[H_N]

 In the reaction between sodium thiosulfate and iron(III) chloride solution, I added four different catalysts and recorded reaction time. Nickel and Iron were quite effective, cobalt and copper were not.

Catalysts:

Cobalt(II) chloride solution
Copper(II) sulfate solution
Nickel sulfate solution
Iron(II) sulfate solution

Any ideas why? I thought reaction time would be tied to reduction/oxidation potential or number of highest orbital electrons, but no clear trend is emerging. I also thought cobalt chloride would be a better catalyst than it was- any ideas why it wasn't effective? Is it temperature dependant, or just doesn't catalyse this reaction well? Any explanation for these results would be great! Thanks!