Particles collected from the fume of Kilauea volcano are largely dilute sulfuric acid droplets containing dissolved salts. The concentrations of salts in the droplets vary markedly depending on the volcanic conditions where collection occurs. A technique has been developed for determining the proportion of sulfate to sulfur dioxide in such fume. Very large variations in these proportions have also been found. All of these variations can be explained as being due to varying degrees of oxidation of H 2S, S and SO 2 at high temperatures by atmospheric oxygen. If such oxidation occurs during extremely explosive eruptions, such as that of Ganung Agung in Bali, large amounts of sulfuric acid droplets containing various sulfates may be injected directly into the stratosphere. Since such droplets are in the micron and submicron size range, they will remain in the stratosphere for long time periods.