PHOSPHATE ION ENRICHMENT IN DROPS FROM BREAKING BUBBLES

Bubble-produced aerocolloids from a 22Na-32PO4 solution show a phosphate enrichment E = (PO43-/Na+) aerocolloid/(PO43-/Na+) solution - 1 which is positive for all drop sizes from 0.25 to 25 μm and may reach 600 for 8-μm drops. Drops arising from the central jets of small bubbles show enrichments up to 10 which are independent of drop size. Drops arising from the film caps of larger bubbles show a superimposed peak enrichment Ê which is log-normally centered on a drop diameter of 8 μm. The mechanism postulated for enrichment is selective adsorption of PO43- as a counterion to surface-active organic molecules (present intentionally or as contaminants in distilled water) followed by ejection into the atmosphere of the enriched surface layer by the surface-microtome behavior of a breaking bubble.