Sciencemadness Discussion Board

Interesting copper complexes of cyanide

woelen - 6-6-2022 at 13:11

I recently obtained a nice amount of sodium cyanide, NaCN. With this I did some interesting experiments:
- formation of complexes of copper
- redox reactions

The experiment with formation of copper is particularly interesting. Especially the colors, obtained in this experiment are surprising. I did not expect that from copper and cyanide. I used very pure copper sulfate to be sure that no other metal ions were interfering.

The experiment can be viewed here:

In the blue bar, click "Experiment by ID" and then in the box enter the number 656.


It is interesting to see that the cyanide easily reduces the copper(II) to copper(I) in this experiment. On the other hand, I also attempted to oxidize the cyanide with dichromate and bromate, but these experiments failed. Not even in dilute H2SO4, the dichromate was capable of oxidizing the cyanide. It remained orange, even on heating. Bromate also was without any effect on the cyanide.

Oxy - 7-6-2022 at 07:59

Nice experiment woelen

The colourful affirmation of crystal field's electronic effects is something that always impresses me

Bedlasky - 7-6-2022 at 11:50

Nice experiment, Woelen!

I found some texts about these Cu/CN complexes here:

pantone159 - 8-6-2022 at 06:58

Nice work, as always!

Btw: I was not able to view this experiment on my Android phone. When I go to your link on the phone, only the left part of the webpage displays, and it is not possible to select the "Experiment by ID" button. It does work fine on my PC.

woelen - 8-6-2022 at 11:35

@Bedlasky: Thanks very much for the links. Very interesting to read about the violet complex. Your info really gives more info on this, the stuff you obtain by googling on combinations of copper and cyanide only cover the formation of (CN)2, but all the peculiar color changes remain unmentioned.

@pantone159: Good to have your feedback on the issue with the webpage on the phone. I see indeed that when the window's size is reduced, then from a certain point it does not display correctly. The text in the blue bar is crammed into a smaller and smaller place, and even put over each other. The text in the white area does wrap around properly. I'll have a look into this and I hope I can easily fix this (I'm not really a frontend programmer, my thing is more to have nice backends and API's, to be used by a frontend programmer who is not me ;) ).

[Edited on 8-6-22 by woelen]

Bedlasky - 8-6-2022 at 12:21

pantone159: I have the same issue, but than I let it display as page for computer. This fix the problem.

Woelen: I googled: reaction of copper(II) with cyanide. When I search some reaction, I usually use "reaction of X with Y in some environment (alkaline, acidic, organic solvent etc.)" format and it usually works pretty well.

woelen - 19-6-2022 at 12:26

I modified the backend side of my online lab journal and now it allows uploading of general documents, like PDF-files. I added the papers, provided by Bedlasky, to the experiment. Not just links to the links, but copies, which remain present on my website.

While having to change the backend because of the documents, I also improved the search function. Teodor mentioned a problem in finding experiments on the basis of supplied compound name. Now it should work correctly with compounds, which have spaces in their name, and the number of spaces does not matter at all anymore. The software is made robust to that.

Now, a final problem is left, and that is that on small screens and in small windows, the webpage does not display nicely. This must be solved at the frontend side of my application. I hope I can quickly solve that issue, hopefully it does not require me to replace a lot of Javascript at the frontend.

[Edited on 19-6-22 by woelen]