The kinetic electrolyte effect of dissolved NaCl, LiCl and Na2SO4 on the oligomerization of the hydrosulfide ion (HS-) into polysulfides then in colloidal sulfur assisted by iron(III) trans-1,2,-diaminocyclohexanetetraacetate (iron(III)-cdta) complexes was studied in anoxic alkaline solutions at 25 +/- 1 degrees C. The three electrolytes have been confirmed to boost the HS- oligomerization reaction considerably. For example, the HS- half-life decreased from 16.7 min in demineralized water (pH = 10.5) to 12.4 min for the corresponding 0.01 mol/L NaCl solution. It further decreased to 5.1 min for a 0.1 mol/L NaCl solution. The kinetic enhancement factor is attributed to the cationic species (i.e. Na+, Li+) both affecting the reactive species' activity coefficients within experimental and calculation accuracy. It improves the initial HS- and iron(III)-cdta reaction rates, reduces the induction period for elemental sulfur formation which in turn enhance the overall HS- consumption rate. The HS- and iron(III)-cdta concentration profiles were also fitted with corresponding rate laws derived from a simplified HS- oligomerization mechanism and application of kinetic electrolyte constants on the activity coefficient Huckel equation. (c) 2006 Elsevier Ltd. All rights reserved.