When nitric acid solution containing carrier-free "'I was heated, a fraction of the '"I was converted to organic iodides, among which methyl iodide was a major component. The yield of organic iodides showed a strong dependence on the concentration of nitric acid. Furthermore, the yield curve referred to reaction time revealed the particular characteristic of a hump appearing in the case of diluted nitric acid solutions. The distribution of I3'I among the various oxidation states in the acid solution has also been studied in its relation to reaction time. The results obtained indicate that organic iodide formation is related with the Io-IOa-oxidation step. The yield curve of the organic iodides is discussed qualitatively, by assuming an intermediate state I* existing between two extreme states of oxidation.

In order to examine the relative importance of the thermal ionic process in the reactions of 80Br from the (I. T.) process with C3H8, we chose C2H6 or CH3Br as diluents. Some assumptions have made in estimating the yield-variation of products from the diluents: 1) the rate of the reduction of the yields of the products from C3H8caused by the addition of the diluent is the same for all of the products and 2) the ionic yield is zero over the whole range of concentrations of C3H8. With these assumptions, the analysis of the results shows that the contribution of the thermal ionic process in these binary systems has only minor importance; the products are, essentially, formed via energetic processes. It is also found that the ratio of n-C3H780Br/i-C3H780Br per bond basis seems to decrease from 1.1±0.1 on the addition of the diluent. This indicates that the formation of i-C3H780Br is a lower energy process, relative to that of n-C3H780Br in the present reaction system.

No abstract

When nitric acid solution containing carrier-free "'I was heated, a fraction of the '"I was converted to organic iodides, among which methyl iodide was a major component. The yield of organic iodides showed a strong dependence on the concentration of nitric acid. Furthermore, the yield curve referred to reaction time revealed the particular characteristic of a hump appearing in the case of diluted nitric acid solutions. The distribution of I3'I among the various oxidation states in the acid solution has also been studied in its relation to reaction time. The results obtained indicate that organic iodide formation is related with the Io-IOa-oxidation step. The yield curve of the organic iodides is discussed qualitatively, by assuming an intermediate state I* existing between two extreme states of oxidation.

The moderator effect of Kr on the reaction of (I.T.)-activated 80Br with CH4 has been examined, keeping the ratio of Br2/CH4 at 0.02 or 0.05. The yield of CH280BrBr shows a slight decrease at the beginning of moderation and then tends to increase with further moderation. These facts suggest an additional formation of CH2-80BrBr via a thermal ionic process in highly-moderated systems. When the concentration of Br2 is varied in the system containing 10 cmHg of CH4 and from 40 to 36 cmHg of Kr, the yield of CH280BrBr first increases and then decreases, showing a broad maximum. This dependence not only partly explains the inconsistence of the present results with those previously reported, but also suggests the competition of two types of reaction in its formation. One must be the reaction of a radioactive radical with Br2, leading to the formation of CH280BrBr: ·CH280Br+Br2→CH280BrBr. The other type of reaction is a scavenging reaction of Br2 for the reacting 80Br atom.