Organic acids were quantitatively extracted from the soils with alcoholic sodium hydroxide solution adjusted at pH 11. The centrifugate of the soil suspension was concentrated, acidified with Dowex 50 (H+) to pH 2, filtered, washed, refluxed, at last steam-distilled. The steam distillate was later concentrated, mixed with 8 [image] NaHSO4 solution and anhydrous sodium sulfate and extracted with ethyl ether. The volatile aliphatic acids extracted was analysed by means of a gas chromatograph, containing a column packed with Chromosorb W, coated with dioctylsabacinate-15% sebacic acid. The residual soil extract in the distillation flask was neutralized with 1 [image] NaOH, evaporated to dryness, again acidified with 8 [image] NaHSO4, saturated with anhydrous Na2SO4 and then extracted with n-butanol-chloroform(l+l). The extract was then neutralized with ammonia, extracted with water, and the humic acid precipitated with hydrogen chloride. The centrifugate was evaporated down to convenient size. Its phenolic acids content was analysed by menas of paper chromatography, using 2% HAc [acetic acid] as the developer. Its non-volatile aliphatic acids was analysed by means of a Michl''s horizontal high-voltage electrophoresis apparatus with a buffer solution at pH 4. 0. The dynamics of the different acids in several soils, having been added with a mixture of volatile acids, is presented.