[auroram42]

Hello everyone! I am a newbie here, so if you can direct me to the right place, it's much appreciated.

I am a science teacher and we're working through a set of chemistry experiments together with my students, but I am not a chemist by background rather a mechanical engineer who likes chemistry!

Anyway, we're doing an experiment and hit a snag. We're doing a cold light experiment using luminol, sodium hydroxide, hydrogen peroxide and (here's the question) K3Fe(CN)6. The question is: can K4Fe(CN)6 be substituted for K3Fe(CN)6? Or I guess my real question is, how different is K4Fe(CN)6 and K3Fe(CN)6 in a reaction? I'd really like us both to learn from this, so any help you can provide is appreciated.

Thanks so much.

[kriggy]

Im not realy sure but I think you need the K3[Fe(CN)6] as the catalyst of dismutation of hydrogen peroxide to get luminiscence. So the K4[Fe(CN)6 wont work because it seems that thats the product in the end.
2 K3[Fe(CN)6] + H2O2 + 2 KOH = 2 K4[Fe(CN)6]H2O + O2

[Corribus]

I think the best answer for this is to do the experiment and find out. If you really want to teach your students how science works, this is the best way. Make a hypothesis, do the experiment, and see what happens. Then you can try to explain the results.

In real science you don't know the answer beforehand.  

[Big-Daddy]

I'm not really sure what reaction you expect, but if the standard procedure is to use K₃Fe(CN)₆, don't replace it with K₄Fe(CN)₆ and necessarily expect the experiment to work. If it's a redox reaction you're talking about, there will be a great difference between how iron in the +3 oxidation state (as in the [Fe(CN)₆]^3- ion) and in the +2 oxidation state (as in [Fe(CN)₆]^4-) would react.

[auroram42]

Thanks everyone for your feedback. We're planning to do it anyway and see how it works, but I wanted to know if there's anything I should consider first!