moles l of n nonylbenzotriazole 84 1 molar ratio of 2 n isomer to 1 n isomer in paraffinic hydrocarbon norpar 12 is prepared and for comparison purposes a solvent extractant without the benzotriazole is also prepared the aqueous feed is contacted with the respective solvent extractants for 1 minute and for 5 minutes as described above and the raffinates are analyzed with the results set forth in table 3 table 3______________________________________separation of cobalt from nickel equilibra cobalt nickel tion time extracted extracted ni coexample min selectivity______________________________________11a 1 7 0 38 0 8 112a 5 7 3 38 3 7 911 1 7 0 49 3 12 912 5 7 0 48 8 12 7______________________________________ control no n nonylbenzotriazole in solvent extractant the foregoing results show a significant increase in both the percent nickel extracted and in the ni co selectivity with the addition of the nonylbenzotriazole to the solvent extractant because the 1 minute and 5 minute selectivities are substantially the same for the controls the system is at equilibrium and the improvement is in equilibrium selectivity the dependency of the enhanced equilibrium extraction upon molar concentration of nonylbenzotriazole is demonstrated by preparing an aqueous feed solution comprising 2 g l of nickel and 2 g l of cobalt both as sulfates and adjusting the ph to 1 5 a solvent extractant is prepared comprising 0 067 mole l of didodecylnaphthalene sulfonic.