[Arijit Gupta]

I am studying the catalysis mechanism of various transition metal ions on Fe3+ + S2O3 2- reaction for my high school project. Cu2+, Fe2+, Ni2+, and Co2+ are the catalysts, Cu2+ being the best among them, which acts by oxidising S2O3 2-, which I've tested and also verified through literature.
I tried to deduce the other catalyst's mechanism in the same way, only to realise that all the others minus Cu2+ don't react at all with S2O3 2-. So, I tried testing (Ni2+ and Co2+) with Fe3+. But, both reactions (nt even sure if any reaction occurs), don't show confirmatory tests for the presence of Fe2+ (I expected Fe3+ to be reduced to Fe2+, since it is one of the products and also known dat Co3+ oxidises s2O3 2-, and comes back to Co2+)
As for Fe2+, it involved quantitative test, for which there's nt enuf equipment in our lab. But, I hv read its exchange reacn with Fe3+, and I assumed that it may be catalysing by increasing the concn of reactants, though I am not sure.
So, it would be nice if anyone can help me with Ni2+, Co2+, Fe2+ mechanism. (maybe there's catalyst incubation in case of Ni2+ and Co2+, which I can't study, but dat's only an assumption)
And also, can anyone help me with this:
During Cu2+ mechanism deduction, I added it to excess s2o3 2-, which turned a greenish tinge instantaneously. By next day, there was a black deposit around the test tube (CuS), and inside there was a colourless liquid, to which I added sodium nitroprusside.
Now,
it turned green ppt.? What's dat abt? By next day, the ppt. Had become whitish.

IN DIRE NEED OF HELP. Please, I want to complete my project.
Anyone? Ni2+, Co2+, Fe2+ mechanism and dat single Cu2+ observation?? Help?
your own experience or any citations?