The oxidation, by oxygen, of the sulphide ion a t very low concentrations in aqueous solutions has been studied at various temperatures and hydrogen ion concentrations. Under all conditions the reaction was close to first order with respect to the sulphide ion when other variables were constant. The rate of oxidation was enhanced by an increase of pH and temperature, and by increasing the 0xygen:nitrogen ratio in the gas mixture. The overall reaction is summarized as follows Wellington, New ZealandThe first reaction is the initial rate-determining step, followed by the rapid removal of S042-and S2032-, and finally the slow oxidation of the S2OS2-ion and elementary sulphur to ion from solution as THE oxidation of hydrogen sulphide by oxygen has been studied mainly in the gas phase in the presence of cata1ysts.l-7 Abel,s however, studied the reaction of hydrogen sulphide and oxygen in aqueous solutions and suggested that it proceeds through the 0,SHion which is formed from HSas electron donor and 0, as electron accept or.Studies of the sulphide ion in aqueous solutions have shown that it is essential to keep all traces of oxygen from the solution to prevent the rapid removal of the sulphide ion as sulphur or sulphoxy compounds.
Pigs were fed for 16 weeks on diets containing 0.1, 1.0, and 10.0 ppm of hexachlorobenzene (HCB). Back fat was sampled during the dosing period and the following 22 weeks. Maximum concentrations of HCB attained in the fat were approximately proportional to the dose rates and were 0.68 ppm, 6.0 ppm, and 56 ppm (group means) respectively, with a biological half life of 10-12 weeks for all levels of administration. The trial indicated that HCB--treated cereals. fed to pigs either accidentally or as a supplementary ration, would give high residues of HCB in body fat.
I t is found that the primary decomposition involves the cleavage of a C-H bond. Both primary and secondary hydrogen atoms are lost. The relative rates of the two processes could not be determined accurately but are estimated to be approxin~ately 1:l. I t is found that a t least 70% of the secondary reactions involves the interaction of hydrogen atom with a propyl radical. The main reaction is the re-formation of propane. An important disproportionation of hydrogen atoms with propyl radicals leading to propylene is shown t o occur. The atomic cracking reaction H + C3H7 + C3Hs* + CzHs + CH3 is also observed. Using mixtures of C3H8 and C3Ds the relative cracking rate of n-propyl-t o isopropyl-derived propane is determined t o be equal to 5. This result is compared with theoretical predictions.
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