The effect of 25 organic substances on the solubility of oxygen in aqueous solutions was studied at 310.15 K (37 degrees C, body temperature) and pure oxygen at barometric pressure, for each of which the Setchenov coefficient was experimentally determined. Acetic acid was the only substance with a slight salting-in effect. All other substances salted-out, e.g., ammonium or sodium salt of organic acids, organic bases or their acid salts with hydrogen chloride, and zwitterionic compounds like beta-alanine, glycine, glycine-glycine, L-lysine and taurine. For organic ions, a specific single-ion parameter H-i for cation or anion was derived from the observed Setchenov coefficient of the organic salt, and the known H-i of either sodium or chloride ion, respectively.