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Enrichment of I relative to Cl and Br in the air, in rain, and in river waters has long been known. To understand this enrichment, experiments were performed to examine the possibility of free evaporation of I from the surface of sea water. The experimental results showed that I can ‘vaporize’ because of the oxidation of iodide ions to free I in sea water under irradiation by solar light of wavelength up to about 560 mμ. On the basis of these results, the rate of I escape can be estimated to be 4×1011 g/yr for the whole ocean surface. This value is in fairly good agreement with the global rate of I deposition in rain.

Abstract18O content in cloud droplets is higher in a closed system than in an open system. It is also higher under a non-equilibrium condition than under an equilibrium condition.In case of the frontal type of precipitation, the observed variation with time in 18O content agrees fairly well with the calculation using an open model. The change in 18O content in convective shower which gives snow pellets can be explained by an open model.The isotopic exchange between falling rain drops and vapor is more effective in enriching heavier isotopes than evaporation.The calculated rate constant of isotopic exchange reaction between falling rain drops and vapor is about half of that given by FRIEDMAN et al. (1962) . A smaller amount of isotopic exchange than calculation was observed in rain water.The relationship between D and 18O contents in precipitation under an equilibrium condition can be expressed as an approximate straight line starting from the original point with a slope less than (aD-1)/(a18O-1) in the region of slight isotopic fractionation.The deviations from the straight line are explained by the effect of kinetic processes. The downward shift below the line is due to kinetic evaporation, while the upward shift is due to either the supply of source vapor under a kinetic condition or isotopic exchange between rain drops and vapor which has evaporated under a kinetic condition.A constant term in Craig's equation for the relation between D and 18O contents is derived by the fact that 18O content in source vapor is lower by 1.2% on an average as compared with D content.

The chemical composition of the air enclosed in ice collected in Antarctica was determined for seven samples of iceberg ice, two of glacier ice, eight of sea ice, and one of pond ice. Samples of sea ice collected on the coast of Hokkaido Island, Japan, were also analyzed for comparison. The pressure of gas in bubbles was measured. Glacier and iceberg ice contained more gases than sea ice or pond ice. The CO2 content of some of the samples was measured by isotope dilution. On the basis of the chemical composition of gas occluded in glacier and iceberg ice, the ice is classified into four types: (1) Ice derived from snow which contains only atmospheric air trapped in interstices between snowflakes. In it a CO2 content of 0.028–0.030% is observed, which is slightly lower than that in the present atmosphere. (2) Ice derived from snow with a small amount of ice originated from supercooled water which constitutes nuclei of snow crystals. (3) Ice mostly derived from meltwater. (4) Ice derived from snow, but the CO2 content is increased up to 0.1% for unknown reasons. The chemical composition of the occluded gases in sea ice is quite different from that of glacier and ice‐berg ice, and the difference seems to result from the change in both the solubility of gases in water and the rate of outgassing during the period of ice formation. The gas content is usually higher in younger sea ice than in older ice. Nitrogen shows greater retention in ice than other gaseous components.

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