A rapid and efficient--almost instantaneous and quantitative--method was devised to differentially leach manganese, nickel, and cobalt to the exclusion of copper and iron from deep sea nodules. In this method, a given weight of raw sea nodules ground to -200 mesh in an aqueous slurry is contacted for 10 min at room temperature with a specified quantity of so2. An independent leaching parameter, r, was defined as the ratio of the number of moles of so2 in the leaching solution to the weight of sea nodules. Variation of metal extraction with r generates sigmoidal curves characteristic of the metals extracted. A threshold value of r is required to initiate the leaching of a given metal from the mixed oxides. Once the threshold is reached, the metal recovery can rise above 95 pct in less than 10 min. For increasing value of r the extractability of various metals from Pacific Sea nodules by so2 follows the order: mn > ni > CO >> fe, al, cu. Disparity in the r values permits a variety of selective leaching systems and metal separations simply by changing the quantity of so2 in the contact solution.