporting

confidence: 75%

mentioning

confidence: 99%

Studies on hydrogen–oxygen systems in the electrical discharge. III. Surface effects

Brunet¹,

Deglise²,

Giguère³

1970

“…That this is so in the case of ozone has been proved abundantly (2). Now, the formation of ozone in our system requires a source of atomic oxygen.…”

Section: Discussionmentioning

confidence: 79%

“…In particular, the evolution of oxygen from the condensed products on warming has often been related quantitatively to the decomposition of Hz04 (2).…”

Section: Introductionmentioning

confidence: 99%

Studies on Hydrogen–Oxygen Systems in the Electrical Discharge. VI. Detection by Laser Raman Spectroscopy of O₂ and O₃ Trapped at 80 °K

Arnau¹,

Giguère²

1973

Further study by Raman spectroscopy of the condensed products from electrically dissociated water vapor and other related systems has revealed the presence, not only of ozone in appreciable amounts, but also of molecular oxygen in still greater amounts trapped at 80 OK. The concentration of ozone relative to the hydrogen oxides varied somewhat with experimental conditions, and also locally due to some segregation effect in the glassy condcnsate. The concentration of trapped oxygen showed still wider fluctuations depending particularly on surface effects in the discharge-flow system. On warming up under vacuum the intensity of the Oz and O3 bands began to decrease even before the crystallization temperature was reached (about 150 OK), thereby confirming that the gas evolution at that stage is mainly a desorption process. Therefore, the often quoted ratio of total evolved Oz to residual H z 0 2 could not be a reliable index of the formation of hydrogen polyoxides, H z 0 3 and H 2 0 4 , in these systems. A mechanism is proposed for the formation in situ of the trapped gases and in particular, for a source of oxygen atoms in dissociated water vapor.The fundamental vibrations of the ozone n~olecule, v, = 1106, v2 = 703, and v3 = 1036 cm-I, were confirmed by polarization and isotope shift measurements.

“…The HO,. radical is also observed when water containing OH radicals, produced by a microwave discharge, is condensed and the problem is discussed in some detail elsewhere (22,23). Recent work (24) indicates that reaction [4] has a surprisingly low activation energy (1.2 kcal mole-').…”

Section: Discussionmentioning

confidence: 99%

Electron spin resonance studies of radicals condensed from irradiated water vapor: reactions of the radicals

Wardman¹,

Seddon²

1969

Electrons and hydroperoxyl radicals are trapped in polycrystalline ice after irradiation of water vapor and rapid condensation to 77 OK. Using higher sample flow rates than in the earlier work of Seddon, Smith, and Bindner, the electron spin resonance spectra of the trapped electrons (e,-) were obtained in both HZO and DZO ice with negligible interference from the underlying HOZ. (DOZ.) radicals. Addition of C(NOZ),, H 2 0 z , (CH,),SO, and OZ as radical scavengers confirmed the earlier prediction that reactions with the radicals do not occur in the vapor phase in this system. The results with C(N02), and H z 0 2 also provided chemical evidence consistent with the spectroscopic assignment for HOz. (DOz.) radicals. Experiments with added isobutylene suggested that hydrogen atoms are formed (possibly in a post-irradiation reaction during condensation) and are also produced on photobleaching et-at 77 OK.