Uploaded September 2016 | Updated September 2026, 1 week ago
In this video we tried to make some impure Chromate solution.
We mixed some Chromium(III)Oxide with Sodium Carbonate and some Potassium Nitrate and heated it using a burner till it became all brown-yellow. After it cooled down water was added and the yellow solution was separated from the green insoluble rests.
Next we tried to test it for the formation of the blue Peroxo complex. So we added some Sulfuric Acid to it. Upon addition the Chromate molecules condensed to the orange Dichromate. For some reason it turned darker and green Cr(III) formed again on the bottom. I am not sure why it reacted that way. Still it turned blue after Hydrogen Peroxide was added proofing that we indeed made some weak Chromate solution.
In this video we tried to make some impure Chromate solution.
We mixed some Chromium(III)Oxide with Sodium Carbonate and some Potassium Nitrate and heated it using a burner till it became all brown-yellow. After it cooled down water was added and the yellow solution was separated from the green insoluble rests.
Next we tried to test it for the formation of the blue Peroxo complex. So we added some Sulfuric Acid to it. Upon addition the Chromate molecules condensed to the orange Dichromate. For some reason it turned darker and green Cr(III) formed again on the bottom. I am not sure why it reacted that way. Still it turned blue after Hydrogen Peroxide was added proofing that we indeed made some weak Chromate solution.
 (???) [no audio]](https://i.ytimg.com/vi/p8TuAZuQeTU/mqdefault.jpg "Cobalt Chemistry: [Co(CO3)3](3-) (???) [no audio]
If Co(II) solutions are treated with alkaline H2O2 Co2O3 and CoO2 may form. If however the precipitate from Sodium Bicarbonate and Cobalt Chloride is oxidized with a 10 M H2O2 at cold temperatures a green product froms.
Well we used worm solutions, 3% Hydrogen Peroxide and Sodium Carbonate but still got a green compound. Of course we cant be sure about its composition that way. It could also be the different oxides but the green color at least indicates some of the complex might have actually formed that way.
The Co(II) is oxidized to Co(III) which forms an insoluble complex with Na2CO3, Na3[Co(CO3)3]. Interesting enough the carbonate can be easily substituted for other ligands making this complex a great precursor to other Co(III) compounds.
We already discussed the chemistry of Co(II) and Co(III) in another video and showed that the oxidation potential is highly dependend on the system you use Cobalt in.")
](https://i.ytimg.com/vi/q70jHweiIog/mqdefault.jpg "Iron Chemistry: [Fe(CN)5(NO2)](4-)
In this video, we show some of the interesting properties of a compound called Sodium Nitroprusside. Often used to analyse Sulphides and Sulphites it shows some interesting chemistry, too.
Here we convert the NO-Ligand in [Fe(CN)5(NO)]2- to NO2 in [Fe(CN)5(NO2)](4-) using Potassium Hydroxide. While basic the reaction shifts towards the yellow NO2-compound. As later H2SO4 is added the pale red Nitroprusside Forms again.
Now you might ask yourself why NO(+) and NO2(-) shift upon addition of OH(-). This reaction is quite similar to a video we have already uploaded. Back then, we tried to add a polysulfide to the same compound and said a NOS-Ligand would form. The Sulphide was a substitute for HS(-) which is the heavier form of OH(-) thus they create a similar compound. We notice that nucleophiles readily attack the Nitrosyl-Nitrogen.
As CN is quite inert here and the Iron doesnt react anyways the complex is a stable substitute for NO(+) and can be used to do reactions with it. It would be interesting to also do the same experiment with Selenides and Tellurides. Those however are quite expensive unfortunately. Maybe we will try to make a Polyselenide and Telluride again and use that.
At the moment we also try to change the NO2(-) for a AsO2(-), yes a Fe-As-coordination. We tried this more than once and it is mentioned in literature to be orange but unfortunately so is the reactant itself.")
![Chromium Chemistry: [2xfaster] Chromium in Gas-Phase (Chromylchloride)](https://i.ytimg.com/vi/qeQLe06sV0E/mqdefault.jpg "Chromium Chemistry: [2xfaster] Chromium in Gas-Phase (Chromylchloride)
Chromyl Chloride is a well known compound in organic chemistry. We tried using its property to become airborne quite easily and tested if the gaseous Chromium would react with some Hydrogen Peroxide in another vial to form the blue Peroxo-complex.
So we prepared two vials, one containing some 3% Hydrogen Peroxide and diluted H2SO4 and the other containing a mixture of KCl and K2Cr2O7. To the second one a few drops of conc. H2SO4 were added. It starts to foam and an orange (hard to see on camera) gas forms. On the video it looks quite pale but it was quite dense in reality. On the glass walls you can see some red drops of liquid Chromyl Chloride. We covered both vials with a beaker and waited. After some time a blue complex forms proofing that the yellow gas is not only Chlorine but also a gaseous Chromium compound.
To understand the structure of Chromylchloride a bit more it is easier to remind yourself that this compound can be prepared if Chromic Acid is reacted with Hydrochloric Acid, too.
Now we had this in the Polychromate video already. Chromic acid is a tetrahedron having two Cr-O bonds and two Cr-OH bonds. Back then we added acid to form a Cr-O-Cr bond. But what if we dont have the H(+) acting here but the Cl(-) ? The Cl(-) could substitute the OH(-)
Cr-OH + HCl to Cr-Cl + H2O. this happens to both of the Cr-OH groups forming the CrO2Cl2. Now the water reacts with this compound so the would would have to be captured here. One way to do this is using conc. H2SO4 which is strongly hygroscopic. And the HCl can be substituted by NaCl for example to reduce the amount of water even more. And we showed that Chromic acid forms if Chromates meet Acids, so the setup can be reduced to having a Dichromate or Chromate, a Chloride salt and some conc. H2SO4.")
